SAFE Key Features And Terminology

User Manual: SAFE Key Features and Terminology

Open the PDF directly: View PDF .
Page Count: 77

Title
Copyright
Disclaimer
Contents
Chapter 01 Welcome to SAFE
Chapter 02 Getting Started
Chapter 03 The SAFE System
Chapter 04 SAFE Modeling Features
Chapter 05 SAFE Analysis Features
Chapter 06 SAFE Design Features
Chapter 07 SAFE Detailing Features
Chapter 08 The SAFE "Screen"
Chapter 09 Key Topics

Key Features and Terminology

SAFE®

DESIGN OF SLABS, BEAMS AND FOUNDATIONIS

REINFORCED AND POST-TENSIONED CONCRETE

Key Features and Terminology

ISO SAF112816M1 Rev. 0

Proudly developed in the United States of America

November 2016

The CSI Logo® and SAFE® are registered trademarks of Computers &

Structures, Inc. Watch & LearnTM is a trademark of Computers & Structures,

Inc. Adobe and Acrobat are registered trademarks of Adobe Systems

Incorported. AutoCAD is a registered trademark of Autodesk, Inc.

The computer program SAFE® and all associated documentation are

proprietary and copyrighted products. Worldwide rights of ownership rest

with Computers & Structures, Inc. Unlicensed use of this program or

reproduction of documentation in any form, without prior written

authorization from Computers & Structures, Inc., is explicitly prohibited.

No part of this publication may be reproduced or distributed in any form or

by any means, or stored in a database or retrieval system, without the prior

explicit written permission of the publisher.

Further information and copies of this documentation may be obtained from:

Computers & Structures, Inc.

www.csiamerica.com

info@csiamerica.com (for general information)

support@csiamerica.com (for technical support)

DISCLAIMER

CONSIDERABLE TIME, EFFORT AND EXPENSE HAVE GONE INTO THE

DEVELOPMENT AND TESTING OF THIS SOFTWARE. HOWEVER, THE

USER ACCEPTS AND UNDERSTANDS THAT NO WARRANTY IS

EXPRESSED OR IMPLIED BY THE DEVELOPERS OR THE DISTRIBUTORS

ON THE ACCURACY OR THE RELIABILITY OF THIS PRODUCT.

THIS PRODUCT IS A PRACTICAL AND POWERFUL TOOL FOR

STRUCTURAL DESIGN. HOWEVER, THE USER MUST EXPLICITLY

UNDERSTAND THE BASIC ASSUMPTIONS OF THE SOFTWARE

MODELING, ANALYSIS, AND DESIGN ALGORITHMS AND COMPENSATE

FOR THE ASPECTS THAT ARE NOT ADDRESSED.

THE INFORMATION PRODUCED BY THE SOFTWARE MUST BE CHECKED

BY A QUALIFIED AND EXPERIENCED ENGINEER. THE ENGINEER MUST

INDEPENDENTLY VERIFY THE RESULTS AND TAKE PROFESSIONAL

RESPONSIBILITY FOR THE INFORMATION THAT IS USED.

Contents

1 Welcome to SAFE

1.1 Introduction 1-1

1.2 History and Advantages of SAFE 1-2

1.3 What SAFE Can Do! 1-3

1.4 An Integrated Approach 1-4

1.5 Modeling Features 1-5

1.6 Analysis Features 1-5

1.7 Design Features 1-6

1.8 Detailing Features 1-7

1.9 An Intuitive Process 1-7

1.10 Work Flow 1-8

2 Getting Started

2.1 Installing SAFE 2-1

2.2 If You are Upgrading 2-1

2.3 About the Manuals 2-2

2.4 “Watch & LearnTM Movies” 2-3

2.5 CSI Knowledge Base 2-3

2.6 Technical Support 2-4

2.7 Help Us to Help You 2-4

SAFE – Key Features and Terminology

3 The SAFE System

3.1 Physical Modeling Terminology 3-1

3.2 Structural Objects 3-2

3.3 Properties 3-3

3.4 Load Patterns 3-4

3.4.1 Vertical Loads 3-4

3.4.1.1 Arrangement of Live Load 3-5

3.4.2 Lateral Loads 3-5

3.4.3 Dynamic Loads 3-6

3.4.4 Temperature Loads 3-6

3.5 Load Cases 3-7

3.6 Load Combinations 3-7

3.7 Design Procedures 3-8

3.8 Detailing Procedures 3-8

3.9 More Information 3-9

4 SAFE Modeling Features

4.1 Overview of the Modeling Process 4-1

4.2 Slab Types 4-2

4.2.1 Two-Way Slabs 4-2

4.2.2 Flat Slabs 4-3

4.2.3 Ribbed Slabs 4-3

4.2.4 Waffle Slabs 4-4

4.3 Mat Foundations and Footings 4-4

4.4 Slabs with Discontinuities 4-5

4.5 Beam Types 4-5

4.6 Post-tensioning 4-5

4.7 Models Exported from ETABS 4-6

4.8 More Information 4-7

5 SAFE Analysis Features

5.1 Overview of the Analysis Process 5-1

5.2 The Analysis Model 5-2

5.3 Linear Static Analysis 5-4

5.4 Nonlinear Analysis for Uplift 5-4

5.5 Nonlinear Analysis for Cracking 5-5

Contents

5.6 Nonlinear Analysis for Long-Term Cracking 5-6

5.7 Modal Analysis 5-7

5.8 Hyperstatic Analysis 5-7

5.9 More Information 5-7

6 SAFE Design Features

6.1 Overview of the Design Process 6-1

6.2 Slab Flexural Design 6-2

6.2.1 Design Strips 6-2

6.2.2 Integration of Moments – Wood-Armer 6-2

6.2.3 Required Reinforcement – Strip Based 6-3

6.2.4 Required Reinforcement – FEM Based 6-4

6.2.5 Slab Rebar Objects 6-4

6.3 Slab Punching Shear Check 6-4

6.4 Beam Flexural, Shear, and Torsion Design 6-7

6.5 Results Output 6-8

6.6 More Information 6-9

7 SAFE Detailing Features

7.1 Overview of the Detailing Process 7-1

7.2 Detailing Preferences 7-2

7.3 Drawing Component Views 7-3

7.3.1 View Properties 7-3

7.3.2 View Text 7-4

7.4 Drawing Sheets 7-4

7.5 Reinforcement Editing 7-4

7.6 Synchronization 7-5

7.7 More Information 7-5

8 The SAFE “Screen”

8.1 The Graphical User Interface 8-1

8.2 File Menu 8-3

8.3 Edit Menu 8-4

8.4 View Menu 8-5

8.5 Define Menu 8-6

8.6 Draw Menu 8-7

8.7 Select Menu 8-7

iii

SAFE – Key Features and Terminology

8.8 Assign Menu 8-8

8.9 Design Menu 8-9

8.10 Run Menu 8-9

8.11 Display Menu 8-10

8.12 Detailing Menu 8-11

8.13 Options Menu 8-11

8.14 Help Menu 8-12

8.15 More Information 8-12

9 Key Topics

9.1 Select or Draw Mode 9-1

9.2 Templates and Defaults 9-2

9.3 Coordinate Systems and Grids 9-3

9.4 Overlapping Area Objects 9-4

9.5 Keyboard Shortcuts 9-5

9.6 Time Saving Options 9-6

9.7 More Information 9-7

Chapter 1

Welcome to SAFE

1.1 Introduction

SAFE is a sophisticated, yet easy to use, special purpose analysis, de-

sign, and detailing program developed specifically for concrete slab and

basemat systems. SAFE couples powerful object-based modeling tools

with an intuitive graphical interface, allowing the quick and efficient

modeling of slabs of regular or arbitrary geometry with openings, drop

panels, post-tensioning, ribs, edge beams, and slip joints, supported by

columns, walls, or soil. Design is seamlessly integrated with the model-

ing and analysis, and provides comprehensive reporting of the required

reinforcement calculated based on a chosen design code. Detailed draw-

ings may be produced effortlessly for slabs and beams designed using

SAFE. SAFE may be used as a stand-alone application, or may be used

in conjunction with ETABS to complete analysis, design, and detailing

of concrete floor plates created in ETABS.

Introduction 1 - 1

SAFE – Key Features and Terminology

1.2 History and Advantages of SAFE

Slab systems are a very special class of structures. They are character-

ized by their simplicity in geometry and loading. They are typically hori-

zontal plates supported vertically by beams, columns, and walls. The

loading is typically comprised of vertical point, line, and surface loads

along with in-plane post-tensioning. Basemats share the same character-

istics as those of elevated slabs, with the exception that basemats are

supported on soil and loaded by columns and walls.

Recognition of the unique characteristics of slab systems led to the orig-

inal development of the SAFE program more that three decades ago.

Early releases of SAFE provided input, output, and numerical solution

techniques that took into consideration the modeling and analysis needs

specific to concrete slabs, providing a tool that offered significant sav-

ings in time over general purpose finite element programs and that in-

creased accuracy in comparison to equivalent frame methods.

As computers and computer interfaces evolved, so did SAFE, adding

computationally complex analytical options such as cracked section

analysis, and powerful CAD-like drawing tools in a graphical and ob-

ject-based interface. Although the current version looks radically differ-

ent from its predecessors of 30 years ago, its mission remains the same:

to provide the profession with the most efficient and comprehensive

software for the analysis and design of slab systems. SAFE automates

the analysis and design process for the structural engineer, resulting in

more sophisticated designs produced with less engineering labor.

Creation and modification of the slab model, execution of the analysis,

checking and optimization of the design, detailing of reinforcement, and

display of graphical results are all controlled through a single interface,

and all aspects of the program are linked via a common database.

SAFE also serves up the latest developments in numerical techniques,

solution algorithms, and design codes, including automatic finite element

meshing of complex object configurations, very accurate shell elements,

sophisticated post-tensioning loads, and the most recent concrete design

codes from around the world.

1 - 2 History and Advantages of SAFE

Welcome to SAFE

1.3 What SAFE Can Do!

SAFE offers the widest assortment of analysis and design tools available

for the structural engineer working on concrete slabs. The following list

represents just a portion of the types of systems and analyses that SAFE

can easily handle:

 Flat slabs

 Flat slabs with perimeter beams

 Slabs with post-tensioning tendons

 Basemats

 Two-way slabs

 Waffle slabs

 Ribbed slabs

 Rectangular or circular slabs

 Geometrically complex slabs with multiple coordinate systems

 T-beam effects

 Spread footings

 Combined footings

 Slabs subjected to any number of vertical load patterns and com-

binations

 Pattern live loads

 Foundation uplift

 Cracked section analysis

 Walls with out-of-plane bending stiffness

 Slab reinforcement calculated based on user-defined design strips

 User controlled placement of slab rebar

What SAFE Can Do! 1 - 3

SAFE – Key Features and Terminology

 Flexural, shear, and torsion design of beams

 Punching shear checks and punching reinforcement design

 Dynamic analysis of floor systems and foundations by exporting

response spectrum analysis results from ETABS to SAFE

 Design for twisting moments

 Reinforcement contours calculated using Finite Element forces

 Automatic transfer of geometry, loading, and support distortions

from ETABS

 Post-tensioning and mild reinforcement detailing

 Material quantity takeoffs

 And much, much more!

1.4 An Integrated Approach

SAFE is a completely integrated system. Embedded beneath the simple,

intuitive user interface are very powerful numerical methods and design

procedures, all working from a single comprehensive database. This in-

tegration means that only one model is necessary to analyze, design, and

detail the entire slab.

Everything is integrated into one versatile package with a single Win-

dows-based graphical user interface. No external modules need to be

maintained, and data transfer between analysis, design, and detailing is

worry free. The effects on one part of the slab from changes in another

part are instantaneous and automatic. The integrated modules include the

following:

 Drafting module for model generation.

 Finite element based analysis module.

 Output display and table generation module.

 Concrete slab and beam design module.

1 - 4 An Integrated Approach

Welcome to SAFE

 Concrete slab and beam reinforcement detailing module.

1.5 Modeling Features

The SAFE slab is idealized as an assemblage of area, line, tendon, and

point objects. Area objects are used to model slabs, openings, soil sup-

ports, walls, ramps, and surface loads. Line objects model beams, col-

umns, braces, and loads. Tendon objects are used to input post-

tensioning loads. Point objects are used for concentrated loads. With rel-

atively simple modeling techniques, very complex slab systems can easi-

ly be considered.

The geometry of the slab can be unsymmetrical and arbitrary, and the

thickness of the slab may vary. Locations of supports and loads may be

completely random and are not limited to the uniform spans typically as-

sociated with equivalent frame techniques.

Construction or expansion joints may be modeled with or without shear

transfer by assigning bending and shear releases to either or both sides of

the line object that represents the joint.

Columns and walls provide both vertical stiffness and rotational stiffness

to give a more accurate representation of the distribution of forces in the

slab.

1.6 Analysis Features

Static analyses, including the effects due to post-tensioning, can be car-

ried out for any number of user-defined load cases, and the load cases

may be combined into any number of load combinations. Forces and de-

flections calculated may include those for both elastic and cracked sec-

tions, and load cases may include creep and shrinkage factors for nonlin-

ear cracked deflection analyses. Hyperstatic analysis is also available

and is based on a predefined static load case.

Basemats and foundations may be subjected to overturning moments that

cause uplift. SAFE offers a nonlinear solution that accounts for zero ten-

Modeling Features 1 - 5

SAFE – Key Features and Terminology

sion in soil springs, as well as allowing soil moduli to vary throughout

the model.

To account for orthotropic effects, different thicknesses may be specified

in the local 1 and 2 directions when defining slab properties. This can be

useful to model slabs that have primarily one-way behavior, where

cracking may be predominant in one direction.

The analysis output may be viewed graphically, displayed in tabular out-

put, sent to a printer, exported to a database or spreadsheet file, exported

to a CAD file, or saved in an ASCII file. Types of output include slab,

beam, and wall forces, reactions, displacements, and design reinforce-

ment.

SAFE also provides dynamic analysis capabilities through modal fre-

quency analysis and handling of response spectrum results exported

from ETABS into SAFE. These capabilities allow for investigation of

things such as floor vibrations and machine foundations.

SAFE utilizes the SAPFireTM analysis engine, the state-of-the-art equa-

tion solver that powers all of CSI’s software. This proprietary solver ex-

ploits the latest in numerical technology to provide incredibly rapid solu-

tion times and virtually limitless model capacity.

1.7 Design Features

Flexural and shear design of reinforced and post-tensioned concrete

slabs and basemats and the flexural, shear, and torsion design of beams

can be performed based on a variety of international design codes. De-

sign accounts not only for the stresses in the members due to post-

tensioning, but also incorporates the tendons as reinforcement. Slab rein-

forcement location and layout is controlled using design strips that can

be user-defined such that they may be non-orthogonal. Associated with

these design strips are widths that can be automated or user-defined, and

both column and middle strips may be specified. Design strip moments

are obtained by integrating the finite element stresses using an algorithm

that accounts for the effects of twisting moments. Users may also draw

1 - 6 Design Features

Welcome to SAFE

their own slab reinforcement, and then ask the program to report where

additional reinforcement is required. Code-based punching shear checks

and if necessary, punching shear reinforcement design, are performed at

columns, supports, and point loads.

1.8 Detailing Features

Drawings showing detailed reinforcement may be produced for both

slabs and beams. The detailing may be based on program defaults, which

represent general detailing based on the designed reinforcement, or on

user-defined preferences. Any number of drawings may be prepared,

containing plan views of reinforcement and tendon layouts, sections, el-

evations, tables, and schedules. Control over reinforcement bar sizes,

minimum and maximum spacing, along with cut-off (curtailment)

lengths is provided through detailing preferences. Drawings may be

printed directly from SAFE or exported to DXF or DWG files for further

refinement.

1.9 An Intuitive Process

The basic approach for using SAFE is very straightforward. The user es-

tablishes grid lines, places structural objects relative to the grid lines us-

ing columns, beams, tendons, walls, and slabs, and assigns loads and

structural properties to those structural objects. Analysis, design, and de-

tailing are then performed based on the structural elements and their as-

signments. Results are generated in graphical or tabular form that can be

printed to a printer or saved to a file for use in other programs.

In using SAFE, you manage the File, Edit the model, change the View,

Define properties or load patterns, Draw new objects in the model, Se-

lect existing objects, Assign properties or loads, Run the analysis and

Design of the model, Display analysis results for checking, detail the

structure by running the Detailing, and apply various Options to achieve

the desired outcome with minimum effort. These actions are the basis for

the program menu structure. Thus, familiarity with the menu commands

and their function is vital to expanding your ability to use SAFE.

Detailing Features 1 - 7

SAFE – Key Features and Terminology

Subsequent chapters of this manual and the Defining

the Work Flow manual describe many of the menu

commands in greater detail. Familiarity with the sub-

menus will enable creation of models for complex Flat

Slabs with Openings, Slabs with Beams, Footings, and

Mats.

The SAFE design manuals explain how SAFE per-

forms concrete beam and slab design with both post-

tensioning and mild reinforcement, in accordance with

applicable design codes.

Information regarding the creation of detailed drawings

may be found in the Defining the Work Flow manual.

1.10 Work Flow

In the manual entitled, Defining the Work Flow, a basic work flow is de-

fined that covers the typical steps necessary for the majority of projects.

Each of the items listed below is discussed in detail and provides a broad

overview of the basic modeling process:

1. Set the Units

2. Begin a Model

3. Define Materials

4. Define Properties

5. Draw Objects

6. Select Objects

7. Assign Properties to the Model

8. Load the Model

9. Define Load Cases

10. View & Edit Model Geometry

11. Analysis and Design

SAFE Menu

Commands:

 File

 Edit

 View

 Define

 Draw

 Select

 Assign

 Design

 Run

 Display

 Detailing

 Options

 Help

1 - 8 Work Flow

Welcome to SAFE

12. Reinforcement Detailing

13. Display Results

14. Output Results and Reports

Work Flow 1 - 9

Chapter 2

Getting Started

2.1 Installing SAFE

Please follow the installation instructions provided in the separate instal-

lation document included in the SAFE package or ask your system ad-

ministrator to install the program and provide you access to it.

2.2 If You are Upgrading

If you are upgrading from an earlier version of SAFE, you should be

aware that the model is now defined in terms of objects, which are auto-

matically and internally meshed into elements during analysis.

This significant change drastically improves the capability of SAFE, and

we recommend that you read the remainder of this manual to familiarize

yourself with this and the many other new features.

Installing SAFE 2 - 1

SAFE – Key Features and Terminology

2.3 About the Manuals

The SAFE documentation consists of three volumes. Volume I “Using

SAFE” in turn consists of three manuals: Key Features and Terminolo-

gy, Defining the Work Flow, and Tutorial. Volume II “SAFE Design”

contains two manuals: Post-Tensioned Concrete Design and Mild Rein-

forced Concrete Design. Volume III is a single document entitled

“SAFE Verification.” Figure 2-1 provides a graphical representation of

the SAFE documentation structure.

Figure 2-1 SAFE Documentation

This manual, Key Features and Terminology, provides overviews of the

SAFE modeling, analysis, design, and detailing techniques, along with

detailed descriptions of the SAFE interface. The Defining the Work Flow

document offers an ordered description of the workflow process in-

volved in using SAFE, from starting a model to detailing the designed

structure. The Tutorial takes the user through the creation, analysis, and

design of an example models.

2 - 2 About the Manuals

Getting Started

Information covering the design theory and methods, in accordance with

various international design codes, is provided in Volume II. Reinforced

Concrete Design and Post-Tensioned Concrete Design features chapters

on the various design codes included in SAFE, including the American,

Australian, British, Canadian, Chinese (requires Chinese license), Euro-

pean, Indian, Hong Kong, New Zealand, and Singapore codes.

The SAFE Verification manual provides comparisons of SAFE output

with independently produced or published results.

It is strongly recommended that you read this volume and view the tuto-

rial movies (see “Watch & Learn



Movies”) before attempting to com-

plete a project using SAFE.

Additional information can be found in the Help facility that is accessi-

ble from within the SAFE graphical user interface.

2.4 “Watch & Learn™ Movies”

One of the best resources available for learning about the features of

SAFE is the “Watch & Learn



Movies” series, which may be accessed

on the CSI website at https://www.csiamerica.com. These movies con-

tain a wealth of information for both the first-time user and the experi-

enced expert, covering a wide range of topics from basic operation to

complex modeling. The movies range from a few minutes to more than a

half hour in length.

2.5 CSI Knowledge Base

CSI maintains a knowledge base containing answers to frequently asked

support questions as well as additional insights on program operation.

This is a good first stop before contacting technical support because

many of the most common, as well as some esoteric questions are an-

swered here. This page is fully indexed and searchable, and may be

found at https://wiki.csiamerica.com.

“Watch & Learn™ Movies” 2 - 3

SAFE – Key Features and Terminology

2.6 Technical Support

If you have questions regarding use of the software, please:

 Consult the documentation and other printed information included

with your product.

 Check the on-line Help facility in the software.

 Visit the CSI Knowledge Base at https://wiki.csiamerica.com.

If you have a current Maintenance Agreement you may request support

in one of the following ways:

 Send an email and your model file to support@csiamerica.com or

your local CSI Partner.

 Visit CSI’s website and Customer Support Portal at

https://www.csiamerica.com.

 Call CSI or your local CSI Partner. Contact details are available at

https://www.csiamerica.com/contact.

Be sure to include the necessary information listed in the ‘Help Us to

Help You’ section whenever you contact technical support.

2.7 Help Us to Help You

Whenever you contact us with a technical support question, please pro-

vide us with the following information to help us help you:

 The product level (Standard or P/T) and version number that you are

using. This can be obtained from inside the software using the Help

menu > About SAFE command.

 A description of your model, including a picture, if possible.

 A description of what happened and what you were doing when the

problem occurred.

 The exact wording of any error messages that appeared on your

screen.

 A description of how you tried to solve the problem.

2 - 4 Technical Support

Getting Started

 The computer configuration (make and model, processor, operating

system, hard disk size, and RAM size).

 Your name, your company’s name, and how we may contact you.

 If calling, please be at your computer where you can run the soft-

ware.

Help Us to Help You 2 - 5

Chapter 3

The SAFE System

SAFE analyzes, designs, and details concrete slab systems that are creat-

ed using the various drawing tools or imported into the graphical user in-

terface. The key to successfully implementing SAFE is to understand the

unique and powerful approach the program takes in modeling, designing,

and detailing slabs. This chapter provides an overview of some of the

special features and their associated terminology.

3.1 Physical Modeling Terminology

In SAFE, reference is often made to objects, members, and elements.

Objects represent the physical structural members in the model. Ele-

ments, on the other hand, refer to the finite elements used internally by

SAFE to generate the stiffness matrices. In many cases, objects and

physical members will have a one-to-one correspondence, and it is these

objects that the user “draws” in the SAFE interface. Objects are intended

to be an accurate representation of the physical members. Users typically

need not concern themselves with the meshing of these objects into the

elements required for the mathematical, or analysis model. For example,

a single area object can model an entire slab, regardless of the number of

Physical Modeling Terminology 3 - 1

SAFE – Key Features and Terminology

spans and variety of loadings. With SAFE, both model creation, as well

as the reporting of results, is achieved at the object level.

This differs from a traditional analysis program, where the user is re-

quired to define a sub-assemblage of finite elements that comprise the

larger physical members. In SAFE, the objects, or physical members

drawn by the user, are typically meshed internally during the analysis,

into the greater number of finite elements needed for the analysis model,

without user input. Because the user is working only with the physical

member-based objects, less time is required both to create the model and

interpret the results.

The concept of objects in a structural model may be new to you. It is ex-

tremely important that you grasp this concept as it is the basis for creat-

ing models in SAFE. After you understand the concept and have worked

with it for a while, you should recognize the simplicity of physical ob-

ject-based modeling, the ease with which you can create models using

objects, and the power of the concept when editing and creating complex

models.

3.2 Structural Objects

As previously stated, SAFE uses objects to represent physical structural

members. When creating a model, start by drawing the geometry and

then assign properties and loads to completely define the slab structure.

The following object types are available, listed in descending order of

geometrical dimension:

 Slab/Area objects are used to model slabs, drop panels, column ge-

ometry, openings, soil supports, and surface loads.

 Wall/Ramp objects are used to model walls and ramps.

 Beam/Line objects are used to model beams and line loads.

 Column objects are used to model columns and braces.

3 - 2 Structural Objects

The SAFE System

 Tendon objects are used to model post-tensioning tendons and tendon

loads. Even though they are drawn in plan similar to a beam object,

they differ from beam objects in that they have a shape profile through

the slab thickness.

 Point objects are automatically created at the corners or ends of all

other types of objects and also can be added anywhere in the model.

Point objects are used to model point loads and point displacements,

as well as for applying point restraints and springs.

As a general rule, the geometry of the object should correspond to that of

the physical member. This simplifies the visualization of the model and

reduces the chances of input error.

3.3 Properties

Properties are assigned to each object to define the structural or support

behavior of that object in the model. Properties under the Define menu,

namely slab, beam, reinforcing bar, tendon, column, wall, soil, and

spring properties, are named entities that must be specified before as-

signing them to objects. If a property is assigned to an object, for exam-

ple a beam property, any changes to the definition of the property will

automatically apply to the beam objects with this property assigned. A

named property has no effect on the model unless it is assigned to an ob-

ject.

Soil subgrade support properties may be assigned to slab/area objects,

and for these properties, SAFE generates spring elements at each mesh

location.

Other properties, such as releases or point restraints, found under the As-

sign menu, are assigned directly to objects. Those properties can be

changed only by making another assignment of that same property to the

object; they are not named entities and they do not exist independently

from the objects.

Properties 3 - 3

SAFE – Key Features and Terminology

3.4 Load Patterns

Static loads represent actions upon the structure, and include force, pres-

sure, temperature, and support displacement. A spatial distribution of

loads upon the structure is called a load pattern.

Any number of load patterns can be defined. Typically, a model will

have separate load patterns for dead load, live load, post-tensioning, pat-

tern live load, static earthquake load, wind load, snow load, temperature

load, and so on. Loads that need to vary independently, either for design

purposes or because of how they are applied to the slab, should be de-

fined as separate load patterns.

After defining a load pattern name, you must assign specific load values

to the objects as part of the load pattern. The load values you assign to an

object specify the type of load (e.g., force or displacement), the magni-

tude, and the direction. Different loads can be assigned to different ob-

jects as part of a single load pattern and each object can be subjected to

multiple load patterns.

3.4.1 Vertical Loads

Vertical loads may be applied to point, beam, and slab objects. Vertical

loads are typically input in the down, or −Z direction. Point objects can

accept concentrated forces or moments. Beam objects may have uniform

or trapezoidal distributed forces, moments, and torsions, as well as con-

centrated point loads, moments, and torsions. Uniform and non-uniform

surface loads can be applied directly to slab objects, including openings.

Vertical load patterns also may include element self weight.

Some typical vertical load patterns used for slabs might include:

 Dead load

 Superimposed dead load

 Live load

 Pattern live load

3 - 4 Load Patterns

The SAFE System

 Snow load

3.4.1.1 Arrangement of Live Load

It is often desirable to apply live loads in varied geometric arrangements

to model how these loads are applied to the real structure. Arranging live

loads in critical patterns can increase the negative and positive moments

in certain panels and columns. Common arrangements of loading include

geometric patterns such as live loads on two adjacent panels and live

loads on alternate panels.

SAFE allows for live loads to be geometrically arranged using two dif-

ferent options. Loading may be arranged using patterns defined by the

user or by patterns created automatically by SAFE. In either case, the

first step is to create a load pattern with a type of Pattern Live or Auto

Pattern Live. If the pattern type is Pattern Live, SAFE will take each Pat-

tern Live load pattern and combine them using the “Range Add” load

combination feature described later. Multiple load patterns are typically

required to capture alternate and adjacent panel loading arrangements for

user-defined cases.

If the pattern type is Auto Pattern Live, the loads associated with the pat-

tern will automatically be divided up internally into smaller “single pan-

el” load patterns based on the panel grid created by the layout of the grid

lines. Results from each of these “single panel” loads are then combined

automatically by SAFE using the Range Add load combination type.

Using the Auto Pattern Live option, rather than the user Pattern Live op-

tion, allows for a varied arrangement of live loads to be generated with a

single load pattern versus the multiple load pattern definitions required

with the user option.

3.4.2 Lateral Loads

SAFE allows deformations in both the in-plane and out-of-plane direc-

tions of the slab. It can handle vertical loads as described previously or

horizontal loads such as internal post-tensioning or external wind. Be-

Load Patterns 3 - 5

SAFE – Key Features and Terminology

cause in-plane deformations can occur, SAFE is appropriate for dia-

phragm studies. Effects caused by lateral loads may be considered using

load and displacement assignments. For suspended slabs, specified slab

deformations (rotations and displacements) may be assigned to columns

and walls to account for frame behavior under lateral loads. If using

ETABS to perform a 3-D building analysis, ETABS allows for the direct

export of floor loads and distortions to SAFE for further analysis and de-

sign.

Overturning of basemats or foundations resulting from lateral loads may

be modeled by applying moments or moment couples to walls and mo-

ments and vertical loads to columns. SAFE provides an explicit nonline-

ar solution to model no-tension (uplift) behavior in the soil.

3.4.3 Dynamic Loads

If dynamic response spectrum loads are exported from ETABS along

with a slab that is imported into SAFE, an additional set of load patterns

will be imported. A separate load pattern will be defined for each mode,

defined as type Other. These load patterns are used by an automatically

generated response spectrum load case that is created during the import

process. Note that response spectrum load cases can not be defined di-

rectly in SAFE.

3.4.4 Temperature Loads

SAFE allows temperature loads to be applied to slab objects, which re-

sults in thermal strains. These strains are given by the product of the Ma-

terial coefficient of thermal expansion and the temperature change of the

slab object. The temperature change may be specified as a gradient

through the thickness of the object, or as a constant, if the top and bot-

tom temperature changes are the same.

3 - 6 Load Patterns

The SAFE System

3.5 Load Cases

A load case defines how loads are to be applied to the structure, and how

the structural response is to be calculated. SAFE automatically generates

a load case for each load pattern that is defined. In addition, user-defined

load cases containing multiple load patterns can be created. Any number

of named load cases may be defined.

Analyses are classified in the broad sense as either linear or nonlinear,

depending upon how the model responds to the loading. The results of

linear analyses may be superposed, i.e., added together after analysis us-

ing combinations (see “Combinations” later in this chapter).

In addition to the typical static load cases, SAFE also provides the capa-

bility to carry out modal and hyperstatic analyses. Response spectrum

load cases can also exist if imported from ETABS.

The results of nonlinear analyses normally should not be superposed. In-

stead, all loads acting together on the structure should be combined di-

rectly within a load case.

3.6 Load Combinations

Load combinations combine the results of previously defined load cases

in an additive or enveloped manner. SAFE allows load combinations to

be named. When a load combination is defined, it applies to the results

for every object in the model.

The design is always based on load combinations, rather than directly on

load cases or load patterns. A combination containing only a single load

case can be created. The design algorithm creates its own default load

combinations based on the selected design code, which can be supple-

mented with any number of user-defined load combinations if required.

If a load pattern with a type of Pattern Live has been created, force quan-

tities will be combined automatically using the Range Add load combi-

Load Cases 3 - 7

SAFE – Key Features and Terminology

nation type. The Range Add combination calculates minimum and max-

imum force quantities for each element.

3.7 Design Procedures

SAFE has two integrated design post-processors, namely Post-Tensioned

Concrete Design (if licensed) and Reinforced Concrete Design; both de-

sign slabs and beams. The concrete slab design procedure is applicable

to slab objects and the beam design procedure is available for beam ob-

jects. Punching shear checks are also carried out at column object loca-

tions, point loads, and supports. Stud rail and rebar tie design options are

available when the punching shear capacity of the slab is not adequate.

Design can be affected by the following:

 The design code, e.g., ACI 318-08, Eurocode 2-2004, or BS8110-97,

among others.

 The post-tensioning loads.

 The design method and strength reduction factors.

 The combinations for which the design is carried out.

 Pattern Live load patterns; these load patterns are used only in strength

design.

 A and B design strips for the slabs, which determine the layout of the

calculated reinforcement. The total moment at each section of the

strips is used to calculate the required flexural reinforcement.

 The punching perimeter.

3.8 Detailing Procedures

SAFE includes the capability of generating detailed reinforcement draw-

ings for slabs and beams. The detailing utilizes the analysis and design

results to determine the required reinforcement quantities. For slabs, the

3 - 8 Design Procedures

The SAFE System

design strips define the orientation of the reinforcement. The detailed re-

inforcement can be modified as desired and detailed component views

can be compiled into drawing sheets that can be printed directly from

SAFE or exported to CAD software for further manipulation.

3.9 More Information

This chapter provides a brief overview of the basic components of the

SAFE system. Additional information can be found in the program Help

and in the “Watch & Learn



Movies” series. The other chapters of this

and the other manuals provide more detailed explanation of the compo-

nents introduced in this chapter.

More Information 3 - 9

Chapter 4

SAFE Modeling Features

SAFE offers an extensive and diverse range of tools to model a wide va-

riety of slab systems. Slab models can be created directly in the SAFE

interface, imported from ETABS, or defined using a drawing imported

from a CAD application. This chapter illustrates a few of the techniques

to make modeling quick and easy using SAFE.

4.1 Overview of the Modeling Process

A model developed using SAFE is different from models produced in

many other structural analysis programs for two main reasons:

 SAFE is optimized for modeling slab systems through tailored model-

ing procedures and design capabilities for concrete slabs and beams.

 SAFE models are object-based and consist of point, line, tendon, and

area objects, to which assignments are made to define structural mem-

bers, such as slabs, walls, ramps, beams, tendons, columns, braces,

and supports, as well as to define loads.

In its simplest form, developing a model requires four basic steps:

Overview of the Modeling Process 4 - 1

SAFE – Key Features and Terminology

 Define materials using the Define menu.

 Define slab, wall (ramp), beam, column (brace), and tendon properties

(sections) and supports using the Define menu.

 Draw a series of slab, wall, beam, column, tendon, and point objects

that represent your slab system, using the various drawing tools avail-

able within the graphical interface.

 Assign structural properties, supports, and loads to objects using the

Assign menu commands. Note that the assignment of structural prop-

erties and supports may be completed concurrently with the drawing

of the objects using the floating forms that appear when the draw

commands are used.

When the model is complete, the analysis may be run.

Note: When a form "floats," the form will remain visible when the cur-

sor is moved over the active window or the mouse button is clicked. This

means that changes can be made to the form without reusing the com-

mand required to bring up the form, which differs from other types of

forms. Floating forms are used in the draw mode so that the type of ob-

ject being drawn, the properties, and other associated attributes can be

changed easily while drawing objects for the model.

4.2 Slab Types

SAFE can be used to model almost any type of elevated slab or basemat/

foundation system, including two-way slabs, flat slabs, ribbed slabs, and

waffle slabs.

4.2.1 Two-Way Slabs

Two-way slabs (flat plates and flat slabs) are probably the most common

concrete slab systems and are easily modeled using SAFE. Because

SAFE is finite element based, when a two-way slab of arbitrary shape is

drawn, SAFE automatically meshes the area objects into isotropic or or-

4 - 2 Slab Types

SAFE Modeling Features

thotropic shell bending elements. These elements are three- or four-node

elements, with six degrees of freedom at each node. The shell elements

capture out-of-plane bending and shear behavior, as well as in-plane de-

formations due to post-tensioning and other loads. Thus, two-way slab

action is automatically accounted for in the SAFE model and unlike

equivalent frame techniques, requires no additional assumptions or cal-

culations.

4.2.2 Flat Slabs

Flat slabs are typically two-way slabs with drop panels at the column lo-

cations to increase the shear capacity of the slab. It is usually advisable

to model the geometric plan dimensions of the drops with area objects so

that the slabs will have the correct span lengths, keeping in mind that

moment varies directly with the square of the span length.

Drop panels modeled using area objects are easily generated by SAFE

using the Draw menu > Quick Draw Areas Around Points command.

Drop panels also can be defined as part of the column property defini-

tion, in which case they are automatically generated when columns are

drawn.

4.2.3 Ribbed Slabs

Ribbed slabs are stiffened by ribs running in one predominant direction.

Modeling this type of system in a conventional finite element program

can be extremely difficult and time consuming because of the meshing

effort involved. However, with SAFE’s object oriented approach and au-

tomated meshing capability, ribbed slabs can be modeled simply by

drawing the area object representing the slab, and assigning a “Ribbed”

slab property type.

Ribs are defined by specifying their depth, their widths at the top and

bottom, and their spacing. SAFE then calculates equivalent slab proper-

ties, such as the moment of inertias and self weight, using the slab and

rib definitions. This calculation takes into account the T-beam behavior

Slab Types 4 - 3

SAFE – Key Features and Terminology

occurring when the slab and ribs work together, with the slab acting as a

flange.

Although an equivalent slab property is used internally when performing

the analysis, the actual geometry of the slab and ribs is used for design

and detailing purposes.

4.2.4 Waffle Slabs

Waffle slabs are similar to ribbed slabs, but instead of ribs in only one

direction, the waffle slab ribs are laid out in an intersecting orthogonal

arrangement. Waffle slabs can easily be modeled by drawing the area

object representing the slab and assigning a “Waffle” slab property type.

In addition, waffle slabs often use drop panels at the column locations.

Similar to ribbed slabs, ribs in a waffle slab are defined by specifying

their depth, their widths at the top and bottom, and their spacing. Again,

SAFE uses equivalent slab properties for the analysis, accounting for T-

beam behavior, while maintaining the slab and rib geometries for design

and detailing.

4.3 Mat Foundations and Footings

Similar to elevated slabs, basemats and footings can be drawn using slab

objects. The shell element in SAFE incorporates shear deformation,

therefore handling slabs that have a large depth-to-span ratio, as is often

the case with foundations. Working in 3-D allows for the accurate repre-

sentation of stiffness and loading from walls and columns, including

overturning moments.

Soil springs can be added quickly to the model. Any number of soil

properties may be defined, so that the subgrade modulus can vary

throughout the foundation. An explicit nonlinear process to model no-

tension (uplift) in the soil springs is available.

4 - 4 Mat Foundations and Footings

SAFE Modeling Features

4.4 Slabs with Discontinuities

The slab release capability of SAFE allows for the convenient modeling

of discontinuities. Releases allow jumps in moment or shear across a

specific line of discontinuity. Releases are assigned to line objects, to ei-

ther one or both sides. Shear and moment releases also can be assigned

to specific slab edges.

4.5 Beam Types

The majority of beams in concrete construction are formed in a rectangu-

lar shape. However, beams can come in other shapes, and SAFE, in addi-

tion to providing the rectangular beam, offers a number of other geomet-

ric beam options, including T-beams, inverted T-beams, L-beams, in-

verted L-beams, and a general beam option that can be used to model

beams not reflected by one of the other categories. If the slab is to be in-

cluded in the bending of any beam, it can be modeled as either a flanged

or rectangular beam. If a rectangular beam is used, SAFE will automati-

cally account for the T-beam action provided by the slab. If a flanged

beam is modeled, SAFE ignores the flange of the T-beam or L-beam

where it is duplicated by the slab, and uses the slab to account for the T-

beam action.

4.6 Post-Tensioning

Post-tensioning places concrete in compression to reduce the tensile

stresses due to flexure. Post-tensioning typically reduces deflections and

the amount of standard reinforcement required.

The post-tensioning option in SAFE allows for prestressing loads to be

applied to the model. Post-tensioning tendons may be drawn either ex-

plicitly by the user, in which case the tendon layout, force and profile are

specified, or the post-tensioning layout can be determined by SAFE. The

tendon distribution is specified as banded or distributed, and acceptable

ranges for both the concrete precompression level and percentage of self

weight to be balanced are input. SAFE then iterates to determine the pro-

Slabs with Discontinuities 4 - 5

SAFE – Key Features and Terminology

file of the tendons that best satisfies the stress and balancing require-

ments.

With the load-balancing method, tendons are selected to directly coun-

teract a percentage of the self weight load. The force in the tendon with

an eccentricity generates a moment that is opposite of the imposed mo-

ment. If the moments were to be perfectly balanced, the net stress in the

member would be just the axial compressive stress from the post-

tensioning. In reality, imposed and post-tensioning moments do not bal-

ance, and the net stress on the section is a combination of axial stress and

unbalanced bending moment stress. This net stress is used in design to

determine the amount of mild reinforcement required.

4.7 Models Exported from ETABS

Often times a concrete floor system defined in ETABS will require fur-

ther refinement during analysis (e.g., deflections based on cracked sec-

tions), as well as design and detailing. This can be accomplished easily

using the link provided between ETABS and SAFE. ETABS allows for

the export of any story level as a SAFE *.f2k text file.

In addition to the geometry and property assignments of the objects,

ETABS provides two additional export options:

 Export floor loads only.

 Export floor loads and loads from above.

Upon importing the ETABS generated model, additional modifications

can be made to the model using the SAFE tools. It should be noted that

changes in SAFE can not be exported back to ETABS, so any changes to

the slab that may affect the ETABS global building model also should be

applied to the ETABS model.

4 - 6 Models Exported from ETABS

SAFE Modeling Features

4.8 More Information

This chapter provides an overview of the modeling features that SAFE

offers for simulating slab systems. Additional information may be found

in the program Help and in the “Watch & Learn



Movies” series.

More Information 4 - 7

Chapter 5

SAFE Analysis Features

This chapter provides an overview of the key analysis features available

within SAFE. The analysis features described include linear static analy-

sis, nonlinear analysis for uplift, and nonlinear analysis for cracking.

In a given run, any number of different analyses may be performed, in-

cluding both linear and nonlinear analyses.

5.1 Overview of the Analysis Process

At the time of analysis, SAFE converts the object-based model into a fi-

nite element model, referred to as the analysis model. The finite element

mesh used in the analysis is based on a user-defined maximum element

size. However, additional meshing lines are automatically introduced at

all locations of objects, object boundaries, and gridlines. Additional user-

defined meshing lines can be introduced at specified locations by adding

additional gridlines or adding line objects with NONE properties and

then assigning them to be included in the analysis mesh.

Overview of the Analysis Process 5 - 1

SAFE – Key Features and Terminology

SAFE automatically creates slab elements by subdividing all of the slab

objects. SAFE also creates beam elements by subdividing all of the beam

objects.

Column and wall objects provide vertical, as well as lateral support to

the slab structure. Alternatively, point or line springs can be used to sup-

port the slab structure.

Soil subgrade modulus properties assigned to area objects are lumped in-

to discrete springs and applied to all of the mesh points that exist on the

area, based on the tributary area associated with each mesh point.

Point loads assigned to point objects are assigned directly to the corre-

sponding finite element mesh point. Point and distributed loads assigned

to beam objects are discretized and applied to the mesh points that exist

on the beam, based on the tributary length associated with each mesh

point. Similarly, surface loads assigned to slab objects are discretized

and applied to all of the mesh points that exist on the slab, based on the

tributary area associated with each mesh point.

The internal meshing performed by SAFE does not alter the number or

size of the objects, which allows for simple revisions and modifications

to be executed at the object level, as well as simple extraction of analysis

results.

5.2 The Analysis Model

The analysis model consists of slab, beam, column, wall, tendon, and

support elements.

Each slab element is an isotropic or orthotropic, shell element. The key

features of the shell elements are as follows:

 Each element node has six degrees of freedom.

 The material property within each element is constant.

 The element includes shear deformation.

5 - 2 The Analysis Model

SAFE Analysis Features

 The thickness of each element is constant, unless orthotropic effects

are considered, for which it is possible to specify three different effec-

tive thicknesses: local 1-axis bending, local 2-axis bending, and twist-

ing.

 The element must lie in the horizontal XY plane.

 The calculation of the self weight of the element is based on the thick-

ness, the planar area, and the unit weight of the material associated

with the element.

 The element moments and shears are calculated at the nodes of the el-

ement.

The beam element in SAFE is based on linear elastic beam theory and

can have properties based on specified cross-section dimensions or on

specified cross-sectional properties, such as area and moment of inertia.

The key features of the beam elements are as follows:

 Beam elements are prismatic.

 The calculation of the self weight of the element is based on the actual

area for rectangular or general sections, and the stem area for flanged

sections, the element length, and the unit weight of the material asso-

ciated with the element.

 The beam moments, shears, and torques are calculated at the two ends

of each element, corresponding to each mesh point.

 The beam must lie in the horizontal XY plane.

The column/brace element is similar in formulation to the beam element.

The main difference is that columns/braces must be vertical/diagonal,

design results are not presented for them, and therefore they are not de-

signed in SAFE.

Wall/ramp elements are modeled as shell elements, similar to the slabs.

Similar to columns/braces, walls/ramps must be vertical/inclined, are not

designed, and do not have design results presented.

The Analysis Model 5 - 3

SAFE – Key Features and Terminology

For soil supports, SAFE generates equivalent linear elastic springs at

mesh points. Compression only (zero tension) conditions in the soil sup-

ports are modeled using nonlinear gap elements. The key features of the

support elements are as follows:

 The support elements are weightless.

 Soil supports have a single vertical degree of freedom.

 The support reaction values are calculated at every supported mesh

point.

5.3 Linear Static Analysis

A linear static load case is automatically created for each load pattern

that is defined. Any number of load patterns and load cases may be de-

fined. Load cases can include multiple load patterns, each with an asso-

ciated scale factor. The results of different static load cases can be com-

bined using load combinations. A linear static analysis is the default and

most common load case type in SAFE.

5.4 Nonlinear Analysis for Uplift

SAFE has an option to request that a nonlinear load case be used to con-

sider soil supports as providing compression only. This capability can be

extremely useful for analyzing basemats and footings.

If the nonlinear uplift analysis type is specified for a load case, nonlinear

gap elements are automatically activated in the soil support springs. The

gap elements can transfer only compressive loads, hence capturing any

uplift behavior. This analysis type requires that any loads acting in com-

bination be added together in the load case, and not in combinations.

5 - 4 Linear Static Analysis

SAFE Analysis Features

5.5 Nonlinear Analysis for Cracking

A nonlinear cracking analysis for slabs may be executed based on user-

specified rebar using Slab Rebar objects, on reinforcing calculated by the

program using the Finite Element Based design, or on reinforcement

specified using the Quick Rebar Specification option.

In the design of slabs, it is generally recognized that the distribution of

moments obtained from an elastic analysis is appropriate for design pur-

poses. However, an elastic analysis may significantly underestimate the

true deflections resulting from cracking.

The estimation of true deflections is a complex task. Guidelines are

available in some design codes, such as ACI 318 Section 9.5. For non-

prestressed, one-way construction, ACI 318 recommends the calculation

of an effective stiffness to obtain the cracked deflections and further ap-

plication of modification factors to account for long-term deflections.

SAFE has the capability to use the recommendation described above for

calculating the effective stiffness of slabs and beams of floor systems

when doing analysis. This technique requires that the reinforcement be

known. Slab reinforcement may be calculated by SAFE or be user-

defined. The automated procedure for calculating the effective stiffness

is as follows:

 Perform an elastic (uncracked) analysis.

 Determine the slab reinforcement from the Finite Element Based de-

sign or from user input.

 Design the beam reinforcement.

 Calculate the cracking moment and cracked moment of inertia for each

element, for each direction of moment, and for top and bottom rein-

forcement.

 Calculate the ratio of effective stiffness to gross-section stiffness for

both local 1 and 2 directions for the slab and beam elements.

Nonlinear Analysis for Cracking 5 - 5

SAFE – Key Features and Terminology

 Reanalyze the structure using the effective stiffness calculated for each

element.

The results for nonlinear cracked analyses include both the displace-

ments and stresses, although again, most design codes allow for the use

of stresses from elastic, or uncracked analyses.

5.6 Nonlinear Analysis for Long-Term Cracking

A nonlinear, long-term cracking analysis can be carried out in a manner

similar to the normal cracking analysis. The long-term analysis requires

creep coefficient and shrinkage strain values in order to account for

creep and shrinkage.

5.7 Modal Analysis

A modal analysis load case can be defined to compute the modal fre-

quencies or periods of the structure. This analysis type is best used with

vertical mass. The modes can be based on Eigen or Ritz vectors, and a

minimum and maximum number of requested modes can specified.

5.8 Hyperstatic Analysis

A hyperstatic analysis can be defined as a load case. This type of analy-

sis is based on an already defined static load case, in which the reactions

from the static load case are applied as loads to an unsupported structure.

5.9 More Information

This chapter provides a general introduction to the primary analytical

features that SAFE offers for linear and nonlinear analysis of slabs.

Much more information may be found in the program Help and in the

“Watch & Learn



Movies” series.

5 - 6 Nonlinear Analysis for Long-Term Cracking

Chapter 6

SAFE Design Features

This chapter provides an overview of the key design features available

within SAFE. The design features described include slab flexural design

with or without post-tensioning, slab punching shear checks and rein-

forcement design, and beam flexural, shear, and torsion design with or

without post-tensioning.

6.1 Overview of the Design Process

After the analysis is complete, the design can be performed. Strength de-

sign loads are generated from built-in default combinations for the cur-

rently selected design code (user-defined load combinations also can be

defined, if needed). Default serviceability combinations also are availa-

ble if the model includes post-tensioning. Using these combinations,

SAFE designs both slabs and beams, and reports the required reinforce-

ment.

For slabs, SAFE uses either design strips or the finite element based de-

sign to calculate the slab flexural reinforcement in accordance with the

selected design code. SAFE also designs the flexural, shear, and torsion

reinforcement of any beam object.

Overview of the Design Process 6 - 1

SAFE – Key Features and Terminology

6.2 Slab Flexural Design

Similar to conventional design, the flexural design of slabs in SAFE in-

volves defining sets of strips in two directions (A and B), integrating the

strip moments and shears (on the basis of the Wood-Armer technique),

and then designing the required reinforcement for each strip in accord-

ance with the selected design code. As an alternative to this strip based

method, SAFE also offers a FEM based design, which is useful for ir-

regular slabs where strip based techniques may not be appropriate.

6.2.1 Design Strips

SAFE provides two principal strip layers used for analysis and design,

namely Layer A design strips and Layer B design strips. The strips are

defined as polylines with associated widths that can vary along the

length of the strip.

The strips need not be mutually perpendicular. The extent of the design

strips is defined by the edges of the area objects defining the slab, and

strips can overlap if needed. The location of the design strips is usually

governed by the support or grid locations. Design strips may be defined

as either Column Strips or Middle Strips – models with post-tensioning

typically have column strips only.

6.2.2 Integration of Moments – Wood-Armer

Use of the Wood-Armer method for the integration of design moments

results in the following steps:

For a particular combination or load case, for each finite element within

the design strip, SAFE calculates the design moments per unit width us-

ing the internal forces. Internal forces are converted to design moments

per unit width in the following manner:

bB B AB

mmm= +

bA A AB

mmm= +

6 - 2 Slab Flexural Design

SAFE Design Features

tB B AB

mmm= +

tB A AB

mmm= +

where mA, mB, and mAB are internal moments per unit width, and mbA and

mbB are design moments per unit width for the bottom of the slab in the

A and B directions, respectively, and mtA and mtB are the design moments

for the top of the slab in the A and B directions, respectively. Design

moments may be factored combinations for strength design, or unfac-

tored moments for service load checks when post-tensioning is present.

The design moments calculated using the Wood-Armer integration will

most likely not completely satisfy equilibrium of the applied loads, but

for a mesh that accurately captures the overall behavior of the slab, this

integration scheme provides a good design. This is the case because the

Wood-Armer integration scheme effectively calculates design moments

when cracking occurs diagonally to the design strip directions.

6.2.3 Required Reinforcement – Strip Based

If post-tensioning is present, stresses are checked at the slab top and bot-

tom for unfactored service level loads. Stress checks are carried out at

three stages, namely at transfer of the prestress load (transfer), after all

losses have occurred and service loads are applied (normal), and after all

losses have occurred and long-term service loads are applied (long term).

These stress checks are carried out at each transverse mesh line along the

length of the strips. The moments are integrated across all elements of

like property in the strip to determine the service moments, which are

converted to stresses assuming a linear strain variation through the sec-

tion depth. If the stress limits are exceeded, mild reinforcement is added

to carry the tensile stresses, as long as they are below the code specified

limits, which can be adjusted in the Design Preferences. Any added mild

reinforcement is then used with the user-defined post-tensioning tendons

to calculate a nominal moment capacity, which is checked against the

factored moments from the strength combinations.

The design of the mild reinforcement for slabs without post-tensioning

also is carried out for a particular strip at each transverse mesh line loca-

Slab Flexural Design 6 - 3

SAFE – Key Features and Terminology

tion along the length of the strip. The moments are integrated across all

elements of like property in the strip to determine the factored design

moments. The required reinforcement for slabs is computed for each set

of elements with the same property type, and then summed to give the

total required reinforcement for the strip. The maximum required top and

bottom strip reinforcement for a particular mesh line is obtained, along

with the corresponding controlling combinations.

As an option, minimum reinforcement requirements may be enforced in

accordance with the selected design code.

6.2.4 Required Reinforcement – FEM Based

The FEM Based design determines the required reinforcement on an el-

ement-by-element basis and is therefore independent of design strips.

Several options are available for refining the display of the required rein-

forcement, including averaging, which will flatten peaks and provide an

averaged required reinforcement over a particular area of the slab.

6.2.5 Slab Rebar Objects

SAFE allows users to place the size, quantity, and location of slab rein-

forcing using Slab Rebar objects. Although this user-defined reinforcing

does not directly affect design results, it can be used when performing a

nonlinear cracking analysis, as well as compared to the required rein-

forcing calculated by the program using the Strip Based or FEM Based

methods.

6.3 Slab Punching Shear Check

The distribution of stresses close to concentrated loads or reaction points

in reinforced and prestressed concrete slabs is quite complex. Punching

shear is one particular failure mode recognized by design codes for

which an elastic plate bending analysis may not provide adequate stress

distribution. Most codes use empirical methods based on experimental

verification to check against punching shear failures. SAFE automates

6 - 4 Slab Punching Shear Check

SAFE Design Features

this check for common geometries. If the check results in a punching

shear ratio greater than unity (i.e., punching failure), SAFE will design

punching shear reinforcement. The SAFE procedure for the punching

shear check carried out for each column, for each design combination is

as follows:

Locate the critical section around the column or point load. SAFE re-

ports whether it assumed the column to be an interior, edge, or corner

column. This determination is based on whether the slab is present

within 10 times the slab thickness along the column edges. A column

is classified as a corner column when two slab edges are found within

10 times the slab thickness. A column with only one slab edge within

10 times the slab thickness is classified as an edge column, and a col-

umn is classified as interior when no slab edges are found within 10

times the slab thickness. For single footings, this determination is

based on the minimum area of the critical section.

Check that each slab element in the area enclosed between the face of

the column and the critical section for punching shear has the same

slab property label. If this is not the case, the slab thickness from

the smallest area within the punching shear perimeter is used.

Use the net shear to check punching shear if a point load or column

(call it load/column A) is within the critical section for punching shear

for another point load or column (call it load/column B).

Calculate punching shear based on net forces in the slab when line ob-

jects (beams, walls, or releases) frame into a column.

Calculate the reactive force and moments at the column for the com-

bination. The shear and moment values used in the punching shear

check are reduced by the load (or reaction) that is included within the

boundaries of the punching shear critical section.

Calculate the distribution of shear stress around the critical section.

Obtain the shear capacity of the critical section.

Slab Punching Shear Check 6 - 5

SAFE – Key Features and Terminology

 Compare the shear stress distribution with the shear capacity. The

comparison is reported as a ratio for the worst combination. A value

above 1.0 indicates failure.

SAFE designs rebar ties or stud rails when such options are activated in

the punching shear design overwrites. The details of rebar ties or stud

rails are documented in the Reinforced Concrete Design Manual and the

Post-Tensioned Concrete Design Manual.

Design overwrites are available to modify the location type, punching

shear perimeter, openings in the slab, and reinforcement pattern, when

the punching shear parameters computed need to be changed.

For computing the punching parameters, the following assumptions are

used:

 Punching shear is calculated for columns punching through a slab or a

drop panel. SAFE also checks the drop panel punching through a slab.

The effect of column capitals is included in the punching shear calcu-

lation.

 SAFE uses the effective depth for computing the punching shear. The

concrete cover to rebar is taken from the design preferences unless a

design strip is present. In that case, the rebar cover is taken from the

design strip.

 Openings within 10 times the slab thickness are automatically includ-

ed in the punching shear calculations. The slab edge within the punch-

ing zone radius is subtracted from the punching shear perimeter.

6 - 6 Slab Punching Shear Check

SAFE Design Features

The vertical component of prestressing force is currently ignored in

computing the punching shear capacity.

6.4 Beam Flexural, Shear, and Torsion Design

In the design of concrete beams, SAFE calculates and reports the re-

quired areas of reinforcement for flexure, shear, and torsion based on the

beam moments, shears, torsion, and load combination factors. The beam

design is executed on an element-by-element basis considering the mo-

ments, shears, and torsion at each nodal point of the element. Following

are some of the assumptions associated with the beam design:

 The beams are designed for major axis moment, shear, and torsion on-

ly. Design for axial force or minor axis moment and shear that may

exist in the beams must be investigated independently by the user.

 The required reinforcement reported by SAFE does not consider ser-

viceability requirements.

 If post-tensioning is present, stresses are checked at the beam top and

bottom for unfactored service level loads. Stresses are checked at the

transfer of the prestress load without losses, with all service loads after

losses, and with sustained service loads after losses. These checks are

done assuming a linear strain variation through the section depth. If

necessary, reinforcement is added to carry tensile stresses. Any added

reinforcement is used with the user-defined post-tensioning tendons to

calculate a nominal moment capacity, which is checked against the

factored moments from the strength combinations.

 The beam section is designed for the maximum positive and maxi-

mum negative factored moment envelopes obtained from all strength

combinations.

 Negative beam moments produce tension in the top fibers. For all but

the inverted flanged beam, the beam is designed as a rectangular sec-

tion.

Beam Flexural, Shear, and Torsion Design 6 - 7

SAFE – Key Features and Terminology

 Positive beam moments produce tension in the bottom fibers. In such

cases, the beam can be designed as a rectangular or a flanged beam.

 For the design of flexural reinforcement in beams without post-

tensioning, the beam is first designed as a singly reinforced beam. If

the beam section is not adequate, the required compression reinforce-

ment is calculated.

 In designing the shear reinforcement for a particular element, the steps

include the determination of the factored shear force, calculation of

the shear force that can be resisted by the concrete, and calculation of

the shear reinforcement required to carry the balance. The effects of

post-tensioning are included.

 In designing the torsion reinforcement for a particular element, the

steps typically include the determination of the factored torsion, calcu-

lation of the critical torsion below which torsion reinforcement is not

required, calculation of special torsion section properties, calculation

of the torsion reinforcement required as closed stirrups, and a check of

the shear and torsion interaction.

6.5 Results Output

The design results can be viewed and saved in many different ways, in-

cluding:

 Display and printing of two- and three-dimensional views of the mod-

el showing design results

 Design results output in tables, compatible with Microsoft Excel or

Access

 Design results tables printed to RTF, HTML, and text files

 Custom reports with design results tables, graphics, and text

 Export of model to DXF, including design results

6 - 8 Results Output

SAFE Design Features

 Summary design information on an object-by-object basis by right

clicking an object while design results are displayed. This information

can be printed or saved to a RTF file.

6.6 More Information

This chapter provides a general introduction to the primary design fea-

tures that SAFE offers for concrete slabs and beams. Additional infor-

mation may be found in the program Help and in the “Watch & Learn



Movies” series. Please also refer to the Reinforced Concrete Design

Manual or the Post-Tensioning Concrete Design manual for information

about code-specific design.

More Information 6 - 9

Chapter 7

SAFE Detailing Features

This chapter provides an overview of the key detailing features available

within SAFE. The detailing features described include detailing prefer-

ences, drawing component views, and drawing sheets, as well as how

these can be edited within the SAFE interface, printed, or exported to

CAD software.

7.1 Overview of the Detailing Process

Detailing can be run after the analysis and design have been completed.

The detailing is run using the Run menu > Run Detailing command.

The first time the detailer is run for a particular model, SAFE will gener-

ate a default set of drawings. Those drawings can be viewed, custom-

ized, printed, and exported from the Detailing tab of the Model Explorer

window or the Detailing menu > Show Detailing command. Additional

drawing sheets can be added and component views can be added or de-

leted from drawing sheets to create a customized set of drawings. If

modifications are made to the model, including geometry, loading, or

properties, the detailing can be rerun with the option of generating a new

Overview of the Detailing Process 7 - 1

SAFE – Key Features and Terminology

set of drawings from scratch or synchronizing the new results with the

previously customized drawings.

7.2 Detailing Preferences

To complete detailing in SAFE, analysis and design data and detailing

preferences are required. Default detailing preferences are built into

SAFE. These default preferences are typical values that should satisfy

the majority of projects, but should be reviewed to ensure they are rele-

vant for the project under consideration.

Some of the key detailing preferences that can be set in SAFE include

the following:

 Dimension and material quantity units

 Bar callout style and content

 Drawing size, layout, scale, and so forth

 Rebar selection rules, including min/max bar sizes, spacing, and the

 Preferred rebar sizes

 Curtailment rules

 Drawing display styles, including line type, weight, color and text

size, font, alignment, color, and so on, for each type of drawing entity

The Detailing menu > Detailing Preferences command allows specifi-

cation of the units and bar mark styles. The Detailing menu > Slab/Mat

Reinforcing Preferences and Beam Reinforcing Preferences each

provide selection rules, curtailment rules, and rebar call notations for

slabs and beams, respectively. The Detailing menu > Drawing Sheet

Setup command allows the properties of the drawing sheet to be set, in-

cluding size, margins, and scales. Finally, the Detailing menu > Draw-

ing Format Properties provides settings for all of the display styles,

such as line types, weight, color, and text properties.

7 - 2 Detailing Preferences

SAFE Detailing Features

7.3 Drawing Component Views

Drawing component views are the building blocks of drawing sheets.

Each view exists only once, but can be included on multiple drawings. A

selection of the component views available include the following:

 Slab plans – framing, top bars, bottom bars, all bars

 Slab sections

 Beam framing plan

 Beam elevations

 Beam sections

 Slab rebar table

 Slab rebar schedule

 Beam rebar table

 Beam rebar schedule

 Tendon layout plan

 Tendon schedule

Additional component views can be found on the Detailing tab of the

Model Explorer window. The component views generated depend on the

objects in the model.

7.3.1 View Properties

Each drawing component view has a set of properties defining the scale,

text and line sizes, and the caption. These properties can be set in the de-

tailing tree of the Model Explorer by right clicking on a drawing compo-

nent view and choosing the Edit View Properties command. The prop-

erties also can be set for each component view on the drawing sheets in

the same way.

Drawing Component Views 7 - 3

SAFE – Key Features and Terminology

7.3.2 View Text

The text on each component view can be edited and rearranged (moved)

by right clicking on the component view in the tree of the Model Explor-

er and choosing the Edit View Text command. Additional text, dimen-

sion lines, and notes also can be added. This feature should be used to

rearrange overlapping text and add any additional notes or dimensions as

necessary.

7.4 Drawing Sheets

A drawing sheet in SAFE is defined with a certain size, containing one

or more drawing component views and is used in a manner consistent

with other CAD programs. Additional drawing sheets can be added or

existing sheets can be deleted.

Drawing component views can be added, deleted, or moved around on

the drawing sheets. Multiple component views can be added to a draw-

ing by right clicking on the drawing and using the various Add Views

commands. Alternatively, while a drawing sheet is in the display, draw-

ing component views can quickly and easily be added by dragging and

dropping them from the tree in the Model Explorer window.

Drawing sheets can be printed directly from SAFE, saved, or exported to

DXF or DWG files for use in CAD software.

7.5 Reinforcement Editing

SAFE provides capability for editing the detailed reinforcement that is

shown in the drawing component views and drawing sheets. For slabs

this is accomplished on a strip-by-strip basis while beams are handled

one beam at a time. Using the edit reinforcement commands, the rein-

forcement location and length can be modified with simple click and

drag mouse operations. The bar size and spacing also can be edited by

clicking on any bar call (mark) and making the necessary changes. Note,

changes should be made with care to ensure that the reinforcement quan-

tity satisfies the required reinforcement for the design loads.

7 - 4 Drawing Sheets

SAFE Detailing Features

7.6 Synchronization

After the detailing has been generated the first time for a model, SAFE

has the ability to synchronize and update the existing component views

and drawings for subsequent runs of the detailing. The synchronization

process maintains previous modifications and edits, to the extent practi-

cable. The following is a summary of the situations when synchroniza-

tion is carried out:

 Changes to the detailing results caused by changes to the detailing

preferences, drawing preferences, or component view properties.

 Editing of section cuts, where possible.

 Editing of text location, where possible. This is determined based on a

comparison of the unedited text position on the previous and new de-

tailed items.

 Editing of reinforcement, as long as the object geometry has not been

changed.

In general, it is recommended that if using the synchronization capabil-

ity, the final drawings be reviewed for correctness.

7.7 More Information

This chapter provides a general introduction to the primary detailing fea-

tures that SAFE offers. Additional information may be found in the pro-

gram Help and in the “Watch & Learn



Movies” series.

Synchronization 7 - 5

Chapter 8

The SAFE “Screen”

This chapter provides an overview of the key features of the graphical

user interface (GUI). As the model is developed using the graphical user

interface, a database file is created concurrently by SAFE. If desired, the

database can be directly edited using the Edit menu > Interactive Da-

tabase Editing command. While this feature is well suited to some sit-

uations, the vast majority of model creation and modification is complet-

ed using the graphical user interface.

8.1 The Graphical User Interface

The graphical user interface, shown in Figure 8-1, includes the main

window, main title bar, menu bar, toolbars, model explorer, display win-

dow, display title bar, status bar, mouse pointer coordinates, and a units

button. Each of these items is described as follows.

Main Window – This window may be moved, resized, maximized, min-

imized, or closed using standard Windows operations. Refer to Windows

help, available on the Start menu for additional information on perform-

ing these actions.

The Graphical User Interface 8 - 1

SAFE – Key Features and Terminology

Main Title Bar – The main title bar includes the program and model

names. The main title bar is highlighted when the program is in use.

Move the main window by left clicking in the main title bar and holding

down the mouse button to drag the window.

Figure 8-1 SAFE graphical user interface

Menu Bar – The menu bar contains the program menus from which var-

ious commands can be selected to perform specific actions.

Toolbars – Toolbars are made up of buttons. Buttons provide "single-

click" access to commonly used commands. Hovering the mouse pointer

over a toolbar button for a few seconds without clicking or holding down

any mouse buttons will display a short description of the button's func-

tion.

Model Explorer – The model explorer allows easy access to model def-

inition data, including property forms, load definitions, and object forms,

as well as analysis and design results. These items are grouped in three

tabs in the Model Explorer, namely Model, Display, and Detailing. Dou-

ble clicking on an item in the tree with the left mouse button will bring

8 - 2 The Graphical User Interface

The SAFE “Screen”

up the associated form or display, while a right click generates a context

menu with additional options.

Display Window – A display window shows the geometry of the model

and also may include displays of properties, loading, and analysis or de-

sign results. A maximum of four windows may be displayed simultane-

ously.

Display Title Bar – The display title bar is located at the top of the dis-

play window. The display title bar is highlighted when the associated

display window is active. The text in the display title bar typically in-

cludes the type of the current view along with any other relevant data,

such as load pattern, load combination, and so forth.

Status Bar – The status bar is located at the bottom of the main window.

Text describing the current status of the program is displayed on the left

side of the status bar.

Mouse Pointer Coordinates – The mouse pointer coordinates are dis-

played on the right-hand side of the status bar. A window does not need

to be active for the mouse pointer coordinates to be displayed. It is only

necessary that the mouse pointer be over the window.

Units Button – Clicking the Units button displays the Units form which

lists the units associated with all input and display items; units are not

typically consistent, i.e., stress may be displayed in ksi units, while ap-

plied loads may be done in psf units. Unit selections may be changed at

any time.

8.2 File Menu

File operations are used to start a new model, open or import an existing

model for display or modification, to import an architectural plan for

tracing, to save or export the current model for use in SAFE or other ap-

plications, and to produce output. File operations are selected from the

File menu.

File Menu 8 - 3

SAFE – Key Features and Terminology

New models can be started from scratch or from predefined templates

built into SAFE.

In addition to opening files in the standard SAFE database format (*.fdb

extension), SAFE also allows import of the following file formats:

SAFE text files (*.$sf and *.f2k extensions), MS Access Database files

(*.mdb extension), MS Excel Spreadsheet files (*.xls extension), or

DXF/DWG files (geometry import only) and DXF/DWG Architectural

Plan.

Models created in SAFE are saved in the database *.fdb and the text

*.$sf formats by default – both of these files contain the complete model.

They may also be exported to the following formats: SAFE text (*.f2k),

MS Access Database (*.mdb), MS Excel Spreadsheet (*.xls), and Auto-

CAD (*.DXF/*.DWG – geometry only).

8.3 Edit Menu

Editing is used to make changes to the model. Most editing operations

work with one or more objects that are selected immediately before us-

ing the edit commands. Editing operations on the Edit menu include the

following:

 Cut and Copy geometry of selected objects to the Windows clipboard.

Geometry information on the clipboard can be pasted into other pro-

grams, such as spreadsheets.

 Paste object geometry from the Windows clipboard into the model.

The geometry can be edited in a spreadsheet application before being

copied and pasted into SAFE.

 Interactive editing of the model in a database format.

 Delete objects.

 Replicate objects in a linear or radial array, or mirror them.

 Move points, which also modifies connected objects.

8 - 4 Edit Menu

The SAFE “Screen”

 Merge points, which also modifies connected objects.

 Align points and their connected objects to specified ordinates or se-

lected lines; this includes trimming or extending selected beam, strip

or tendon objects.

 Divide selected beam or slab objects into smaller objects.

 Join selected line objects at a common joint.

 Merge selected area objects.

 Expand or shrink the size of area objects.

 Add tendon objects to selected design strips and beams.

 Adjust the horizontal layout and vertical profile of selected tendons.

 Add user-defined slab reinforcing.

 Generate design strips based on grid lines or support locations.

8.4 View Menu

View options, which affect the active display, may be set for each dis-

play window individually. The options listed below are available on the

View menu and from the toolbar.

 Set Default 3D View – A 3-D view shows the entire model from a

vantage point. The default view provides a perspective view of the en-

tire model and can be rotated using the Rotate 3D View button.

 Set Plan View – A plan view is generated in a single plane parallel to

the X-Y coordinate plane.

 Set Elevation View – An elevation view is generated in a single verti-

cal plane

 Set Display Options – Various options are available to control how

objects appear in a display window. These options primarily affect

View Menu 8 - 5

SAFE – Key Features and Terminology

views of the undeformed shape, including changing visibility, labeling

of objects, showing an extruded view, as well as others.

 Zoom Features – Zoom In to see more detail, or Zoom Out to see

more of the structure. A rubber-band zoom also can be used to draw a

window to zoom into. Restore Full View zooms in or out, as neces-

sary, to fit the view of the entire model in the active window.

 Pan – Panning allows dynamic movement of the structure around the

display window by clicking and moving the mouse.

8.5 Define Menu

Define operations are used primarily to create named entities that are not

part of the geometry of the model. These entities, accessed from the De-

fine menu, include the following:

 Material properties

 Slab and beam section properties and design parameters

 Reinforcing bar sizes

 Tendon properties

 Column and wall properties

 Soil subgrade properties

 Point and line spring properties

 Coordinate/grid systems

 Group names

 Mass source

 Load patterns

 Load cases

8 - 6 Define Menu

The SAFE “Screen”

 Load combinations

Definition of these entities does not require prior selection of any ob-

jects, and some of these entities also can be defined during the assign-

ment operations from the Assign menu.

8.6 Draw Menu

Drawing is used to add new objects to the model or to modify one object

at a time. Objects include beams, columns, slabs, walls, tendons, design

strips, gridlines, dimension lines, and slab rebar. To draw, SAFE must be

in Draw Mode, which is activated by clicking one of the draw buttons

on the toolbar or using a Draw menu command.

In Draw Mode, the left mouse button is used to draw and edit objects,

and the right mouse button terminates the current drawing action.

Depending on the type of object to be drawn, a floating properties form

appears that can be used to specify various structural and support proper-

ties for the object. For example, as column objects are drawn, column

properties can be assigned simultaneously, beam objects may be as-

signed beam structural properties, and similar options exist when draw-

ing other object types.

8.7 Select Menu

SAFE uses a “noun-verb” concept; that is, a selection is made and then

an operation is performed. Certain editing, assigning, printing, and dis-

play operations require a prior selection of objects. Selection is used to

identify those objects to which the next operation will apply.

To make a selection, SAFE must first be in Select Mode, which is acti-

vated by clicking one of the select buttons on the toolbar. Alternatively,

selecting any command from the Select menu puts SAFE into Select

Mode.

Several types of selection are available in SAFE, including:

Draw Menu 8 - 7

SAFE – Key Features and Terminology

 Selecting individual objects.

 Drawing a window or polygon around objects.

 Drawing line segments that intersect objects.

 Selecting objects by material property.

 Selecting beam, column, slab, wall, or tendon objects by property.

 Selecting objects by soil subgrade or point and line spring properties.

 Selecting objects by groups.

 Selecting objects by labels.

 Selecting all objects.

 Reselecting previously selected objects.

In Select Mode, the left mouse button is used to select/deselect objects,

and the right mouse button is used to review the properties of objects.

8.8 Assign Menu

Certain assignments may be made when drawing an object, such as beam

structural properties when drawing a beam object. However, additional

assignments or changes to assignments may be made to selected objects

using the Assign menu commands. Some of the assignment operations

available from the Assign menu include:

 Assigning slab properties.

 Assigning openings to area objects.

 Assigning vertical offsets to slabs.

 Assigning rib locations for ribbed and waffle type slabs.

 Assigning beam properties.

8 - 8 Assign Menu

The SAFE “Screen”

 Assigning tendon properties.

 Assigning column/brace properties.

 Assigning wall/ramp properties.

 Assigning soil subgrade properties to area objects.

 Assigning releases to slab, beam, and column objects.

 Assigning point, beam, tendon, and surface loads.

 Assigning objects to named groups.

 Assigning points and lines to be included in the analysis mesh.

8.9 Design Menu

The Design menu is used both before and after running the analysis and

design. Before running the design, the design preferences and design

combinations are accessed from the Design menu. The design prefer-

ences specify the design code to be used, cover to reinforcement, stress

check limits, and other relevant parameters. The combinations to be con-

sidered for design also are specified from the Design menu.

Design overwrites can be applied to the structural objects to adjust the

design input values and parameters on an object-by-object basis. Over-

writes can be applied to slabs, beams, and punching checks. These over-

writes can be applied before or after design.

8.10 Run Menu

Before running the analysis and design, the desired maximum mesh size

should be set. This can be accomplished using the Run menu > Auto-

matic Slab Mesh Options command. If performing a nonlinear cracking

analysis, the reinforcement used for calculating the cracked moment of

inertia should be specified using the Run menu > Cracking Analysis

Options command.

Design Menu 8 - 9

SAFE – Key Features and Terminology

The analysis and design can be run together using the Run menu > Run

Analysis & Design command or by clicking the Run Analysis & De-

sign button on the toolbar.

The program saves the model in a SAFE database file, then checks and

analyzes the model. When the analysis is complete, a deformed shape

will be displayed. The cursor can be moved over the slab to view the

displacements for any location on the slab.

8.11 Display Menu

The Display menu commands are used to view the model and the results

of the analysis. Graphical and tabular displays are available in SAFE.

Display types may be chosen from the Display menu and most of them

also can be accessed using toolbar buttons.

 Graphical Displays – Different types of graphical displays may be se-

lected for each display window. Each window also may have its own

view orientation and display options. Available displays of the model

input include the undeformed geometry and applied loads. Analysis

results can be displayed graphically for any case that has been run, and

include deformed shapes, beam moment and shear diagrams, slab

force and stress contour plots, integrated force and moment diagrams

for design strips, and reaction forces, including bearing pressures.

Design results can be displayed for slabs and beams in the form of

required reinforcement. Additional options are available to refine the

required reinforcement display if desired. Additionally, deformed

shape plots may include mode shapes if a dynamic analysis is per-

formed, and all shapes can be animated.

 Tabular Displays – Tabular information can be displayed for selected

objects using the Display menu > Display Tables command. Choose

the tables to be viewed and for which load patterns and load cases the

data should be presented. If objects are selected, only data for the

selected objects will be displayed. If no objects are selected, the tables

include data for the entire model. Advanced options exist to control

8 - 10 Display Menu

The SAFE “Screen”

the format of the tables and to create filters that will display only data

that satisfy specified criteria.

 Tabular data also can be directly exported or printed from the tabular

display, or by using commands available on the File menu.

8.12 Detailing Menu

After a complete structural model has been analyzed and designed, the

reinforcement can be detailed. Before running the detailing, the Detail-

ing menu commands should be used to define the detailing preferences,

including items such as drawing size and layout, curtailment rules, de-

sired bar sizes, rebar call (mark) notations, rebar shapes, min and max

bar size and length, and so on.

After the detailing has been completed, additional commands on the De-

tailing menu can be used to edit the reinforcement, add or modify sec-

tion cuts, and add or modify drawing sheets. Several other detailing

commands are available from the right click context menus, when right

clicking on drawing component views or the items on the detailing tree

in the Model Explorer window.

8.13 Options Menu

The Options menu provides various commands that affect the overall

operation of SAFE. Input, output, and display units can be reviewed and

modified here. A set of global preferences define the merge tolerance,

screen font size, zoom increment, and similar parameters. Colors of in-

dividual items, as well as general color schemes may be controlled. The

number of windows to display, along with which layers of an architec-

tural plan should be shown, can be set using this menu. SAFE also offers

the user the choice between two graphics modes, Standard and DirectX;

DirectX provides a rendered look to the model but may not be supported

by all computers.

Detailing Menu 8 - 11

SAFE – Key Features and Terminology

8.14 Help Menu

The program Help is available from this menu. Documentation and veri-

fication manuals in PDF format are accessed through the Help menu as

well. A link to the CSI website, as well as information about the current-

ly installed version of SAFE and its associated license file, also are

available from the Help menu.

8.15 More Information

This chapter provides a general introduction to the SAFE graphical user

interface and main menu structure. Additional information may be found

in the program Help by pressing the F1 function key on the keyboard.

8 - 12 Help Menu

Chapter 9

Key Topics

This chapter provides information on some of the key topics and features

available in SAFE. It briefly describes the two modes of user operation

for SAFE, the templates and defaults, the coordinate systems and grid

lines, the slab overlap hierarchy, some of the useful keyboard shortcuts,

and some time saving options.

9.1 Select or Draw Mode

The two distinct modes in SAFE are the Select mode and the Draw

mode. The select mode allows selection of objects and is used for editing

operations, making assignments to objects, and viewing or printing re-

sults. The draw mode allows drawing objects. By default, the program is

in select mode.

The draw mode is automatically enabled when one of the drawing com-

mands from the Draw menu or the corresponding toolbar buttons is

clicked. The available drawing commands include the following:

 Draw Column/Point Objects

Select or Draw Mode 9 - 1

SAFE – Key Features and Terminology

 Draw Beam/Line Objects or

 Draw Wall Objects

 Draw Design Strips

 Draw Tendon Objects

 Draw Slab/Area Objects , , , or

 Draw Grids

 Draw Dimension Lines

 Draw Slab Rebar Objects

The draw mode remains enabled until one of the following actions is car-

ried out to return to the select mode:

 Click the Select Object button on the toolbar

 Press the Esc key on the keyboard.

 Select a command from the Select menu.

9.2 Templates and Defaults

SAFE provides a number of templates that allow for the rapid generation

of models for a range of slab and foundation systems. These templates

serve as a good starting point because they can be modified easily or ap-

pended to as needed. SAFE includes default parameters, some of which

are building code specific. These defaults are accessed using "Prefer-

ences" throughout the various aspects of the program.

By using the built-in templates and defaults, a model can be created in a

matter of minutes. Even if the template does not exactly match the struc-

ture under consideration, it can act as a good starting point for building

9 - 2 Templates and Defaults

Key Topics

the desired model. The SAFE Help topics contain additional information

on using the templates and modifying the program defaults.

9.3 Coordinate Systems and Grids

All locations in the model are ultimately defined with respect to a single

global coordinate system. This is a three-dimensional, right-handed, Car-

tesian (rectangular) coordinate system. The three axes, X, Y, and Z, are

mutually perpendicular and satisfy the right-hand rule. SAFE always

considers the +Z direction as upward. By default, a positive load acts in

the –Z (downward) gravity direction.

All slab, beam, and point objects lie on the XY (horizontal) plane. Ten-

don objects also are laid out on the XY plane, but also have a profile in

the Z-direction. Vertical offsets may be assigned in SAFE to slabs and

beams (called cardinal points).

Additional coordinate systems may be defined to aid in developing and

viewing the model. For each coordinate system, you can define a three-

dimensional grid system consisting of “construction” lines used for lo-

cating objects in the model. Each coordinate/grid system may be of Car-

tesian (rectangular) or cylindrical definition, and is positioned relative to

the global system origin. Any number of gridlines in the X or Y direc-

tions with arbitrary spacing can be defined, as well as arbitrary general

gridlines.

When starting a new model from a template, grid spacing must be uni-

form. Thereafter, grid lines can be added, moved, and deleted. When a

grid line is moved, it is possible to specify that points located on the grid

line should or should not be moved with it.

Setting up one or more grid systems for a model has many benefits. If

the grid is set up to match the architectural grid, it will allow for easier

transfer of data between architectural drawings and the model. Drawing

operations also tend to “snap” to gridline intersections (default) unless

this feature is turned off. When the analysis is run and the internal finite

Coordinate Systems and Grids 9 - 3

SAFE – Key Features and Terminology

element mesh is created, the defined gridlines are used to help guide the

meshing.

9.4 Overlapping Area Objects

Area objects are used not only to model slabs, but also drops and the

stiffened area objects directly above columns and walls. Modeling drops

and these stiffened regions using area objects ensures that the geometry

of the structure is accurately represented, i.e., that the span lengths are

correct. Thus, overlapping area objects often occur at support locations,

where it is not uncommon to have a slab, a drop, and a stiffened member

at the same plan position. Drop panels and stiff area objects also are de-

fined using the Define menu > Slab Properties command, and when

drawing the area objects to represent these members, SAFE knows to use

the following hierarchy when the objects overlap.

An area object that is completely embedded within another area object

takes precedence, e.g., SAFE will use the property of the stiff area object

when it lies completely within a drop, and the property of the drop when

it lies within the slab. On the occasion where a drop or stiff area object is

not completely embedded within a single area object, but rather spans

between two or more area objects, SAFE will assign a hierarchy based

on the Analysis Property Data Type. An area object with a stiff type will

replace an area object with a drop type, which in turn will replace an ar-

ea object with a slab type.

Thus, for a model containing slab and stiff area objects, SAFE will use

only the stiff area properties in the stiff area locations when generating

the internal finite element mesh and will ignore the overlapping slab

properties. Area objects that have an analysis property data type of Stiff

have a modification factor of 100 applied to the bending stiffnesses, and

are flagged for no design.

Occasionally multiple slab area objects (as opposed to drops and stiff ar-

ea objects) may be drawn such that they overlap. Again, a slab area ob-

ject completely embedded within another slab area object takes prece-

9 - 4 Overlapping Area Objects

Key Topics

dence. In the case where one slab area object does not lie completely

within another object, the last object drawn takes priority.

Important Note: Only the properties of the overlapping area objects are

ignored; any surface loads applied to those redundant objects are not

omitted and will be applied in an additive manner. Therefore, although

the areas of overlap typically are small in comparison to the total area of

the slab, it is generally recommended that load assignments be made to

only one object at any given location. Typically the load should be as-

signed to the primary slab area objects, and surface loads should not be

assigned to drops or column area objects.

It also should be noted that any area object drawn as an opening or as-

signed as an opening using the Assign menu > Slab Data > Opening

command will take precedence over an area object at the same location

with a property assignment. Area objects used as openings are by default

unloaded. However, an option exists to load openings with the same sur-

face loading as the area objects they replace, which can be done when

drawing the opening or by using the Assign menu > Slab Data > Open-

ing command.

9.5 Keyboard Shortcuts

SAFE includes several keyboard and mouse shortcuts for quickly and

easily carrying out various operations. The following list summarizes

some of the available keyboard and mouse shortcuts:

 Various key combinations for accessing menu commands, many of

which are typical Windows keyboard shortcuts, such as CTRL +S to

save, CTRL +C to copy, and many others. The shortcut key combina-

tions are listed next to the menu items.

 Use the mouse roller wheel to zoom in and zoom out.

 Press down and hold the mouse roller wheel while in a Display Win-

dow, then drag the mouse to Pan the model.

Keyboard Shortcuts 9 - 5

SAFE – Key Features and Terminology

 While holding the Shift keyboard key, press down and hold the mouse

roller wheel while in a Display Window, then drag the mouse to rotate

the model.

 Visual copying can be carried out by first selecting a set of objects,

then while holding the CTRL keyboard key, click and hold the left

mouse button and drag the mouse pointer to a new location to copy the

selected objects.

 While drawing, pressing the ‘N’ keyboard key will toggle through the

activated snap options.

9.6 Time Saving Options

SAFE includes several options that help minimize the time spent creat-

ing models. A selection of these options is described in the following:

 Model Explorer – Allows quick access to model definition data,

analysis

results, design results, and detailed drawings through an expandable

hierarchical tree menu system.

 Quick Drawing – Allows drawing of point, line, and area objects us-

ing a single mouse click, including slabs, beams, drop panels, and col-

umns.

 Snap To – Allows placement of structural objects with accuracy, us-

ing an extensive set of customizable snap settings.

 Draw {Object Type} Form – Allows assignment of attributes to the

object while drawing the object.

 Import .DXF/.DWG Architectural Plans – Allows import of archi-

tectural plans that can then be used as a reference for defining SAFE

models. The plans themselves are not part of the structural model, but

rather act as templates that can be traced, using snap features, to gen-

erate a model.

9 - 6 Time Saving Options

Key Topics

 Create Report – Generates a summary report for the model, with a

single button click, including model geometry, assignments, proper-

ties, analysis results, and design results.

9.7 More Information

This chapter provides a selection of the key topics within SAFE. Addi-

tional information on these topics and other aspects of the program may

be found in the program Help, the other manuals, and in the “Watch &

Learn



Movies” series.

More Information 9 - 7

SAFE Key Features And Terminology

Navigation menu

Versions of this User Manual:

Views

Navigation