Introduction To CSi Bridge
User Manual: Introduction to CSiBridge
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Introduction to CSiBridge
CSiBridge®
Introduction to
CSiBridge®
ISO BRG102816M1 Rev. 0
Proudly developed in the United States of America
October 2016
Copyright
Copyright Computers & Structures, Inc., 1978-2016
All rights reserved.
The CSI Logo® and CSiBridge® are registered trademarks of Computers & Structures,
Inc. Watch & LearnTM is atrademarks 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 CSiBridge® and all associated documentation are proprietary and
copyrighted products. Worldwide rights of ownership rest with Computers & Structures,
Inc. Unlicensed use of these programs 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
2
Introduction
1.1
Organization
1-2
1.2
Recommended Reading/Practice
1-2
Create a Concrete Box Girder Bridge
2.1
Example Project
2-2
2.2
Start the Model
2-3
2.3
Bridge Wizard
2-4
2.4
Layout Line
2-6
2.5
Deck Section
2-8
2.6
Bridge Object
2-9
2.7
Parametric Variation
2-12
i
Introduction to CSiBridge
2.8
2.9
3
ii
2-15
2.8.1
2.8.2
2.8.3
2.8.4
2.8.5
Spans
Abutments
Bents
Diaphragms
Prestress Tendons
2-16
2-18
2-20
2-22
2-23
Update the Linked Bridge Model
2-27
Load the Bridge Model
3.1
Lanes
3-3
3.2
Vehicles
3-5
3.3
Vehicle Classes
3-8
3.4
Load Patterns
3-9
3.5
Load Cases
3-10
3.5.1 Moving Load Case
3.5.2 Other Load Cases
3-10
3-11
Additional Loads
3-12
3.6
4
Bridge Object Assignments
Analysis and Results of a Bridge Model
4.1
Bridge Responses
4-1
4.2
Run Analysis
4-2
4.3
Display Results
4-3
4.3.1 Graphical Displays
4.3.2 Output Tables
4-3
4-5
Chapter 1
Introduction
Modeling, analysis, and design of bridge structures have been integrated into
CSiBridge to create the ultimate in computerized tools tailored to meet the
needs of the engineering professional. The ease with which all of these tasks
can be accomplished makes CSiBridge the most versatile and productive software program in the industry.
Using CSiBridge, engineers can easily define complex bridge geometries,
boundary conditions and load cases. The bridge models are defined parametrically, using terms that are familiar to bridge engineers, such as layout lines,
spans, bearings, abutments, bents, hinges, and post-tensioning. The software
creates spine, shell, or solid object models that update automatically as the
bridge definition parameters are changed.
CSiBridge design allows for quick and easy design and retrofitting of steel and
concrete bridges. The parametric modeler allows the user to build simple or
complex bridge models and to make changes efficiently while maintaining total
control over the design process. Lanes and vehicles can be defined quickly and
include width effects. Simple and practical Gantt charts are available to simulate modeling of construction sequences and scheduling.
The CSiBridge includes an easy to follow Wizard that outlines the steps necessary to create a bridge model.
1-1
Introduction to CSiBridge
Completely integrated within the CSiBridge design package is the power of the
SAPFire analysis engine, including staged construction, creep and shrinkage
analysis, cable tensioning to target forces, camber and shape finding, geometric
nonlinearity (P-delta and large displacements), material nonlinearity (superstructure, bearings, substructure, and soil supports), buckling, and static and
dynamic analysis. All of these apply to a single comprehensive model. In addition, AASHTO LRFD, CAN/CSA-S6, EUROCODE, JTG-D62, Russian SNiP
and IRC designs are included with automated load combinations and superstructure design. The AASHTO latest load rating and seismic design are also
contained in CSiBridge.
1.1
Organization
This manual is designed to introduce you to CSiBridge design when modeling
concrete box girder bridges and precast concrete girder bridges. Chapter 2 describes basic steps involved in creating a bridge model. Chapter 3 explains how
loads are applied, including the importance of lanes, vehicle definitions, vehicle classes, and load cases. Chapter 4 touches on the analysis and display of design output.
1.2
Recommended Reading/Practice
It is strongly recommended that you read this manual and review any applicable “Watch & Learn” Series™ tutorials, which are found on our web site,
http://www.csiamerica.com, before attempting to design a concrete box girder
or precast concrete bridge using CSiBridge. Additional information can be
found in the on-line Help facility available from within the software’s main
menu.
1-2
Organization
Chapter 2
Create a Concrete Box Girder Bridge
This chapter demonstrates the steps that are necessary to create a bridge model
using CSiBridge. The example bridge model, shown in Figure 2-1, will be used
throughout this chapter to help the user understand the various steps that are
necessary to build a bridge model. The example model used in this chapter is
the same as that used in a “Watch and Learn” tutorial that can be viewed by
visiting CSi’s website at www.csiamerica.com. The Watch and Learn video,
entitled ”Bridge – Bridge Information Modeler,” presents a 30-minute tutorial
that will further guide the user through the model creation of the example
bridge.
Figure 2-1 3D view of example concrete box girder bridge model
Example Project
2-1
Introduction to CSiBridge
2.1
Example Project
The example bridge is a two-span prestressed concrete box girder bridge with
the following features:
Abutments: The abutments are skewed by 15 degrees and are connected to
the bottom of the box girder only.
Prestress:
The concrete box girder bridge is prestressed with four 5.0-in2
tendons (one in each girder), with a jacking force of 1,080
kips each.
Bents:
There is one interior bent with three 5 feet 0 inches square
columns.
Deck:
The deck is a Concrete Box Girder with a nominal depth of 5
feet 0 inches. The deck has a parabolic variation in depth
from 5 feet 0 inches at the abutments to a maximum of 10 feet
0 inches at the interior bent support.
Spans:
The bridge has two spans of approximately 100 feet 0 inches
each.
Figure 2-2 Elevation view of example bridge
Figure 2-3 Plan view of example bridge
2-2
Example Project
Chapter 2 - Create a Concrete Box Girder Bridge
2.2
Start the Model
1. Click the File > New command and the form shown in Figure 2-4 will display. For this example, select Kip,ft,F for the units if it is not selected already.
Figure 2-4 New Model form
2. Click the Blank button. By default, two blank CSiBridge windows display.
A single window will provide a larger view that is often easier to use during model creation phase. Click the X in the upper right-hand corner of one
of the windows to close it so that only one CSiBridge window is displaying, with only the global axes present. Note the expand arrow immediately
to the left of the X; clicking that arrow will display a list of available windows and the option to add a new window.
3. Click the File > Resources command to locate the Help and Documentation information that you can use to learn more about CSiBridge.
Start the Model
2-3
Introduction to CSiBridge
4. Click the Home > Bridge Wizard command to access the Bridge Wizard
form shown in Figure 2-5.
Figure 2-5 CSiBridge Wizard
The Wizard can be used to guide the user through the model creation steps. Alternatively, the commands on the tabs (e.g., Layout, Components) can be used
to complete a model. The commands on the tabs also are given in the text the
follows.
2-4
Start the Model
Chapter 2 - Create a Concrete Box Girder Bridge
2.3
Bridge Wizard
The Bridge Wizard walks the user through all of the steps required to create a
bridge object model in CSiBridge. The basic bridge modeling process is as follows:
Step 2 Layout Lines defines the bridge layout linethat is, the horizontal
and vertical alignment of the bridge.
Step 3 Basic Properties defines basic properties and Step 4 Bridge Component Properties defines bridge-specific properties.
Step 5 Bridge Object Definition, Step 6 Parametric Variation Definitions,
and Step 7 Bridge Object Assignments define the bridge object and make all
associated assignments.
Step 8 Update Linked Model creates an object-based model from the bridge
object definition.
Step 9 Lane and Vehicle Definitions, Step 10 Function Definitions, Step 11
Load Case Definitions and Step 13 Moving Load Case Results Saved define
analysis items and parameters, including lanes, vehicles, load cases, and desired output items.
Click on any row in the summary table to jump to the associated step. After
you have clicked in the summary table, the up and down arrow keys can be
used to move up or down one step at a time. The user can use the Step control
located below the summary table to move to the first step (<<), previous step
(<), next step (>) or last step (>>). Type a step number in the Step control and
press the Enter key to jump directly to that step. The tree view to the left shows
the items that are currently defined in the model. Clicking on an item in the tree
view displays the step associated with that item.
For each step in the Bridge Wizard (except Step 1 Introduction), a button displays immediately below the summary table text. Clicking the button opens the
form associated with the step. In a few cases, the button may be disabled. That
occurs when prerequisite steps have not been completed, such as:
A layout line and a deck section property must be defined before a bridge object can be defined.
Bridge Wizard
2-5
Introduction to CSiBridge
A bridge object must be defined before any bridge object assignments can be
made.
A layout line definition or frame objects must exist in the model before lanes
can be defined.
For Step 7 items, a Bridge Object drop-down list also displays immediately below the summary table text. That list can be used to select the bridge object to
which assignments are being made.
2.4
Layout Line
The first step in creating a bridge object is to define the layout line. Layout
lines are reference lines used for defining the horizontal and vertical alignment
of the bridge and the vehicle lanes. Layout lines are defined using stations for
distance, bearings for horizontal alignment, and grades for vertical alignment.
Layout lines may be straight, bent or curved, both horizontally and vertically.
Horizontal curves are circular with spirals, if necessary. Vertical curves are
parabolic.
5. On the Bridge Wizard, double click Step 2 Layout Line to display the Define Bridge Layout Line form. Alternatively, using the tabs, click the Layout > Layout Line > Expand arrow command.
6. Click the Add New Line button to display the Bridge Layout Line Data
form shown in Figure 2-6. It is recommended that the axis of the bridge be
defined in the West/East direction (note the Initial Bearing). This orients
the bridge left to right across the CSiBridge window, which may make it
easier to navigate through the model later. CSiBridge viewing features are
described later.
2-6
Layout Line
Chapter 2 - Create a Concrete Box Girder Bridge
Figure 2-6 Specify layout line data
7. Type 200 into the End Station edit box in the Initial and End Station Data
area of the form (note that the Units are Kip,ft,F). Recall that the bridge in
the Example (Section 2.1) has two spans of 100 feet each, for a total span
of 200 feet.
8. Click the Horizontal Layout Data Quick Start button. The Quick Start
buttons can be used to quickly define a layout line and then the layout line
can be edited as necessary. At least one layout line and one deck section
must be defined before a bridge object can be defined. Also, a layout line
(or frame objects) must exist in the model before lanes can be defined.
9. For this example, select the Straight option.
Layout Line
2-7
Introduction to CSiBridge
Figure 2-7 Quick Start form to specify layout line horizontal data
Click the OK buttons on the Bridge Layout Line Data and Define Bridge
Layout Line forms to apply the selection, close the forms, and continue
with the next step.
2.5
Deck Section
Deck sections are used to define the bridge superstructure. Various parametric
deck sections are available, including concrete box girder, concrete flat slab,
precast concrete girder, and steel girder deck sections.
10. Double click Item 4.1 Deck Section on the Wizard (or the Components >
Superstructure Item > Deck Sections > Expand arrow command) to
display the Define Bridge Deck Sections form. Click the Add New Section
button to display the Select Bridge Deck Section Type form, which is
shown in Figure 2-8.
2-8
Deck Section
Chapter 2 - Create a Concrete Box Girder Bridge
Figure 2-8 Select a bridge deck section
For this example, a concrete box girder section with vertical side walls is
required.
11. Click the Ext. Girder Vertical button in the upper left-hand corner of the
Select Bridge Deck Section Type form. This will display the Define Bridge
Section Data- Concrete Box Girder - Vertical form shown in Figure 2-9.
Deck Section
2-9
Introduction to CSiBridge
Figure 2-9 Specify deck section properties
The Define Bridge Section Data form is used to define the specific material
property and geometries that represent the superstructure deck section. After a deck section has been defined, it can be assigned to a Bridge Object
(see Bridge Object, Step 7 on the Bridge Wizard). If desired, the bridge
superstructure can be specified to vary parametrically along its length. This
will be completed for this example and is described after the Bridge Object
has been defined in the next section. Click the OK buttons on the Define
Bridge Section Data and Define Bridge Deck Sections forms.
2.6
Bridge Object
At least one layout line (Steps 5 through 9 of this Introduction) and one deck
section property (Steps 10 and 11 of this Introduction) must be defined before a
bridge object can be defined. The bridge object definition is the main component of the CSiBridge modeler.
2 - 10
Bridge Object
Chapter 2 - Create a Concrete Box Girder Bridge
12. On the Bridge Wizard, double click Item 5 Bridge Object and click the
Add New Bridge Object button (or click the Bridge > Bridge Object >
New command), then choose the “General Bridge” type in the Bridge Type
form and click OK button to display the Bridge Object Data form, which is
shown in Figure 2-10.
Figure 2-10 Specify Bridge Object data
The lower left-hand corner of the Bridge Object form shows a plan view of
the bridge. Green lines denote the Abutments and red lines denote the Layout Line. Initially, the length of the bridge will default to the length of the
layout line; however, the length of the bridge can be modified to any length
that is less than the length of the layout line.
The following is included in the bridge object definition:
Bridge Object
2 - 11
Introduction to CSiBridge
Bridge spans are defined.
Deck section properties are assigned to each span.
Parametric deck section variations may be assigned to each span.
Abutments, including their skews, are assigned at each end of the bridge.
Bents, including their skews, are assigned at each bent location.
Diaphragms, including their skews, may be assigned along each span.
Hinges, including their skews, may be assigned along each span.
Additional discretization points, including their skews, may be assigned
along each span.
Superelevations may be assigned.
Prestress tendons may be assigned.
Girder Rebar
Loads
Bridge staged construction groups may be assigned.
13. Rename the span label as “Span2” and click the Modify button. Then divide the bridge model into two spans typing 100 in the “End Station ft.”
edit box and typing “Span1” in the “Span Label” edit box in the Define
Bridge Object Reference Line area of the form. Then click the Add button.
This will locate the station 100 feet from the left end of the layout line and
place the only interior bent used in this example model. After the station
value of 100 ft has been added, the plan image of the bridge will change to
reflect the inclusion of a bent, as shown in Figure 2-11 (click the Show Enlarged Sketch button to display this form).
2 - 12
Bridge Object
Chapter 2 - Create a Concrete Box Girder Bridge
Figure 2-11 Plan view of the Bridge Object
Although not applicable to this example, to make changes to a deck section
within a span, divide the span into segments using the same steps for adding a
bent, except specify that a bent property of “None” be assigned where there is
no bent support.
2.7
Parametric Variation
Parametric variations can be used to define variations in the deck section along
the length of the bridge.
14. On the Bridge Wizard, click Item 6 Parametric Variations and the Define/Show Variations button (or use the Components > Superstructure
Item > Parametric Variations > Expand arrow command) to display the
Define Parametric Variations form. On that form click the Add New Variation button to display the Variation Definition form shown in Figure 212. Note that the default name of the variation definition is PVAR1.
Parametric Variation
2 - 13
Introduction to CSiBridge
Figure 2-12 Define a Parametric Variation for the first span
Almost all parameters used in the parametric definition of a deck section
can be specified to vary. More than one parameter can vary at the same
time, if necessary. Each varying parameter can have its own unique variation. Example uses of parametric variations include varying the bridge
depth and the thickness of girders and slabs along the length of the bridge.
The variations may be linear, parabolic, or circular. After a variation has
been defined, it can be assigned as part of the deck section assignment to
bridge objects (see Item 7.1 Deck Sections on the Bridge Wizard).
15. Click the Quick Start button to access the Parametric Variation – Quick
Start form shown in Figure 2-13.
2 - 14
Parametric Variation
Chapter 2 - Create a Concrete Box Girder Bridge
Figure 2-13 Select the Parametric Variation alignment type
Note that the Parabolic Line option has been selected for use in this example. After closing the form and returning to the Variation Definition form.
Adjust the entries on the Variation Definition form to match those shown
in Figure 2-12 by typing directly in the edit boxes and clicking the Modify
button.
When the PARV1 definition is applied to the bridge deck, the depth of the
bridge increases (positive dimension change) and the increase is parabolic
in shape until the distance of 90 feet has been reached. Thereafter, the
depth of the bridge desk remains flat over the remaining 10 feet.
It is intended that PARV1 will be applied to the first span, and a second variation PARV2, which is a mirror image of PARV1, will be applied over the second span. PARV2 is defined in the same manner as PARV1, except a LinearParabolic shape is selected on the Parametric Variation – Quick Start form, and
the values in the “Distance ft.” and “Dim Change ft.” edit boxes on the Variation Definition form are as shown in Figure 2-14.
Parametric Variation
2 - 15
Introduction to CSiBridge
Figure 2-14 Parametric Variation Definition for the second span
Alternatively, the parametric variations PARV1 and PARV2 can be combined
as a single parametric variation PARV3 for the entire bridge length as shown in
Figure 2-15. Note that it is valid to start the variation with negative distance.
2 - 16
Parametric Variation
Chapter 2 - Create a Concrete Box Girder Bridge
Figure 2-15 Parametric Variation Definition for the entire bridge
Note that the PARV1, PARV2 and PARV3 variations have been defined but
have not been assigned to the spans at this stage in the process.
2.8
Bridge Object Assignments
Figure 2-16 lists the series of Item 7 Bridge Object Assignments that can be
made to the model.
On the Bridge Wizard, click on any of the 7.1 through 7.14 items to activate
the forms needed to assign the selected item to the bridge object. Alternatively,
to access to the 7.1 through 7.10 items, open the Bridge Object Data form and
select an item from the Modify/Show Assignments list shown in Figure 2-17.
(Open the Bridge Object Data form by double clicking Item 5 Bridge Object
Definition on the Bridge Wizard and clicking the Modify/Show Bridge Object button, or click the Bridge > Bridge Objects > Modify command.)
Bridge Object Assignments
2 - 17
Introduction to CSiBridge
Figure 2-16 Items to which assignments can be made using Bridge Objects
Figure 2-17 Modify/Show Assignments list box
2.8.1
Spans
16. To assign a deck property or apply a variation to a span, click Item 7.1
Deck Section and the Assign/Show Deck Sections button on the Bridge
Wizard, or on the Bridge Object form (Figure 2-10), select the Spans item
from the Modify/Show Assignments list (shown in Figure 2-17) and click
the Modify/Show button (or click the Bridge > Bridge Object > Spans
2 - 18
Bridge Object Assignments
Chapter 2 - Create a Concrete Box Girder Bridge
command). This will display the Bridge Object Span Assignments form
shown in Figure 2-18.
Figure 2-18 Assign a parametric variation to a bridge span
17. Double click on the “No” displayed in the Span1 Section Varies spreadsheet cell to activate the Bridge Section Variation Definition form shown
in Figure 2-19.
18. Click in the Variation column, click on the General Data, Total Depth item
to display a drop-down list that includes PVAR1, PVAR2 and PVAR3.
19. Click on PVAR1 to assign the previously defined PVAR1 variation to the
first span of the bridge and select “Distance Measured from Start of Span”.
Alternatively, PVAR3 can be used along with the selection of “Distance
Measured from Start Abutment”.
20. Repeat these steps, but double click the “No” displayed in the ToEndAbu
spreadsheet cell and select PVAR2 from the drop-down list to assign the
PVAR 2 variation to the second span. Alternatively, PVAR3 can be used
along with the selection of “Distance Measured from Start Abutment”. Or
simply select “Reference to Another Span” and specify the first span as the
reference span if the alternative method is used for the first span.
Bridge Object Assignments
2 - 19
Introduction to CSiBridge
Figure 2-19 Specify the defined variation to be assigned
to the selected bridge span
Assigning PARV1 to the first span and PARV2 to the second span means that the
depth of the superstructure will increase according to the parametric variation. It is
noted that when the width of the bridge deck section is varied along the bridge
length and the supports are skewed, the alternative method of defining a parametric
variation for the entire bridge length with some extended distance and assigning it
to all spans along with the selection of “Distance Measured from Start Abutment”
is recommended.
2.8.2
Abutments
The abutment assignments provide very important boundary conditions for the
bridge model. Special attention should be given to the bearing properties, bearing locations, and abutment direction (skews) if any.
21. Click Item 7.3 Abutments and the Assign/Show Abutments button on the
Wizard, or on the Bridge Object form (Figure 2-10), select the Abutments
item from the Modify/Show Assignments list (shown in Figure
2-16) and click the Modify/Show button (or click the Bridge > Bridge
2 - 20
Bridge Object Assignments
Chapter 2 - Create a Concrete Box Girder Bridge
Object > Supports > Abutments command). The Bridge Object Abutment Assignments form shown in Figure 2-19 displays. Abutment assignments can be made to each end of the bridge. The form in Figure 2-20
shows the data for the Start Abutment.
Figure 2-20 Assign abutments to a Bridge Object
22. Modify the form where necessary to match the data shown in Figure 2-20:
b. End skew N15E denotes North, 15 degrees East
c. End diaphragm property, if any None is specified
g. Substructure assignment for the abutment, which may be None, an
abutment property, or a bent property the default BABT1 property definition is selected
e. Vertical elevation and horizontal location of the substructure
these parameters are explained further later in this manual
h. Bearing assignment type can be either Girder by Girder (default) or
General. The default option is selected
Bridge Object Assignments
2 - 21
Introduction to CSiBridge
d. and f. The bearing property, elevation, and rotation angle from the
bridge default Note that the bearing elevation refers to the action point of the bearing.
Note also that the elevations specified for the substructure and the
bearings are Global Z coordinates.
23. Make similar assignments to the End Abutment.
2.8.3
Bents
The bent assignments also provide very important boundary conditions for the
bridge model. Special attention should also be given to the bent bearing properties, bent bearing locations, and bent direction (skews) if any.
Figure 2-21 Assign bents to a Bridge Object
24. Click Item 7.4 Bents and the Assign/Show Bents button on the Bridge
Wizard, or on the Bridge Object form (Figure 2-10), select the Bents item
from the Modify/Show Assignments list (shown in Figure 2-17) and click
the Modify/Show button (or click the Bridge > Bridge Object > Sup-
2 - 22
Bridge Object Assignments
Chapter 2 - Create a Concrete Box Girder Bridge
ports > Bents command). The Bridge Object Bent Assignments form
shown in Figure 2-21 displays.
25. Modify the Bridge Object Bent Assignments form if necessary to match
the form shown in Figure 2-21.
•
a. Specify where the bent assignment is being applied The bent
assignments is applied to the bent at the end of Span1 (i.e., Station
100). Since the example model has only a single bent, other bent
station locations do not exist and do not need assignments.
•
b. and c. For the example model, the Superstructure Continuity Conditions is Continuous. If the model had superstructure discontinuities, a diaphragm property as well as a restrainer property, restrainer vertical elevation and initial gap openings at the top and bottom
of the superstructure could be specified on each side of the discontinuity. However, for this example, the Diaphragm Property has a
None property (i.e., no diaphragm is assigned).
•
d. A previously defined bent property and an orientation for the bent
can be specified. For this model, the defaults are being used.
•
e. Vertical elevation (see e. on Figure 21) and horizontal location of
the bent
•
f. and g. The bearing property, elevation, and rotation angle from the
bridge default can be specified. For bents at superstructure discontinuities, bearings are separately specified on each side of the discontinuity (see b. on Figure 21).
•
h. Bearing assignment type can be either Girder by Girder (default) or
General. The default option is selected.
If the superstructure is discontinuous over a particular bent, the
bent property for that bent must be defined as a discontinuous superstructure. To make this definition, click Item 4.7 Bents and the
Define/Show Bents button on the Bridge Wizard to display the
Define Bridge Bents form and click the Modify/Show Bridge
Bent button (or the Components > Substructure Item > Bents
Bridge Object Assignments
2 - 23
Introduction to CSiBridge
command) to access the Bridge Bent Data form and select the
Double Bearing Line (Discontinuous Superstructure) option.
Note that the elevations specified for the restrainer, bent and the bearings
are Global Z coordinates. Typically, along each bearing line there is one
bearing for each girder.
2.8.4
Diaphragms
A diaphragm assignment includes a diaphragm location, property, and orientation. In-span diaphragms are assigned as part of the Bridge Object definition.
Diaphragms that occur at abutments, bents and hinges are assigned as part of
the bridge object abutment, bent and hinge assignments, respectively.
Although you can assign any diaphragm property within a span, a concrete diaphragm will be used by the program only if it occurs within a span with a
concrete deck section, and similarly, a steel diaphragm will be used by the program only if it occurs within a span with a steel deck section.
26. For this example, click Item 7.6 Diaphragms and the Assign/Show
Diaphragms button on the Bridge Wizard, or on the Bridge Object form
(Figure 2-10) select the In-Span Cross Diaphragms item from the Modify/Show Assignments list (shown in Figure 2-16) and click the Modify/Show button (or click the Bridge > Bridge Object > Span Items > Diaphragms command). The Bridge Object In-Span Cross-Diaphragm Assignments form shown in Figure 2-22 displays.
27. Use the form to specify that the diaphragm property, BDIA1, be applied at
the quarter points for each span.
2 - 24
Type 25 in the Distance edit box and click the Add button.
Type 50 in the Distance edit box and click the Add button.
Type 75 in the Distance edit box and click the Add button.
Select Span2 from the Span drop-down list, type 25 in the Distance
edit box, and click the Add button.
Bridge Object Assignments
Chapter 2 - Create a Concrete Box Girder Bridge
Select Span2 from the Span drop-down list, type 50 in the Distance
edit box, and click the Add button.
Select Span2 from the Span drop-down list, type 75 in the Distance
edit box, and click the Add button.
Figure 2-22 Bridge Object In-Span Cross-Diaphragm Assignments
2.8.5
Prestress Tendons
Tendon assignments may be added to a bridge model by clicking Item 7.8 Prestress Tendons and the Assign/Show Tendons button on the Bridge Wizard, or
on the Bridge Object form (Figure 2-10) select the Prestress Tendons item from
the Modify/Show Assignments list (shown in Figure 2-17) and click the Modify/Show button (or click the Bridge > Bridge Object > Prestress Tendons
command) to access the Assign Prestress Tendons form. The Add New Tendon button is then clicked to display the Bridge Tendon Data form shown in
Figure 2-23.
Although no changes are required for the example model, tendon assignments
include the following data:
Location of the start and end of the tendon
Bridge Object Assignments
2 - 25
Introduction to CSiBridge
The vertical and horizontal layout of the tendon
Tendon section properties, loss parameters, and jacking options
The tendon load specified as a force or a stress
Figure 2-23 Bridge Tendon Data form
The tendon modeling option, which is to model the tendon as loads or as elements. (If the model will be used in CSiBridge Superstructure Design, the
tendons must be modeled as elements.)
Several Quick Start buttons are available to assist in defining the tendon
geometry. Figure 2-24 shows an example of a Quick Start form.
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Bridge Object Assignments
Chapter 2 - Create a Concrete Box Girder Bridge
Buttons also are available that access forms to define the Vertical and Horizontal Layout data. On those forms, Parabolic Calculator buttons access forms
that assist in the defining the parabolic tendon layouts by points.
The tendon loads typically are assigned using PRESTRESS as the load pattern
type. The load pattern can be added by clicking on the “+” button to the left of
the Load Pattern Type drop-down list on the Bridge Tendon Data form, which
displays the form shown in Figure 2-25. That form can be modified easily.
Figure 2-24 Tendon Layout Quick Start form
Bridge Object Assignments
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Introduction to CSiBridge
Figure 2-25 Define Load Patterns form
After a tendon has been defined, it can be copied to all of the girder locations
using the form shown in Figure 2-26.
Figure 2-26 Assign Prestress Tendon form
After clicking the Copy to All Girders button, click the Show All Tendons
button to view all of the assigned tendons, as shown in Figure 2-27.
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Bridge Object Assignments
Chapter 2 - Create a Concrete Box Girder Bridge
Figure 2-27 Bridge Tendon Layout Display
2.9
Update the Linked Bridge Model
Anytime the bridge object definition is modified, the linked model must be updated for the changes to appear in the CSiBridge object-based model.
28. For this example, click Item 8 Update Linked Model and the Update
Linked Model button on the Bridge Wizard, or click the Bridge > Update
> Update command, to display the form shown in Figure 2-28.
Update the Linked Bridge Model
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Introduction to CSiBridge
Figure 2-28 Update Linked Bridge form
The Update Bridge Structural Model form has several options.
29. Select a Bridge Object and Action Select the Bridge Object (in this example, there is only bridge object). For the Action, select Update Linked
Model. The options available in the drop-down list can be explained as follows:
− Update Linked Model The updating process essentially creates the entire object-based bridge model based on the information contained within
the Bridge Object definitions. If an object based model of the bridge object already exists, it will be deleted when the new object-based model is
updated. The new object-based model will include all of the latest
changes to the bridge object definition. User-defined features such as
foundation elements, and other supplemental framing elements that are
defined outside of the Bridge Module will not be updated. The user
needs to review and ensure the compatibility between the updated objectbased bridge model and the user-defined elements.
− Clear All from Linked Model This option clears the bridge model display, resulting in a blank screen. It does not delete the model, which can
be redisplayed by choosing the Update Linked Model option.
− Convert to Unlinked Model option CAUTION! This is a one-way
command and cannot be undone. After a model has been converted to an
unlinked model, the model cannot be updated using CSiBridge (i.e., the
commands on the Bridge Wizard or the tabs).
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Update the Linked Bridge Model
Chapter 2 - Create a Concrete Box Girder Bridge
Structural Model Options Use these options to create a spine model, an
area object model, or a solid object model. The type of object based model
created from the bridge object definition can be switched at any time. Note
that the Bridge > Update > Auto Update command is a toggle that allows
the bridge model to be automatically updated by the program every time a
change is made.
− Update as Spine Model Using Frame Objects option Use to create the
model with frame objects.
− Update as Area Object Model option Use to create the model using
area objects.
− Update as Solid Object Model option. Use to create the model using
solid objects.
− Preferred Maximum Submesh Size edit box. Use the area or solid option and associated edit box to specify the automatic area mesh for analysis. This option allows area objects to be divided into smaller objects in
the object-based model, and meshed into elements in the analysis model.
Discretization Information options.
− Maximum Segment Length for Deck Spans edit box. Use to specify
the maximum length of the frame objects, area objects, or solid objects in
the deck spans in the resulting object-based model.
− Maximum Segment Length for Bent Cap Beams edit box. Use to
specify the maximum length of the frame objects, area objects, or solid
objects in the bent cap beams in the resulting object-based model.
− Maximum Segment Length for Bent Columns edit box. Use to specify
the maximum length of the frame objects, area objects, or solid objects in
the bent columns in the resulting object-based mode
Update the Linked Bridge Model
2 - 31
Chapter 3
Load the Bridge Model
This chapter describes the various bridge loading options that are available in
CSiBridge. This chapter focuses mainly on vehicular live loading. The latter
part of this chapter describes application of temperature loads as well other
bridge related loads. Seismic loading is covered in the Bridge Seismic Design
manual.
A moving load analysis can be used to determine the response of a bridge
structures as a result of the weight and centrifugal effects of vehicular live
loads. CSiBridge provides power and flexibility for determining the maximum
and minimum displacements, forces, and stresses due to multiple-lane loads on
complex structures, such as highway interchanges. The effects of vehicle live
loads can be combined with static and dynamic loads, and envelopes of the response can be computed.
Lanes are required if vehicular loads are to be added to a bridge model. Lanes
represent the line or area where the live loads can act upon the superstructure.
Lanes may have width and can follow any straight or curved path. Multiple
lanes need not be parallel or of the same length, so that complex traffic patterns
may be considered. The program automatically determines how the lanes load
the superstructure, even if they are eccentric to a spine model. Conventional influence lines and surfaces resulting from the loading of each lane can be displayed for any response quantity. Vehicle live loads can be selected from a set
of standard highway and railway vehicles, or user-defined vehicle live loads
3-1
Introduction to CSiBridge
can be created. Vehicles are grouped into vehicle classes, such that the most
severe loading of each class governs.
Two methods can be used to calculate the effects of vehicular live loads, namely, influence-based enveloping analysis and step-by-step analysis with full correspondence. The basic steps required for these two types of analysis are as follows:
Influence-based enveloping analysis:
Vehicles move in both directions along each lane of the bridge. Using the influence surface, vehicles are automatically located at such positions along the
length and width of the lanes to produce the maximum and minimum response quantities throughout the structure.
Each vehicle may be allowed to act on every lane or be restricted to certain
lanes. The program can automatically find the maximum and minimum response quantities throughout the structure resulting from placement of different vehicles in different lanes. For each maximum or minimum extreme response quantity, the corresponding values for the other components of response also can be computed.
Step-by-step analysis:
Any number of vehicles can be run simultaneously on the lanes, each with its
own starting time, position, direction and speed. Step-by-step static or timehistory analysis can be performed, with nonlinear effects included if desired.
For most design purposes, the enveloping-type analysis using Moving-Load
Load Cases is most appropriate. For special studies and unusual permit vehicles, the step-by-step approach can be valuable.
For the example model, moving live loads will be analyzed using the influenced-based enveloping method. The steps that are necessary to define this
type of load case are described in the text that follows and begin with lane definitions.
3-2
Chapter 3 - Load the Bridge Model
3.1
Lanes
A traffic lane is defined with respect to a reference line, which can be a bridge
layout line or a line (path) of frame elements. The transverse position of the
Lane center line is specified by its eccentricity relative to the reference line.
Lanes are said to “run” in a particular direction, namely from the first location
on the reference line used to define the lane to the last. A width for each lane
can be specified, which may be constant or variable along the length of the
lane. When a lane is wider than a Vehicle, each axle or distributed load of the
vehicle is moved transversely in the Lane to maximum effect. If the lane is narrower than the vehicle, the vehicle is centered on the Lane and the vehicle
width is reduced to the width of the lane.
As an example, two 12-foot-wide lanes, each having an offset of 8’-0” from the
centerline of the sample bridge, are added as follows.
1. Click Item 9.1 Lanes and the Define/Show Lanes button on the Bridge
Wizard or the Layout > Lanes > Expand arrow command to access the
Define Lanes form shown in Figure 3-1. Lanes can be added along the
layout line or along a defined frame line.
Figure 3-1 Define Lanes form
2. Click the Add New Lanes Defined from Layout Line button to add the
lane along the layout line defined in Chapter 2. The Bridge Lane Data
form shown in Figure 3-2 will display.
Lanes
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Introduction to CSiBridge
Figure 3-2 Bridge Lane Data form
3. Enter data to match that shown in Figure 3-2. Note that the Lane data includes two lines that define the start and end stations, centerline offset
and lane width. The lane display color also can be selected.
4. Define a second lane as described in Steps 2 and 3, except use the lane
offset distance set at −8 feet.
Use the Home > Display > More > Show Lanes command to view the lanes
as shown in Figure 3-3.
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Chapter 3 - Load the Bridge Model
Figure 3-3 3D view of bridge model and lanes
When skewed abutments exist, the layout lines should extend beyond the
length of the bridge by a small amount. This way the lanes can start and end a
small distance from the abutments such that the lanes will completely cover
(and load) the deck areas near the skews. This was not completed in this example model.
3.2
Vehicles
Any number of vehicle live loads, or simply vehicles, may be defined to act on
the traffic lanes. Standard types of vehicles known to CSiBridge can be used or
the general vehicle specification can be used to create user-defined vehicle
types. All vehicle live loads represent weight and are assumed to act downward, in the –Z global coordinate direction. Each vehicle definition consists of
one or more concentrated or uniform loads, or both.
Axle loads act at a single longitudinal location in the vehicle. Uniform loads
may act between pairs of axles, or extend infinitely before the first axle or after
the last axle. The width of each axle load and each uniform load is specified
independently. Those widths may be fixed or equal to the width of the Lane.
Vehicles
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Introduction to CSiBridge
Longitudinally, axle loads are similar to a point load. Transversely, axle loads
may be represented as one or more point (wheel) loads or as distributed (knifeedge) loads. Knife-edge loads may be distributed across a fixed width or the
full width of the lane. Axle loads may be zero, which can be used to separate
uniform loads of different magnitude.
Longitudinally, the uniform loads are constant between axles. Transversely,
these loads may be distributed uniformly across the width of the lane, over a
fixed width, or they may be concentrated at the center line of the lane.
5. Click Item 9.2 Vehicles and the Define/Show Vehicles button on the
Bridge Wizard or the Loads > Type > Vehicles > Expand arrow command to access the Define Vehicles form shown in Figure 3-4.
Figure 3-4 Define Vehicles form
Use the form to import Standard or add General Vehicle definitions. The
Standard Vehicles available in CSiBridge represent vehicular live loads
that are specific to various design codes. A more complete description of
the standard vehicle types and properties is available in the Analysis Reference Manual.
The general vehicle may represent an actual vehicle or a notional vehicle
used by a design code. Most trucks and trains can be modeled using the
CSiBridge General Vehicle. The General Vehicle consists of n axles with
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Chapter 3 - Load the Bridge Model
specified distances between them. Concentrated loads may exist at the
axles. Uniform loads may exist between pairs of axles, in front of the
first axle, and behind the last axle. The distance between any one pair of
axles may vary over a specified range; the other distances are fixed. The
leading and trailing uniform loads are of infinite extent. Additional
“floating” concentrated loads may be specified that are independent of
the position of the axles.
6. On the Define Vehicles form, click the Import Vehicle button to access
the Quick Add Vehicles form shown in Figure 3-5.
Figure 3-5 Add Standard Vehicle form
7. Expand the library and select the desired vehicle. For the example model,
added the HL93S, HL93M and HL93K vehicles.
If the desired vehicle is not part of the list, return to Step 6 and click the
Add Vehicle button to define a general vehicle..
View the specific properties of a vehicle definition by clicking the Modify/Show button on the Define Vehicles form to view the properties for
the ASHTO LRFD HL93-S vehicle displays form shown in Figure 3-6.
Click the Vertical Loading button to show the details of the vertical
loading data.
Vehicles
3-7
Introduction to CSiBridge
Figure 3-6 General Vehicle Data form
3.3
Vehicle Classes
Vehicle classes must be defined to analyze a bridge model for vehicle live loads
using a moving load case. A vehicle class is simply a group of one or more vehicles for which a moving load analysis is performed (one vehicle at a time).
8. Click Item 9.3 Vehicle Classes and the Define/Show Vehicle Classes
button on the Bridge Wizard or the Loads > Type > Vehicle Classes >
Expand arrow command to access the Define Vehicle Classes form.
Click the Add New Class button to access the Vehicle Class Data form
shown in Figure 3-7 (alternatively click the Loads > Type > Vehicle
Classes > New command).
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Chapter 3 - Load the Bridge Model
Figure 3-7 Vehicle Class Data form
9. Select the Vehicle Classes and scale factor as shown in the figure. Specifying this data is necessary to be able to define a Moving Load Case.
3.4
Load Patterns
A load pattern is a specified spatial distribution of forces, displacements, temperatures, and other effects that act upon the structure. A load pattern by itself
does not cause any response in the structure. Load patterns must be applied in
load cases to produce results. Use Item 11 Load Pattern Definitions and the Define/Show Load Patterns button on the Bridge Wizard or the Loads > Load
Patterns command to display the Define Load Patterns form and define the
load pattern.
The “Bridge Live” load pattern Type can be used to specify that one or more
vehicles move across the bridge. For each vehicle, specify a time that the vehicle starts to load the bridge, the initial vehicle location, the direction of travel,
and the speed. When used in a multi-step static or multi-step dynamic (direct
integration time history) load case (see Section 3.5), this type of load pattern is
useful in evaluating special vehicle loads.
Load Patterns
3-9
Introduction to CSiBridge
3.5
Load Cases
A load case defines how loads are applied to a structure (e.g., statically or dynamically), how the structure responds (e.g., linearly or nonlinearly), and how
the analysis is performed (e.g., modally or by direct-integration). Any load case
type can be used when analyzing a bridge model. Static, response spectrum,
and time history load case types are useful for seismic analysis. Pushover analysis can be performed using a nonlinear static load case. Staged construction
analysis also is performed using nonlinear static load cases.
Several analysis options are available that are specialized for analysis of vehicle live loads. Moving load cases compute influence lines for various quantities
and solve all permutations of lane loading to obtain the maximum and minimum response quantities. Multi-step static and multi-step dynamic (direct integration time history) load cases can be used to analyze one or more vehicles
moving across the bridge at a specified speed. These multi-step load cases are
defined using special bridge live load patterns that define the direction; starting
time and speed of vehicles moving along lanes (see Section 3.4).
3.5.1
Moving Load Case
10. Click Item 12.2 Load Cases and the Define/Show Load Cases button on
the Bridge Wizard or the Analysis > Load Cases > Expand arrow
command to access the Define Load Cases form shown in Figure 3-8.
The Dead and Modal load cases are default load cases.
Figure 3-8 Define Load Cases form
3 - 10
Chapter 3 - Load the Bridge Model
11. Click the Add New Load Case button to display the Load Case Data
form.
12. Scrolling down the Load Case Type drop-down list and click on “Moving Load.” The form will adjust to appear similar to that shown in Figure
3-9. Select the lanes to be loaded and the vehicle class (vehicle or group
of vehicles) with which to load them. No specific data has been identified for this example model.
Figure 3-9 Load Case Data - Moving Load form
3.5.2
Other Load Cases
When other load patterns types have been defined, such as earth pressures, temperature, braking, and so forth (see Section 3.4), additional load cases can be
defined to analyze these load pattern types. Combinations of the load cases can
be made automatically in accordance with the supported codes using the
Design/Rating > Add Defaults command; select the Bridge Design option on
the resulting Add Code-Generated User Load Combinations form. This step is
described in greater detail in the Bridge Superstructure Design manual, Chapter
2.
Load Cases
3 - 11
Introduction to CSiBridge
3.6
Additional Loads
Parapets, wearing surfaces, haunches and other superimposed loads that are not
included in the self weight of the structure can be added to the Bridge Object
using the Load > Loads Type > {Point, Line, Area, Temperature} Load
command. As an example, parapets loads could be represented as line loads
and may be added using the Loads > Loads Type > Line Load > New command, which display the Bridge Line Load Definition Data form shown in Figure 3-10. Note that the form has been modified so that the Load Name is “LeftParapet,” the Load Value is 0.90 k/ft, and the transverse load location is 0.5
feet from the reference location, which is the Left Edge of the Deck.
Figure 3-10 Bridge Line Load Definition Data form
Point and area loads may be defined similarly. After the bridge loads have been
defined, they may be added to the bridge object using the Bridge > Bridge
Object > Loads > {Point, Line, Area, Temperature} Load command, which
displays the form (or one similar for point or area loads) shown in Figure 3-11.
3 - 12
Chapter 3 - Load the Bridge Model
Figure 3-11 Line Load Assignments Form
With the form displayed, click the Add New button and any default line load,
or any line load created using the Bridge Line Load Definition Data form can
be assigned to the identified Load Pattern and Bridge Object. If multiple line
loads have been defined, the Line Load Name cell will consist of a drop-down
list of the defined loads.
The Add or Add Copy button may be used to associate the previously defined
{point, line, area}load to a specified location (the parameters used to specify
the location vary depending on the type of load) and Transverse Variation.
The Define Line (or Point or Area) Loads button can be used to define additional line (or Point or Area) loads that can then be assigned using the Line (or
Point or Area) Load Assignments form.
The load pattern type also may be specified by clicking the Define Load Patterns button, which will display the Define Load Pattern form (that also displays when the Loads > Load Patterns command is used). Specification of the
appropriate load pattern type is essential when using code generated load combinations.
Additional Loads
3 - 13
Chapter 4
Analysis and Results of a Bridge Model
This chapter describes the various steps necessary to analyze a bridge model
and observe the analysis results. When a bridge model is loaded with an influence-based moving vehicle load case, the user may select the type of bridge responses and the calculation refinement level used to determine the responses.
After the analysis of a Linked Bridge model has been completed, several display options can be used to observe the analysis results described in this chapter.
4.1
Bridge Responses
Analysis of moving load cases involves calculations that are computationally
intensive and can take a significant amount of time in larger models. The
Analysis > Bridge > Bridge Responses command can be used to select the response quantities to be saved. Only the results specified will be calculated and
saved by the program. The Moving Load Case Results Saved Parameters form
can be used to explicitly specify the analysis results to be generated from a
moving load case.
Bridge Responses
4-1
Introduction to CSiBridge
Figure 4-1 Moving Load Case Results Saved options form
If Correspondence is selected to be considered, for each maximum or minimum
response computed, the corresponding force, moment, or stress quantities that
occur at the same time as the maximum or minimum value also are reported.
For example, in a frame object, when the maximum M3 moment is calculated,
if correspondence is specified, the P, V2, V3, T and M2 values that occur at the
same time as the maximum M3 value also are reported. Including correspondence increases the program calculation time and the quantity of response output.
4.2
Run Analysis
After the bridge model geometry, load patterns, and load cases have been defined, the bridge model is ready for analysis. Use the Analysis > Analyze >
Run Analysis command to activate the analysis. That command displays the
Set Load Cases to Run form shown in Figure 4-2.
4-2
Run Analysis
Chapter 4 - Analysis and Results of a Bridge Model
Figure 4-2 Set Load Cases to Run form
Use the Run/Do Not Run button to select the load cases to run, and the Run
Now button to start the analysis.
4.3
Displaying Results
The user may choose to display the analysis results graphically or digitally.
4.3.1
Graphical Displays
The Home > Display > Show Bridge Supserstructure Forces/Stresses command can be used to display force and stress results, an example of which is
shown in Figure 4-3.
Graphically the shell member forces or stresses may be displayed when the
bridge models have been modeled as area object models. A sample of the
graphical display is shown in Figure 4-4.
Displaying Results
4-3
Introduction to CSiBridge
Figure 4-3 Bridge Object Response Display
Figure 4-4 Graphical Results
4-4
Displaying Results
Chapter 4 - Analysis and Results of a Bridge Model
Point to a shell object of interest and right click on the shell object to view an
enlarged area force or stress result, as shown in Figure 4-5:
Figure 4-5 Shell Element Force Results
Moving the pointer over the selected area object will display the stress variations.
4.3.2
Output Tables
The analysis results may be displayed in tabular form using the Home > Display > Show Tables command, which accesses the form shown in Figure 4-6.
Use the various options on the form to select the input or output quantities and
specify the tables to be displayed. All of the tables that are available for display
also can be exported and reported as part of a user-defined custom report. The
report writing features are explained further in the code-oriented Bridge Superstructure Design manual.
Displaying Results
4-5
Introduction to CSiBridge
Figure 4-6 Choose Tables for Display form
4-6
Displaying Results
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