AASHTOWare BrR Training · superstructures. For this training, we will be analyzing a tangent...

AASHTOWare BrR Training

Modeling and Analysis of a

Single Span Steel Beam

with a Corrugated Metal Deck

By

OSE

- 1 -

Contents

PLAN SET……………………………………………………………………………………………………………………………………………. - 2 -

CREATE A BRIDGE MODEL ................................................................................................................... - 4 -

Description ...................................................................................................................................... - 4 -

Save................................................................................................................................................. - 5 -

BRIDGE WORKSPACE ........................................................................................................................... - 5 -

MATERIALS ...................................................................................................................................... - 6 -

Select Structural Steel .................................................................................................................. - 6 -

Select Beam Shapes ......................................................................................................................... - 7 -

Selecting I-beam Shapes .............................................................................................................. - 7 -

Appurtenances ................................................................................................................................ - 9 -

Diaphragm Definition..................................................................................................................... - 10 -

Factors .......................................................................................................................................... - 11 -

SUPERSTRUCTURE DEFINITIONS ........................................................................................................ - 12 -

Load Case Description .................................................................................................................... - 13 -

Framing Plan .................................................................................................................................. - 14 -

Diaphragm Layout ......................................................................................................................... - 15 -

Deck .............................................................................................................................................. - 17 -

Structure Typical Section ............................................................................................................... - 18 -

Member Loads............................................................................................................................... - 22 -

Member Definition ........................................................................................................................ - 22 -

Profile Definition ........................................................................................................................... - 25 -

Lateral Support .............................................................................................................................. - 26 -

Copying Member Alternatives ....................................................................................................... - 27 -

Linking Members ........................................................................................................................... - 28 -

Live Load Distribution Factors ........................................................................................................ - 29 -

Model Validation ........................................................................................................................... - 30 -

Bridge Alternatives ........................................................................................................................ - 31 -

RUNNING ANALYSIS........................................................................................................................... - 33 -

APPENDIX .......................................................................................................................................... - 40 -

- 2 -

W21x62

5 DIAPHRAGMS @ 12’5”

60’ C/C BEARINGS

5’ 5’

4’3” SPACING (TYP)

5 GA 3”X9” CORRUGATED DECK

- 4 -

CREATE A BRIDGE MODEL Click the create bridge icon near the upper left corner to create a new bridge.

Description

The Structure File Number (SFN) should be entered in the Bridge ID and NBI Structure ID fields. The County-Inventory

Route-Straight Line Mileage is entered in the Name field. For this training, the bridge is in Pickaway County on

Township Route 205 at SLM 2.50. Location, Facility Carried, and Feat. Intersected should all be entered to match

SMS data. Although not required, selecting the appropriate main structure type will simplify the bridge workspace

by removing some structure type specific folders. More detail is provided on the ODOT Structures website in the

Bridge Management Section. Links provided in the appendix. For help, the user can always press F1 at any point

to get help with the currently opened window.

Create Bridge

SFN

Bridge

Name

Inventory

Route

Structure

Type Information

entered here

should

match SMS

- 5 -

Save

At this point, it is recommended to save the model. This can be done either through File/Save or by

clicking the Save icon. It’s also important to remember that the software does NOT auto-save. It is

recommended to save often as the software can become unstable in some instances. Saving time is

minimal so a standard practice is to save after closing each window or at least every few windows to be

sure not to loose large amounts of entry.

BRIDGE WORKSPACE This is the main workspace you will use when creating and modeling a bridge. From here you can access, create and

edit all the information for the bridge model.

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MATERIALS

The materials folder allows you to create material definitions for use within the model. For most of the selections

within BrR, you will either be able to define a specific material or simply select a predefined material from the library.

For this training, select ASTM A7 and A36. As shown below, in the ODOT library, ASTM A7 steel is listed under

“AASHTO M94(1961)”. For organization, after the material is selected the name can be changed from “AASHTO

M94(1961)” to “ASTM A7”. Each material can be created by double clicking the requisite folder and clicking Copy

from Library. Select the material needed for the bridge and then click OK. Repeat this process for both steel grades.

Select Structural Steel

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Select Beam Shapes

The next folder is Beam Shapes. From here, you can select shapes for prestressed, steel, and timber beams. This is

a similar process to selecting materials. When selecting a shape from the library, you can start typing the required

shape into the Shape Designation field and the list will autosort to match. For example, if you type “W33” into the

Shape Designation field the list will reduce to only include W33 I-beam shapes. If the shape is manually entered, the

properties as are not automatically calculated by the program. You would need to go to the “Properties” tab and

manually enter the section properties.

Selecting I-beam Shapes

For steel I-beam shapes, there is an additional field to select from W, S, H and HP shapes. This option can be selected

before you copy from library to select the proper list of possible shapes. There are also cases where there are two

definitions for a given shape based on year. These shapes are often almost exctly the same, although there may be

some subtile differences in section properties. In this case, select the appropriate year based on the date built.

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Selecting I-beam Shapes(Cont’d)

A second I beam section will need to be selected for the diaphragm definition. Follow the same procedure used

for the I-beam defined in the last section.

- 9 -

Appurtenances

This folder allows you to define parapets, medians, railings, and/or a generic shape. Select from a predefined list of

railing definitions by using the library or manually create the rail. A name is required for the shape and using a

descriptive name such as “TST Rail” or “Deep Beam Rail” is an easy way to add information without opening the

definition. In this case, a name such as “30” Rail” can give some detail without opening the definition. Another key

note is to make sure you enter a Railing Load (kips/ft) otherwise the program will not include the weight in the

analysis. For this model the Railing Load will be set to 0.001 kips/ft. This is done because BrR does not allow non-

composite loads to be applied to the deck, and the software doesn’t allow for a zero-weight rail and a rail must be

placed on the deck for the analysis to run without errors. The railing loads will be applied to the members via

Member Loads. The width for side-mounted rails is generally set to 0in, given that the rail does not reduce the

overall travelway width. Be sure to check the travelway dimensions to verify the railing location later in the modeling

process.

4’

11

1/8

”

2’

6”

Unit Weight

Set to 0 for

Side-Mounted

Rails

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Diaphragm Definition

The Diaphragm folder allows you to create the definitions for multiple types of diaphragms such as concrete, steel

channel, and different steel angle types. For this example, we have an I-beam diaphragm. You will first select a

“Type 4” diaphragm, assign the W21x62 shape with the vertical orientation and select ASTM A36 steel. In the next

section, you will need to define your connection types and locations measured in inches from top and bottom or the

web to the center of the connection. The diaphragm weight is not automatically calculated so you will need to

manually calculate the weight and enter it later in Framing Plan Detail.

18”

- 11 -

Factors

From the Factors folder you can select the factors for your analysis using the Copy from Library option. You can

select factors for each code as needed. For load rating purposes, select the latest specifications for LFD and LRFD.

- 12 -

SUPERSTRUCTURE DEFINITIONS Double clicking the “SUPERSTRUCTURE DEFINITONS” folder will give you the option to select your superstructure

definition type. You can choose from a Girder System, Girder Line, Floor System, Truss, RC Slab, and Multi-Cell Box

superstructures. For this training, we will be analyzing a tangent single span steel beam. Select the Girder System

option and click OK. Set the appropriate number of spans, number of girders, enter span lengths, and select the

member type. The deck type will also need to be changed to “Corrugated”. After selecting a deck type, if you click

OK and then open this superstructure definition again, you will not be able to revise the deck type. If the wrong

deck type is selected, you must delete the existing superstructure definition and create a new definition with the

correct deck type.

Span Lengths

(bearing/bearing)

Member

Types

Deck Type

- 13 -

Load Case Description

From here, you can select your required load cases. There is an option to add the basic load cases by clicking “Add

Default Load Case Descriptions” button. This will add DC1, DC2, DW, and SIP Forms. These can be renamed or

deleted as necessary, or you can create more, depending on your needs. It can be beneficial to create individual

load cases for different utilities or additional wearing surfaces to clearly identify why the additional load is being

applied. As mentioned earlier, the railing load cannot be applied directly to the deck as a non-composite load so the

DC1 load case will be used to assign the load. After adding default load cases, DC1 (non-Composite) can be renamed

to “Railing” and will be assigned later in Member Loads.

- 14 -

Framing Plan

The framing plan detail allows you to enter the girder spacing, skew, diaphragms, and lateral bracing. The skew can

be either a positive or negative number depending on if it’s a left forward (+) or right forward (-) skew. The girder

spacing can be entered separately for each girder bay. If the girders are splayed, you will need to set the Girder

Spacing Orientation to Along Support to enter variable girder spacing. You can also hover the mouse pointer over

most input values and a box will display the value converted to other units.

- 15 -

Diaphragm Layout

The framing plan shown on the plans has 5 intermediate crossframes spaced at 12’-5” per bay and end bays at 5’-0”

on both ends. The first crossframe in bay 1 is at the abutment bearings and therefore should have a start distance

of 0 ft for the left and right girder with a Diaphragm Spacing of 0 ft and Number of Spaces set to 1. Click “New” to

create the next intermediate crossframe. This crossframe will also have a starting distance of 0ft for the Left and

Right Girder but will have a Diaphragm Spacing of 5 ft and 1 space. The Load (crossframe weight) of 0.265 kips

(4.25ftx62lb/ft = 263.5lb) and the definition will need to be set. Once the first intermediate crossframe is set clicking

either New or Duplicate will set the start distance based on the previous crossframes end distance but only Duplicate

will copy the Load and Definition. Click Duplicate and set the diaphragm spacing to 12.4167 ft and the number of

spaces to 4. To place the end crossframe click “New” and enter both (Left and Right) Start Distances to 60 ft. Right

click “Framing Plan Detail” and select “Schematic” to verify crossframe placement as shown below.

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Diaphragm Layout (Cont’d)

Now that Girder Bay 1 is set the “Copy Bay To…” feature can be used to complete the remainder of the

diaphragms. The copy feature can be used because all the diaphragms have the same spacing in each bay. To

copy to the other bays, the bay that will be copied from needs to be active. In this case, Bay 1 will need to be

active to perform the copy operation. Once Bay 1 is active click the “Copy Bay To…” button. Then select all bays

that will be copied to and click apply. Then verify the placement by viewing the Framing Plan schematic.

- 17 -

Deck

Set the Default rating method to LFD and Analysis Modules to AASHTO LFD and AASHTO LRFR. Enter the dimensions

of the 3x9 corrugated metal flooring and click “Compute Properties”. The 3x9 corrugate metal dimensions were

determined using a current standard and verified by the section modulus. This plan set also shows the minimum

section modulus for the corrugated metal flooring of 3.26in3/ft compared to the calculated section modulus of

3.35in3/ft. The Load under Section Modulus is the load due to the corrugated metal. In this case 11.78 psf will be

used.

Wheel Load distribution (Tire Contact Area) – Standard Specifications for Highway Bridges - Article 3.30; HS-20 tire

contact area is 10” in the direction of traffic and 20” wide.

An error is causing the deck analysis to fail when using the

AASHTO LFD and LRFR Analysis Modules. Change both to

the “Legacy” module to bypass this error. This error has

been reported and should be fixed with the next update.

- 18 -

Structure Typical Section

In this section you will define the width of the bridge deck, overhang widths, thickness of the deck, location of the

parapets and/or rails, lane position, and the wearing surface. You can also display the schematic of the typical

section by right clicking the “Structure Typical Section” and selecting “Schematic”.

At this point, there is very little detail included with the Typical Section Schematic. As information is added in the

next few steps, the schematic will become a very useful tool in verifying the inputs are correct. It is a good practice

to leave the schematic open as this display updates automatically as more information is added. The initial deck

thickness comes from the Deck window, Plank Depth (3”) + Thickness above plank (3”).

- 19 -

Structure Typical Section (Cont’d)

This section allows you to enter the deck width by entering the distances from the left and right deck edges to the

reference line and the left overhang width. It is helpful, when entering these values, to set the reference line in the

center of the deck. This will allow you easily define a vehicle path at the center of the bridge for non-standard gauge

vehicle analysis.

The Parapet, Railing, and Generic tabs allow you to enter railing and barrier information. Click “New” to create a

rail. For this bridge, two rails will be needed one on the left and one on the right with both of them set to

DC2(composite) for Load Case. BrR does not allow non-composite load to be placed on the deck and also does not

allow of a zero weight railing to be placed on the structure.

- 20 -


The lane position can be easily set by clicking the “Compute…” button at the bottom of the window and verify the

calculated travelway(s) are/is correct with the schematic.

The wearing surface tab allows for multiple different types of wearing surface to be applied to the superstructure.

You can assign preset material such as asphalt, concrete, Latex modified concrete, and monolithic concrete or you

can create your own case. For corrugated metal decks with asphalt it is not recommended to include additional

thickness in the Wearing Surface tab. The program will only apply this load to the beam and will not include this

additional weight in the analysis for the deck. The total thickness should be applied in the Deck window as “Thickness

above plank” as described earlier.

- 21 -


You can now see the total deck width, the travelway width, the deck overhang widths, and beam spacing in the

schematic. This is a good way to verify you have correctly entered the information into the Structure Typical Section

window.

- 22 -

Member Loads

In Member Loads additional loading due to utilities, pilasters, light Poles, or in this case, Non-Composite

Railing loads. This load can be applied either as a point loads at railing support locations or as a

continuous uniform load. For simplicity, the rail will be applied used a uniform load at 0.125kips/ft.

Member Definition

Now that you have defined all the different elements of the beams, we can start putting the bridge together. Expand

the “Members” folder by clicking the “+”, then double click the “Member Alternative” folder or right click and select

“New” to create for beam. In the first window, you will select the material and girder type. This bridge is a rolled

steel beam.

- 23 -

Member Definition (Cont’d)

Next you will see the Member Alternative Description window. The fields in on this window are the member

alternative name, End bearing location, and addition self-load. Whatever name convention you choose is acceptable

for the member, but a standard rule of thumb is to simply follow the naming convention of the plan set you are

working with. In this case, use “Beam 1”. End bearing locations are the distances the beam goes past the centerline

of the abutment bearing. Left meaning the rear abutment and right is the forward abutment. The additional self-

load is generally set to 2% for bridges with no splices, welded splices or if you add point loads to account for splice

weight. 5% can be used if you have plate splices and are not adding point loads at splice locations. This is just a

general rule of thumb and the additional weight should be adjusted to fit the given situation.

- 24 -

Member Definition (Cont’d)

The other tab that is useful in this window is the Control Options tab. You can modify some of the analysis options

for this member, if you so choose. You can allow plastic analysis, allow moment redistribution, ignore shear, and

several other analysis options. For this training we will leave the control options set to default.

- 25 -

Profile Definition

Girder Profile allows you to assign a section or sections to a beam line. Use the dropdown arrow to select from the

list of predefined shapes from the Beam Shapes folder. For this bridge, select the W36x160 section for the entire

length (60ft) of the beam and select ASTM A7 steel or AASHTO M94(1961) if you didn’t change the name. In this

window, you can also include cover plates in the Top and Bottom Cover Plate tabs. You will not need cover plates

on this bridge.

- 26 -

Lateral Support

This section allows you to define the range of top flange lateral support. You can also use the “Locations” tab to

define discrete points if needed. For corrugated metal decks the Locations tab will be used to define discrete points

of lateral support. In this case, the 3x9 corrugations will have support locations at 9” spacing.

Note: The program assumes brace points at diaphragm locations.

- 27 -

Copying Member Alternatives

After you complete Beam A you can simply copy and paste Beam 1 from G1 to G2 and them rename it to Beam 2.

Before you copy and paste it’s always a good idea to save at this point. Although it’s not very common, copy and

paste operations can sometimes create an unstable model and can cause the program to crash. It is recommended

to frequently save the model before and after using the copy and paste feature.

Note: If you have stiffeners included before copy they will likely need to be deleted and set again for skewed bridges.

Rename to

“Beam 2”

- 28 -

Linking Members

To reduce analysis time, you can use the “Link with” feature. You can link a member by opening the member (in this

case G5) you want to link with a member you already created (G1) by using the dropdown to select the appropriate

member to link with. You can also link the remainder of the interior beams to G2.

Note: Only link members with identical section properties and beam spacing. If you link say G3 (interior beam) with

G1 (exterior beam) the result will not be valid.

You can see when a member is linked with another when the name of the member is G5 (G1). This shows that G5 is

linked with G1 and only G1 will be analyzed.

- 29 -

Live Load Distribution Factors

Now that the bridge has been defined you can now auto calculate the Live Load Distribution Factors (LLDF). You will

need to go into each member alternative a “Compute from Typical Section” for each beam not linked. For this bridge

only G1 (Beam 1) and G2 (Beam 2) will need LLDFs populated. You can auto calculate for LFD but currently LRFD

must be manually calculated.

- 30 -

Model Validation

One of the tools you may find useful is the Validate button. If you select member alternative Beam A, an icon in the

top will be avalible to be utilized. When you click Validate this will show you any erros or warnings currently in your

model. There may be other errors during analysis, but this give a good starting point to debug bridge models. This

validation will also run whenever you save your model.

Validate

Validation

Window

- 31 -

Bridge Alternatives

Bridge Alternatives are used to assign Superstructure Definitions so that they can be analyzed from the Bridge

Explorer. This first thing you need to do is create a bridge alternative by double clicking the “Bridge Alternatives”

folder. For this example, you can set a name for the alternative as shown below.

From here, we can create a superstructure for this alternative by double clicking the “SUPERSTRUCTURES” folder. It

is recommended to name this superstructure similar to the superstructure definition that we built earlier and are

planning on analyzing.

- 32 -

Bridge Alternatives (Cont’d)

Next, we will need to create the superstructure alternative and call out the definition that it will be linked to for

analysis. We will do this by double clicking the “Superstructure Alternative” folder and then giving the

superstructure alternative a name. Then, a Superstructure Definition needs to be populated and linked with this

alternative. Use the drop-down box and select the superstructure definition that you would like to analyze, and

then click “OK”.

After creating our bridge alternative tree, the Bridge Workspace, showing the alternatives, should look like

something similar the screen shot below. This is another good time to save your model.

- 33 -

RUNNING ANALYSIS To run the analysis from the bridge explorer window, right click on the bridge you just created and select Rate.

- 34 -

Running Analysis (Cont’d)

The Analysis Settings window will open and display the current Rating Method, Analysis Type, Vehicle Selection, and

Vehicle Summary. You can access preset template by clicking the “Open Template” button. You should have

multiple templates, but the two primary templates are the “ODOT_LFR_Legal_SHV_EV” and

“ODOT_LRFR_Legal_SHV_EV”. These templates should be selected based on the design code and/or the desired

rating method. Click “Open Template” at the bottom of the window and select the “ODOT_LFR_Legal_SHV_EV”

template and click open. After the template is loaded, click OK to run the analysis. If the ODOT templates are not

available, a new template can be created by selecting the desired Rating Method, Analysis Type, and adding the

required vehicles to the Vehicle Summary in the proper category. This can be used as a one-time analysis or can be

saved for future use by clicking “Save Template”.

- 35 -


When the analysis is complete, click OK and the results will appear. This is your controlling load ratings for each

vehicle. You can see ratings for each girder by selecting the vehicle of interest and clicking “View Structure Rating

Results” and then clicking “View Member Rating Results”. From here, you can see the rating for member G1, G2 and

the Deck.

- 36 -


If the same process is used for a legal vehicle, as the SU5, the Deck is not listed. The reason for this is that BrR doesn’t

support Legal Operating Vehicles for Corrugated Deck analysis. It’s recommended to run the deck analysis from

within the Bridge Workspace which is covered in the next section.

- 37 -


The analysis can also be ran from within the bridge workspace. By running the analysis from the bridge workspace,

you can access more specific details about the analysis. You can find details about the location and mode of the

critical rating factor. You can also view the spec check results of each individual beams line. As mentioned in the

previous section, running the analysis for the Deck is best performed within the Bridge Workspace. First, the Analysis

Setting will need to be changed by moving all the legal vehicles to Operating as shown below. ODOT doesn’t have a

designated template for corrugated metal decks but the “ODOT_LFD_BoxCulvert_SU_EV_OH” template uses this

same configuration.

- 38 -


The results for the Deck analysis results are presented in a table similar the one show below. This table includes the

Rating Method, Rating Factor, Controlling Location and its Limit State. For the Deck Analysis, each load is analyzed

as a simple and continuous span.

View Spec Check

Run Analysis

Controlling Ratings

Controlling

Locations

- 39 -


The other members can be analyzed with the same procedure using the “ODOT_LFR_Legal_SHV_EV”

template and selecting the member of interest.

- 40 -

APPENDIX

Ohio DOT Structures – Bridge Management Section

http://www.dot.state.oh.us/Divisions/Engineering/Structures/BridgeManagementSection/Pages/default

.aspx

Description Conventions

http://www.dot.state.oh.us/Divisions/Engineering/Structures/BridgeManagementSection/Documents/B

rR_Description_Conventions_2017-05-12.docx

AASHTOWare BrR Training · superstructures. For this training, we will be analyzing a tangent...

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Transcript of AASHTOWare BrR Training · superstructures. For this training, we will be analyzing a tangent...