AASHTOWare BrR Training · forward (-) skew. The left open rotation refers to the geometry of each end of the culvert. Finally, the box length is measured along the culvert center

AASHTOWare BrR Training

Modeling and Analysis of a

Reinforced Concrete Box Culvert

By

OSE

- 1 -

Contents

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

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

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

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

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

Materials ......................................................................................................................................... - 6 -

Select Concrete ............................................................................................................................ - 6 -

Select Reinforcing Steel ............................................................................................................... - 7 -

Select Soil .................................................................................................................................... - 8 -

Factors ............................................................................................................................................ - 9 -

CULVERT DEFINITIONS ....................................................................................................................... - 10 -

Roadway Plan View ....................................................................................................................... - 11 -

Culvert Loads ................................................................................................................................. - 12 -

Culvert Alternatives ....................................................................................................................... - 13 -

RC Box Culvert Geometry............................................................................................................... - 14 -

RC Box Culvert Thickness ............................................................................................................... - 24 -

RC Box Culvert Loads ..................................................................................................................... - 24 -

RC Box Culvert Reinforcement ....................................................................................................... - 25 -

Model Validation ........................................................................................................................... - 29 -

Bridge Alternatives ........................................................................................................................ - 30 -

RUNNING ANALYSIS........................................................................................................................... - 32 -

APPENDIX .......................................................................................................................................... - 37 -

- 2 -

Useful design information

- 3 -

- 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 Holmes County on State

Route 514 at SLM 7.98. 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 lose 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.

- 6 -

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 f’c 5000 psi concrete. Each material can be created by double clicking the corresponding

folder and clicking on “Copy from Library”. Select the material needed for the bridge and then click OK.

Select Concrete

- 7 -

Select Reinforcing Steel

Repeat the previous process to select the 65 ksi reinforcing steel. You will also need to add a Soil material.

- 8 -

Select Soil

Finally, you will need to add a Soil material.

- 9 -

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.

- 10 -

CULVERT DEFINITIONS

Double clicking the “CULVERT DEFINITONS” folder will prompt you to enter the name of your culvert. Enter the name

and click OK.

- 11 -

Roadway Plan View

The roadway plan view will define the general geometry of the culvert. The skew is measured relative to the roadway

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

forward (-) skew. The left open rotation refers to the geometry of each end of the culvert. Finally, the box length is

measured along the culvert center line. In this case the skew is 10° RF so you will enter -10, and the ends of the

culvert are squared so you will enter 90 degree rotation for both and the length is 70 ft.

- 12 -

Culvert Loads

This section is related to the soil material selected and refers to the soil pressure conditions for the culvert. You

can select how the soil pressure will be applied to the structure and modify the water unit load. The default

options are usual conditions, therefore, only select the soil material from the drop down and click OK.

- 13 -

Culvert Alternatives

The culvert alternatives folder allows you to add one or more typical culvert geometries. Double click on Culvert

Alternatives, in the pop-up window, enter a name for the alternative. There are several options such as exposure

factors and earth pressure conditions, however, the default values are usually appropriate. The exception to this is

the Construction Type. It is very important that you select the correct option. Select Precast and click OK.

- 14 -

RC Box Culvert Geometry

In this section, you will define the geometry of the cross section of the box culvert. The number of cells allows you

to create multi-cell sections. The cell height and cell width refer to clear distances as shown in the schematic present

in the window. The bottom slab present is used to define whether the structure is a frame (3-sided box culvert),

when the value is not checked, or a box culvert, when it is checked. The construction joint location is measured from

the top of the bottom slab, therefore, If there is no construction joint you can enter it as the negative value of the

bottom slab thickness. To enter haunches, click on the check box and enter the haunch dimensions. Enter the

information shown below:

- 15 -

End Conditions

This section allows you to define special loading conditions for the culvert. An important option is Moment release

at bottom of walls which is used when modeling three sided culverts where rotation occurs at the bottom of the

walls (i.e. not integral with foundations). Side sway support can be assumed for this structure.

- 16 -

Bar Mark Definition

This screen will allow the creation of the reinforcement used in the structure. Unfortunately, BrR does not allow

the use of bent welded wire reinforcement as a reinforcement type. Therefore, welded wire will have to be

converted to equivalent rebar reinforcement. In the case of our model, we are given a required steel area in in2/ft

which allows for a more straightforward use of traditional rebar definitions.

Enter the name of the definition, the steel grade, the bar size and the type of bar. The schematic on the left of the

window is a good guidance to enter the dimensions.

- 17 -

Enter the bar mark definitions as shown:

- 18 -

- 19 -

- 20 -

- 21 -

- 22 -

Note: For this culvert, As7 and As8 bars are identical, therefore, you could potentially use the same definition for

both locations.

- 23 -

Culvert Segments

The culvert segments window allows the creation of multiple culvert segments in cases where reinforcement or

material properties change throughout the culvert. Usually only one typical culvert section will need to be defined.

Double click on Culvert Segments and enter a name for the culvert, the material refers to the concrete to be used.

The Distance from left end of culvert to start of segment and Length of segment field are used to locate a particular

cross section in the culvert. Since our example has only one culvert segment type we can input 0 for the distance

and 70 ft for the length.

- 24 -

RC Box Culvert Thickness

This section is self-descriptive, enter the thicknesses for the top and bottom slabs and for the walls. Enter 12” in all

fields.

RC Box Culvert Loads

Enter the data based on the diagrams provided, this information can be obtained from the plans and shop drawings.

You can use the Copy from Library button to enter the wearing surface unit load. The live load distribution factors

can be modified if desired.

- 25 -

RC Box Culvert Reinforcement

This section allows you to place the reinforcement in the culvert section. There are seven tabs that will be useful in

placing each bar based on its location. Additionally, each tab contains a schematic to guide the input.

From the shop drawings, enter the information as shown below:

Top Slab – Top Bars:

On this screen we will only enter the As7 bars, the clear cover will be 2 inches, you can calculate the distance from

the centerline and enter it as a negative number, or simply check the Centered option. The spacing is calculated to

provide 0.29in2/ft using a #4 bar as 8.28”.

Top Slab – Bot Bars:

Next, enter the As2 bars:

- 26 -

Bot Slab – Top Bars:


Bot Slab – Bot Bars:


- 27 -

Corner:

Next, enter As1 corner bars. The wall clear cover and slab clear cover will be 2in. The Location refers to the side that

the corner will be pointing to. The Wall Number refers to which wall the bar is placed in, they are measured from

left to right. You will need to enter one line for each corner bar location:

Wall:

Next, enter As4 bars. One field to note in this screen is the Location, which is not the same field as in the corner

bars. The Location refers to which side of the wall the bar cover is being measured from. You will also need one

line for each wall:

- 28 -

Schematic:

Right click on RC Box Culvert Reinforcement and then click on Schematic to verify that the bars have been placed

correctly.

- 29 -

Model Validation

One of the tools you may find useful is the Validate button. If you select a culvert segment, an icon in the top will

be available to be utilized. When you click Validate this will show you any errors 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

- 30 -

Bridge Alternatives

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

Bridge Explorer. The 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 culvert for this alternative by double clicking the “CULVERTS” folder. It is recommended

to name this superstructure similarly to the culvert definition that we built earlier and are planning on analyzing.

- 31 -

Bridge Alternatives (Cont’d)

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

We will do this by double clicking the “Culvert Structure Alternatives” folder and then giving the culvert structure

alternative a name. Then, a Culvert Definition needs to be populated and linked with this alternative. Use the drop-

down box and select the culvert 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 screenshot below. This is another good time to save your model.

- 32 -

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

- 33 -

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 templates by clicking the “Open Template” button. You should have

multiple templates, but the two templates applicable to culverts are “2019 ODOT_LRFR_Mainline IR”, and “2019

ODOT_LRFR_Non-IR”. These templates should be selected based on the design code and/or the desired rating

method, and the location of the structure. Click “Open Template” at the bottom of the window and select the

“ODOT_LRFR_Non-IR” 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”. Please note that for LFR, legal vehicles

must be added under the Operating section (NOT Legal Operating) and that the

- 34 -


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”. If the culvert was composed of members of varying section

or reinforcement you would be able to access results for each section that has been modeled.

- 35 -


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

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

rating factor. You can also view the results of the specification checks of each individual culvert segment. First, the

Analysis Setting will need to be set up by loading the analysis template as shown below

- 36 -


The 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.

View Spec Check

Run Analysis

Controlling

Component

Controlling

Locations

View Results

- 37 -

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