Start the LEAP Bridge software application by clicking on Start > All Programs > Bentley > LEAP Bridge.
Set the Design Code to ‘India_IRC’ and fill the project information as shown in the figure below. The units are preset to SI (Metric) units for the IRC code.
Figure W-4: Project tab information
Click the Geometry tab, and start the modeling of the bridge using the ABC (automated bridge creator) Wizard. The Wizard can be launched simply by clicking on the ABC Wizard icon in the toolbar.
Begin entering the information shown in Figure W-5 to enter bridge superstructure cross-section and span details. If detailed information about the geometry of the bridge including the alignment information, cross-section and vertical profile is available, the optional information can also be input at this stage.
After completing the superstructure input, click on Next to move to step 2 and input information for the stem wall abutment as shown in Figure W-6 shown below. The input is fairly straightforward and can be completed quickly by simply inputting the values for various input fields. If the information for end abutment is same, simply use the copy button to copy the current abutment information to end abutment.
Figure W-5: ABC Wizard, Step 1, Superstructure details
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Figure W-6: ABC Wizard, Step 2, Substructure details (Start Abutment)
Once the input for the abutment is complete, click on the Pier drop down in the top left hand corner of the window. Simply copy the abutment properties to the end abutment (Number 2) using the copy tool available on this screen.
Next enter the values for the material properties as shown in figure W-8 below. These values will be used as defaults when data is transferred from LEAP Bridge to CONBOX or RC-PIER. Once the initial model is built with these properties, the user will be able to override these default settings in the component programs.
If all information for these three steps in ABC wizard is accurate, the status window will reflect the same, and you can press the finish button to complete the initial description and view the generated 3D model in the Geometry tab of LEAP Bridge as shown in Figure W-9.
Now that the initial model has been created, you could play around with some of the options available for rotation, zoom, pan operations by either using the right mouse menu (context sensitive menus) or simply accessing the appropriate functions on the tool bar.
Figure W-8: ABC Wizard, Step 3, Materials.
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Figure W-9: 3D Bridge model in LEAP Bridge.
Now is a good time to save the input. Click on File/Save and provide a name “Tutorial 3.xml” to save the file.
Next click on the SuperStructure tab, and the click on the CONBOX button, all of the pertinent data is automatically transferred to CONBOX and CONBOX is displayed as shown in Figure W-10 below. Let us now complete the input process in CONBOX and complete the design of the superstructure.
Figure W-10: CONBOX Project tab with information completed automatically.
Since our demonstration model is quite simple, the definitions for Geometry in ABC Wizard were quite sufficient and no further changes are required in the Geometry tab for Alignment, Pier, Layout and Cross-section. However we do wish to add the superimposed dead loads such as the crash barriers, footpath and wearing surface, so simply click on the Geometry tab, and then click on the Crash Barriers button. Make sure to hit the Include All button, and all of the dead loads are automatically considered in the appropriate load groups for analysis. Click OK to close this dialog and view the updated section view showing the 2D graphics for the barrier and footpath on the cross-section.
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Figure W-11: Crash Barriers definition screen
Figure W-12: Updated 2D graphics of bridge cross-section after adding crash barriers etc.
Now, since we don’t have PT tendons in this slab, move to the loads and analysis tab in CONBOX. By default all of the initial and final load cases, the appropriate loads and factors all per IRC have already been predefined as shown in Figure W-14 and W-15. Note that some loads such as temperature gradient and construction will need to be manually deleted from this list of loads, to focus on workflow for this particular example.
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Figure W-14: Load Combinations (for Initial)
In the figure above, the right hand side tree with the BR01 (current box girder bridge) Loads are the library of loads on this particular bridge, and they can be edited here, and all instances of those particular loads are automatically updated wherever they are used. To use these loads simply drag and drop them over to the left hand pane in the appropriate Case (initial or final) and Combination. ( Service I, Ultimate I, etc.) or use the option in the right-click menu to automatically add the load to all load combinations.
Figure W-15: Expanded view of BR01 Loads in Library.
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Figure W-16: Load Combinations (for Final)
You can verify and if required edit and modify the load factors for each combination under both initial and final loads. Simply double click on the Load combination name in the left hand side window to bring up a dialog which looks similar to the screen shown in Figure W-17.
Figure W-17: IRC Load Combination Factors dialog, shown here for “Service I Final”.
Click on the Run Analysis button on the Loads/Analysis button to run the actual longitudinal analysis, moving the trucks along the bridge and then performing an automatic transverse distribution of loads using the Courbon’s method. Once the Analysis is complete, the Run Analysis button turns into View Analysis and you could look at the detailed reports (either as graphs or tabular data).
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Figure 18: Results on the Design Tab
Figure W-19: Design Parameters dialog
In the main menu click on Settings > Design Parameters to bring up the dialog showing the design parameters per IRC, as shown in Figure W-19. Notice that since we are only working with Reinforced concrete, some of the fields for PT concrete are locked. Review the settings here, but since no changes are required, click cancel to close this screen and go back to the program.
On the Design Tab, click on Rebar and in the Dialog which comes up, select Bar size MS25-GR1 and perform an autodesign. Program comes up with a rebar pattern as shown in Figure W-20. Click OK to accept and close the dialog.
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Next click on the Stirrups dialog and select MS12-GR1 for the stirrup size, 6 for number of legs and 150mm for spacing and do an auto design. Program comes up with a stirrup schedule which you could clean up to make it more construction-friendly and click OK to accept the reinforcement and also optionally copy this back to the model.
You can view the results in CONBOX, by simply clicking on the Print icon in the toolbar to bring up the dialog shown below in Figure W-21.
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Figure W-21: Print dialog in CBX.
Now that the design of the superstructure is complete, Click OK to close CBX and transfer information back to the LEAP Bridge model for further processing of the substructure. Notice now that the reinf. has been updated in the superstructure (visible when the transparency option is selected in the 3D view).
See figure W-22 below.
Figure W-22: Rebar and representative stirrups in the 3D bridge model in LEAP Bridge.
Click on save the project. Next click on the SubStructure tab, select AB01 in Abut/Pier list and then click on the RC-PIER button, all of the pertinent data is automatically transferred to RC-PIER and it is displayed as shown in Figure W-23 below. Let us now complete the input process in RC-PIER and complete the analysis & design of the substructure.
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Substructure design
Figure W-23: RC-PIER Project tab with information completed automatically.
Switch to Geometry tab and note that all the geometry information is filled in correctly. Click on Abutment configuration. For this example, we will continue with Stem wall as defined in ABC wizard in LEAP Bridge.
Figure W-24: Abutment configuration showing stem wall properties
You can review the superstructure parameter information as imported from CONBOX. For this example, we need to define eccentric footing for stem wall. Click on Footing|Pile dialog and change the from column distance in z direction to 4.8 m as shown below.
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you For this example, we need to define the bearing locations. Click on bearing dialog and define the bearings at every 2m distance.
Figure W25: Bearing data
Select single bearing line option. Define the 1st bearing at 2 m from the cap left end. Define 2nd bearing at 2 m from the previous bearing location. Define 5 bearings. Click OK to accept these changes. The complete pier geometry can be reviewed in 3D view under geometry tab.
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Figure W-26: 3D Graphical view of pier
You can rotate; zoom in/out using the graphical options given below the 3D view. You can switch to 2D view to copy or print the pier geometry.
Next, move to load tab to define the load applied on pier and select the desired load groups as per IRC specifications.
For this example, primarily you will consider dead, live, wind and braking force. Select dead load (G) from the list of loads available and click to select it. Select Dead load case (G) and click edit to open the load dialog. Click generate button to open the auto load generation options as shown in W-27 and select import load from superstructure option. Select the dead load G & SG to import the load on pier1, as shown in Figure W-28
Figure W-27: Auto dead load generation dialog.
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Figure W-28: Dead load imported from superstructure
Upon clicking “Generate” button will distribute the dead load on bearings as shown in Figure W-29.
Figure W-29: Load case dialog
Click OK to accept these values and close the dialog.
In the similar way, select live load and select generate load. Keep the default IRC rule option and import the live load reactions for Class A, 70 R from superstructure as these are already computed during superstructure design as shown in Figure W-30. Depending on the carriageway width, program generates numerous live load combinations based on IRC 6-2000 specifications. Among these generated combinations, it isolates the most critical combinations producing the maximum effect in the individual members. On the same dialog, select the option to generate longitudinal forces. This will generate the breaking force for each combination.
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Figure W-30: Live load generation
Click OK to accept the load cases. Note that, program has generated 7 critical live load combinations.
You can click on “LL details” to check the details of each live load positioning. Note: You can edit the individual load case to check the bearing reaction, but if you click OK after editing, program erases the live load details descriptions.
Figure W-31: List of selected loads
Now, select wind load case (Ws) and click edit to generate the wind load forces on structures. Generate the wind load for multiple range of wind angle 30 to -30. You can generate the wind load force acting on live load simultaneously or independently. For this example, we will generate the wind on live load simultaneous by selecting wind acting on live load option. Depending on the bridge location, and pier elevation, correct wind pressure acting on substructure will be selected.
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Figure W-32: Wind load generation dialog
Once all the required load cases are defined, select the Service I and Service IIIA, load groups. Next, move to analysis tab. Click on Analysis and design parameter to check the permissible stress values. For this example, we will not make any changes and use the default parameters. Select “Yes” to allow program to generate the default load combinations. You can review the analysis results for each load case or for particular combination at each specific member node.
Figure W-33: Analysis results dialog
Now, you are ready to design the individual components – the stem wall and footing according to IRC specifications. Switch to stem tab and select Autodesign. This prompts the dialog to select the rebar size. Select MS32- GRI and MS-6-GR1 for stirrup size. Program comes with its own reinforcement and stirrup schedule, which can be edited manually. Click on Design status to review the flexure, shear and torsion design. If at any locations, design fails, program flags that location.
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Figure W-34: Stem design tab
Similarly, design the footing. In the footing design, you can use Autodesign as explained earlier or manually define the reinforcement. Depending on the footing type, this dialog will be slightly different.
For combined footing, user can define the reinforcement start and end location. For this example, we have defined spread footing and will be using Autodesign and use 90 degrees hook on both sides to check the design status. You can design all the footing at the same time by checking the box for
“Autodesign all “. Select FTG03 from the available list and click Autodesign. Use MS28-GR1.
Figure W-36: Footing design tab
You can view the results in RC-PIER by simply clicking on the Print icon in the toolbar to bring up the dialog shown below in Figure W-37.
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Figure W-37: Print dialog in RC-PIER.
Now that the substructure design is complete, Click OK to close RC-PIER and transfer information back to the LEAP Bridge model. Notice now that the reinf. has been updated in the substructure (visible when the transparency option is selected in the 3D view). See figure W-38 below.
Figure W-38: Abutment reinforcement display in 3D model of LEAP Bridge.
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