Superstructure Design

Superstructure design in CSiBridge is completed in accordance with the AASHTO STD 2002 or AASHTO LRFD 2007 code for concrete box girder bridges or the AASHTO 2007 LRFD code for bridges when the superstructure includes Precast Concrete Box bridges with a composite slab. Additionally, steel I-beam bridges with composite slabs may be designed in accordance with the AASHTO 2007 code. Design using CSiBridge is based on load patterns, load cases, load combinations and design requests. The Bridge Superstructure Design manual describes the algorithms used in those guidance documents. This topic briefly describes the steps involved in completing superstructure design using CSiBridge.

  1. Define the bridge orientation and geometry (i.e., layout lines and lanes), specify the components (e.g., deck sections, bents, abutments), identify the loads (e.g., vehicles, dead and bridge live loads in load patterns, point/line/area loads) and the functions to apply the loads during analysis; bring those items together in the bridge object definition and update the bridge model.

  2. Use the Analysis > Load Cases > New command and the Analysis > Bridge > Bridge Response command to specify the load cases to be used in analysis and the moving load case results to be saved (i.e., the bridge response), respectively.

  3. Use the Analysis > Analyze > Analysis Options command to specify the available degrees of freedom and then use the Analysis > Analyze > Run Analysis command to run the analysis. The design is based in part on the results of the analysis of the specified loads and functions.

  4. Use the Design/Rating > Load Combinations > New command or the Design/Rating > Load Combinations > Add Defaults command to specify the combinations of load patterns to be designed (i.e., user-specified load combinations or default combinations). The design request cannot be run until the load combinations have been defined. The various types of combinations and the abbreviations for them are provided in Chapter 2 of the Superstructure Design manual.

  5. Use the Design/Rating > Superstructure Design > Preferences command to verify that the preferences are acceptable.

  6. Use the Design/Rating > Superstructure Design > Design Requests command to display the Bridge Design Requests form. Clicking the Add New Request button will display the Bridge Design Request Superstructure form. Use that form to specify the check type, the portion of the structure to be designed (i.e., the station ranges), and the loads to be considered (i.e., the demand sets). As necessary, click the Design Request Parameters Modify/Show button to display the Superstructure Design Request Parameters form and adjust the design parameter values.

  7. Use the Design/Rating > Superstructure Design > Run Super command to run the design request as specified. The Bridge Object Response Display form will display after the design request has been run. Use the form to review the results or use the Show Tables button to display the data in tables that can be printed or exported in Microsoft Excel or Access formats.

If the model is of a steel I-beam bridge with a composite deck, the Design/Rating > Superstructure Design > Optimize command can be used after analysis and design to display the Bridge Object Superstructure Design and Optimization form. The options on the form can be used to interactively optimize design of the bridge model.

  1. Use the other display features available on Home > Display to display analysis results on your model or on the screen in a tabular format.

  2. If desired, use the Orb > Print > Print Tables  command to print input and output data to a file or to the printer in tabular form compatible with Word, standard text editors, and .html editors. Or use the Orb > Report > Report Setup command and the Orb > Report > Create Report command to generate output in a variety of report formats, including user specified contents, for selected groups of objects, using a selected orientation, with a cover page and hyperlinked contents, using selected load patterns, load cases/combos, output options, and selected results, and compatible with Word, standard text editors, and .html editors.


See Also

Modeling Process

Seismic Design

Bridge Rating