Seismic Design

Seismic design in CSiBridge is completed in accordance with the AASHTO Guide Specifications for LRFD Seismic Bridge Design. The Bridge Seismic Design manual uses an example project to explain in significant detail the seismic design process. This topic briefly describes the basic steps required to complete seismic design.

  1. Define the bridge orientation and geometry (i.e., layout lines and lanes), specify the components (e.g., deck sections, bents, abutments), bridge object definition, and update the bridge model.

  2. Use the  Loads > Functions > Type > Response Spectrum > New >AASHTO 2007 command or the  Loads > Functions > Type > Response Spectrum > New > NCHRP 20-07 command to specify the longitude and latitude or the postal code of the bridge location. CSiBridge will determine the ground motion hazard using this data. Alternatively, the user can define a response spectrum file to meet this data input requirement. Site effects, such as soil site classification, also can be defined.

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

  4. Use the Design/Rating > Seismic Design > Design Requests command to display the Bridge Seismic Design Requests form. Clicking the Add New Request button will display the Bridge Design Request Substructure Seismic form. Use that form to specify the bridge object to be designed and to review the design request parameters. Clicking the Design Request Parameters Modify/Show button will display the Substructure Seismic Design Request Parameters form and adjust the design parameter values as necessary.

Note:  It is not necessary to execute an analysis of the bridge model before running a seismic design.

  1. Use the Design/Rating > Seismic Design > Run Seismic command to run the design request as specified. The Bridge Seismic Display form will display after the design request has been run. Use the form to review the results in tabular form or use the File menu commands to print the data or export it in Microsoft Excel or Access formats. The Design/Rating > Seismic Design > Report command can be used to generate a report of the seismic design run.

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

  3. 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.

The Bridge Seismic Design manual provides further information to enhance understanding of the seismic design process, including dead load analysis and cracked section properties, response spectrums and demand displacements, capacity displacement analysis, and demand/capacity ratios.

 

See Also

Modeling Process

Superstructure Design

Bridge Rating