Description |
Seismic Analysis of Regular Highway Bridges. MICROSARB implements procedure 1 of the Applied Technology Council (ATC-6) seismic design guidelines for straight regular highway bridges with Single Mode Spectral Analysis Method (SMSM) for seismic analysis of "regular" highway bridges. The basic assumption behind the Single Mode Spectral Method is that for a bridge with no abrupt change of geometry, mass and stiffness along its length, the seismic response can be determined by considering only the fundamental mode of vibration of the bridge. According to ATC-6, regular bridges need to be analyzed twice in each of the transverse and longitudinal directions. One analysis is for a uniform unit load to determine the fundamental mode shape of the bridge, and the other for pseudo seismic loads to determine the design lateral loads. This leads to a space frame analysis in the transverse direction of the bridge. By developing two separate models (one for each direction), and incorporating substructuring techniques for bents, the analysis can be simplified. The ATC-6 procedure 1 is such an approach. In order to simplify the input phase, the user can link to the AutoCAD drafting package to prepare data interactively. Alternatively, formatted input files may be used. |