Displacement‐based seismic design of multi‐degree‐of‐freedom bridge structures

Abstract

The concept of displacement‐based design is attractive for seismic design, primarily because it places the focus of design directly on displacement demand, and hence damage, rather than on force‐reduction or behaviour factors. A procedure is presented which extends the simple concept of displacement‐based design to complex multi‐degree‐of‐freedom (MDOF) bridge structures. The procedure is based on the assumption of a displaced shape for the structure, and the subsequent reduction of the system to an equivalent single‐degree‐of‐freedom (SDOF) system. The process is shown to work well for the design of a symmetrical bridge, while suffering some shortcomings when applied to a highly irregular bridge. The topic of design‐oriented displacement response spectra is also briefly addressed.