On the non-iterative procedure of direct displacement-based seismic design for portal R.C. bridges: Using inelastic design spectrum

In general, iterative procedures are required by the direct displacement-based seismic design method. This paper presents a non-iterative displacement-based method for the design of portal R.C. bridges based on the inelastic design response spectrum. By Combining the properties of structural stiffness and yielding, a rational, efficient and accurate method is established, where not only the strength and stiffness of members depend on the pre-selected target displacement and ductility ratio, but the cross-sections of those can also directly be determined form the two pre-chosen values without any iteration. In addition to the examples that are used to illustrate the proposed procedure, the dynamic inelastic time history analysis and the static nonlinear analysis (pushover analysis) are also included to verify this procedure. It is concluded by the study that iterations are not needed in direct displacement-based design if the force-deformation relationships of designed structures can be derived.