New Lateral Force Distribution for Seismic Design of Structures

In the conventional seismic design methods, heightwise distribution of equivalent seismic loads seems to be related implicitly on the elastic vibration modes. Therefore, the employment of such a load pattern does not guarantee the optimum use of materials in the nonlinear range of behavior. Here a method based on the concept of uniform distribution of deformation is implemented in optimization of the dynamic response of structures subjected to seismic excitation. In this approach, the structural properties are modified so that inefficient material is gradually shifted from strong to weak areas of a structure. It is shown that the seismic performance of such a structure is better than those designed conventionally. By conducting this algorithm on shear-building models with various dynamic characteristics, the effects of fundamental period, target ductility demand, number of stories, damping ratio, postyield behavior, and seismic excitations on optimum distribution pattern are investigated. Based on the results, a more adequate load pattern is proposed for seismic design of building structures that is a function of fundamental period of the structure and the target ductility demand.