A Seismic Design Lateral Force Distribution Based on Inelastic Response

It is well recognized that structures designed by current codes undergo large inelastic deformations during major earthquakes. However, lateral force distributions given in the seismic design codes are typically based on results of elastic response studies. In this paper, current code lateral force distributions are reviewed in view of the results obtained from nonlinear dynamic analyses of several example structures. It is concluded that code lateral force distributions do not represent the maximum force distributions that may be induced during nonlinear response. That may lead to inaccurate predictions of deformation and force demands, causing structures to behave in a rather unpredictable and undesirable manner. A new lateral force distribution based on study of inelastic behavior is developed by using relative distribution of maximum story shears of a number of example structures subjected to a variety of earthquake ground motions. The results show that the proposed lateral force distribution is more rational and gives a much better prediction of inelastic seismic demands at global as well as at element levels.