A modified lateral load pattern for linear static analysis

One of the most widely used among the existing methods proposed by the codes for the seismic analysis of structures is linear static analysis. Several methods have been presented for determining the static lateral load pattern. In spite of the simplicity of the existing procedures, their accuracy is not desirable, especially for structures in which the influences of higher modes are significant. In this study, a new method is developed to improve the lateral load pattern in linear static analysis. To achieve the proposed lateral load distribution, firstly, the average response of structure subjected to some earthquakes is acquired. Then, regarding the dynamic of structures, the static lateral load pattern compatible with the average response is developed. Eventually, to derive a straightforward and hands on lateral load distribution, using a statistical study, some relations coupled with a graph are developed. Since the proposed method is developed based on the structural responses resulting from linear dynamic analysis (time-history analysis), it is shown that the suggested way despite its simplicity and efficiency, presents appropriate accuracy in predicting the response of the structures subjected to seismic excitations. The developed method is evaluated for a set of structures with different fundamental periods. Results show that the method gives higher accuracy in comparison with the static method of Iranian standard 2800 and FEMA 356. Also the developed procedure can be considered as an appropriate technique for determining lateral load distribution in seismic codes.