A modified lateral load pattern for linear static analysis

Document Type : Research Article


1 Department of Civil Engineering, Shahed University, Tehran, Iran

2 Department of civil engineering, Kermanshah university of technology, Kermanshah, Iran

3 Department of Civil Engineering, University of Kurdistan, Tehran, Iran


linear static analysis is one of the most widely used methods proposed by the codes for the seismic analysis of structures. Several methods have been presented for determining the static lateral load pattern. In spite of the simplicity of these procedures, their accuracy, especially for structures in which the influences of higher modes are significant, is not desirable. 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 responses of some structures subjected to some earthquakes are acquired. Then, regarding the dynamic responses of the structures, the static lateral load pattern compatible with the average responses 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 responses of the structures subjected to seismic excitations. The developed lateral load is applied for three frames with 5, 10 and 14 stories. The inter-story drifts of these frames are achieved under 14 earthquake excitations. After that, the proposed lateral loads of code 2800 and FEMA 356 are used on these frames and the responses are derived. The outcomes show that whereas the average error of the proposed lateral load for these frames is around 7, 5 and 7%, the average errors of code 2800 and FEMA 356 are almost 20, 10 and 25%. Comparing the inter-story drifts for the developed lateral load pattern with the dynamic results, validates its performance. 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.


Main Subjects

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