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Steel and Composite Structures
  Volume 4, Number 3, June 2004 , pages 189-209
DOI: https://doi.org/10.12989/scs.2004.4.3.189
 


Combined effect of the horizontal components of earthquakes for moment resisting steel frames
Alfredo Reyes-Salazar, Jose A. Juarez-Duarte, Arturo Lopez-Barraza and Juan I. Velazquez-Dimas

 
Abstract
    The commonly used seismic design procedures to evaluate the maximum effect of both horizontal components of earthquakes, namely, the Square Root of the Sum of the Squares (SRSS) and the 30-percent (30%) combination rules, are re-evaluated. The maximum seismic responses of four threedimensional moment resisting steel frames, in terms of the total base shear and the axial loads at interior, lateral and corner columns, are estimated as realistically as possible by simultaneously applying both horizontal components. Then, the abovementioned combination rules and others are evaluated. The numerical study indicates that both, the SRSS rule and the 30% combination method, may underestimate the combined effect. It is observed that the underestimation is more for the SRSS than for the 30% rule. In addition, the underestimation is more for inelastic analysis than for elastic analysis. The underestimation cannot be correlated with the height of the frames or the predominant period of the earthquakes. A basic probabilistic study is performed in order to estimate the accuracy of the 30% rule in the evaluation of the combined effect. Based on the results obtained in this study, it is concluded that the design requirements for the combined effect of the horizontal components, as outlined in some code-specified seismic design procedures, need to be modified. New combination ways are suggested.
 
Key Words
    seismic inelastic response; three-dimensional moment resisting steel frames; horizontal components; time history analysis; multi degree of freedom systems.
 
Address
Alfredo Reyes-Salazar, Jose A. Juarez-Duarte, Arturo Lopez-Barraza and Juan I. Velazquez-Dimas; Facultad de Ingenieria, Universidad Autonoma de Sinaloa, Ciudad Universitaria, Culiacan, Sinaloa, CP 80040, Mexico
 

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