SEISMIC CODE ANALYSIS OF MULTISTORY ASYMMETRIC BUILDINGS

Static torsional provisions in most seismic codes require that the lat eral force at each floor level be applied at some distance from the re ference centre at that floor. However, codes do not specify how to det ermine the locations of these centres. As a result, several different definitions of the reference centres are being used to implement the c ode analysis. This investigation examined how the results using variou s reference centres differ and which of these centres would lead to re sults that are in agreement with those of dynamic analysis. For this p urpose three different buildings ranging form torsionally stiff to tor sionally flexible were analysed. It was shown that for the class of bu ildings studied in this investigation that although the locations of t he reference centres were quite different, the results were very simil ar and nearly independent of the reference centre. Comparison of resul ts calculated from static code equivalent lateral force procedures and results from dynamic response spectrum analyses showed that the stati c code procedures led to design forces very close (flexible wall) or s lightly conservative (stiff wall) when compared to the dynamic analysi s for the torsionally stiff building. However, the static code procedu res significantly underestimated the design forces of the stiff walls and significantly overestimated the design forces of the flexible wall s for the torsionally flexible buildings. (C) 1998 John Wiley & Sons, Ltd.