Improved earthquake resistant design of torsionally stiffasymmetric steel buildings

摘要

In a companion paper as well as in earlier publications, it has been shown that in asymmetricframe buildings, designed in accordance with modern codes and subjected to strong earthquakeexcitations, the ductility demands at the so called "flexible" edges are consistently and substantially higherthan the ductility demands at the "stiff' edges of the building. In some cases the differences in thecomputed ductility factors between elements at the two opposite building edges exceeded 100%. Similarfindings have also been reported for code designed reinforced concrete buildings. This is an undesirablebehavior as it indicates no good use of material and the possibility for overload of the "flexible" edgemembers with a consequent potential for premature failure. In the present paper, a design modificationwill be introduced that can alleviate the problem and lead to a more uniform distribution of ductilitydemands in the elements of all building edges. The presented results are based on the steel framesdetailed in the companion paper. This investigation is another step towards more rational design of non-symmetric steel buildings.