10-10-2014, 02:11 PM
Since the inception of the inclusion of the aspect of safety of structures against
earthquake ground motions in the structural design, the available literature
proves that no significant study of the influence of the shape of the structure in
plan has been taken into consideration during analysis.
About three decades ago, it was Luthers, who gave the first thoughts to it. He
warned that an asymmetric plan shape might lead to torsional vibrations owing
to the eccentricity of mass and stiffness centers of the structure. Later on, in the
sixties, Biggs and in the seventies, Dowrick did a superficial study in this regard;
Dowrick suggested that an asymmetric plan shape can best be avoided rather
than designed for. But a perfectly symmetric plan shape is very difficult to
achieve. It can be limited by the shape of site, soil conditions, purpose of the
building and a variety of other constraints.
Hence in the present project, this aspect of shape of the structure in plan has been
studied in depth and fairly good results regarding the influence of shape on the
response have been obtained. Based on this, extensive studies can be continued
in this regard, to develop some general criteria for designing structures with
asymmetric plan shapes, subjected to earthquake ground motions.