Seismic stability and the force reduction factor of code-designed one storey asymmetric structures

This paper evaluates the stability bounds of the force reduction factor R of unidirectionally loaded UBC designed asymmetric one-storey systems having different mass and stiffness distributions. It is shown that whereas the instability effects due to torsional response are neutralized by the asymmetry-related over-strength, instability bounds may still be lower than the R-values prescribed by the code. Results of a limited study indicate that bidirectional ground motion tends to reduce further the safety margin against dynamic instability