The response of single-storey buildings to earthquakes is strongly influenced by the flexibility of the diaphragm. Flexibility increases the period of the building, magnifies the ductility demand on the lateral load resisting system (LLRS), and changes the manner in which the inertia forces are distributed along the length of the diaphragm. These effects are influenced by the manner in which the LLRS responds. In particular, pinched hysteretic behaviour of steel braces can lead to a further increase in the ductility demand on the LLRS.
An analytical study is carried out to examine the
various influences of diaphragm flexibility. The study improves on previously suggested methods for finding an appropriate force reduction factor for the seismic design of LLRS. The magnification in bending moment and shear force is investigated. Finally, the effects of the nonlinearity of the diaphragm on the response of the system and the design approaches are studied.