Volume :

1

Issue :

2

Abstract :

Diaphragm action is responsible for distributing lateral loads arising due to seismicity and wind loads among the lateral force resisting (LFR) members consisting of columns, bracings and shear walls in a typical reinforced concrete structure. Hence, the role of diaphragms is to provide structural integrity, i.e., maintain the floor system’s gravity load carrying capacity while undergoing diaphragm action. Precast diaphragms could be designed as rigid or flexible depending upon the site and seismicity requirements. Too much of rigidity or flexibility is dangerous to structural behavior due to incompatible deflections and too large deflections respectively. Damage to precast concrete diaphragms is observed in many past earthquakes across the globe. About thirty large panel precast concrete roof panels sustained damage and collapse due to the failure of generating sufficient diaphragm action in the 2001 Bhuj earthquake in India. So, there is an immediate need to analyze and design the diaphragm for high seismicity. In our Indian Standard code of practice for precast concrete, there are no provisions for load distribution in diaphragm systems in high seismic zones. Here in this paper a formula for the distribution of loads in the diaphragms and an empirical formula for the maximum and minimum diaphragm forces have been suggested for the Indian code of practice for precast concrete structures.