Effect of spandrel beam to double tee connection characteristic on flexure-controlled precast diaphragms

Precast spandrel beams are often used on the perimeter of precast buildings to support the precast floor units. These elements are typically not considered part of the lateral force resisting system. However, the presence of the spandrel beams in the floor system may modify the strength, stiffness, and deformation capacity of the precast floor diaphragm. The nature of this response is highly dependent on the characteristics of the details connecting the spandrel to the precast floor system. These details are often welded connections used primarily for erection stability and designed without diaphragm action in mind. With emerging design methodologies for precast diaphragms requiring better-defined performance, the impact of the spandrel beams must be accounted for. Accordingly, analytical research is presented here that examines the effect of spandrel-beam-connecting details on the global characteristics and local demands of a flexure-controlled precast floor diaphragm. Design recommendations are provided.