Experimental investigations on punching shear of lightweight aggregate concrete flat slabs

Lightweight aggregate concrete due to the relatively low bulk density is used for casting the flat slabs of multistory buildings. However, a significant concentration of internal forces within support zones result in the need for placing an additional punching shear reinforcement. Despite the fact that double-headed studs are the most popular type of transverse reinforcement, the European technical approvals (ETA) do not apply for using that in flat slabs made of lightweight aggregate concrete. In order to verify the efficiency of shear reinforcement in the form of double-headed studs in the lightweight aggregate concrete slabs in the Research Laboratory of the Department of Concrete Structures (KBB) experimental investigations were carried out. The tests included a total of 9 elements of 2400 x 2400 mm dimensions in a plane and the thickness of 200 mm. The variable parameters were the longitudinal reinforcement ratio and the cross-section of punching shear reinforcement. Very high efficiency of double headed-studs has been found. Their application allowed for increase in the load carrying capacity reaching from 16 to 73% (depending on the reinforcement ratio) with respect to the specimens without transverse reinforcement.