Experimental investigation of the effect of the longitudinal reinforcement content of ring beams on the cyclic behavior of masonry spandrels

In many unreinforced masonry (URM) buildings reinforced concrete (RC) ring beams are introduced at each storey in order to maintain the integrity of the building when subjected to seismic loading. Such ring beams also contribute to the in-plane resistance of URM walls consisting of vertical piers connected by ring beams and often also by horizontal URM spandrels. The entity of the RC ring beam and the URM spandrel is in the following referred to as composite spandrel. Although numerical simulations have shown that composite spandrels have a significant influence on the seismic behavior of URM walls, their contribution has often been neglected since vital experimental evidence on the cyclic behavior of spandrel beams was lacking. The paper discusses important phenomena affecting the cyclic force-deformation behavior observed during full-scale quasi-static cyclic tests on composite spandrels. In particular the effect of the longitudinal reinforcement content of the RC ring beam on the interaction between URM spandrel and RC ring beam as well as on stiffness, strength and deformation capacity of the composite spandrel are discussed. Based on the test results first recommendations concerning the design and analysis of RC ring beams in URM structures are presented.