Prestressing the negative moment region of composite beams, August 1971

Two simply supported steel-concrete beams with prestressed slabs designated PSC-18 and PSC-28 were tested under negative moment (slab in tension). ·These beams were designed to simulate the prestressed negative moment region of a two-span continuous composite beam. Each of the simple span beams had a span length of 15r-on. The cross section of each beam consis ted of a 6-in. x 60-in. reinforced concrete slab connected to a W2lx62 rolled steel beam by 4-in. high .bY 3/4 in. diameter head steel studs. The stud connectors were attached to the steel beams in two patterns; concentrated groups and equall~ spaced. A prestress force was applied to the slab of each beam by means of four 7/8-in. diameter STRESSTEEL bars placed in four thin steel tubes which were cast into the slab. In one beam the prestress force was applied prior to making the shear connection while in the other the prestress force was applied after the shear connection was made. The purpose of this investigation was two fold: (1) To study the effect of prestressing on the behavior of composite beams under negative moment. (2) To compare the effectiveness of concentrated groups to stud connectors with equally spaced connectors. ii.