SHEAR CONNECTION IN COMPOSITE BEAMS INCORPORATING PROFILED STEEL SHEETING WITH NARROW OPEN OR CLOSED STEEL RIBS

摘要

Most Australian steel deck profiles have a reentrant narrow open steel rib, a closed lap-joint rib, or a combination of both. A series of tests has been conducted to examine the influence of the narrow open steel rib on the performance of the shear connection in composite beams with the profiled steel sheeting ribs laid perpendicular to the beams. Where two or more studs are used at a cross-section, it was found that the minimum transverse spacing had to be increased to 80mm for the connection to behave in a similar manner to that in a solid slab. Rib punch-through of the narrow open steel rib is acceptable provided its effect on reducing the shear capacity of connectors is sufficiently small that it can be ignored in design. Another series of tests has been conducted to examine if the presence of closed lap ribs had any effect on the shear connection. It was found that studs, pairs or single, could be placed adjacent to the closed lap rib without any reduction in stud shear strength compared to that in a solid slab. For profiles consisting of only closed lap ribs at 300 mm centres, three stud pairs could be fitted to each pan at a nominal longitudinal 100 mm spacing which, allowing for a construction tolerance, means the studs can be placed within only 45 mm clear of the webs of the ribs. For steel sheeting parallel to the beam, an additional requirement for the maximum spacing of the studs has been developed. The objectives of this are to prevent the occurrence of a brittle rib-shearing failure and to ensure that straight reinforcing bars placed transverse to the steel beam are effective as longitudinal shear reinforcement. If this limit is exceeded, additional waveform reinforcement is rfecessary to cross the horizontal shear surface passing at the level of the tops of the ribs that can form in the region between the shear connectors. New design rules that account for all of these factors have recently been introduced into Australian Standard AS 2327.1, or are being considered for inclusion, and are described in the paper.