Hysteretic performance of Reduced Web Section (RWS) connections with demountable slabs and effect of composite action

Abstract

Little attention has been paid to reduced web section (RWS) connections with composite slabs under cyclic loading. RWS connections have been proven to act as ductile fuses with a most promising and straightforward choice that requires only one perforation within a beam web without removing the concrete slab. Thus, it could be an economic benefit in terms of both manufacture, usage, and seismic retrofit, while limiting instability, protecting non-ductile elements. This paper introduces an experimental test of demountable steel-concrete composite bolted reduced web section (RWS) connections. A single circular opening with diameter equal to 0.8 of the beam’s depth, was fabricated near the beam-column joint. Two different parameters are investigated, the effect of the web opening location, and the presence or absence of bolted shear studs over the protected zone. The assessment of retrofitted connections was also examined by creating a web opening of the solid-webbed specimen after exposing it to cyclic actions representing moderate seismicity. Based on the results, employing composite RWS connections as a retrofit non-seismically designed buildings, can provide an excellent solution in terms of strength, ductility and energy dissipation. This was achieved by the formation of the Vierendeel mechanism, resulting in concentrating the high plasticity on the beam, which in turn leads to an increase in the deformability and ductility of the connections. The presence of composite action over protected zone could lead to a lower capacity of RWS connection, regardless of extra row of studs. This was attributed to high stress demands not only in the bottom flange of beam, but also in the top Tee-section of opening. All RWS connections were capable of satisfying the seismic requirements of ANSI/AISC 358-16, ANSI/AISC 341-16 and EC8. Moreover, the bolted shear studs showed an excellent seismic performance and could be easily dismantled after testing.