Developments of prefabricated steel-concrete composite beams with novel steel-yielding demountable bolt connectors

Abstract

This paper developed prefabricated steel-concrete composite beams (PSCCBs) with novel steel-yielding demountable bolt connectors (SYDBCs). This new connecting system adopted the post-installed bolts and concrete plug blocks to interlock the prefabricated concrete slab and underneath I-beam, which significantly improves the construction efficiency. The concept design of the PSCCBs with SYDBCs was firstly introduced. Followed, four push-out tests with PSCCBs using SYDBCs were tested to investigate their shear behaviours at the component level. Push-out test results showed that compared with the casted-in bolt connectors, the developed SYDBCs slightly reduces the shear stiffness (about 20%) and yielding load, but does not affect their ultimate shear strength. Moreover, the SYDBCs exhibit better shear ductility than the casted-in bolt connectors with the same size. Two PSCCBs designed with post-installed normal bolts (NBs) and SYDBCs were also tested under two-point loading to study their ultimate strength behaviour. Test results showed that PSCCBs using SYDBCs exhibited reduced elastic stiffness (by about 22%), but equivalent ultimate strength (difference is 3%) to those PSCCBs using casted-in bolt connectors. Finally, two T-joints using the casted-in steel-concrete composite beams and PSCCBs with SYDBCs were tested under cyclic loading to study their seismic performances. Using SYDBCs has quite limited influences on the stiffness, ultimate bending resistance, and energy dissipation of the T-joint with composite beams (reductions equal to about 10%). This further confirms the applicability of the developed SYDBCs for the PSCCBs in steel framed buildings.