Experimental investigation of precast RC interior beam-column-slab joints with grouted spiral-confined lap connection

The behavior of precast concrete (PC) structures subjected to seismic load depends mainly on the type, location, and reliability of the connections between precast components. To investigate these, the precast beam-column joints are usually tested. However, the research on the seismic performance of the precast beam-column joints containing transverse beams and slabs remains limited and most of the adopted connections are expensive. In this paper, a simple and inexpensive grouted spiral-confined lap (GSCL) connection was proposed and forty-five pull-out tests on this connection were carried out to determine the suggested lap length of deformed bars. Based on these results, an experimental study was carried out on four large-scale PC interior beam-column-slab joints containing transverse beams and slabs in order to further verify the reliability of the GSCL connection and explore reasonable precast assembling patterns for such joints. Three precast assembling patterns, that represent three arrangements of precast members and cast-in-place concrete as well as the location of connections, were designed. Four joints, including one monolithic specimen and three precast specimens, were tested under combined constant axial load and reverse lateral loading. The test results confirm that the proposed GSCL connection can significantly reduce the lap length of reinforced bars compared to the traditional lap connection. Moreover, the test results indicate that the GSCL connection can be applied in seismic regions. Two precast assembling patterns for such PC interior joints with the GSCL connection can be recommended to apply in seismic regions because the corresponding precast joints exhibited better seismic performance than the monolithic joint.