Static Performance of Pre-Fabricated and Cast-in-Place Joints Formed by Inserting Steel Secondary Beam into Concrete Girder

Joints formed by inserting steel secondary beam (SSB) into concrete girders have been increasingly used in engineering practice (e.g., electric power). To demonstrate the static performance of these joints, two key variables including the construction method (prefabricated, cast-in-place) and the insertion form of SSB (unilateral, bilateral) were considered. The test results indicated that the failure mode of each joint was concrete punching by the inserted SSB. Compared with the joint specimens with unilateral insertion of SSB, the failure mode of the joint with bilateral insertion was changed from multiple to single cracking, exhibiting more obvious brittleness. When high-performance cement-based grouting materials were incorporated into the joint, the assembly and ductility of the joint were effectively improved. Compared with the cast-in-place counterparts, the displacement ductility coefficients of joints with prefabricated unilaterally and bilaterally inserted beams were enhanced by 22.9% and 41.3%, respectively. Moreover, a theoretical model was developed to evaluate the punching shear resistance of such joints with favorable accuracy.