Experimental study on the flexural behavior of cold-formed U-shaped steel-encased confined prestressed RC beam

This paper discusses the flexural behavior of a cold-formed U-shaped steel-encased confined prestressed RC beam (CUSCPC). In this system, the U-shaped thin-walled steel girder provides the restraining stress to the partially confined concrete beams, participates the deformation of the composite beam under servicing loads and serves as a permanent formwork for the prestressed concrete (PC) beam during construction. Shear studs are welded on the inside of the closed end of U-shaped steel girder to provide a full shear connection between the concrete and thin-walled steel plate. Same number of CUSCPC specimen but with no shear studs were made for comparison purposes. Two additional parameters were also considered: ratio of tension reinforcement and ratio of P/S strands. The test results show that all specimens have excellent ductility and display a flexural failure pattern. The brittle behavior disappears due to the triaxial stress state of the partially confined concrete beam encased with the U-shaped thin-walled steel girder. It is also found that the load-bearing capacity of the CUSCPC beams with shear studs is increased by 5–10%, compared with the conventional PC members and the CUSCPC beams with no shear studs.