Experimental study on seismic behavior of steel reinforced ultra-high strength concrete column-steel reinforced normal-strength concrete beam composite frame

To investigate the seismic behavior of steel reinforced ultra-high strength concrete (SRUHSC) column-steel reinforced normal-strength concrete (SRNSC) beam composite frame, two one-fourth scale two-span, three-story frame specimens were designed and constructed, and one of them is SRNSC frame. Low reversed cyclic loading tests were conducted on two frame specimens. The failure process and modes were described, meanwhile the hysteretic curves, skeleton curves, bearing capacity, displacement ductility, energy dissipation capacity, stiffness, and strength degradation were compared and analyzed. The research results show that the failure patterns of SRUHSC frame is similar to the SRNSC frame. When the experimental axial loading ratio is 0.38, the beam hinge failure mechanism is achieved for the two frames, and the hysteretic curves are plump. Moreover, the displacement ductility coefficients of two frames are all more than 3.0, which shows that the specimens have excellent seismic behavior with sufficient ductility. However, in terms of bearing capacity, displacement ductility, energy dissipation capacity, strength and stiffness degeneration, etc., SRUHSC column-SRNSC beam composite frame is totally better than the SRNSC frame, which indicates that encasing structural steel and high-strength stirrups into the ultra-high strength concrete is a good way for alleviating the problem of brittleness and improving structural carrying capacity by significantly making use of the compressive high strength property and enhancing the structural ductility. Therefore, the seismic performance of the SRUHSC column-SRNSC beam composite frame structure system is effectively improved. © 2016, Editorial Office of Journal of Building Structures. All right reserved.