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In order to study the seismic behavior of CFRP-reinforced seismic-damaged joints in composite frame consisting of concrete-filled square steel tubular (CFSST) columns and steel beams, four one half scaled models of exterior joints in composite frame consisting of CFSST columns and steel beams were designed and manufactured. The test consisted of pre-damage loading, rehabilitation with CFRP and destruction tests under lateral cyclic loading. The effectiveness of CFRP-strengthened seismic-damaged joints and the reinforcement effect on different levels of seismic damage were studied. Based on the test data, the hysteretic loops, skeleton curves, the CFRP strain, ductility, dissipative ability, ultimate strength and stiffness degradation, etc. were obtained. Results show that CFRP-strengthened seismic-damaged exterior joints in composite frame consisting of CFSST columns and steel beams meets the strong column-weak beam requirement of seismic design, and the failure modes of all joints are bending failure of beam. The reinforcement with CFRP has a significant on increasing the ultimate capacity and the seismic behaviors of the joints. The study indicates the rehabilitated joints can reach or even exceed the level of their original seismic performances before seismic damage in a certain extent of damage level. [ABSTRACT FROM AUTHOR]

To study the seismic behavior of unsymmetrical steel reinforced concrete column, cyclic loading tests were carried out on 12 columns with T-shaped section steel and 12 columns with L-shaped section steel. The test parameters included shear span ratio, axial compression ratio, stirrup ratio and presence of cross tie. Mechanical process, failure mode, hysteretic characteristics, skeleton curves, ductility and energy dissipation ability were taken into comparison. The result indicates that unsymmetrical steel reinforced concrete column possesses good seismic performance under constant axial compression and cyclic horizontal load. The failure modes include bonding failure, shear-bond failure, shear compression failure and shear-composition failure. Obvious asymmetry phenomenon of positive and negative hysteresis loop are shown. The span ratio has great influence on failure mode and shear-composition failure usually takes place in L-shaped steel section column. With the increase of axial compression ratio, the ductility decreases, which is obvious in L-shaped steel section column. The ductility and bearing capacity of the T-shaped steel section columns are improved greatly with the increase of stirrup ratio, but not obvious for T-shaped steel section column with smaller span ratio. Cross ties can improve bearing capacity, limit strength and stiffness degradation and enhance deformation capacity of L-shape steel section columns clearly. [ABSTRACT FROM AUTHOR]