Experimental study on the seismic behavior of steel

A research program on the seismic behavior of steel-reinforced ultra-high-strength concrete exterior joints is conducted herein by testing 11 specimens under a reversed cyclic loading profile. This study analyzes the testing results in terms of the load–displacement relationship, ductility, energy dissipation capacity, strength and stiffness degradations, steel panel strain, and confinement in the specimen joints. The axial compression and stirrup volumetric ratios are two significant parameters dominating the shear behavior of the steel-reinforced ultra-high-strength concrete frame exterior joints. The effect of the axial compression ratio on the shear capacity of the steel-reinforced ultra-high-strength concrete frame exterior joints characterized by a dividing point is also proposed. Furthermore, a design formula for the shear strength of the joint core area is derived using the strain analysis method with the shear model that considers the inner concrete compression strut, outer concrete compression strut, steel web panel shear mechanisms, and stirrup confinement mechanisms. The formula is verified by the experiment results