Experimental Investigation On Seismic Behavior Of High-Strength Concrete Interior Joints Partially Reinforced By Steel Fiber

Because of its high strength, durability and light weight, high strength concrete is widely used in high-rise buildings. But it also has little ultimate deformation and brittle failure state. Steel fiber reinforced concrete can not only bring excellent mechanical properties in tension, bending moment and shear, but also have better effects on improving the ductility and the energy dissipation capacity of the frame joints. The experimental research of six steel fiber reinforced high-strength concrete frame interior joints with the low cyclic reversed loading method has been conducted. The influences of steel fiber volume ratio and stirrup ratio on the seismic performance are investigated. The main contents are as follows:(1) The phenomena of the specimens that contain crack-modes and the failure pattern were described. It shows that the steel fiber has better effects on blocking the development of cracks and increasing the cracking load of the frame joints.(2) The ratio of the longitudinal displacement due to kinds of deformation to global displacement of the frame as well as their regularities was analyzed. And the effects of steel fiber volume ratio and stirrup ratio on the seismic behavior were discussed. It shows that the steel fiber could improve the deformation behavior of beam and change the position of the plastic hinge. Increasing the steel fiber volume ratio or stirrup ratio could decrease shear deformation in joint core and its ratio to the global displacement.(3) Strains of reinforcement in joints were analyzed. It is demonstrated that the steel fiber could decrease the strains of reinforcement and increase the ultimate strength.(4) Through measuring hysteretic curves and skeleton curves of the specimens, the seismic performance of the frame interior joints such as ductility, performance degradation and energy dissipation capacity were analyzed. It shows that, with the steel fiber volume ratio raised, hysteretic curves are more ductile, ductility and energy dissipation capacity have made a remarkable improvement, and the performance would degrade slower. Using the steel fiber in place of the stirrup in the high strength reinforced concrete frame joints could improve the seismic behavior.