Experimental Research On Small Span-to-Depth Ratio Coupling Beams With PVA Fiber Reinforced Concrete

The coupling beams in reinforced concrete coupled shear wall are key components to seismic behavior used in tall building, which play a link role between the wall limbs. Under earthquake excitation, the reasonable design of coupling beams of shear wall yield firstly, then the earthquake energy will be dissipated through the plastic hinge. Because of the limited size of the hole, the span-depth ratio of coupling beam is usually smaller and the nominal shear stress is higher. The coupling beams which have higher stiffness are dominated by shear deformation. A new type of fiber reinforced composite is applied to coupling beams in this test in order to change the failure mode into ductile failure, which will improve seismic performance. The results show that the addition of fiber could postpone coupling beam’s cracking, and improve significantly the spalling state of the coupling beam specimens and the maximum carrying capacity of coupling beams. Fiber reinforced concrete coupling beam has good energy dissipation capacity and its displacement ductility is also increased.In this paper, two beams of fiber reinforced concrete and a coupling beam of normal concrete is made. And a coupling beam of normal concrete as contrast specimen. Seismic performance and shear performance of the fiber reinforced concrete coupling beams are analyzed. The main research content is as follows.(1)In this experiment, fiber reinforced concrete is used instead of the normal concrete to make two beams of fiber reinforced concrete. Fiber reinforced concrete has the following materials: domestic polyvinyl alcohol fibers, the local ordinary Portland cement in Shanxi, natural river sand in xi’an region of Shanxi province, water in xi ’an region of Shanxi province, the fly ash, water reducing agent. The domestic polyvinyl alcohol fibers and the local material in Shanxi in fiber reinforced concrete coupling beam is the difference between this test and other test.(2) The failure mode, hysteretic property, ductility, energy dissipation, strength degradation, stiffness degradation and the effect of seismic behavior of the coupling beam of fiber reinforced concrete and normal concrete are analyzed.(3) Based on this experiment and existing research results, combining the coupling beams in code for design of concrete structure and the steel fiber reinforced concrete coupling beams in specification of fiber concrete structure of our country, calculation formulas for the fiber reinforced concrete coupling beams are set up.(4) According to the law of fracture development, failure mode and the stain distribution of rebar of fiber reinforced concrete coupling beams, the computing mechanism of strut-and-tie model for the fiber reinforced concrete coupling beams with diagonal bars is analyzed. By the comparison of the calculation results with the measured values, a calculation formulas for the fiber reinforced concrete coupling beams with diagonal bars is proposed.