Tomoya TAKAHASHI

Evaluation equations for ultimate shear capacity and allowable shear strength of SFRC shear walls were proposed, and their validity was examined using the results of previous experiments and analysis. It was confirmed that the experimental maximum shear capacity could be evaluated accurately and on the safe side by using an equation that accumulates the shear strength that steel fibers can bear to the shear capacity equation (truss-arch mechanism) for RC shear walls. In addition, it was confirmed that the experimental maximum capacity could be simulated using a finite element analysis model that simplified the SFRC material properties.

In-plane cyclic loading tests were performed to examine the flexural properties of SFRC walls. The test results revealed that steel fiber reinforcement mitigated damage to the walls and enhanced deformation performance. Steel fibers also increase both flexural and shear capacities and suppress shear stiffness degradation after shear cracking. By taking these factors into account, skeleton curves that fit experimental results were obtained. SFRC specimen with 0.30% wall reinforcement and shear to flexural capacity ratio of 1.00 showed superior deformation performance than RC specimen with 1.13% reinforcement and the ratio of 1.14. SFRC increases the toughness performance of walls.

Concrete short-span beams might suffer bond splitting failure during a large earthquake due to their short development length. Steel Fiber-Reinforced Concrete is known to be effective in enhancing the performance of concrete members. However, there are not many studies on bond splitting failure of Steel Fiber-Reinforced Concrete members. Therefore, we carried out bond splitting tests of Steel FiberReinforced Concrete assuming corner and side split type failures. We proposed an evaluation method for bond splitting strength considering their material properties. In addition, the evaluation method was verified using the results of tests of short-span Steel FiberReinforced Concrete beams.

Concrete short-span beams might suffer severe damage during a large earthquake. Steel Fiber-Reinforced Concrete is known to be effective for increasing the resilience of concrete members. However, there are not many studies that relate its material properties to improvement in structural performance of Steel Fiber-Reinforced Concrete members. Static loading tests using short-span Steel FiberReinforced Concrete beams of the shear-failure type were carried out to evaluate its shear properties. Based on the experimental results including others, formulas to evaluate shear strength considering material properties were proposed.

The quantitative evaluation of tensile ductility of steel fiber reinforced concrete (design strength 30-60 MPa) containing 0.5-1.0% steel fiber with hooks at the ends was investigated. The maximum value of tensile stress after cracking in the tensile softening curve could be roughly evaluated by the linear formula of compressive strength. The influence of aggregate type, coarse aggregate content and air content on the formula was relatively small. Similarly, the average value of tensile stress up to 1 mm crack width in the tensile softening curve could be roughly evaluated by the linear formula of compressive strength.

In-plane lateral loading tests were conducted to investigate the structural performance of SFRC shear walls. The test results revealed that steel fiber reinforcement mitigated damage to the walls and enhanced their shear capacity. The number of shear cracks on the SFRC walls at an interstory-drift angle of 1/200 was twice as significant as on the RC wall, and the maximum and residual crack widths were approximately half. Shear stiffness degradation after cracking reduced as the steel-fiber volume ratio increased. 0.5% and 1.0% steel-fiber volume ratios increased the maximum shear capacities by 11% and 17%, respectively.

In this study, flexure and shear tests were conducted to clarify the structural performance of reinforced concrete beam with plastic hinge relocation methods. The main parameters were shape of cross section (T-shape, Rectangular), method of hinge relocation (Mechanical reinforcing bar splice, Cut-off), distance from stub face of relocated critical section, shear span ratio, and amount of transverse reinforcement. The study has revealed that the restoring force characteristics and the failure mode of the beam can be evaluated by using evaluation formulas currently in use.