Calculation Of Shear Capacity Of Concrete Slabs Considering Depth Of Shear Compression Zone And Shear Span Ratio

In the past experimental research on the shear bearing capacity of oblique sections of reinforced concrete structural members,in order to ensure the shear failure of oblique sections,the test specimens were often designed as "strong bending and weak shear".This makes the configuration of longitudinal tendons relatively large.When shear failure occurs,the tensile stress of longitudinal tendons is lower than the yield strength,and the pin action of longitudinal tendons contributes significantly to the shear capacity.In actual engineering,the bending moment and shear force of the control section of the continuous beam in the support and the control section of the beam end of the frame beam are large.According to the principle of "strong shear and weak bending",the control section of the continuous beam in the continuous beam and the control section of the beam end of the frame are subjected to tensile yield before shear failure,and the control section of the continuous beam in the continuous beam and the control section of the frame beam are subjected to shear loading.The force should not include the pinning effect of the longitudinal tendons.In the case of continuous beam internal control section and frame beam end section,the shear section and bending moment are simultaneously subjected to shear failure.According to the compression-shear correlation curve,the bending moment or the shear force is different,and the relative shear-compression zone height is also different.The factors that affect the bearing capacity of the control section of the bearing are not only related to the magnitude of the bending moment and shear force,but also to the ratio of the bending moment and shear force.These are not considered in current codes and standards.In order to investigate the influence of the relative shear compression zone height and shear span ratio on the shear bearing capacity of the control section of the concrete slab bearing under the premise of the tensile longitudinal tendon yielding,four different relative shear compression zone heights and different shear span ratios were designed and manufactured.Test piece and 1 loading box.The test piece consists of a board with only longitudinal ribs at the top of the board,upper and lower outrigger members penetrating the board at the free end of the board,a flat column with the same width as the board,and a bottom beam for rooting the flat column.With the help of the above test schemes,the shear tests of concrete slabs with 1.06%,1.20%,1.40%,and 1.60% of the longitudinal reinforcement ratio of the top tension of the slab were completed.The test results show that as the reinforcement ratio of the longitudinal reinforcement at the top of the concrete slab increases,the height of the bending-shear control section relative to the shear compression zone increases,the compressive stress and shear stress are coupled,and the shear strength of the concrete in the shear compression zone where the compression stress is greater Decreased,the shear strength of the concrete in the shear compression zone where the compressive stress is smaller increases.Based on the experimental data fitting,the calculation formulas of the shear capacity of the concrete slab considering the influence of the relative shear compression zone height and shear span ratio are obtained.