无腹筋部分预应力UHPC薄腹梁抗剪性能试验研究

Study on Shear Resistance of Partially Prestressed UHPC Thin-web Beams without Web Reinforcement

为研究高强钢筋无腹筋部分预应力UHPC薄腹梁的抗剪性能,对7根不同剪跨比和预应力度的试验梁进行抗剪试验,验证其平截面假定,并对其承载力、延性、斜裂缝倾角及宽度、预应力筋应力增量和挠度等进行分析。研究结果表明:试验梁不完全满足平截面假定;梁的极限承载能力随剪跨比的增加而减小、随预应力度的增加而增大,延性的变化规律与之相反;斜裂缝倾角和宽度均随剪跨比和预应力度的增加而减小;同级荷载下预应力筋的应力增量随剪跨比的减小和预应力度的增加而减小。弹性阶段预应力度越大,梁的反拱值越大,挠度越小;弹塑性阶段剪跨比越大,梁的变形越大,刚度退化越快。提出高强钢筋部分预应力UHPC梁抗剪承载力计算的建议公式。

In order to study the shear performance of high-strength reinforced partially-prestressed UHPC thin-web beams without web reinforcement,shear tests were conducted on seven test beams with different shear span ratios and prestress degrees to verify the assumption of plane section,and to analyze their bearing capacity,ductility,angle and width of diagonal cracks on the beam,stress increment and deflection of prestressed tendons.The results show that the test beams do not fully meet the plane section assumption.The ultimate bearing capacity decreases with the increase of the shear span ratio and increases with the increase of the degree of prestress while the variation of ductility is opposite.The critical shear angle and width decrease with the increase of shear span ratio and prestress degree.The stress increment of prestressed tendons under the same load decreases with the decrease of shear span ratio and the increase of prestress degree.The bigger the prestress degree in elastic stage,the greater the value of the inverse arch and the smaller the deflection.The larger the shear span ratio in the elastic-plastic stage,the greater the deformation of the beam,and the faster the stiffness degradation.Recommended formulas for calculating shear capacity of partially prestressed UHPC beams with high strength reinforcement are proposed.