高温后高强混凝土剪切裂缝与拉剪箍筋销栓作用

为研究高温后高强混凝土的剪切裂缝和拉剪箍筋销栓作用,浇筑了两种强度高强混凝土Z形试件.分别对试件进行了200,400,800°C的高温试验,通过高温后试件的直剪试验,研究了温度和混凝土强度对剪切裂缝的影响.基于弹性地基梁理论建立了箍筋销栓作用模型,结合实测的剪切裂缝宽度和裂缝滑移,计算得到高温后高强混凝土与箍筋之间的销栓剪应力.研究结果表明:除200°C以外,高强混凝土的裂缝峰值位移(裂缝峰值宽度和裂缝峰值滑移)随温度的升高而增大;无论经历多高的温度,混凝土的强度越高,裂缝峰值位移越小;箍筋的销栓剪切应力与裂缝滑移呈线性关系,销栓剪切刚度随温度的升高而降低,随混凝土强度的增大而增大;销栓剪切应力随温度的升高而增大,随混凝土强度增大而减小.

Shear Crack and Tensile shear Stirrup Dowel Action of HSC After Elevated Temperatures

In order to study the shear crack and the tensile shear stirrup dowel action of high strength concrete (HSC) after elevated temperatures, two Z shaped HSC specimens were cast. After being exposed to 200°C, 400°C and 800°C, the push off tests of specimens were conducted to study the effect of the elevated temperature and the concrete strength on the shear crack. The dowel action model was developed based on the beam on elastic foundation theory, and the dowel shear stress between HSC and stirrup after elevated temperatures was calculated in combination with the measured crack width and crack slip. The results show that except for an exposed temperature of 200°C, the crack peak deformation (crack peak width and crack peak slip) increases with the increase of temperature. As the strength of concrete (at any temperature) increases, the peak crack deformation decreases. The dowel shear stress of the stirrup exhibits a linear relationship with the crack slip, and the dowel shear stiffness reduces as the exposed temperature rises and increases as the concrete strength increases. The dowel shear stress increases as the exposed temperature rises and reduces as the concrete strength increases.