后浇UHTCC既有混凝土复合梁弯曲疲劳性能试验研究

Experimental study on flexural fatigue property of existing concrete beams restricted by post-poured UHTCC layer

为研究疲劳荷载作用下超高韧性水泥基复合材料(UHTCC)对混凝土的增强作用,将UHTCC外浇层作为保护层,对既有着混凝土梁体一侧浇注UHTCC而制成的UHTCC/混凝土复合梁(UC复合梁)进行三点弯曲疲劳加载试验.实验结果表明:在疲劳荷载作用下,UC梁截面变形符合平截面假定;UHTCC层产生若干条可见裂缝,其数目随应力水平的下降而减少,混凝土层裂缝数目为1～3;复合梁随荷载循环的疲劳变形曲线表现出延性特征,呈现三阶段发展,变形能力随应力水平的下降而降低;在高周疲劳情况下,复合梁S-N双对数疲劳曲线线性良好.由此表明,利用超高韧性水泥基复合材料作为保护层能分散既有混凝土的表面裂缝,提高复合梁的变形能力和寿命.

In order to investigate the enhancing effect of ultra-high toughness cementitious composites（UHTCC） on plain concrete under fatigue loads,three-point flexural fatigue tests on existing concrete beam with new UHTCC layer（UC composite beam） being poured on one side were carried out.The experimental results show that the plane section assumption is applicable for the UC beams under fatigue loads.Several visible cracks are formed in the UHTCC layer.The number of the cracks decreases with the decrease of the stress levels,while 1 to 3 cracks are observed in the concrete layer.The multiple-cracking characteristic of the composite beam exhibits three-stage ductile fatigue deformation,and the deformation ability decreases with the decrease of the fatigue stress levels.Under high cycle fatigue,the S-N bi-logarithm curve behaves linearly.Therefore,UHTCC can be used as a protective layer to redistribute and disperse the fatigue cracks in the existing concrete.It can increase the deformation capacity and prolong the fatigue life of the composite beam.