斜拉桥钢-UHPC组合桥面分次浇筑接缝抗裂性能

Cracking Resistance of Segmented-casting Joints in Cable-stayed Bridge with Steel-UHPC Composite Deck

因较好解决了钢桥面疲劳开裂和沥青铺装层易破损问题,钢-UHPC(Ultra-high Performance Concrete,超高性能混凝土)轻型组合桥面在新建斜拉桥中逐步推广;然而,宽幅钢-UHPC轻型组合桥面不可避免地涉及分次浇筑,接缝处钢纤维拉接作用失效,导致接缝抗裂强度显著下降。为了有效降低分次浇筑接缝处UHPC桥面与铺装层的病害风险,开展了多型UHPC接缝的抗裂性能试验与对比分析。采用多尺度有限元仿真分析斜拉桥的全过程受力状态,计算识别出宽幅钢-UHPC桥面在施工和运营阶段的高拉应力区域,据此制定了斜拉桥UHPC分次浇筑接缝的设置原则。设计了五型UHPC分次浇筑接缝供工程比选,包括加粗钢筋接缝、斜向接缝、锯齿接缝、矩形接缝和异形钢板接缝;含对照组,共制作了7组UHPC接缝试件开展直拉试验,根据测试得到的最大裂缝宽度-应力曲线进行了UHPC分次浇筑接缝的抗裂性能对比分析。分析表明:斜拉桥施工阶段的UHPC层高开裂风险区明显不同于运营阶段,施工体系转换将使得最大拉应力峰值达7.543 MPa,超过了传统凿毛接缝的初裂名义应力。试验表明:与整体浇筑试件相比,传统凿毛接缝抗裂性能最差,初裂名义应力降低幅值高达78%;加粗钢筋接缝与斜向接缝的抗裂性能相当,初裂名义应力降低幅值分别为34%与35%;锯齿接缝、矩形接缝与异形板接缝抗裂性能优越,初裂名义应力降低幅值最大仅为16%左右。综合考虑异形钢板接缝的抗裂性能与施工便利性,推荐为应用工程实施方案。

As the fatigue cracking of steel decks and the vulnerability of asphalt pavements are well solved,steel-ultra-high-performance concrete(UHPC)light composite decks are gradually being widely employed in new cable-stayed bridges;however,the wide-width steel-UHPC light composite bridge deck inevitably involves partial pouring,and the tensile action of the steel fiber at the joint fails,resulting in a significant decline in the crack resistance of the joint.To effectively reduce the risk of damage to the steel bridge deck and pavement at the segment-casting joint,a crack resistance test and comparative analysis of multiple types of UHPC joints were conducted.The multiscale finite element method was adopted to simulate and analyze the entire process stress state of the cable-stayed bridge,and the high tensile stress area of the wide steel-UHPC bridge deck in the construction and service stages was identified,then the setting principle of the UHPC segment-casting joints of the cable-stayed bridge was formulated.Five types of UHPC segment-casting joints were designed for engineering comparison and selection,including thickened reinforcement-enhanced wet joints,oblique wet joints,serrated wet joints,rectangular wet joints,and irregular-shaped steel plate-enhanced wet joints.Including the control group,a total of seven groups of UHPC joint specimens were established for the direct tension test.A comparative analysis of the cracking performance of the UHPC segment-casting joints was performed according to the maximum crack width-stress curve obtained from the test.The analysis and tests demonstrate that the high-crack risk zone of UHPC layer in the construction phase of the cable-stayed bridge significantly differs from that in the service phase,and the maximum tensile stress peak reached 7.543 MPa due to the transformation of construction system,which exceeds the nominal initial crack stress of traditional chiseling-grossness wet joints.Compared with integrally cast specimen,the cracking resistance of the traditional chiseling-grossness wet joint was the worst,the reduction amplitude of the nominal initial crack stress of that reached 78%.The cracking resistances of the thickened reinforcement-enhanced wet joints and oblique wet joints were equivalent,the reduction amplitudes of the nominal initial crack stress were 34%and 35%,respectively.The cracking performance of the serrated wet joints,rectangular wet joints,and special-shaped steel plate-enhanced wet joints were superior,and the maximum reduction amplitude of the nominal initial crack stress was only 16%.The cracking performance of the irregular shaped steel-plate-enhanced wet joints is superior to that of the other joints.Thus,it is recommended as a comparison scheme and is applied to support projects.