钢-UHPC组合桥面板分段浇筑矩形接缝的轴拉性能

钢-UHPC(ultra-high performance concrete)组合桥面板中UHPC分段浇筑接缝导致局部的抗拉性能下降，可能引发严重的耐久性及安全问题。以实际工程中的组合桥面板UHPC矩形接缝为对象开展抗拉性能试验研究和理论分析。通过对组合桥面板接缝试件进行轴拉试验，考察了配筋率对矩形接缝区域抗裂性能的影响，揭示了矩形接缝的抗裂机理，探讨了接缝界面的黏结性能。试验结果表明：接缝开裂始于角隅处，接缝区域UHPC裂缝发展不明显，且接缝断裂面相对平整，属于脆性破坏。矩形接缝的抗裂机理分为横边抗裂与纵边抗脱离。接缝的抗裂能力取决于新旧UHPC界面的黏结强度，且接缝在轴拉状态下的界面黏结强度为3. 6～4. 7MPa。根据试验结果，对于处于轴拉状态下的UHPC矩形接缝，在按接缝不开裂或控制开裂宽度小于0.05mm进行设计时，构件的名义拉应力应分别低于3.5MPa或6.0MPa。此外，针对UHPC轴拉本构模型，基于能量等效原理及UHPC塑性简化模型，提出了UHPC软化段的等效残余抗拉强度，进而推导了配筋UHPC轴拉构件的主裂缝间距计算公式及接缝与UHPC主裂缝间距计算公式。对比试验结果，推导的主裂缝间距公式具有较好的精度，以期为实际工程应用提供理论参考。

Axial tension behavior of segmented-casting rectangular joint of steel-UHPC composite bridge deck

Segmented-casting UHPC joint of steel-UHPC composite bridge deck may lead to degradation of its local tensile performance, which may further result in severe durability and safety problem of bridge deck. Direct tensile test and theoretical analysis were conducted on UHPC rectangular joint of steel-UHPC composite bridge deck. Based on axial tension tests, the impact of reinforcement ratio on axial tension behavior of rectangular joint was investigated, the crack resistance mechanism of rectangular joint was explained, and the interfacial bond strength of UHPC was discussed. Test results show that the crack of rectangular joint initiated at the corner of rectangular joint. The crack of UHPC layer around joint didn’t propagate prominently, and fracture surface of joint is relatively flat compared with that of continuous UHPC layer. The crack resistance of transverse edges and slip resistance of longitudinal edges contribute to the crack resistance of rectangular joint. Bond strength of UHPC rectangular joint under axial tension is 3.6～4.7MPa. According to test results, for UHPC rectangular joint under axial tension, the recommended design axial tension of joint was lower than 3.5MPa and 6.0MPa for forbidding crack and allowing the maximum crack width of 0.05mm respectively. Besides, equivalent residual tensile strength of UHPC in the softening stage of axial tension constitutive model was proposed basedon energy equivalence principle and simplification of softening stage for UHPC axial tension constitutive model, and the calculation formula for main crack spacing of R-UHPC member under axial tension was derived. Compared with the experimental results, the derived formula for calculating crack spacing has a high accuracy, and could provide theoretical reference for practical engineering application.