UHPC组合桥面板梯形湿接缝抗裂机理与计算方法

Crack Resistance Mechanism and Calculation Method for Trapezoidal Wet Joints in UHPC Composite Bridge Decks

摘要:

为研究钢-超高性能混凝土（UHPC）组合桥面板中梯形湿接缝的抗裂机理及裂缝宽度计算方法，依托背景工程设计制作了1个含湿接缝的桥面板足尺节段试件进行负弯矩纯弯荷载试验，结果表明：配置补强钢筋的情况下，虽然裂缝萌生于UHPC梯形湿接缝界面部位，但接缝部位的裂缝宽度为0.02和0.05 mm时，名义拉应力分别为10.3和12.9 MPa，实桥设计荷载下UHPC拉应力峰值3.84 MPa，可见湿接缝负弯矩抗裂性能较好，满足工程要求。同时，引入界面损伤本构和UHPC收缩效应开展有限元模拟和参数化分析，结果表明：UHPC收缩效应会在接缝部位产生较高拉应力，削弱其抗裂能力；初开裂荷载对接缝尺寸较敏感；采用增大直径的方法提高截面配筋率对接缝初裂荷载提升效果有限，直径从8 mm增加到16 mm，开裂荷载仅提高2%。此外，对比试验和公式计算结果可得，现有的混凝土裂缝宽度计算方法高估了UHPC接缝的抗裂性能，修正后的公式对接缝裂缝宽度的预测较好。

Abstract:

To study the crack resistance and width calculation method of trapezoidal wet joints in steel-ultra-high performance concrete （UHPC） bridge decks， one full-scale specimen with wet joints was designed and fabricated for a negative bending test. According to the test results， the cracks appeared at the interface of UHPC trapezoidal wet joints under the configuration of reinforcement， the nominal tensile stresses were 10.3 and 12.9 MPa at the crack widths of 0.02 and 0.05 mm at the joint， respectively， and the peak tensile stress of UHPC under the design load of the real bridge was 3.84 MPa， which showed that the wet joints with negative moments had a better performance of cracking resistance in line with the engineering requirements. Meanwhile， FE simulation and parametric analysis were carried out by introducing the damage principal and UHPC shrinkage effect. The results indicate that the UHPC shrinkage effect would lead to high tensile stress in the joint region， which would weaken its cracking resistance. The initial cracking load was more sensitive to the size of the joints， and increasing the diameter of reinforcements would have a slight improvement on the cracking resistance of the joints. The increase of the diameter from 8 mm to 16 mm only increases the cracking load by 2%. In addition， comparing the results of the tests and the formulae， it can be seen that the existing method of calculating the crack width of concrete overestimates the crack resistance of UHPC joints， and the modified formulae were better at predicting the crack width of joints.