UHPC箱梁桥面体系主要设计参数优化及试验研究

Main Design Parameters Optimization and Experimental Research on UHPC Box Deck System

为获取UHPC箱梁桥面体系主要设计参数的合理取值范围,以某单跨跨径102 m的UHPC简支箱梁桥为背景,通过单参数影响效应分析和ANSYS优化设计模块分析对桥面板厚度h 1、上弦板高度h 2、上弦板厚度b及上弦板间距L的合理取值进行优化设计,并对优化后的UHPC箱梁桥面体系开展1∶2缩尺模型试验和有限元模拟,最后对UHPC箱梁桥面体系抗裂性能参数(上弦板受拉钢筋直径和上弦板高度)进行分析。结果表明:h 1、h 2、b和L合理取值范围分别为UHPC单箱室顶板(不含翼缘)横向跨度的1/40~1/35、1/10~1/8、1/37~1/31和1/2.8~1/1.4,对于背景工程h 1、h 2、b应分别不小于14、55、15 cm,L应不大于4 m;ANSYS优化结果与力学特性指标优化结果参数取值较为接近,优化后背景工程全桥UHPC体积减少约11.0%;试验梁上弦板发生面内受弯破坏,为UHPC箱梁桥面体系最不利受力部件;试验梁开裂应力值是正常使用极限状态设计值的2.14倍,具有较高安全储备,优化方案能满足工程应用要求;增大上弦板受拉钢筋直径及上弦板高度整体上可有效提高UHPC箱梁桥面体系的抗裂性能。

The reasonable ranges of primary design parameters of the deck system consisting of UHPC box girders,UHPC panels and UHPC stitching joints between panels are studied.An existing simply-supported UHPC box girder bridge spanning 102 m is used as a case.The parameters,including UHPC panel thickness h 1,the diaphragm depth h 2,diaphragm thickness b,and diaphragm interval L,were optimized based on the single parameter influential effect analysis and design optimization simulated in ANSYS.A 1∶2 scale-down mockup of the UHPC deck after optimization was prepared for tests,and finite element analysis was conducted.The parameters associated with the anti-cracking performance of the UHPC deck(diameter of tension rebars in the diaphragms and diaphragm depth)were analyzed.It was concluded that the reasonable ranges of h 1、h 2、b and L are 1/40-1/35,1/10-1/8,1/37-1/31,and 1/2.8-1/1.4 of the transverse spanning of the top plate(exclusive of flanges)of the single-cell UHPC box girder,respectively.The values of h 1,h 2 and b should not be less than 14,55 and 15 cm,and L should not exceed 4 m.The optimization in ANSYS basically agrees with the optimization of the indexes of the mechanical property of the UHPC deck,resulting in 11.0%saving of the UHPC used for the whole bridge.The diaphragms are prone to lateral bending failure(in the surface),which are considered the components under most adverse loading condition.The stresses causing cracks are 2.14 times of the design values,indicating large safety margin.Enlarging the diameter of tension rebars in the diaphragms and increasing the depth of diaphragms can effectively improve the anti-cracking performance of the UHPC deck system.