某正交异性板钢箱梁斜拉桥UHPC组合桥面改造方案研究

某跨江大桥为主跨460m的斜拉桥,运营多年后正交异性板钢箱梁出现大量裂纹,提出采用超高性能混凝土(UHPC)组合桥面(由配钢筋网的UHPC层与钢桥面板通过短栓钉组合而成)进行改造。为选择合适的改造方案,采用有限元法建立原钢箱梁和UHPC组合桥面钢箱梁(UHPC层厚4.5,5.5,6.0cm)模型,分析各疲劳细节应力及UHPC层应力;开展UHPC层配置钢板条的组合结构模型试验,验证其疲劳性能。结果表明:UHPC组合桥面降低了钢箱梁各疲劳细节最大应力幅,降幅为11%~88%,顶板疲劳细节处裂纹尖端最大应力幅降幅达92%;疲劳荷载作用下,UHPC层顶面应力较低,钢桥面板开裂后UHPC层底面应力较大;采用钢板条对5.5cm厚UHPC层的组合结构加强后,UHPC层名义开裂应力达43.2MPa,200万次疲劳寿命达22.1MPa,疲劳性能满足要求,选择该方案进行改造。

Study of Renovation Schemes for UHPC Composite Deck of a Steel Box Girder Cable-Stayed Bridge with Orthotropic Deck

A river-crossing bridge is a cable-stayed bridge with a main span of 460 m.After many years of operation,an array of cracks occur in the steel box girder and orthotropic bridge deck,and to address the cracking problem,a renovation plan of using ultra-high performance concrete(UHPC)composite deck is proposed.The UHPC layer with reinforcement mesh is supposed to connect with the steel deck plates via short bolts.To figure out the proper renovation solution,the finite element method was used to establish the models of the original steel box girder and the steel box girder covered with UHPC composite deck(the UHPC layer was set at 4.5,5.5,and6.0 cm,respectively),to analyze the stresses in each fatigue detail and the UHPC layer.Model test was also carried out to verify the fatigue performance of the composite structure containing UHPC layer and steel plate strips.The results show that the UHPC composite deck reduces the maximum stress amplitude of each fatigue detail in the steel box girder,by about 11% to 88%,and the maximum stress amplitude at the crack tips in the fatigue details of top plate decreases by92%.The stresses in the top face of the UHPC layer are low under the action of fatigue loads,and when there are cracks in the steel deck plates,the stresses in the base of the UHPC layer are great.When the composite structure with 5.5 cm-thick UHPC layer is strengthened by steel plate strips,the nominal cracking stress in the UHPC layer reaches up to 43.2 MPa,and the fatigue life is of 22.1 MPa under 2 million numerical cycles.All the data prove that the fatigue performance of the UHPC composite deck meets the requirements,and the renovation solution was employed.