UHPC在圬工拱桥加固中的应用

Application of UHPC to Strengthen Masonry Arch Bridge

为研究超高性能混凝土(UHPC)在圬工拱桥加固中的适用性,针对贵州省2座在役实腹式圬工拱桥的拱圈病害,提出采用UHPC加固,并开展加固设计、施工和荷载试验研究。参考钢筋混凝土增大截面法,在红岩桥(三跨14.14 m实腹式石拱桥)上开展试应用,拱腹增设15 cm厚UHPC加固层,加固层同原结构采用植筋方式粘结;在此基础上,采用极限分析法,分别考虑界面粘结良好和界面脱粘2种状况,对七星关桥(跨径20 m通行重载交通实腹式石拱桥)开展了分析,从偏安全的角度,采用了原拱圈下缘增设12 cm厚、两侧增设10 cm宽UHPC加固层的方案。结果表明:UHPC加固拱桥的施工工艺可借鉴传统钢筋混凝土增大截面法,其施工质量优于后者;界面植筋能够保障UHPC层与原结构协同受力,考虑界面脱粘的加固设计偏安全;加固后2座圬工拱桥运营状况良好,UHPC在圬工拱桥加固中有较好的应用前景。

Two in-service solid spandrel masonry arch bridges in Guizhou Province were strengthened with ultra-high performance concrete(UHPC)to remedy the arch deteriorations.Based on these two cases,the applicability of using UHPC to strengthen masonry arch bridges has been researched,and studies on the strengthening design,implementation and load tests have been performed.The Hongyan Bridge(a solid spandrel stone arch bridge with three spans of 14.14 m)was retrofitted by adding reinforced concrete to enlarge the cross section of the arch,where a 15 cm-thick UHPC course was placed onto the arch soffit and bonded with the original structure via the planted reinforcing bars.The Qixingguan Bridge(a solid spandrel stone arch bridge with span length of 20 m)had no limitation to heavy-loaded vehicles before rehabilitation.The strengthening effect of UHPC on the bridge was analyzed by the limit analysis method in the two scenarios of effective interface bonding and interface debonding.Considering a conservative safety margin,the bridge was strengthened by encasing the soffit with 12 cm-thick UHPC course,and the course was extended out to the spandrel wall,forming 10 cm-wide flangings.It is shown that the UHPC can be utilized together with reinforcing bars for structural rehabilitation in the manner of enlarging the cross-section of the original structures,and the strengthening effect is better than normal concrete.By planting reinforcing bars,the UHPC course can collaborate with the original structure to carry loads,and the reinforcement design considering interface debonding leaves conservative safety margin.After rehabilitation,the two masonry arch bridges are in good service condition.UHPC is a promising material for masonry arch bridge rehabilitation.