丫髻沙大桥桥面系加固设计

Strengthening Design of Floor System of Yajisha Bridge

针对丫髻沙大桥(主桥为主跨360m的三跨连续中承式钢管混凝土拱桥)运营期间桥面系出现的病害(部分纵梁、横梁连接处高强螺栓松动、断裂,连接角钢开裂、断裂,部分横梁腹板与下翼缘连接处焊缝开裂等),进行原因分析及桥面系加固设计。经分析,汽车荷载增加引起桥面系横梁的应力增加,降低钢结构的疲劳性能是引起桥面系病害的主要原因。加固设计活载维持原设计荷载标准不变,通过增设止裂孔,增加钢横梁截面,增设大纵梁,改变纵梁、横梁的连接方式对桥面系进行系统加固,采用有限元计算及试验检验了加固措施的安全性及有效性。

In the light of the deteriorations （the loosening and breaking of the high-strength bolts at connections of part of the stringers and cross beams, the cracking and breaking of part of the connecting angle steels and the cracking in the welding seams at connections of part of the cross beam webs and lower flanges） having occurred in the floor system of the Yajisha Bridge （the main bridge is a three-span half-through continuous concrete-filled steel tube arch bridge with a main span 360 m） in the operation period, the causes leading to the deteriorations were an-alyzed and the strengthening of the floor system of the bridge was designed. According to the a-nalysis, it was concluded that the main cause leading to the deteriorations was the increase of stress in the cross beams of the floor system and the decrease of fatigue performance of the steel structure caused by the increase of truck load. In the design, the live load criterion for the strengthening of the floor system remained unchanged and the floor system was to be systemati-cally strengthened by adding the crack stopping holes, increasing the sections of the cross beams and longitudinal girders and changing the connecting ways of the stringers and cross beams. Fi-nally, the safety and effectiveness of the strengthening measures were verified by the finite ele-ment calculation and tests.