FRP-胶合木-UHPC组合梁桥设计与试验

Design and experiment of FRP-Glulam-UHPC composite girder bridge

为适应我国桥梁建设环境友好转型发展的需要,并针对传统木-混凝土组合梁自重大、长期变形大及耐久性不足,难以应用到中等跨径桥梁的问题,提出一种可整体预制、整跨吊装的FRP-胶合木-UHPC组合梁桥。对20m、30m跨径的FRP-胶合木-UHPC组合梁桥试设计,并与同等跨径的传统木-混凝土组合梁桥和预应力混凝土梁桥进行材料用量和经济性的对比;对30m跨径的试设计桥梁进行荷载组合效应计算,根据计算结果以中国桥梁设计规范为基础,同时参考欧洲规范5,基于弹性设计法对FRP-胶合木-UHPC组合梁桥的承载能力极限状态和正常使用极限状态进行设计计算;对30m跨径的试设计桥梁按照纵向1∶5的比例缩尺,设计制作了2根试验梁模型,并进行试验研究。研究结果表明:20m跨径的试设计桥梁的自重分别减至传统木-混凝土组合梁和预应力混凝土梁的72.7%和48.0%,全寿命造价分别为二者的79.1%及106.4%;30m跨径的试设计桥梁的自重减至预应力混凝土梁的49.3%,全寿命造价为它的134.0%;试设计FRP-胶合木-UHPC组合梁桥具有足够的抗弯与抗剪承载力,活载作用下的结构挠度小于限值,满足工程受力要求;按照欧洲规范5进行设计,结构具有较大安全储备,理论计算偏安全;FRP的植入使组合梁的极限承载能力提高了约8.6%,并能改善其破坏形态、提高延性。

The FRP-Glulam-UHPC composite girder bridge which can be fully precast and integrally hoisted was proposed, in order to meet the demands from environment-friendly transition and development of bridge construction in China, and in order to address the ever-existing problems for conventional timber-concrete composite girder, including heavy dead weight, large long-term deflection and inadequate durability, which make it hard to be applied to medium-span bridges.The material consumption and economical efficiency of trial design of 20 m and 30 m span FRP-Glulam-UHPC composite girder bridge were compared with those of conventional timber-concrete composite girder bridge and prestressed concrete girder bridge with the same span;the design value of load combination for the 30 m-span trial bridge were obtained by calculation, and based on the calculated value, the domestic bridge codes and Eurocode 5 were adopted for structural analyses in ultimate limit state and serviceability limit state using the elastic design method.Two test models were designed and manufactured according to the scaled 30 m-span trial bridge at the longitudinal ratio of 1∶5, and the detailed experimental study was conducted.The findings show that the dead weight of 20 m-span trial bridge girder can be reduced to 72.7% and 48.0% of the conventional timber-concrete composite girder and prestressed concrete girder, respectively, while its life cycle cost is 79.1% and 106.4% of the above two bridge types.The dead weightof 30 m-span trial bridge girder can be reduced to 49.3% of the prestressed concrete girder, while its life cycle cost is 134.0% of the prestressed concrete girder.The flexural and shear behaviors of the trial FRP-Glulam-UHPC composite girder bridge meet the requirement of engineering application, while the structural deflection under living load is less than limit value, indicating that the bridge has enough rigidity.The FRP-Glulam-UHPC composite girder bridge designed based on Eurocode 5 has large safety reserve, revealing that the design method is relatively conservative.With the application of FRP, the bearing capacity of the composite girder can be increased by 8.6%, and the failure pattern can be improved with good ductility.