800m级钢-UHPC组合桁式拱桥概念设计与可行性研究

提出了一种特大跨径钢-UHPC组合桁式拱桥新体系。新体系拱桥用UHPC箱型拱肋承受巨大的轴力,采用钢腹杆钢横联规避开裂的风险;相比传统混凝土拱桥,新体系拱桥自重大幅度降低;相比钢拱桥,其不存在厚板焊接困难的问题;采用斜拉扣挂分多次悬臂合龙施工法,扣索只需承受单次合龙的主拱自重并多次循环利用,施工临时措施费用大大降低,因而具有良好的经济性。通过对跨径800m的钢-UHPC组合桁式拱桥的试设计,结果表明:主拱分3次合龙时,斜拉扣挂只需承担36%的主拱自重,拱肋最大压应力为64.9 MPa,无拉应力,各施工阶段的稳定性、应力、刚度等均满足要求。平均每平米桥面主拱圈材料用量指标为:钢材380kg,UHPC 0.61m3,自重2.03t。对比研究表明新型钢-UHPC组合桁式拱桥具有显著的技术经济优势,可适用于500~1 000m级跨径的拱桥。

Conceptual Design and Feasibility Study of an 800 m Scale Steel-UHPC Composite Truss Arch Bridge

A new design for a super-long-span steel-ultra-high-performance-concrete (UHPC) composite truss arch bridge was proposed in which the UHPC was applied to box arch ribs for bearing large axial forces, and steel was used for web members and transversal connectors to avoid the risk of cracking. This type of composite arch bridge has a much lower deadweight than traditional concrete arch bridges and avoids the need for welding on thick steel plates as compared to steel arch bridges. The cantilever construction method that employs several iterations of closure processes was adopted during the erection of main arch segments. In this scope, the temporary erection cables must merely bear the deadweight of two truss arches and transversal connectors during each closure and are recycled several times, thereby considerably reducing the cost of temporary supports for construction. Therefore, it has good economy. A trial design of a steel-UHPC composite truss arch bridge with a main span of 800 m was proposed. The results reveal that only approximately 36% of the main arch's self-weight is borne by the erection cables if the cyclic construction method with three closure processes is applied. The UHPC arch ribs are always in compression at a maximum compressive stress of 64.9 MPa. In addition, the stability, stress, and stiffness of each component during each construction stage meet the requirements of the code. The average material consumption index of the main arch per square meter is:steel of 380 kg, UHPC of 0.61 m³, and deadweight of 2.03 t. The comparative study shows that the steel-UHPC composite truss arch bridge has significant technical and economic advantages and is suitable for a bridge with a main span in the range of 500-1 000 m.