大跨径T梁体外预应力加固锚固块设计研究

Research on Anchoring External Prestressing Tendons with Wedges in Long-Span T Beam Strengthening

针对大跨径T形梁桥体外预应力加固中,普通混凝土结构锚固块构件普遍存在尺寸大、增加恒载多、施工复杂、工期长等问题,以某公路跨黄河特大桥为背景(主桥采用77×50 m预应力混凝土T梁),设计高强耐候钢结构和超高性能混凝土(UHPC)2种锚固块,分析2种体外预应力加固锚固块的可行性。采用有限元软件建立2种锚固块及T梁实体模型,分析锚固块应力和变形,以及T梁锚固区局部应力,结果显示2种锚固块应力和变形及T梁锚固区应力均满足设计要求。考虑施工、造价等方面,选择高强耐候钢结构锚固块方案,并在该桥上进行试验跨研究,试验结果表明:高强耐候钢结构锚固块的应力和位移均在理论设计限值内,该体外预应力加固锚固块技术可行。

In the strengthening of long-span T beam bridges with external prestressing tendons,the wedges made of normal concrete are often large,which will add excessive dead loads to the structure and are not favorable in terms of the ease-of-construction and schedule.A Yellow River road bridge was taken as a case for the study.The superstructure of the main bridge consists of 77 spans of 50 m-long prestressed concrete T beams.Two types of wedges were prepared,including the high-strength weathering steel wedges and UHPC wedges,and the feasibility of the two types of wedges in anchoring external prestressing tendons was analyzed.The solid finite element models of the two types of wedges as well as the T beam were established to analyze the stress condition and deformation of the wedges as well as the local stresses in the anchor region of the T beam.The results meet design requirements.However,the wedges made of high-strength weathering steel are recommended out of the construction and cost consideration.And the wedges were installed in a span of the Yellow River bridge for test.The results demonstrate that the stresses and displacement of the wedges made of high-strength weathering steel are within the theoretical design range and the proposal of using the steel wedges to anchor the external prestressing tendons is feasible.