体外预应力角隅矩形齿块锚固区的拉压杆模型及配筋设计

STRUT-AND-TIE MODEL AND REINFORCEMENT DESIGN FOR CORNER RECTANGULAR ANCHOR BLOCK OF EXTERNAL TENDONS

针对体外预应力混凝土箱梁桥中的角隅矩形齿块锚固区,研究了拉压杆模型构形及其配筋设计方法。首先通过应力场分析、传力路径的拓扑优化找形以及抗剪钢筋作用机理分析,揭示了产生局部拉应力集中的四种作用效应以及锚固力由承压面经角隅齿块向壁板传递过程中的两种荷载传递机制。同时,利用有限元数值分析结果,拟合出锚固力在箱梁腹板与翼板间分配比例的计算公式,在此基础上,构建两个平面内的精细化桁式拉压杆模型以恰当反映角隅齿块各部位受拉、受压、受剪规律及配筋设计需求。以所提出的拉压杆模型为基础,并结合美国AASHTO桥梁设计规范,给出了角隅矩形齿块锚固区的配筋设计方法,设计示例表明该方法具有良好的实用性,可供工程设计参考。

The strut-and-tie model（STM） and reinforcement design method for corner rectangular anchor block of external tendons were studied in this paper.The paper investigated the stress concentration and transferring path of the anchor force through stress distribution analysis,topology optimization,cracking pattern observation,and shear friction mechanism application.It is revealed that the stress concentration can be characterized by four typical local actions and the anchor force is transferred into the slab from the anchor plate through the arch and truss mechanism.Meanwhile,the formula for calculating the allocation of the anchorage force between the box girder web and flange was suggested based on the results of finite element analysis.And two individual refined trussed plane STMS were proposed to account for the properties of tension,compression and shear in corner rectangular anchor blocks.Moreover,the reinforcement design method was given through the combination of the proposed STM and AASHTO LRFD Specification.Finally,a worked design example was presented to demonstrate the effectiveness and convenience of the proposed method.