体外预应力桥梁锚固块构造分析及拉压杆模型法配筋研究

采用3种有限元分析模型进行体外预应力桥梁锚固块的应力分析,分别考虑角钢、钢垫板、体外预应力钢管,钢筋网和分布钢筋对锚固块的影响,并对3种有限元模型计算结果进行分析对比。另外,对单孔锚固的T梁锚固块直接利用美国ACI-318-05混凝土结构规范中的拉压杆模型进行配筋设计;对多孔锚固的箱梁锚固块,忽略横向应力和竖向应力的相互影响,利用弹性应力法建立箱梁锚固块的横向和竖向配筋的拉压杆模型进行配筋设计。研究结果表明,在体外预应力锚固块与主梁相接部位中设置角钢有效地降低了这一位置由于大吨位张拉力引起的应力集中;设置了钢垫板、角钢、体外预应力钢管以及锚固区钢筋网和分布钢筋后,锚固区是安全的。因此,运用拉压杆模型法对体外预应力锚固块的配筋设计是合理可行的。

Structure Analysis of Anchorage of External Prestressed Bridge and Reinforcement Calculation by Strut-and-tie Model

Three finite element models were established to analysis the stress of the anchorage zone of the external prestressed bridge,considering the function of angle iron,steel tie plate,external prestressed steel tube,reinforcement network and distributing reinforcement.Form the analysis of the results of the three finite element models,some anchorage conformation suggestions are given.Then the reinforcement of single anchorage of T-beam are designed directly using the strut-and-tie model from the concrete construction design code of ACI-318-05.For the multihole anchorage of box girder,ignoring the interference of the transversal and vertical stress,the strut-and-tie model is established for reinforcement based on the elastic stress analysis.Finally,the anchorage reinforcement design devices are given.It is found that the angle iron which setup at the connection of the anchorage of external prestressed bridges and girder can effectively resolves the problem of stress concentration aroused by the huge tensile force.With the angle iron,steel tie plate,external prestressed steel tube,reinforcement network and distributing reinforcement,the anchorage of external prestressed bridges is safe.The result shows that the method of reinforcement designs for the anchorage of external prestressed bridges by the strut-and-tie model is reasonable and practical.