PHC管桩的开裂弯矩和极限弯矩计算

预应力高强混凝土(PHC)管桩的受弯性能是管桩产品合格与否的重要指标。目前PHC管桩的开裂弯矩和极限弯矩的计算通常都是按照GB50010—2002《混凝土结构设计规范》中的方法进行的。但PHC管桩的混凝土强度已经超出了规范的适用范围,计算结果并不能真实反映PHC管桩的实际承载能力。结合试验测试结果,根据PHC管桩的离心成型生产工艺和高强度的特点,提出对现有PHC管桩抗裂弯矩和极限弯矩计算方法的修正建议。验算结果表明,采用修正方法计算所得的PHC管桩开裂弯矩和极限弯矩与试验实测值吻合良好。

CALCULATION METHODS OF CRACKING MOMENT AND ULTIMATE FAILURE MOMENT OF PRESTRESSED HIGH STRENGTH CONCRETE PIPE PILES

Flexural behavior is one of the most important qualifying index of prestressed high strength concrete (PHC) pipe pile. The calculation methods of cracking moment and ultimate failure moment of PHC pipe piles are based on the approaches in the Code for Design of Concrete Structures (GB 50010-2002) at present. In fact, the concrete strength grade of PHC pipe piles are beyond the adaptable scope of the GB 50010-2002 Code. The approaches in the code for estimating the cracking moments and ultimate failure moments of PHC pipe piles can not well match the actual bearing capacities. In this paper, combining with the analysis of the flexural experimental results and the behavior of centrifugal shaped producing method of PHC pipe piles, new approaches for calculating the cracking moment and ultimate failure moment of PHC pipe piles are proposed based on the present methods in the code. Comparing analysis shows that the calculation results by the modified methods are well agreed with the experimental results of PHC pipe piles. The suggested approaches for estimating the flexural capacities of PHC pipe piles are suitable in practice design.