预应力RPC箱梁开裂弯矩计算方法

A calculation method for cracking moment of prestressed reactiv e powder concrete box girder

预应力箱梁是现有活性粉末混凝土(RPC)桥梁的主要结构形式。以预应力RPC箱梁受弯性能为主要研究目的,应用ANSYS通用程序建立有限元模型,对RPC梁受弯过程的荷载-位移曲线、开裂、极限荷载等受力行为进行分析。有限元分析结果与试验结果吻合良好。应用有限元方法、以混凝土强度为参数的分析表明,RPC梁的初裂荷载、钢筋屈服荷载和极限荷载比普通混凝土梁可分别提高34.1%、34.3%和35.1%。对RPC箱梁开裂弯矩计算方法开展了分析。现行规范《公路钢筋混凝土及预应力混凝土桥梁设计规范》(JTG D62-2004)算法中截面塑性影响系数r值不能准确反映RPC的材性,计算结果比试验值偏大较多,不宜采用;提出了预应力RPC箱梁开裂弯矩计算方法,其计算结果与多根RPC梁试验结果的比值为0.91~0.96,能满足工程计算精度的要求,可供预应力RPC梁设计计算参考。

Prestressed box girder is the main structural form of reactive powder concrete(RPC) bridge. To understand the flexural behavior of prestressed box girder, a finite element model is built using the ANSYS software to analyze the behaviors of girder, such as the load-displacement relationship, cracking and ultimate load. It is found that the FEM analyzing results were in good agreement with the experimental results. FEM analysis based on strength parameters of concrete also indicates that the initial cracking load, reinforcement yielding load and ultimate load of RPC girder can be improved about 34.1%, 34.3% and 35.1%, respectively, compared to the normal concrete girders. Furthermore, the calculation method for cracking moment of RPC box girder was studied. It is found that in the Chinese Code JTG D62-2004, the material properties of RPC can't be accurately reflected by the section plasticity influence coefficient, r,and the calculation method shall not be employed because the calculation results are much larger than the experimental results. Hence,a calculation method was proposed for the cracking moment of prestressed RPC girder, and the ratio of calculation results and test results of multiple girder specimens may range from 0.91 to 0.96. It is demonstrated that the proposed method can meet the requirement of engineering calculation precision, and can be referred in the design of prestressed RPC box girder.