设置预拱度对梁体长期徐变效应的影响

传统思路认为桥梁在施工中通过预先设置预拱度，可以抵消结构使用荷载引起的挠度，使桥面高程达到一理想位置。但是对混凝土结构预先设置拱度，由于改变了结构轴线线形，梁体轴线线形改变的同时其受力体系也发生了变化。比如对一根直线梁而言如设置了预拱度，其梁体轴线为曲线，其受力将不再是直线而是类似于拱。考虑预应力效应后，具有预拱度的梁将发生初始弯曲变形，其变形结果必然不同于直线形梁的变形。因而，对于预应力实体梁来说通过梁理论分析方法将具有预拱度的梁体按照具有初弯曲的梁段对待，建立梁体考虑徐变效应的挠度表达式并以此验证前述推理方法的正确性。

INFLUENCE OF THE PRE-CAMBER FOR LONG-TERM CREEP EFFECTS OF BEAM

The traditional idea that the bridge construction by pre - set pre - camber can offset structural loads caused by the deflection and made the bridge deck elevation reach to an ideal location. But when pre - set camber is set for the concrete structure, the stress system of the structure has also been changed because of changes in the structural axis. For example, if the pre - camber is set for a straight line beam, the beam axis will be changed into curve, the force is similar to arch. After considering prestressing effect, the beam being set the pre - camber undergo an initial bending deformation, which is different from the linear deformation of the beam. Thus, it is right for the beam with pre - camber to be treated as the beam with initial bending according to beam deflection, form deflection equation considering creep effect, and verify the correctness of the foregoing reasoning.