一、前言箱形截面梁由于抗扭刚度比其它截面型式的梁大,因而在大跨度铁路桥梁中被普遍采用。我国铁路桥梁,在已经设计、制造最大跨度为40m的预应力混凝土简支箱梁的基础上,现正着手设计跨度64m的箱形截面预应力混凝土连续梁,和48m的预应力混凝土简支箱梁。铁路桥跨因不通过梁作横截面弯曲中心的外力(列车摇摆力、离心惯性力、偏心竖直荷载、 I. INTRODUCTION The box girder is widely used in large-span railway bridges because of its torsional stiffness greater than that of other cross-section girders. Based on the design and manufacture of prestressed concrete simple box girders with a maximum span of 40m, the design of China’s railway bridges is proceeding with the design of box-shaped prestressed concrete continuous beams with a span of 64m and 48m prestressed concrete simple-box Beam. Due to the railway bridge span not cross-beam bending center of the external force (train swing force, centrifugal inertial force, eccentric vertical load,