中文摘要：

由于超限超载车辆迅速增长，梁底开裂已成为板梁桥营运中的首要病害。以往所使用的粘贴钢板加固，钢材使用率低，加固效果并不理想。根据提高主梁抗弯刚度可减小主梁挠度及内力，并最终抑制梁底开裂的原理，首次提出π型钢板加固法。现利用 ANSYS 程序进行空间非线性有限元仿真计算。对π型钢板与粘贴钢板加固后主梁进行对比分析，得出π型钢板加固对提高主梁极限承载力、防止主梁底板开裂，效果优于粘贴钢板加固；对比分析使用不同腹板高度与钢板厚度的π型钢板加固后的主梁极限承载力，得出π型钢板腹板高度对提升加固效果的影响较钢板厚度大；进一步对比分析π型钢板应用于不同跨径板梁的稳定性问题，提出不同跨径板梁对π型钢板截面尺寸的具体要求。

英文摘要：

Due to the factors of vehicles overloading, cracking on plate beam bottom has become one of the primary problems in plate-beam bridge operations. In sticking steel slab technology, steel products utilization rate is low, so the reinforcement effect is not ideal. According to the principle that the increase of the primary beam flexural stiffness can decrease the maximum vertical deflection and internal forces of the primary beam under the same load, and eventually reduce the beam bottom cracks, the author first proposed the π-type steel strengthening technology. And by utilizing ANSYS program to carry out the space nonlinear finite element simulation calculation, the author compared the effect of primary beam bottom crack prevention by changingπ-type steel height and ribbed slab thickness with sticking steel slab technology, Following are the conclusions drawn by the authors：the resisting force and the ability to resist deformation of the plate beam in the limit state of the former case improved a lot more than the latter one, and the effect of improving capacity and preventing primary beam bottom crack is better by usingπ-type steel technology than sticking steel slab technology. The author also further compared and analyzed the stability problem of π-type steel used for plate beam with different lengths and optimized theπ-type steel cross section dimensions.