Abstract: Generally a diaphragm is set between the rof of the pier and the mid-span in order to enhance the rigidity refers to the bend-resistance of the box-beam structure in the same direction with the bridge and the twist-resistance cross wise．However，near the diaphragm section，the diference of strength function is obvious comparing to the convention section，which is usually be ignored during the design process．Taking the rof-board crack near the pier of a bridge for example，the diaphragm 's influences on the mechanics function of the roof-board are analyzed specifically．The results show that the strength situation is obviously different between the rof-board around the diaphragm and those section far away from it．

Key words: diaphragm , box·beam, robboard, rigidity, Poisson effect

摘要： 为增强箱梁结构顺桥向的抗弯刚度和横向抗扭刚度，一般都在墩顶和跨中设置横隔板，但横隔板对附近区段 箱梁的受力性能是否有不可忽略的影响，这是通常设计中未曾清晰认识的问题．现以某大桥墩顶附近顶板开裂这一 情况为例，具体分析墩顶横隔板对顶板力学性能的影响．结果表明顶板的受力情况在横隔板附近与远离横隔板的区 域存在明显差异．

关键词: 横隔板, 箱梁, 顶板, 刚度, 泊松效应