一、问题的提出宝成铁路嘉陵江11号大桥原来净空严重不足,抬高线路又受两端隧道的控制,若把上承梁改换为同跨度的下承梁可达增大桥下净空的目的。为避免大量的墩台及基础改建工程,仅在原墩台上接高一个钢筋混凝土悬臂顶帽,取得了节省工程和缩短工期的效果。如图1所 First, the problem raised Baocheng Jialing River Bridge on the 11th of the original serious shortage of clearance, lifting the line by both ends of the tunnel control, if the replacement of the beam with the span of the next beam up to increase the purpose of clearance under the bridge. In order to avoid a large number of piers and foundation reconstruction projects, only a pier abutment up a reinforced concrete cantilever cap, and achieved savings in engineering and shorten the duration of the effect. As shown in Figure 1