钢箱-混凝土组合梁桥施工期开口钢箱的稳定性分析

Stability Analysis of Tub Girder for Erection Phase of Steel Box-Concrete Composite Bridges

钢箱-混凝土组合梁桥具有自重轻、施工速度快等特点,但在开口钢箱与混凝土桥面板形成组合作用前,钢梁在施工阶段的稳定性可能成为控制设计的因素。文章以跨径25 m钢箱-混凝土组合梁桥为对象,运用三维有限元模型,对其在最不利施工阶段的整体稳定及局部稳定进行参数分析,研究表明,开口钢箱设置单斜撑式上口平联能有效增强侧向扭转稳定性;为保证开口钢箱的整体稳定性,钢箱间侧向横撑的合理间距范围是1/3L0～1/2L0;当平联节间长度与箱梁开口宽度之比β小于6时,可满足钢箱腹板局部稳定性要求;翼缘的宽厚比bf/tf的取值范围在7≤bf/tf≤12时,可满足钢箱翼缘局部稳定性要求。

Steel box-concrete composite girder bridges are characterized by their light weight and rapid construction. However, the stability of tub girders can be critical during erection before tub girder and concrete deck being composited. Based on a fulldepth decked bridge with 25 m span length, the global and local stability in the unfavorable construction stage is analyzed based on 3D models. The results indicate that single diagonal bracing between top flages can increase the lateral-tortional stability of tub girder significantly. The spacing of cross frames should be designated between 1/3 L0 and 1/2 L0 in order to ensure the global staibility of steel tub. The local stability of the web can be satisfied, as the ratio of joint spacing of lateral bracing to top width of steel tub （β） is less than 6. And the local stability of top flage can be guaranteed when the ratio of flage＇s width to thickness （bf/tf） ranges from 7 to 12.