温度梯度作用下钢管混凝土拱桥拱脚混凝土裂缝控制研究

针对姚湾东南公路桥，采用HohaiRCFE-S程序建立拱脚局部模型，并分析拱脚在均匀升温、均匀降温及分别组合日照和气温骤降作用的4种工况下的应力状态，发现日照和气温骤降作用显著增大拱脚混凝土拉应力，提高开裂风险。为控制拱脚开裂，提出以裂缝宽度控制为目标的混凝土拉应力限制条件，对增厚外包混凝土厚度、增设剪力钉、设置拱肋弦杆支撑、拱脚混凝土顶面布置钢板和顶面附近施加预应力等5种控裂措施，分别建立有限元模型并进行应力对比和控裂效果分析。结果表明：均匀升温+日照和均匀降温+气温骤降工况下，仅增厚外包混凝土厚度或增设剪力钉不能满足拉应力控制要求；设置拱肋弦杆支撑或钢板控裂效果差；施加预应力可明显减小拱脚混凝土拉应力；施加预应力+增设剪力钉、施加预应力+外包混凝土厚度两种组合方案在4种工况下均表现出良好的控裂效果。

Research on Crack Control of Concrete at Arch Foot in Concrete-Filled Steel Tube Arch Bridge Under Temperature Gradient Action

Temperature gradient action is an important reason for the cracking of concrete at arch foot in concrete-filled steel tube arch bridge during the service period. For Yaowan southeast highway bridge, the local model of arch foot was established by HohaiRCFE-S program, and the stress states of arch foot under four working conditions of uniform temperature rise, uniform temperature drop and superposition of sunshine and suddenly-decreased temperature respectively were analyzed. It was found that the sunshine and suddenly-decreased temperature significantly increased the tensile stress of concrete at arch foot and improved the risk of cracking. In order to control the cracking of arch foot, the limiting conditions of the concrete tensile stress aiming at crack width control were proposed. Five crack control measures were established respectively, such as increasing the thickness of surrounding concrete, adding shear nails, setting chord supports between arch ribs, placing the steel plate on the top surface of concrete and applying prestress near the top surface, and the stress comparison and crack control effect were analyzed. The results show that under the working conditions of uniform temperature rise + sunshine and uniform temperature drop + suddenly decreased temperature, only increasing the thickness of surrounding concrete or adding shear nails cannot meet the requirements of the tensile stress control. Setting chord supports or placing the steel plate has a poor crack control effect, and applying prestress can obviously reduce the tensile stress of concrete at arch foot; The two combination schemes of applying prestress + adding shear nail and adding prestress + increasing the thickness of surrounding concrete show a good crack control effect under four working conditions.