Thermal Effects and Anti-Crack Performance Optimization of Bridge Pylons Under Extreme Weather Conditions
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摘要:
为深入研究我国西部横断山脉地区极端天气下桥塔的温致效应，以某大跨悬索桥为工程背景，分析极端天气下该桥混凝土桥塔的温度场以及温度应力分布特征，并提出相应的抗裂优化措施. 首先，基于桥址区实测数据，提出桥址区极端天气的识别与模拟方法；然后，采用ANSYS有限元软件分析了桥塔的温度分布以及温度应力分布特征；最后，针对桥塔外表面存在开裂风险的问题，提出了2种提高桥塔外表面抗裂性能的优化方案，包括桥塔外表面涂装有机涂料方案和外包超高性能混凝土UHPC （ultra high performance concrete）方案. 结果表明：在强降温天气下，桥塔表面拉应力极值为2.19 MPa，存在较大开裂风险；当采用抗裂优化措施后，两种优化方案均能有效降低混凝土桥塔表面的拉应力极值；对于桥塔外表面涂装有机涂料方案，白色有机涂料优化效果最佳；对于桥塔外包UHPC方案，当UHPC厚度为0.08 m时优化效果最佳. 通过对比2种抗裂优化方案的经济性和施工难易程度，推荐采用白色有机涂料优化方案.
Abstract:In order to evaluate thermal effects on bridge pylons in extreme weather in Hengduan Mountain region of western China, a method was applied to a long span suspension bridge that the characteristics of the temperature field and temperature stress of the bridge pylon were analyzed, and two anti-crack strategies were investigated. First, a scheme was introduced to identify and simulate the extreme weather at the bridge based on measured data. And then the characteristics of the temperature field and the associated temperature stress of the pylon in simulated extreme weather were analyzed with the software ANSYS. Finally, two strategies were proposed to solve the issue of potential crack of the pylon under extreme weather condition, adding organic coatings or a layer of UHPC (ultra high-performance concrete) on the pylon surface. The results indicate that the pylon is at risk of cracking when the tensile stress at its surface reaches 2.19 MPa in strong cooling weather. And both strategies can effectively reduce the maximum tensile stress of the surface to a safe level. As for the strategy of adding the organic coatings, the white organic coating is more favorable; so is the layer of UHPC of 0.08 m. Compared with their budget and construction, adding white organic coating is recommended as the better anti-crack strategy for the bridge pylon in this study.
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图 2 桥址区全自动气象站布置
Figure 2. Layout of the automatic meteorological station at the bridge site
图 4 识别和模拟的强降温天气气温
Figure 4. Air temperature of identified and simulated strong cooling weather event
图 9 桥塔外表面最大拉应力时程
Figure 9. Time-history of maximum tensile stress of the pylon cross section
图 10 桥塔断面应力分布图
Figure 10. Stress distribution of cross section of the pylon cross section
图 11 桥塔外表面涂装有机涂料后的最大拉应力时程
Figure 11. Time-history of maximum tensile stress of the pylon surface with organic coating
图 12 采用有机涂层后桥塔RC层不同深度拉应力值
Figure 12. Tensile stress values at different depths of pylon RC with organic coating
图 13 桥塔表面外包UHPC后最大拉应力时程
Figure 13. Time-history of maximum tensile stress of the pylon surface with UHPC
图 14 采用外包UHPC后桥塔RC层不同深度拉应力值
Figure 14. Tensile stress values at different depths of the pylon RC of UHPC
表 1 两种抗裂优化方案比较
Table 1. Comparison between the two anti-crack strategies
优化方案 应力减少量/% 物料价格/
（元•m−2）PⅣ-1 PⅣ-2 PⅣ-3 白色有机涂料 15.76 15.70 19.71 72 覆盖 0.08 m UHPC 23.23 18.39 28.61 600 
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