考虑气候变化背景下基础冲刷对桥梁抗震性能的影响
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摘要
桥梁是现代交通体系中必不可少的组成部分,桥梁受到外界自然环境变化的影响不容忽视。近年来,由于全球气候变化现象明显,越来越多的学者开始关注气候变化对桥梁结构的影响,但这方面的研究还不够深入,本文选择气候变化引起的基础冲刷对桥梁抗震性能的影响为研究课题,具有较为重要的理论研究意义与实际应用价值。
本文首先根据联合国政府间气候变化专门委员会提出的气候变化的三种情景,出于全球范围考虑,认为亚洲地区的河流径流量增加,以某铁路大桥为例,预测了未来气候变化条件下桥墩基础冲刷深度的改变量；随后,为了研究地基冲刷对桥梁动力性能的影响,对比分析了几种考虑土结相互作用方法对桥梁动力特性和地震响应的影响,选择了比较合理的分层土模型；接着根据前面的基础冲刷深度预测,改变桩基础的埋深,减少相应土弹簧数量和刚度,采用反应谱法和时程分析法对桥梁地震动响应进行了对比分析；最后,用推倒分析方法计算了不同气候变化情景下、不同侧向力模式下桥墩的抗震性能变化。主要结论如下：随着基础冲刷的深度不断增大,结构刚度减小、地震响应增大,特别是在桩顶位置,桩失去了土体约束,桩顶弯矩增幅比较明显；对比不同基础冲刷深度下的推倒曲线可知,随着冲刷深度的增加,桥墩结构屈服状态对应的侧向抗力变小,而墩顶水平位移则增大,承台和桩基础的震动响应增大,致使塑性铰不断下移；并且随着冲刷深度的增大,推倒分析中的侧向力加载模式需考虑高阶振型的影响。
The bridge is an integral part of the modern transport system, the influence of climate changes cannot be ignored. In recent years, climate change is significant, more and more researchers begin to study the influence on bridge caused by climate changes; however, it is not deep enough. In this paper, the influence of scour of foundation caused by climate change has been considered on the seismic performance. And it is essential from both perspectives of theory and practical project application.
According to the A1B、 A2and B1scenarios gave by Intergovernmental Panel on Climate Change, for global consideration, fluvial runoff" increased in the Asian region. Taking a railway bridge as an example, changes of the pier scours depth under the conditions of future climate have been forecasted. Then, in order to study the influence of foundation scour on dynamic performance of bridge, several methods considering SSI have been comparatively analyzed, a reasonable layered soil model has been adopt. According to the forecast of the scour depth, buried depth of the pile foundation has been changed and the corresponding soil spring number and stiffness has been reduced, the comparative analysis of the seismic response had been made by the response spectrum method and the time history analysis method. Pushover analysis has been applied to calculate the seismic performance of bridge pies under different climate change scenarios and distribute lateral load patterns. The main results are given in follow: With the depth of scour is continuously increasing, the structure stiffness is reduced and the earthquake response increased, especially on the pier top, the restriction of the soil around the pile was lost and bending moment grows apparently.Comparing the pushover curve under different scour depth, with increasing of the scour depth, corresponding lateral force shrunk while horizontal displacement on the pier top is increased.With the vibration response of bearing platform and pile foundation increasing,plastic hinge continuously shift down. And higher modes influences are considered in distribute lateral load patterns of push-over analysis.
本文首先根据联合国政府间气候变化专门委员会提出的气候变化的三种情景,出于全球范围考虑,认为亚洲地区的河流径流量增加,以某铁路大桥为例,预测了未来气候变化条件下桥墩基础冲刷深度的改变量；随后,为了研究地基冲刷对桥梁动力性能的影响,对比分析了几种考虑土结相互作用方法对桥梁动力特性和地震响应的影响,选择了比较合理的分层土模型；接着根据前面的基础冲刷深度预测,改变桩基础的埋深,减少相应土弹簧数量和刚度,采用反应谱法和时程分析法对桥梁地震动响应进行了对比分析；最后,用推倒分析方法计算了不同气候变化情景下、不同侧向力模式下桥墩的抗震性能变化。主要结论如下：随着基础冲刷的深度不断增大,结构刚度减小、地震响应增大,特别是在桩顶位置,桩失去了土体约束,桩顶弯矩增幅比较明显；对比不同基础冲刷深度下的推倒曲线可知,随着冲刷深度的增加,桥墩结构屈服状态对应的侧向抗力变小,而墩顶水平位移则增大,承台和桩基础的震动响应增大,致使塑性铰不断下移；并且随着冲刷深度的增大,推倒分析中的侧向力加载模式需考虑高阶振型的影响。
The bridge is an integral part of the modern transport system, the influence of climate changes cannot be ignored. In recent years, climate change is significant, more and more researchers begin to study the influence on bridge caused by climate changes; however, it is not deep enough. In this paper, the influence of scour of foundation caused by climate change has been considered on the seismic performance. And it is essential from both perspectives of theory and practical project application.
According to the A1B、 A2and B1scenarios gave by Intergovernmental Panel on Climate Change, for global consideration, fluvial runoff" increased in the Asian region. Taking a railway bridge as an example, changes of the pier scours depth under the conditions of future climate have been forecasted. Then, in order to study the influence of foundation scour on dynamic performance of bridge, several methods considering SSI have been comparatively analyzed, a reasonable layered soil model has been adopt. According to the forecast of the scour depth, buried depth of the pile foundation has been changed and the corresponding soil spring number and stiffness has been reduced, the comparative analysis of the seismic response had been made by the response spectrum method and the time history analysis method. Pushover analysis has been applied to calculate the seismic performance of bridge pies under different climate change scenarios and distribute lateral load patterns. The main results are given in follow: With the depth of scour is continuously increasing, the structure stiffness is reduced and the earthquake response increased, especially on the pier top, the restriction of the soil around the pile was lost and bending moment grows apparently.Comparing the pushover curve under different scour depth, with increasing of the scour depth, corresponding lateral force shrunk while horizontal displacement on the pier top is increased.With the vibration response of bearing platform and pile foundation increasing,plastic hinge continuously shift down. And higher modes influences are considered in distribute lateral load patterns of push-over analysis.
引文
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[4]周峰.气候变化对建筑工程的影响研究[D].北京：北京交通大学2009.
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[7]王元丰,韩冰.极端气候事件对桥梁安全性的影响分析[J].土木工程学报,2009,42(3)76-80.
[8]Vivian Meloysund, Kim Robert Liso, Jan Siem, K ristofferApeland.Increased snow loads andwind actions on existing buildings:reliability of the Norwegian building stock[J]. Journal of Structural.2006:1813-1820.
[9]Peters G, DiGioia AM, Hendrickson JC, Apt J. Transmission line reliability, climate change and extreme weather [J].Electrical Transmission Line,2006:12-25.
[10]Michael Camilleri, Roman Jaques, Nigel Lsaacs. Impacts of climate change on building performance in New Zealand[J].Build Research & Information,2001,29(6):440-450.
[11]郭彤,李爱群,李兆霞,等.大跨桥梁结构状态评估方法研究进展[J].东南大学学报,2004.
[12]王景红,王熙泰.气象因素对公路建设的影响与对策[J].陕西气象,2004(3)：42-43.
[13]刘聪,张忠义,黄世成.桥梁气象专题研究与服务气象科技[J].2004,32(6)：399-403.
[14]白虎志,李栋梁,董安祥.青藏铁路沿线的大风特征及风压研究[J]8.冰川冻土,2005.
[15]王唐修,姜鑫民.谈气候变化影响及对策[J].能源与环境.2002(12)：38-40.
[16]朱贝宝.秦沈客运专线饶阳河特大桥承台冬季施工技术[J].建筑施工,2003,25(2)：123-125.
[17]阚译.桥渡冲刷[M].北京：中国铁道出版社,2004
[18]詹磊,董耀华,惠晓晓.桥墩局部冲刷研究综述[J].水利电力科技,2007,33(3)1-13.
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[20]Wolf J, Meek J, and Sung C.Cone Models for a Pile Foundation, in PilesUnder Dynalmc Loads, Geotech. Spec. Pub.34,ASCE.94-113
[21]袁万城.大跨度桥梁空间非线性地震反应分析.上海：同济大学博士学位论文,1990.
[22]朱唏,王大庆.桩基桥墩考虑土结构相互作用抗震计算方法的研究[JJ.铁道学报,1992(4)：81-90.
[23]郑海荣.桩-土-上部结构(桥墩).流体相互作用体系的地展反应分析[J].桥梁建设,1992(4)：67-74.
[24]蒯行成,沈蒲生.层状介质中群桩水平动力阻抗的简化计算方法[J].振动工程学报,1998,11(3)：258-264.
[25]孙利民,后藤洋三.桩基础桥墩的非线性地震反应分析.第25届日本地震工学研究发表会论文集.p873-840,1999.7
[26]胡聿贤.地震工程学(第二版)[M].北京,地震出版社.2006.
[27]赵淳,杨朝晖.桥梁抗震分析方法研究[J].现代商贸工业,2009,1.391-392.
[28]宗德玲.基于PUSHOVER分析的桥梁抗震能力评估方法研究[D].南京：南京工业大学硕十学位论文,2004.5.
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