SGER: Soil-Structure Interaction of Bridge Columns in Frozen Environmenmts

SGER：冰冻环境中桥柱的土-结构相互作用

• 批准号: 0502117
• 负责人: Sri Sritharan
• 金额: --
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2006-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0502117&HistoricalAwards=false
• 关键词: SGER; Soil; Structure; Interaction; Bridge

Abstract for: SGER: Soil-Structure Interaction of Bridge Columns in Frozen Environments, CMS-0502117 PI: Sritharan, Iowa State UniversityThe seasonal freezing that occurs in much of the U.S. is expected to significantly influence the lateral behavior of civil structures, especially bridges. Research on material behavior shows that at temperatures near -20 degrees C concrete properties are altered by 20 to 50 percent, ductility of steel may be completely lost, and soil properties are enhanced by up to two orders of magnitudes. Consequently, the lateral load response of structures, which is dictated by soil-foundation-structure interaction and the ductility capacity of structural members, is dependent on environmental conditions. With the potential for large seismic events in various states that experience seasonal freezing, an investigation of the temperature effects on the lateral load response of soil-foundation-structure systems becomes of paramount importance. This project explores temperature effects on soil-foundation-structure systems by studying bridge Columns supported on cast-in-drilled-hole (CIDH) pile shafts. Through a large-scale outdoor Experimentation, lateral load responses of three bridge columns in warm and frozen ground conditions will be studied to understand the seasonal temperature effects on soil-structure interaction as well as system ductility. A preliminary analytical investigation revealed that freezing conditions at a ground temperature near -20 degrees C may reduce structure displacement capacity by 70% and increase column shear demand by 35%, due to relocation and reduction in spread of plasticity in the pile shaft. An analytical study utilizing the measured material properties and in-situ soil test data will be performed to characterize the responses of the three bridge column systems. Comparing the analytical and experimental results, seismic design implications of the effects of seasonal freezing on soil-foundation-structure systems will be presented. In addition, a plan for detailed investigation on this subject area will be developed. The results of the proposed exploratory study are expected to improve design of soil-foundation-structure systems under extreme lateral loads such as those induced by earthquakes, thus contributing to construction of safer, more reliable structures in regions that experience seasonal freezing.

摘要：冻土环境中桥梁柱的土-结构相互作用，CMS-0502117 PI：Sritharan，爱荷华州立大学美国大部分地区发生的季节性冰冻预计将显著影响土木结构，特别是桥梁的横向性能。对材料性能的研究表明，在接近零下20摄氏度的温度下，混凝土性能会发生20%到50%的变化，钢材的延性可能会完全丧失，土壤性能会提高多达两个数量级。因此，结构的横向荷载响应取决于环境条件，它由土-基础-结构相互作用和结构构件的延性能力决定。由于在经历季节性冻结的各种状态下可能发生大地震事件，研究温度对土-基础-结构体系横向荷载响应的影响变得至关重要。本课题以钻孔灌注桩(CIDH)桩身为研究对象，探讨温度对土-基础-结构体系的影响。通过大型室外试验，研究了三根桥柱在高温和冻土条件下的横向荷载反应，以了解季节性温度对土-结构相互作用以及体系延性的影响。初步分析表明，地温接近零下20摄氏度的冻结条件可能会使结构的位移能力降低70%，而柱的剪切需求增加35%，这是因为桩身的迁移和塑性扩散的减少。利用实测的材料特性和现场土工试验数据进行分析研究，以表征三种桥柱体系的响应。将分析结果与试验结果进行比较，提出季节性冻结对土-基础-结构体系影响的抗震设计意义。此外，还将制定一项关于这一主题领域的详细调查计划。拟议的探索性研究结果有望改善在地震等极端横向荷载作用下的土-基础-结构系统的设计，从而有助于在经历季节性冰冻的地区建造更安全、更可靠的结构。