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

摘要：SGER：冰冻环境中桥梁柱的土-结构相互作用，CMS-0502117 PI：Sritharan，爱荷华州州立大学美国大部分地区发生的季节性冰冻预计会显著影响土木结构的横向行为，尤其是桥梁。对材料性能的研究表明，在接近-20摄氏度的温度下，混凝土性能会改变20%至50%，钢的延展性可能完全丧失，土壤性能会提高两个数量级。因此，由土-基础-结构相互作用和结构构件的延性能力决定的结构的侧向荷载响应取决于环境条件。随着大的地震事件在不同的国家，经历季节性冻结的潜力，调查的温度对土壤基础结构系统的横向荷载响应的影响变得至关重要。本计画借由钻孔灌注桩（CIDH）支撑桥梁柱，探讨温度对土壤-基础-结构系统的影响。通过大型室外试验，研究了三个桥梁柱在温暖和冻土条件下的横向荷载响应，以了解季节温度对土-结构相互作用以及系统延性的影响。初步分析调查显示，由于桩身塑性的迁移和扩散减少，在接近-20 ℃的地面温度下的冻结条件可能会使结构位移能力降低70%，并使柱剪力需求增加35%。将利用测得的材料特性和现场土壤测试数据进行分析研究，以表征三个桥梁柱系统的响应。比较分析和实验结果，季节性冻结对土壤基础结构系统的影响的抗震设计的意义。此外，还将制定一项关于这一主题领域的详细调查计划。 拟议的探索性研究的结果预计将改善土壤-基础-结构系统在极端横向载荷（如地震引起的载荷）下的设计，从而有助于在经历季节性冻结的地区建造更安全、更可靠的结构。

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.