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Effects of loading obliquity on field performance of rocking shallow foundations in cohesive soil
Géotechnique ( IF 5.8 ) Pub Date : 2020-12-14 , DOI: 10.1680/jgeot.19.p.033
Keshab Sharma 1 , Lijun Deng 2
Affiliation  

This paper presents a field study of obliquely loaded rocking shallow foundations resting on cohesive soil. Lateral snap-back and cyclic loading tests at an oblique angle of 45° with respect to the footing axes were carried out. During the snap-back tests, an initial drift ratio was applied to the deck and then the system was released to enable the free vibration. The cyclic loading consisted of five packets containing three to four cycles of similar displacement amplitude. The rocking system consisted of a 1·5 m by 1·0 m concrete footing, steel column and deck. The factors of safety against bearing failure were varied from 4 to 20. It was observed that the system primarily rocked in plane. The moment capacities about footing axes deviated from the calculated values at the orthogonal loading conditions. A method of estimating the rocking moment capacity of a footing subjected to oblique loading was developed and validated by the tests. Natural periods, damping ratio, re-centring ratio, settlement and stiffness degradation during the tests are discussed and compared with the results from previous studies with orthogonal loading. The soil–footing contact area was approximately triangular. A method of calculating the critical contact area was developed based on the bearing capacity theory with two-way eccentricity and then confirmed by observation.

中文翻译:

倾斜载荷对黏性土中摇摆浅层基础场性能的影响

本文提出了对粘性土上倾斜加载的摇摆浅地基进行的现场研究。相对于基础轴以45°的倾斜角进行了侧向折回和循环载荷测试。在回弹测试期间,将初始漂移比应用于甲板,然后释放系统以实现自由振动。循环载荷由五个包组成,这些包包含位移幅度相似的三到四个周期。摇摆系统由1×5 m x 1·0 m的混凝土基础,钢柱和甲板组成。防止轴承故障的安全系数从4到20。观察到该系统主要在平面上摇摆。在正交载荷条件下,围绕支脚轴的力矩能力与计算值有所偏差。开发了一种估计受倾斜载荷作用的地基摇摆能力的方法,并通过测试进行了验证。讨论了测试期间的自然周期,阻尼比,重心比,沉降和刚度退化,并将其与以前在正交荷载下的研究结果进行了比较。土壤与地面的接触面积大约为三角形。基于双向偏心的承载力理论,提出了一种计算临界接触面积的方法,并通过观测得到了证实。土壤与地面的接触面积大约为三角形。基于双向偏心的承载力理论,提出了一种计算临界接触面积的方法,并通过观测得到了证实。土壤与地面的接触面积大约为三角形。基于双向偏心的承载力理论,提出了一种计算临界接触面积的方法,并通过观测得到了证实。
更新日期:2020-12-14
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