土体阻尼对全(部分)埋入单桩基础自振特性的影响研究

The influence of soil damping on the free vibration characteristics of pile all or partially embedded in soil

自振频率和振型是反映结构动力特性的重要物理量,对结构设计和动力分析具有重要作用。基于回传射线矩阵法(MRRM),首先推导出全埋入单桩基础在桩顶自由、桩底分别为自由和固定条件下发生轴向自由振动时波数、振型和自振频率的解析解;而后研究部分埋入单桩基础横向和轴向自由振动时的自振特性,探讨了4种工况,工况1～3同时考虑土体弹簧和土体阻尼作用,工况4仅考虑土体阻尼作用,分析了土体阻尼对部分埋入单桩基础自振频率和振型、衰减系数的影响规律。结果表明:土体阻尼对低阶自振频率和振型的影响较大,在结构的低频振动分析中不可忽略。

Natural frequencies and vibration modes can reflect structural dynamic characteristics,and are important for structural design and dynamic analysis.Based on the reverberation-ray matrix method(MRRM),analytical solutions of the wave number,vibration modes,and natural frequencies of the pile all embedded in soil are derived,while the pile occurs axial free vibration which is free on the top,and free or fixed on the tip.Then,the vibration characteristics of a two-dimensional(2D)partially embedded pile are investigated.Four different cases are discussed,the effects of the soil damping and spring on vibration characteristics are considered in the cases1-3,while only the soil damping is considered in the case4.The influences of the soil damping on the natural frequencies,vibration modes and attenuation coefficients of the pile are also analyzed.The results are shown that the influence of the soil damping on low order natural frequencies and vibration modes is great,which is not negligible in the analysis of low frequency vibration of the structure.