Study on Aseismic Design of High Ductility Aseicmic Joint Spliced Pile Foundation

研制了一种新型高延性抗震接头（HDAJ），取代了传统的焊接接头。首先，我们进行了一系列的弯曲实验来阐明新剪接的特性。然后，采用考虑几何非线性和材料非线性的非线性有限元方法对实验结果进行了仿真，验证了该方法的有效性。通过该方法，我们进行了参数化研究，探讨了HDAJ接桩在液化引起的大地面位移作用下的有效性。数值分析表明，在一定荷载作用下，桩结构承受的地面位移几乎是普通预应力高强混凝土桩承受的两倍。虽然表明了HDAJ接桩在液化引起的大地面位移作用下的有效性，但必须进行动力响应分析。由于HDAJ型接桩具有极强的承受力，在强震作用下可能产生较大的响应位移而超出允许范围，这成为HDAJ型接桩的缺点。反之，如果响应位移与PHC相同或更低水平。在桩基上，HDAJ接桩所产生的弯矩将大大降低。这意味着HDAJ拼接桩将承受强地震运动，而普通桩由于弯矩过大而产生塑性铰。在此基础上，采用非线性有限元法对HDAJ型接桩进行动力响应分析，探讨其在强震作用下的有效性。在进行数值分析之前，我们对HDAJ桩和PHC桩进行了轴向荷载下的循环弯曲试验。通过模拟实验中的弯矩-转角关系，我们通过改变地面模型、输入运动等进行了参数化动态分析。研究结果表明：(1)HDAJ桩的最大响应位移不大于普通PHC桩。(2)引入HDAJ后，显著降低了桩的最大弯矩，提高了桩基体系的安全性。少

Instead of traditional welding splicer, a new High Ductility Aseismic Joint (HDAJ) was developed. We first, conducted a series of bending experiments to elucidate the characteristics of the new splicing. Then, we simulated the results of the experiments by using a nonlinear finite element method which took into account both geometric and material nonlinearities to show the validity of the method. By using the method, we performed parametric study to investigate the effectiveness of HDAJ spliced piles when subjected to liquefaction-induced large ground displacements. The numerical analyses revealed that the pile structure would sustain ground displacements almost twice the magnitude of that sustained by ordinary Pre-stressed High strength Concrete (PHC) piles for a given load.Although the effectiveness of HDAJ spliced pile when subjected to liquefaction-induced large ground displacements was shown, dynamic response analyses must be done. Because the HDAJ spliced pile is extremely deferr … More able, large response displacements might be caused by strong earthquake motions and exceed the allowance, which becomes a drawback of the HDAJ spliced pile. On the contrary, if the response displacement is same or less level compared with that of PHC. Piles, the bending moment induced in the HDAJ spliced pile would be extremely reduced. This means that the HDAJ spliced pile will be sustain the strong earthquake motion while ordinary piles will yield plastic hinges due to excess bending moments.From this point of view, we performed dynamic response analyses to investigate the effectiveness of HDAJ spliced piles subjected to strong earthquake motions by using nonlinear FEM. Prior to the numerical analyses, we conducted cyclic bending tests under axial loads of HDAJ spliced piles and PHC piles. By modeling the bending moments-rotational angle relationships from the experiments, we carried out parametric dynamic analyses, by changing ground models, input motions, and so on. The main results are:(1)The maximum response displacements of HDAJ spliced piles are not larger than those of ordinary PHC piles.(2)The maximum bending moments induced in piles are remarkably reduced by introducing the HDAJ which means that the HDAJ increases the safety of pile foundation system. Less