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，以阐明新的拼接的特点。然后，我们模拟的实验结果，通过使用非线性有限元方法，考虑了几何和材料的非线性，以显示该方法的有效性。利用该方法，我们进行了参数研究，以探讨HDAJ拼接桩的有效性时，受到摩擦引起的地面大位移。数值分析表明，在给定荷载作用下，HDAJ拼接桩结构所承受的地面位移是普通预应力高强混凝土（PHC）桩的近2倍，虽然HDAJ拼接桩能有效地抵抗由地基位移引起的地面大位移，但仍需进行动力响应分析。由于HDAJ拼接桩具有极高的抗弯强度， ...更多信息 在强震作用下，HDAJ拼接桩的位移响应可能会较大，超过允许值，这是HDAJ拼接桩的一个缺点。反之，若反应位移与PHC相当或更小。桩，在HDAJ拼接桩引起的弯矩将大大减少。从这一点出发，本文采用非线性有限元法对HDAJ拼接桩在强震作用下的动力响应进行了分析。在数值分析之前，我们进行了HDAJ拼接桩和PHC桩轴向荷载下的循环弯曲试验。通过对试验数据的分析，建立了桩身弯矩-转角关系模型，并通过改变地基模型、输入运动等方法进行了参数动力分析，得到了以下主要结论：（1）HDAJ拼接桩的最大响应位移并不大于普通PHC桩;（2）HDAI的引入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