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

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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