수평저항력 보강 Wing Pile의 말뚝지지력 특성

Abstract

Although there have been many studies on pile foundations subjected to vertical loading. the domestic studies on pile under horizontal load have been limited. The horizontal load caused by the earthquake is very strong. The structures such as marine structures, retaining walls, bridges are subjected not only vertical loads but also horizontal ones. Excessive displacement or breakage of the piles subjected to horizontal loads, as the ones caused by vertical loads, have detrimental effect on the superstructure, suggesting that the studies on the analysis and review of the pile subjected to the horizontal loads are needed urgently. In the existing pile construction, a pile was inserted into the ground, a concrete foundation was laid on top of the pile, and a plate under the column member was joined to the upper part of the concrete foundation. This connection method between pile and column member is, however, vulnerable to lateral load due to wind load or seismic load because the column member is fixed only to the upper end of the pile. In addition, the pile twisted by lateral load may not provide proper support to column member, which may cause deformation and breakage of the pillar member, leading to failure of proving proper support to superstructure by the pillar member. The purpose of this study was, therefore, to develop a Wing Pile, which allows the pile member and column member to overlap with each other, and the lateral load to be supported not only by pillar member but also by pile member in order to address above problems. The Wing Pile connecting the lower foundation and the upper column was designed to have two kinds of B, distance from center to end, to be 150 and 300 mm, respectively and to have H of 450 mm. A total of 17 piles were under field test including five for static load test, five for uplift load test, five for horizontal load test, and two for moment test and the bearing capacities of general pile and Wing Pile were verified, analyzed, and compared. The results of field load test showed that bearing capacity, horizontal resistance, and moment resistance of Wing Pile is higher by 1.5-4, 4-4.5, 4 times compared to general ones, respectively. It was found that the improved horizontal resistance and bearing capacity are corresponds to wing area of upper fixed pile, suggesting that the resistance is proportional to wing area. It should be noted, however, that the ground survey should be performed in advance in order to confirm the type and the workability of the indentation, and the depth should be considered for the reinforcement against horizontal force to a proper depth.