鋼管杭の簡便杭頭接合方法に対する構造実験

抄録

This paper discusses bending test results of steel pipe pile jointed footing by simple method, i.e. , a pile 60 cm in diameter and 9 mm in thickness is buried simply in footing with 10 cm depth, and plain concrete is filled inside up to l.5 times as long as pile diameter. Three cases of axial load condition are selected. The first and second tests are 0 t and 180 t in compression corresponding to the pullout load and push-in load, respectively, by rocking vibration of superstructure with load change equal to 90 t of the estimated bearing capacity of the pile. The third test is 30 t in tesion. which is supposed as pullout load condition. Loading system is as follows ; in order to simulate bending moment of pile in the ground by horizontal load, an concentrated load is applied at intermediate point between pile head joint and the other pinned supporting point of pile. Conclusions derived from tests results are summarized in the followings. 1) The degree of restraint for rotation at pile head α_r is small as 0.26 without axial load and 0.81 with axial load at the allowable bending moment of pile. But the apparent α_r becomes extremely large in both cases at the ultimate state as if the pile head is completely fixed condition. 2) The ultimate strength of steel pipe piles with simple joint method under the horizontal force is controlled by the occurrence of local buckling of pile. The local buckling strength is affected by the thickness-radius-ratio t/r as well as the case of uniform compression. It is necessary, therefore, to apply Eq. (3) or (4) which are derived as functions of r/t or t/r. Concrete filled inside of pile is available to prevent the occurrence of local buckling. 3) Even though the case of large degree of restraint for rotation between pile and footing, the apparent α_r is reduced if the overall rotation of frame is produced, and the bending moment becomes larger at the lower part of pile than at the pile head joint. It should be noticed, therefore, that there are some cases the ultimate strength may be controlled by the bending capacity of pile itself than that of pile head joint, even if α_r between pile and footing is large.