Abstract
Things that length of pile is over 60 times pile diameter in Design Standard of Building Foundation Structure reduce allowable bearing force of pile only % value which is leaved 60 from value which is pile length divided by a pile diameter. On steel piles, however, we use value which is substituted above mentioned 60 for 120. It is the present condition that the standard in case of Reinforsed Concrete (RC) pile is applied to Prestressed Concrete (PC) pile, too. According to the intention to prove this Standard, the base which established L/D=60 or 120 is very fragile. Only the reasoning is differences of stiffness of joint parts and pile materials between two kinds of piles. So, this two points, i. e. we aim at stiffness of joint parts and pile materials, we performed comparative experiments and theoretical consideration among RC, PC and Steel pipe (SP) and we investigated handling to be changed or not to PC pile. To three specimens of RC, PC and SP pile, we elect things that are nearly equal to their permanent allowable bearing force, and the outside diameter of RC pile made 400mm, of PC pile did 300mm and of SP pile did 318.5mm. Loading was, at the start, added to the extent of given axial stress and next, bending moment by means of two points loading was did.
