It is reported in Part 1 that cast-in-place reinforced concrete piles with enlarged pile point have two problems in seismic design. The first is enlargement of pile heads accompanying increase of constructions. The second is the possibility of brittle shearing failure occuring before bending failure. In order to solve the problems, small scale model tests are carried out and the following results are obtained. (1)The head of piles should be reinforced by steel pipes, i.e. , the head should be concrete filled steel pipes, so that enlargement of pile head and brittle failure can be avoided. (2)Usage of steel pipes with ribs on inner surface are recommended to gain high bond strength between concrete and steel pipes so that bearing capacity is higher than that using ordinary steel pipes with flat inner surface. In the following report, Part 2, construction tests and bearing capacity tests of piles of actual size are reported.
