To reinforce the adhesive force of concrete by penetration a steel pipe so as to bore a plurality of holes and inserting a one side bolt-like shear connector projectingly into the inner surface and filling up concrete inside the steel pipe.

Drilling positions are marked on the outer surface of a steel pipe in the circumferential direction and the height direction, thereby boring a plurality of through holes 1a from the outside surface. A one side bolt type shear connector, which is provided with a screw 2a at a pin tail necks 2b and 2c in the middle part and furthermore formed with a tapered area or a dia- expanded area 2d, is inserted into the holes 1a from the outside. Furthermore, a sleeve 4 is inserted into the holes 1a while a nut 5a of a tool 5 is threaded with the screw 2a of the shear connector 2, thereby towing upward the sleeve beyond the point at which the movement comes to a halt due to the deformation in the tapered area or the dia-expanded area 2d and then, sheared at the neck area 2b and fixed with the steel pipe 1 to a satisfactory extent by the sleeve 4. This construction makes it possible to project the shear connector into the steel pipe from the outside without using a special device and enhance the adhesive force of concrete.