PURPOSE: To secure good fixing strength by joining the main bars of two intersecting beams with each other at their intersecting point, and thereby accomplishing a fixation part in the form of a lattice.

CONSTITUTION: Beams 2, 2' perpendicular to each other are joined with a B- pillar 1, and the main bar groups 2a, 2a' of these beams 2, 2' are threaded in the joint of B-pillar and arranged as reinforcing bars. A bundling wire 4 for ex. is hitched at this intersection of the two main bars 2a, 2a' and twisted, and these main bars 2a, 2a' are joined to constitute a fixation part in the form of a lattice. The tensile force T applied to one of the beams 2a is, as a shearing force, transmitted to the main bars 2a' of the other beam 2', and the force S is opposed with the pressure bearing force F of the concrete of joint part. Thus a good fixing force is secured.