partition plate 7 continuously extending to the gusset plate 5 mounted to the central position of the reinforcing plate 4 in the quadrangular prismatic width direction is placed in parallel to other inner partition plates 7 on both sides of the central inner partition plate 7 on the contrary in the modification shown in fig4 the central inner partition plate 7 continuously extending to the gusset plate 5 mounted to the central position of the reinforcing plate 4 in the quadrangular prismatic width direction and another central inner partition plate 7 orthogonal to the above central inner partition plate 7 are placed in cross shaped arrangement 0062 fig6 and 7 show a different embodiment of the reinforcing plate 4 the reinforcing plate 4 in this embodiment is formed in the shape of a band so as to be placed around the outer surface part in the column section as equivalent to the outer surface part of each column 1 into one body the reinforcing plate placed as described the above is applied on the assumption that there is no desire to expose the reinforcing plate 4 to the outer surface from the viewpoint of designs for instance the following is a conceivable situation applied to the case where there is no desire to expose the reinforcing plate to the outer surface that is the reinforcing plate will be placed around the outer surface part of each column 1 into one body as described the above on the assumption that the columns 1 and the beams 2 are constructed using concreting in site whereas there is no need for placing the reinforcing plate around the outer surface part of each column 1 in case of.