PURPOSE: To make a manual gauging operation unnecessary, and to make a joint with a low cost and high accuracy possible by force-fitting a standardized and short cylindrical backing strip with a specified interference into a steel pipe whose edge shape is made uniform by force-fitting an expanding jig.
CONSTITUTION: Expanding jigs 12 are force-fitted into both edge parts as shown by an arrow P to make the inner dimension of a steel pipe (square column) 7 cut in a length L uniform, and the steel pipe is formed into a specified shape and dimensions. Backing strips 13 with specified dimensions, are applied to both ends of the expanded and formed steel pipe (square column) 7, and are force-fitted by a force-fitting jig 14 as shown by an arrow P, leaving a specified dimension Δ L. By making the specified dimension ΔL a definite dimension all over the periphery, the steel pipe (square column) 7 is correctly fixed at right angles to the center line by the end face on the projection side of the backing strip 13 with the specified dimension. When making the steel pipe (square column) 7, a diaphragm and a steel pipe column butt one another, a common center line becomes straight. And, when performing welding in this state, a straight column member is composed.
TAKEZAWA YOSHIO