| 摘要 |
<p>A method and apparatus for preventing a sag of a panel, in which a plate (2) to be attached to a skeleton is located on the skeleton supported by a supporter, both end parts of the plate (2) are gripped by grasp electrodes (3) of a resistance heating device (l), current is caused to flow through the plate (2) by the grasp electrodes (3) to preheat the plate 92) to a predetermined temperature and to thermally expand it, the plate (2) is welded to the skeleton by a welding machine, and a tensile residual stress is developed in the plate by a thermal shrinkage deformation attendant upon cooling of the plate (2) after the welding. In a case where the plate (2) has a cut-away part (B Fig 6) electric conduction members (4) for short-circuiting the cut-away part are interposed in this part so as to form electric conduction paths for the preheating of the plate (2). </p> |
