| Budget Amount *help |
¥15,000,000 (Direct Cost: ¥15,000,000)
Fiscal Year 2005: ¥4,800,000 (Direct Cost: ¥4,800,000)
Fiscal Year 2004: ¥10,200,000 (Direct Cost: ¥10,200,000)
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| Research Abstract |
In Hanshin-Awaji earthquake (1995), many members of large steel structures were damaged. After the earthquake, the local buckling deformations of many members were rapidly corrected by heating and pressing. However, correcting large deformation like buckling, the ultimate strength of the members is unknown. So it is necessary to confirm safety and reliability of members corrected by heating.
A series of compressive tests was carried out for virgin cruciform column and one corrected by heating. According to the results, buckling deformation modes of projection panels corrected by heating were variously changed by the degree of residual imperfection. And deformations up to the ultimate situation of corrected projection panels became larger than those of virgin panels. However, the ultimate strength of projection panels corrected by heating was almost equal to those of virgin materials.
To elucidate the reason why the compressive behavior of specimens corrected by heating differs from that
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of virgin specimens, elastic-plastic large deformation analysis was carried out. When considering only residual imperfection, the experimental phenomena could not be simulated. Then considering not only residual imperfection but also the rise of yield stress made by work hardening, the experimental phenomena could be simulated totally. From the analysis, it was elucidated that the reason why the buckling mode of specimens corrected by heating changed was both residual imperfection and the increase of yield stress made by work hardening.
In order to verify the major factors affecting compressive behavior of box column corrected by heating, a series of experiment was carried out and it was simulated by elastic-plastic large deformation analysis. The results were same tendency as the case of cruciform column. It was elucidated that two factors as residual imperfection and increase of yield stress involved in large plastic deformation dominated the compressive behavior of the steel members corrected by heating.
The alternative load test was carried out for the structural model of a bridge pier with considering the knowledge obtained from cruciform column and box column.
According to the results, if heating temperature was made to be under A1 transformation temperature at heating correction, residual imperfection could be largely corrected by using water without spoiling the mechanical properties. Whether the ultimate strength was decreased or not was decided by the magnitude of the local deflection which was remained without completely corrected by heating. Therefore, although the restoration to the original state was desirable to be as complete as possible to the original state, if the complete restoration was difficult, heating correction to the opposite direction of buckling should be performed somewhat larger. Less
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