As a reinforcement method for steel bridges, the patch plate reinforcement using high-strength stud bolts has been developed. However, the method of determining the number of bolts and patch plate thickness has not been clarified, and the rational design method of the patch plate reinforcement has not been established. In this study, the tensile loading tests were conducted on box-section specimens reinforced with patch plates. As a result, by adding more stud bolts, the relative displacement between the main plate and the patch plate was restrained, and the load-sharing ratio of the main plate increased, approaching the cross-sectional area ratio. Increasing the thickness of the patch plate increases the relative displacement, and the load-sharing ratio of the main plate became larger than the cross-sectional area ratio.
A new type of PC steel bar brace for moment resistance steel frames has been proposed, which is called Displacement Restraint PC steel bar Brace (DRB). Prestressed disc springs at the ends of the DRB provide initial stiffness to the DRB. Free-fall contact tests were conducted with and without disc springs at the end of the DRB to confirm the impact load at contact. Quasi-static loading tests were also conducted to confirm the motion of the ends of the DRB and the impact load at contact under inter-story deformation at a certain frequency and amplitude. Furthermore, the effectiveness of providing initial displacements and initial stiffnesses is confirmed by time history response analyses.
Recently, seismically isolated buildings are required to secure a safety margin against extreme ground motions. A possible countermeasure is to install a fail-safe mechanism in the seismic isolation layer. When the seismic isolation layer deforms beyond a certain displacement, the fail-safe mechanism is activated to prevent excessive displacement. This study investigates the influence of the hysteresis characteristics of the fail-safe mechanism using steel members on the seismic response characteristics of seismically isolated buildings.
When attaching members with high strength bolts, the filler plate is processed to have projections and is sandwiched between the new members to ensure the coefficient of slip without removing the paint film of the existing structure that contains lead. Considering that the bolts are subject to relaxation due to the paint film, we considered retightening and increasing the primary tightening axial force. A slip test was carried out to verify the slip strength of the filler plate with projections.
Repair and reinforcement using CFRP sheets is currently being promoted for corrosion damage of steel bridges. On the other hand, it is expected that the limit state design method will be applied to repair and reinforcement in the future. In this study, we investigated an analytical method that can reproduce the nonlinear behavior of CFRP laminated steel members caused by the high elongation elastic putty material used to prevent of delamination. As a result, a method was obtained to model the resin material with interface elements. The stress reduction effect of the putty material and the delamination of the sheet can be reproduced by using a quadrilateral distribution as the shear stress-relative displacement relation of the putty material.
The patch plate reinforcement is currently being designed based on the crosssectional area ratio, but in reality, the load sharing ratio of the patch plate does not match the cross-sectional area ratio. In this study, we discussed the slip load and yield load of patch plate reinforcement which is applied by high-strength stud bolt and high-strength bolt. In addition, focusing on the load sharing ratio of the patch plate, we performed the parametric analysis, and we elucidated the mechanism of the patch plate load transmission, and the effects of the number of bolts, axial force, bolt arrangement, patch plate thickness.