Deteriorated RC slab deck of steel girder bridge is necessary to replace under half - width service construction for short time in Japan. Therefore it tends to replace composite RC deck to non-composite Precast PC deck, however, reinforcement of the main girders is required. In this study, frame analysis is conducted to confirm and to suggest a method to reduce reinforcement for girder. In addition, FEM analysis is conducted to evaluate the composite action between deck and girder. As a result of frame analysis, the amount of girder’s reinforcement could be reduced by taking cross-beam before combine the Precast PC deck in transverse direction. As a result of FEM analysis, the main girder with the Precast PC deck showed the incomplete composite action.

Recently, the security and integrity of large thin-walled steel cylinders (TSCs) have been threatened by an increasing number of high-magnitude earthquakes. To develop a sustainable economy and infrastructure, existing tanks must be strengthened. In this study, we investigate the strengthening effects of circumferential CFRP layers on the increasing load-carrying capacities of TSCs under compressive load through finite element analysis (FEA) and experiments. The results show that circumferential CFRP layers, particularly high-strength CFRP sheets, can increase the load-carrying capacity of TSCs. In addition, numerical results are found to correspond well with experimental results.

Seismic bellows dampers, which are connected between girder and abutment, are subjected to girder bending rotations due to live load. Since their occurrence frequencies are very high even though stresses due to live load are small, high-cycle fatigue properties of dampers must be examined. Fatigue properties of bellows dampers are evaluated based on high cycle fatigue tests and finite-element analyses (FEA). Firstly, bending rotation angles of girder end parts are calculated using fatigue-load (F-load), which is used for fatigue evaluation of road bridge design. Using the obtained rotation angles, stresses of bellows dampers are calculated by three-dimensional FEA models. Fatigue strength of bellows dampers is examined by high-cycle fatigue tests of bellows damper specimens. Fatigue strength of bellows dampers for live load is evaluated by test results and calculation results based on fatigue design of road bridge specification.

In this study, a hysteresis model of hysteresis dampers using bent steel plates for base-isolated structu res （BSPD） is proposed. The BSPD comprise four bent steel plates bent into a trapezoid. The bent steel plates are connected together in the shape of a cross. Since the mechanical behavior of the BSPD depends on the shape of the bent steel plates, the influence of the shape on the seismic response characteristics of base-isolated structures is investigated.