In this paper, the mechanical properties such as the toughness and the strength of the submerged arc weld (SAW) metal are investigated. Main target is the fillet weld metal by one pass SAW used for the built-up H-shaped beam. For comparison, the JIS deposited metal is also prepared. Charpy absorbed energy vE0 of the JIS deposited metal was higher than the specified value of JIS. On the other hand, vE0 of the fillet weld metal was lower than the JIS deposited metal, and some of the fillet weld metal was lower than the specified value of JIS.
This paper investigates on the plastic deformation capacity of built-up H-shaped beam connected with RHS column. A total of sixteen specimens was tested under cyclic loading, with beam size, notch toughness and depth of penetration of submerged arc weld (SAW) as primary test variables. Test results showed that the increase in notch toughness of SAW lead to improvement of plastic deformation capacity, while the decrease in weld penetration did not correlate to decrease in plastic deformation capacity. FEA were also performed to provide insight into the impact of the beam size and the penetration of SAW on the plastic deformation capacity of the specimens.
This paper investigates the toughness of submerged arc weld metal included in preassembled type build-up H-shaped beam which prevent the premature brittle fracture of moment connection. Deformation capacities before fracture of many kind of moment connections containing rolled H-shaped section beam are analyzed statistically and the indices of the deformation capacity are defined to evaluate the toughness. The relationship between the deformation capacity of the moment connection containing pre-assembled type build-up H-shaped beam and the toughness are investigated considering with the destruction property and the effect of loading protocol using the indices, which reveals the necessary value of the toughness to prevent the premature brittle fracture.
Fatigue design method of steel bellows damper during earthquake excitations is examined. Bellows dampers are connected between a girder and an abutment in order to reduce damage of superstructures and substructures. Low-cycle fatigue properties of the bellows damper are examined based on low cycle fatigue tests of the bellows damper and nonlinear dynamic response analyses of girder bridges with the bellows damper connected at both ends. Fatigue strength of the bellows is evaluated using P/V difference method which is one of cycle counting methods and Miner's cumulative damage law. Fatigue damage evaluation is performed by three methods using plastic strains，total displacements and plastic displacements of the bellows dampers as indices respectively. Further，a damage index based on cumulative plastic displacements is proposed. Validity of the proposed damage index is verified compared with the three methods of fatigue damage evaluation.
The use of buckling-restrained braces (BRBs) as energy dissipation dampers is attempted for seismic performance improving of steel rigid-frame piers. In this study, the effectiveness of BRBs which connected the steel rigid-frame piers with gusset-plate to protect the structures under cyclic loading is examined by test. Compared with load carrying capacity of the original structure, the strengthened model with BRBs is equivalent to deformation capacity and ultimate strength. After the test, it was found that further attention should be paid to the design of the stiffener for suppresses out-of-plane deformation of the gusset-plates.
This study is aimed at evaluating the residual properties of high strength structure steel (HSSS) after a fire. Tensile coupons obtained from the HSSS Q690 sheets were heated to various temperatures up to 900 °C, and then were cooled down in furnace to ambient temperature. Tensile coupon tests were carried out to obtain their post-fire mechanical properties and ductile fracture behaviors. Test results showed that the HSSS can keep the unchanged mechanical properties after it experiences temperatures up to 600 °C. As a result, prediction equations are obtained to evaluate the post-fire properties of HSSS.
For investigating effect of heating and cooling process simulating fire on mechanical properties of Steels for Bridge High Performance Structure (SBHS), a series of experiment was carried out. The heating of 600℃ did not change the mechanical properties of SBHS from those without heating and cooling. The heating of 900℃ and air cooling decreased the mechanical properties of SBHS due to softening. The heating of 900℃ and water cooling increased the ultimate strength due to hardening; however, it decreased the yield stress and elongation of SBHS to the level below that required by JIS.