A damage criterion is proposed to govern the macrocrack initiation for welded structures. Non-linear FE analyses on welded T-joints are performed by using ABAQUS. Numerical results show that the damage criterion gives good prediction for the macrocrack initiation in welded T-joints. Fracture toughness tests on SS400 are carried out to obtain Jic in terms of the JSME Standard. According to the modified CEGB assessment procedure, the ultimate Collapse load and the crack driving force of cracked T-joints are investigated by FE analyses. Cracked T-joints are tested under the combined loads of tension and bending. Numerical and experimental results are compared with the criterion curve. The results indicate that the modified CEGB approach is suitable for the safety assessment of defected welded T-joints.
The aim of this study is to improve structural behaviors of precast RC slabs on composite girder bridges by introducing prestress with external cables. In this study, the composite girder bridge models with precast RC slabs were fabricated in the laboratory. The prestress was introduced into the models by external cables. Cable arrangement was straight to introduce prestresses into the slab effectively. In this paper, several prestressing methods are tested, and the effects of each prestressing methods are discussed through elastic behaviors and punching shear capacities of the slabs.
A practical 3-dimensional analytical method for earthquake response of steel towers in a power transmission system is described. The method takes into account the differ ence in elevation of conductor support points of adjacent towers, the difference in horizontal angle of lines and the difference in length of spans. Earthquake response analysis using this method was compared with the results of a 500kV conventional 2-dimensional analysis in a horizontal plane. The study also included the effect of the vertical earthquake on the response of the tower, which can not be obtained from the 2-dimensional analysis.
The modified structural details of horizontal and vertical stiffeners to meet the requirement of robotics welding are needed in plate girder fabrication. This paper presents the relation between vertical stiffener-end-gaps and fatigue cracking. Fatigue tests are carried out on specimens which have different details between a flange and a vertical stiffener used for connection with a cross beam. The details considered are a vertical stiffener-end welded or tightly fitted to a flange, and vertical stiffener-end-gaps of 35 mm and 55 mm. Except for a vertical stiffener-end welded to a flange, fatigue cracks are caused at the vertical stiffener-ends and at the fillet welds between a flange and a web. The examination of the local stresses in the web at the vertical stiffener-ends makes a condition to prevent the cracking at the fillet welds.
In buffeting analysis of low-frequency structures such as long-span bridges, Davenport's simple formula for the coherence of turbulence is known to lead to overestimation of responses. This paper presents extended Roberts-Surry and Thompson formulas for application to such situation. The effect of modal response correlation is also discussed by Complete Quadratic Combination (CQC) method. Responses by analysis of 890m-long cable-stayed bridge showed good agreement with the measured responses of a model in wind tunnel test.
ERW(Electoric Resistance Welded) pipes are manufactured from a steel coil with various cold-forming works - mainly uncoiling, leveling, forming and sizing. Since the steel is given great plastic deformation in these processes. it is necessary to consider multi dimensional stress state. The manufacturing processes give much effect on the mechanical characteristics of the steel, as a result, ERW pipes get the material initial imperfections such as residual stress and change of yield stress. In this report, these initial imperfections are estimated by qualitative and quantitative analysis.