The space and rigidity of the intermediate diaphragms have been designed based on the design handbook issued from Japan Road Association, in which the large rigidity is precondition, or by computer calculation using BEF analogy model. The former sometimes gives large or impractical rigidity, while the latter method gives much freedom of design, because arbitrary space and rigidity can be chosen and the distortional stress is also calculated. In this paper, aiming at rationalization of the design, the method based on BEF analogy model is proposed, in which the accuracy the distortional stress by analogy calculation is compared with that by FEA and also the economical advantage of using this method is presented.
In 2007, the building standard law of Japan was revised and a specification of column overdesign factor (COF) was added in case of square tube columns. Our researches deal with existing non-conformed steel buildings using STKR columns according to being not satisfied with the specification of COF. In this paper, in order to enhance the full-plastic moment of column, reinforcement with steel plates and steel angles are proposed. An experimental verification of reinforced columns was conducted to investigate elasto-plastic behavior and confirm the validity of reinforcement design method. As a result, specifications for providing required bending moment to STKR columns were clarified.
In the case of H-shaped section bracing, the flexural buckling strength can be improved by increasing the cross section over the middle portion. For example, the increase in sections is accomplished by welding additional plates. The compression tests in inelastic ranges were conducted on the pin-ended columns reinforced H-shaped section by welding plates. The buckling behavior and the mode are examined for the members having a variety of proportion. It is found that the corresponding buckling strength can be larger than the column curve of the design standard for steel structures.
Use of high-strength steel is one of the factors for rationalizing designs of steel bridges. However, high-strength steel can incur problems with weldability, such as the occurrence of weld cracks. One approach to mitigating such problems is to employ under-matched welded joints; however, the tensile strength of transverse butt-welded joints is uncertain. In this study, tensile tests and elasto-plastic analyses were performed on these joints made of three types of steel with different tensile strengths and soft weld metals. On the basis of the experimental and analytical results, we propose an expression for obtaining tensile strengths of transverse butt-welded joints.
Fatigue strength of overlap welded joints in which transverse fillet welds were provided was investigated under an out-of-plane bending condition. Fatigue test results demonstrated the joints were failed by weld toe cracks, and the fatigue strength was equal to that of non-load carrying cruciform joints. When intermittent fillet welds were provided, the fatigue strength was reduced, but it was properly evaluated by using the hot spot stress approach.
The behavior of offset beam-to-column connection panels with exterior diaphragms under axial load is examined by using finite element analysis in this paper. In the analysis, seven cruciform subassemblages tested in the previous study are simulated and the models are validated by comparing numerical results with experimental data. Parameters used in this analytical study are width-to-thickness ratio, applied axial load on the column, difference between beam depths at both sides of the connection panel and the collapse mechanisms of connections. Accuracy of the proposed strength calculation formulae are investigated and collapse mechanisms of the connection are identified. Major findings are as follows: 1) the assumed collapse mechanisms coincide with the experimental results; 2) Stiffness and strength of the connection panels can be properly evaluated by the proposed formulae with the axial force ratio equal to or less than 0.5.
In this study, through fatigue tests of specimens with outside or both side fillet welds joints between deck plate and trough ribs, the effect of inside fillet weld was investigated on fatigue durability of orthotropic steel deck with trough ribs by comparing the fatigue behaviour of outside fillet welded joints and both side fillet welded joints. As a result, in both side fillet welded joints, fatigue cracks were initiated at the toe and root of inside fillet welds, and propagated into the deck plate. The inside fillet welds had little effect on fatigue durability of fillet welded joint between deck plate and trough rib.
This paper studied the weathering steel bridge that has exposed 30 years in air environment at the location different river and urban areas. Corrosive environment survey, rust survey and exposure test using attachable small test pieces were investigated. Rust evaluation of weathering steel bridges were carried out. In exposure test, amount of long-term corrosion loss that was estimated by exposure test using attachable small test pieces of one year and multi-year were compared.
The Matadi Bridge, a suspension bridge in Democratic Republic of Congo, was completed in May 1983 by the Japanese ODA. For the main cables of this bridge, the wrapping paste and the wrapping wire combination against the corrosion was adopted. In Japan, this combination was found out to be inadequate, and a dry air injection system was introduced. Therefore it was feared that the corrosion of this cable might be found. To examine the present condition, the main cables were unwrapped and investigated at the site. Some corrosion was found as expected. This paper reports this inspection.