Extensive damage was induced due to the Hyogo-ken Nambu Earthquake in the Rokko Island Bridge. The pivot shoes in the south side of the bridge were collapsed and the superstructure fell off from the shoes down to the framed pier and moved to the east side . The transverse displacement caused by the lateral movement was about 3 m. Some of the upper lateral bracings connecting two plane arch ribs were buckled. Dynamic response analyses are carried out to examine the causes of these damages. The results show that the buckling of the upper lateral bracings was caused by the lateral movement and the inclination of the superstructure.
Butt welds with a backing strip are widely used in the joints of longitudinal trough ribs of orthotropic bridge decks. Fatigue strength of transverse butt welded trough joints with a tack welded backing strips in steel deck panels was examined by bending fatigue tests and fatigue failure surface observations. Also local stress behaviour was examined by applying finite element method analysis. A total of 26 specimens with 5 different tack weld details were tested. The results of the fatigue tests show that there is almost no difference in the fatigue strength of butt welded trough joints made using the different details. The study indicates that the most influential factor regarding the fatigue strength performance of butt welded joints having a backing strip is the presence of defects in the weld root.
The tower link pins for long-span suspension bridge of Seto-ohashi Bridges, available for automobiles and high speed trains, are subjected to wear due to low-speed and heavy-load osillaitions. The link system for vertical bearings of this bridges is a unique system, called ‘tower link’, equipped with oil-less cylindrical bearings consisting of pins and bushes embedded solid lubricant. This report presents a summary of (1)development process, including material selection, experiments, and studies, (2)preparation of design and manufacturing guidelines of tower links.
We investigated long term fatigue behavior of web gusset j oint in floor-beam-to-main-girder connection, by means of a constant amplitude fatigue testusing plate girder specimens and fatigue crack propagation analysis. Fatigue strength of the joint represented by the principal stress range satisfies Category F of the JSSC Fatig ue Design Recommendation, which is one rank higher than the category regulated by the Recommendation .
This paper presents results of experim ental and numerical studies on the effects of undermatched welds on high -strength and heavy-section steels. The studies involved HT-780, HY-100, and HY-130 steels for high-strength steels and A572Gr60 (W14x370) for heavy section steels, whose tensile strength is approximately 750, 700, 900, and 500 MPa, respectively. The objective was to reduce requirements for preheating temperatures, while preventing crack initiation and improving fracture toughness, using undermatched welds for the first several passes of partial- and fullpenetration groove-welded joints involving high-strength and heavy -section steels .
It has been a popular practice to apply the blast treatment to the frictional joint of the hot dip galvanized steel . However, this method is never free from any problems in terms of the cost, the quality ( peeling of hot dip galvanized coating ), and the delivery date. For this reason, we have taken up in our study the phosphate treatment and the ceramic coating as a method of frictiona surface treatment that can be applied easily. A s a result, it turned out that the phosphate treatment was an excellent frictional suface treatment, whereas it turned out that the ceramic coating suffered some problems.
A simplified method for determining the buckling strength of axially -loaded concrete filled steel tubular columns is discussed and a design equation was derived and developed. It is based on the mathematical equation that was developed by Rondal - Maquoi, was used to represent SSRC multiple-column curve (The Structural Stability Research Council, 1976). The general validity of this approximate approach is demonstrated by comparison with both computed exact collapse loads or experimental column tests.
When existing simple span bridges are converted into a continuous span rigid support conditions have to be changed to elastic supports in order to absorb and distribute the energy of large horizontal motion due to earthquake loading. However, development of reaction force and additional stresses on the slab due to the unequal displacement of the elastic supports have been overlooked . In this study, a simple span bridge specimen is tested and analyzed to investigate stress increase of the concrete slab when the rigid supports are replaced by the elastic supports to accommodate the structural conversion. Durability of concrete slab under the elastic support is also discussed.
Various fracture modes were observed in the connections with stiffener rings between steel beam flange and concrete -filled circular tube column by the experimental research works carried out previously by other Japanese investigators, The yield line mechanisms are proposed for the observed fracture modes, and estimation formulae of the local plastic and ultimate strengths of the connection are proposed in this paper. The fracture mode of the connection can be predicted properly by this research work, and the estimated local plastic and ultimate strengths agree well with the experimental results regardless of the test series carried out previously.
In order to estimate the ultimate strengths of slender RC and SRC columns, new formulae have been proposed being based on the superposed strength method . In this paper, the accuracy of the formula is discussed in comparison with the experimental strength.
A new type of steel and concrete composite continuous girder bridge is developed using steel U-section as main girders, in which steel U girder is composite with RC slab in span center where positive bending moment is critical, whereas concrete is poured into the steel U-section and pre stressed at the intermediate supports where negative bending moment is critical. Experiments and analysis are carried out to investigate the static bending behaviors of this new girders. It is found that composite action can be attained for the positive bending moment portions, steel section and pre-stressed concrete work as one piece for the negative bending moment portions, and calculations based on the RC method has good agreement with experimental data. A trial design is also conducted taking three-span continuous girder with span of 60m, which shows that the new bridge system can be economical.
In order to investigate the effects of bolt-hole arrangement and edge distance of bolted joints on the ultimate tensile strength and failure modes of H-shaped tension members, we conducted tension tests of the H-shaped members jointed with high-strength bolts. We proposed formulas to predict the ultimate tensile strength of flanges and webs for net section fracture, tearing fracture and end fracture. The experimental results confirmed that the ultimate strength of the H-shaped member was obtained by the sum of both strength of flange and web. The ultimate strength of the prediction formulas, which were previously obtained from the steel plate joint tests, to the H-shaped members was discussed. SS400 steel, 590Mpa-grade and 780Mpa-grade high-quality steels were used for test specimens.