Kunitaro Hashimoto

Experimental Study on the Biaxial Loading Effect on Group Stud Shear Connectors of Steel-Concrete Composite Bridges

Abstract Clustering stud shear connectors with minimized spacing based on specifications to form group studs are useful for concrete slab prefabrication and prestress installation efficiency in steel-concrete composite bridges. To date, many long-span composite bridge girders have been designed with wide transverse cantilevers and web spacing, and most of these girders use group studs. The concrete’s self-weight and the weight of moving loads result in a significant transverse bending-induced effect generally consisting of bending stresses and tensile concrete cracks. In this sense, the studs are actually under longitudinal interlayer shear force that is influenced by the transverse bending-induced effect. This biaxial loading effect has not been investigated experimentally. Thus, standard and newly designed push-out tests and corresponding analyses were carried out. In addition, the stud arrangement effect also was of concern. In this study, the ratio of stud height to shank diameter was approximately 6....

Influence of Asphalt Surfacing on Fatigue Evaluation of Rib-to-Deck Joints in Orthotropic Steel Bridge Decks

AbstractNumerous fatigue cracks were observed recently in orthotropic steel bridge decks that have been in service for a long period of time. A fatigue crack initiating from the rib-to-deck (RD) joint may especially produce asphalt surfacing damage, and hence have an impact on traffic safety. In fatigue evaluation of RD joints, in most current design specifications the asphalt surfacing is just treated as a layer dispersing wheel loads, in which the wheel loads are uniformly distributed on the deck plate and the effect of the composite stiffness of the deck plate and asphalt surfacing is neglected. In this study, comprehensive finite-element and load models were used to investigate the asphalt surfacing influence on the wheel load dispersal and composite stiffness. The analysis result shows that wheel loads are not uniformly distributed on deck plates but are concentrated on the weld joints, the asphalt surfacing could significantly decrease the stress magnitude around the RD joints, and this decrease may...

CORROSION INVESTIGATION OF WEATHERING STEEL BRIDGES ON SEVENTH NORTH KOBE LINE IN HANSHIN EXPESSWAY

阪神高速道路7号北神戸線の耐候性鋼橋に対して，詳細な防食状態や塩分量の調査が1998年～2008年の10年間実施されてきた．本報告では，その結果をまとめ，傾向分析を行った．ここでは，外観評点とさび厚，さび厚と板厚減少量，保護性さび形成状態と外観評点，および腐食状態と塩分量との関係に着目して傾向分析を行った．これらの結果より，外観評点によって，さび厚や保護性さび形成状態などの腐食状態をある程度把握できることがわかった．また，冬期の凍結防止剤の散布によって橋梁に供給される塩分量が想定以上に多いこと，付着塩分量と外観評点やさび厚などのさびの状態との関係と腐食損傷には一定の相関関係があることがわかった．