Kunitomo Sugiura

Performances and damages to steel structures during the 1995 Hyogoken-Nanbu earthquake

Described herein are the performances of and damages to steel bridges and viaducts during the Hyogoken-Nanbu earthquake in relation to past design specifications. A particular emphasis is placed on the performance of steel bridge piers and their buckling, low-cycle fatigue and brittle crack failures. Numerical simulation of typical damage such as elephant-foot buckling, failure of bearing devices and dynamic interaction of steel piers from adjacent reinforced concrete piers is carried out and possible causes are discussed. Finally, concluding remarks on the key concepts for earthquake-resistant design of bridges, several recommendations for the improvement of steel pier design and comments on future research needs are made.

Polymer concrete-filled steel tubes under axial compression

Abstract Concrete-filled steel tubular (CFT) structures are rapidly emerging as one of the inevitable structural systems for earthquake resistance, as they have been known to exploit the best attributes of both steel and concrete, resulting in higher stiffness, strength and ductility. However, the limitations imposed by certain drawbacks of cement concrete and which are not alleviated or moderated by the encasing steel tube, e.g. its high shrinkage, creep, brittleness, reactivity and low tensile strength, may be a hindrance to the rapid and diversified application of CFTs, in line with current emphasis on ductility-based seismic design. In this context, studies are presently being conducted on filled steel composite members, employing lighter, more ductile, high tensile strength and inert polymer-based fill materials for the steel tube. Findings of these studies relating to the elasto-plastic response of filled steel composite stub columns subjected to axial compression highlight the significant increase in strength and/or ductility of epoxy polymer concrete-filled steel columns.

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...

Long-term bridge health monitoring focusing on the Mahalanobis Distance of modal parameters

Maintaining civil infrastructure, including bridges, has been a keen technical issue in developed countries and will surely be one in developing countries in the near future. An effective maintenance strategy strongly depends on timely decisions on the health condition of the structure. Bridge health monitoring (BHM) using vibration data is widely recognized to be one of the effective technologies that aid decision-making on bridge maintenance. This research focuses on long-term BHM expecting that changes in physical properties of the bridge subject to aged-deterioration progress slowly. In the practical application of the long-term BHM, one of the difficulties is that the observed vibration data includes environmental influences such as temperature change. In order to achieve high accuracy in evaluating modal parameters of the bridge, other influencing variables have to be taken into consideration. In this study, temperature is considered as the main environmental factor by means of a regression analysis. The Mahalanobis distance (MD), a multivariate statistical distance, is adopted to emphasize potential changes in the identified modal parameters. The validity of the proposed approach is investigated utilizing vibration data measured at a real bridge in service.

BOND CHARACTERISTICS OF CARBON FIBER REINFORCED PLASTICS TO STRUCTURAL STEELS

Fiber reinforced plastics (FRP), as a structural material in lieu of using steel or concrete, can provide many opportunities for structural engineers to propose new structural systems. Even though material properties and their application to aerospace structures can be found in the literature, little information is available on the application of FRP to bridge and building structures. This paper studies the bond strength of carbon FRP to structural steels in order to develop the composite structure of steel and FRP. It is concluded that the strong anisotropy of FRP may cause local shear stress concentration, resulting in premature debonding.

Vibration-response due to thickness loss on steel plate excited by resonance frequency

The degradation of steel structure due to corrosion is a common problem found especially in the marine structure due to exposure to the harsh marine environment. In order to ensure safety and reliability of marine structure, the damage assessment is an indispensable prerequisite for plan of remedial action on damaged structure. The main goal of this paper is to discuss simple vibration measurement on plated structure to give image on overview condition of the monitored structure. The changes of vibration response when damage was introduced in the plate structure were investigated. The damage on plate was simulated in finite element method as loss of thickness section. The size of damage and depth of loss of thickness were varied for different damage cases. The plate was excited with lower order of resonance frequency in accordance estimate the average remaining thickness based on displacement response obtain in the dynamic analysis. Significant reduction of natural frequency and increasing amplitude of vibration can be observed in the presence of severe damage. The vibration analysis summarized in this study can serve as benchmark and reference for researcher and design engineer.

Experimental Study of Asphalt Surfacing Influence on Rib-to-Deck Joints Considering Temperature and Dynamic Effects

AbstractNumerous fatigue cracks have been observed in many orthotropic bridge decks that have been in service for a long time. The cracks around rib-to-deck (RD) joints might affect traffic safety. In most current design specifications, the asphalt surfacing is treated merely as a layer dispersing wheel loads. To investigate critical transversal load cases for RD joints and to assess the influence of temperature and dynamic loads on stresses around RD joints, a full-size orthotropic bridge-deck specimen with asphalt surfacing was subjected to wheel loads under different thermal and dynamic conditions. Experimental results show that the most critical transversal load cases occurred when dual wheels traveled over the RD joint and also around adjacent RD joints. Stresses around RD joints were found to be extremely sensitive to asphalt temperature and dynamic loads. Hence, the asphalt’s temperature, vehicle speeds, and the number of heavy axles of trucks should be considered when evaluating RD joint fatigue life.

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．

EFFECT OF TENSILE FORCE AND SHEAR FORCE ON BENDING STRENGTH AND STIFFNESS OF HIGH STRENGTH BOLTED TENSILE JOINTS

高力ボルト引張継手では, 予め, 高力ボルトに高い軸力が導入され, 継手面には材間圧縮力が発生する. したがって, 引張力あるいは圧縮力などのボルト軸方向の外荷重のみではなく, せん断力に対しても摩擦接合として抵抗するため, 高力ボルト引張継手は, これら以外の断面力も伝達できる多面的な継手形式と言える. しかし, この種の継手に関する既往の研究の多くは引張力のみを対象としており, 組合せ荷重下での検討は十分になされていない. したがって, 本研究では, 本継手を実構造物の接合法として適用するために, 実際に近い荷重状態下での力学的挙動を, 断面力として, 引張, 曲げ, およびせん断力を想定し, これらを作用させた載荷実験により明らかにし, 実橋部材の継手構造に適用可能であることを確認した.