Kuniei Nogami

After-fracture redundancy analysis of an aged truss bridge in Japan

Abstract In the next 20 years, more than half of the bridges in Japan would be in service for more than 50 years. These include truss bridges those are generally considered to be non-redundant and fracture critical. With ageing, these bridges are facing an increasing risk of bridge collapse under extreme conditions. Therefore, it is essential to evaluate alternate load paths on existing bridge structures to avoid bridge collapse or replacement. In this paper, after-fracture redundancy of truss bridges is investigated through a case study for a five-span continuous truss bridge. Field tests were performed, and the displacements on key sections were measured in the test. According to the experimental observations and test results, a numerical model capable of simulating the present truss bridge was built and was used to investigate the after-fracture redundancy of the target bridge. Fracture of truss members in typical locations was considered in the numerical analyses, and the ‘R’ values of both intact and damaged trusses were compared. On the basis of the numerical results, a critical member in this bridge was also determined.

Measurement of Corroded Gusset Plate Connection of Steel Truss Bridge and Evaluation for Its Corrosion State

Notable accidents that the diagonal members of the steel truss bridges have broken due to the corrosion damage have occurred recently. Therefore it is expected to establish the rational and efficient maintenance management technique depending on the bridge types and structure characteristics. In this study, for the corroded gusset plate connection of the steel truss bridge which was cut out from the steel truss bridge, we measured the corrosion shape in detail using the laser measurement equipment, and evaluated the actual state of the surface corrosion outside and inside of the gusset plate connection.

ULTIMATE BEHAVIOR, STRENGTH AND STABILITY DESIGN OF GIRDERS IN CABLE-STAYED BRIDGES

本研究では, スパン600mの斜張橋を対象に, 弾塑性有限変位解析を用い, 桁高, 材質, 塔位置のケーブル吊間隔, 中央径間と側径間のスパン比が終局挙動や強度に与える影響を明らかにするとともに, 安定照査を不要とできる最小桁高選定に関する設計資料を提供している. 検討結果から, スパン600m程度までのマルチケーブルタイプ斜張橋であれば, 材質に関係なく桁高として2m以上を選べば全体の座屈安定性に関する照査は不要とできる可能性を示す.

EFFECT OF INELASTIC BEHAVIOR OF CABLES ON ULTIMATE BEHAVIOR AND STRENGTH OF CABLE-STAYED BRIDGES AND THE POSSIBILITY OF REDUCTION OF THE SAFETY FACTOR

本文ではケーブルの非弾性挙動を考慮した弾塑性有限変位解析を用い, ケーブルの安全率の設定が斜張橋の終局挙動, 強度に与える影響を明らかにする. 斜張僑では, 桁に大きな圧縮軸力が生じていることから, ケーフウレの塑性伸びにより終局状態となる. そのため, 終局強度はケーブルの塑性化または桁の降伏が生じるいずれか小さい方の荷重倍率で支配される. また, 面内耐力の観点からは, ケーブルの降伏点に対する安全率として現行の2.0から1.7へ低減できる可能性を示す.

OPTIMUM DEPTH OF A PLATE GIRDER DESIGNED BY ALLOWABLE STRESS METHOD

It seems there are too many formulations about optimum depth of a plate girder and one may wonder which is most preferable for his case. The authors studied the problem by theoretical but rather classical way taking into account every factors having effect to the depth.The result shows the effect of specified allowable compressive stress formulation and the number of sectional changes in a girder must be considered and these factors lower the optimum depth of it. In case of rather short span, the practical limit on the compressive flange area has large effect, even that is not explicitly specified in a code.