Examination of a fatigue durability evaluation method for deck-through cracks at the longitudinal rib to floorbeam connections of orthotropic steel decks

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04669
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 22020:Structure engineering and earthquake engineering-related
• Research Institution: Hosei University
• Principal Investigator: Uchida Daisuke 法政大学, デザイン工学部, 教授 (30650535)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 疲労 / 鋼床版

Outline of Final Research Achievements

Fatigue design of orthotropic steel deck bridges is based on specification design, but fatigue durability evaluation leads to rationalization of design and maintenance management. In this study, we focused on deck-through cracks originating from welds between deck plates and longitudinal ribs, and fatigue tests were performed on specimens at the longitudinal rib to floorbeam connections.
As a result, we focused on the fact that deck-through cracks propagated to about 80% of the thickness of the deck plate and then stopped, cracks were generated from the surface of the deck plate, and the cracks penetrated the plate. Then, fatigue strength curves were shown with the fatigue life as the number of loadings until the crack stops, including the results of past fatigue tests. In addition, we investigated the strain reference point for the stress range of the weld root when using it for fatigue durability evaluation.

Free Research Field

鋼構造

Academic Significance and Societal Importance of the Research Achievements

閉断面リブを用いた鋼床版橋梁のデッキプレート厚はデッキと縦リブ溶接部から発生するデッキ進展き裂を抑制するために最小板厚が16mmと規定されているが，橋梁の位置する路線の大型車交通量に応じたデッキ厚の決定は合理化につながる．本研究では疲労試験データを蓄積と既往の疲労試験データを再整理により溶接ルート部から発生したき裂が停留するまでの寿命で疲労強度曲線を構築できる可能性を示した．さらに，当該箇所にスカラップを設けない現行構造に対し，き裂の発生起点となる溶接ルート部の応力範囲を参照するひずみを提案した．この研究成果は当該箇所の疲労耐久性評価に必須であり，その実現に大きく近づいたと考えられる．