基于多失效模式损伤度相容的钢桥面板抗疲劳设计方法

Fatigue-resistant design method of steel bridge deck based on multi-modes failure damage compatibility

疲劳荷载是决定正交异性钢桥面板疲劳寿命的外因,重载条件下钢桥面板的短寿问题尤为突出。多构造细节和多疲劳失效模式是钢桥面板疲劳问题的基本属性,其疲劳性能由构造细节疲劳寿命最短的疲劳失效模式决定。考虑剪切结构应力的疲劳寿命效应,基于疲劳裂纹扩展速率与疲劳寿命间的相关关系规律,提出了同时适用于钢桥面板多构造细节和多失效模式疲劳性能评估的广义等效结构应力法,实现了相关构造细节和失效模式疲劳抗力指标的统一表征;进而以构造细节为单位,将钢桥面板结构划分为多级子系统,提出了疲劳损伤累积相容性指标,建立了基于多失效模式损伤度相容的钢桥面板抗疲劳设计方法;在此基础上以有效延长重载条件下钢桥面板的疲劳寿命为主要目标,对三类钢桥面板结构的疲劳性能进行了理论分析和疲劳试验研究。研究结果表明:所提出的广义等效结构应力法适用于钢桥面板各构造细节及其相关失效模式的疲劳性能评估,通过所提出的方法能够准确确定钢桥面板的主导疲劳失效模式;所提出的基于多失效模式损伤度相容的钢桥面板抗疲劳设计方法,可为有效提高钢桥面板的疲劳寿命提供科学依据。

Fatigue load is the external factor that determines the fatigue life of orthotropic steel bridge decks, and heavy load especially leads to a great reduction in the fatigue life of the structures.Multiple structural details and multi-modes failure are the basic properties of steel bridge decks, whose fatigue performance is determined by the fatigue failure mode of the structural detail with the shortest fatigue life.Based on the relationship between fatigue crack growth rate and fatigue life, a generalized equivalent structural stress method is proposed considering the fatigue life effect of shear structural stress, which is capable of evaluating the fatigue performance of steel bridge decks with multiple structural details and multi-modes failure.This method can uniformly characterize the fatigue resistance indicators of all of the relevant structural details and failure modes.Furthermore, the steel bridge deck structure is divided into multi-level subsystems by taking the structure details as the unit and the fatigue damage accumulation compatibility index is proposed.And the fatigue-resistant design method of steel bridge deck based on multi-modes failure damage compatibility is established.In addition, the fatigue properties of three types of steel bridge deck structures are theoretically analyzed and measured in fatigue test with the compatibility of multi-modes failure.The main goal of this work is to effectively prolong the fatigue life of steel bridge decks.The research results show that the proposed generalized equivalent structural stress method is suitable for the fatigue performance evaluation of each structural detail of the steel bridge deck and itsrelated fatigue failure modes, and can accurately determine the dominant fatigue failure mode of the steel bridge deck.The proposed fatigue-resistant design method of steel bridge deck based on multi-modes failure damage compatibility facilitate to guide the design of steel bridge deck, and provide a scientific basis for effectively improving the fatigue life of steel bridge deck.