正交异性钢桥面板顶板贯穿型疲劳裂纹的应变疲劳分析与可靠度优化设计研究

The fatigue cracks through deck plate in orthotropic steel deck are harmful to the safty of the bridge deck and difficult to be repaired. The high-cycle stress-based fatigue design based on the norminal stress method is usually employed for the deck plate in orthotropic steel deck. However, in the practical projects, the deck plate are prone to fatigue cracking and the fatigue life is far less than the estimated life according to the stress-based fatigue design method.The acutal tests reveal that residual stresses in the weld zone of deck plate are close to yield strength of the material, which may cause the low-cycle strain-based failure with the simultaneous action of traffic loadings.. In this project, the fatigue performance analysis and reliability-based optimal design methods for deck plate in orthotropic steel deck are investigated based on the strain-based fatigue damage theory, which includes: 1) The coupling mechanism between the welding residual stress and structural restraint stress of the deck-rib welded details is investigated based on the residual stress tests and numerical modeling, based on which the distribution model of residual stress in the deck plate is proposed for the fatigue analysis; 2) The initiation-expansion mechanism for the fatigue cracks through deck plate is investigated based on a series of strain-based fatigue tests, based on which the strain-based fatigue analysis method cosidering the effect of residual stress is proposed; 3) The reliability analysis method for the strain-based fatigue failure of the deck plate is investigated and the influences of the key design parameters on the strain-based fatigue reliabiltiy are detailed studied, based on which the optimal fatigue design method for the deck plate is proposed.

钢桥面板顶板贯穿型疲劳裂纹对桥面系安全使用危害大并且修复困难。钢桥面板顶板大多采用基于名义应力法的高周应力疲劳设计方法。然而，实际工程中顶板易发生疲劳开裂，远没有达到按照应力疲劳破坏预估的寿命。已有测试表明，顶板焊缝区域的残余应力水平接近材料屈服强度，与车辆荷载的双重作用容易造成低周应变疲劳破坏。.本项目基于应变疲劳损伤理论研究钢桥面板顶板的疲劳性能分析与可靠度优化设计方法，包括：1）基于残余应力测试与数值模拟研究顶板-纵肋焊接细节的焊接残余应力场和结构约束应力场耦合机理，建立适用于钢桥面板顶板疲劳分析的残余应力场分布模型；2）通过系列应变疲劳试验研究顶板贯穿型疲劳裂纹的萌生-扩展全过程机理，建立考虑残余应力影响的钢桥面板顶板应变疲劳分析方法；3）研究顶板应变疲劳可靠度分析方法，详细考察钢桥面板关键设计参数对顶板应变疲劳可靠度的影响规律，建立钢桥面板顶板的抗疲劳优化设计方法。

钢桥面板顶板贯穿型疲劳裂纹对桥面系安全使用危害大并且修复困难。钢桥面板顶板大多采用基于名义应力法的高周应力疲劳设计方法。然而，实际工程中顶板易发生疲劳开裂，远没有达到按照应力疲劳破坏预估的寿命。本项目以公路钢桥面板顶板贯穿型疲劳裂纹为研究对象，研究钢桥面板顶板的疲劳性能与考虑残余应力影响的疲劳寿命评估方法。研究成果主要包括：1）基于残余应力测试与数值模拟考察钢桥面板关键设计参数对顶板-纵肋焊接细节的残余应力分布的影响规律，建立适用于钢桥面板顶板疲劳分析的残余应力统一分布模型；2）通过建立钢箱梁焊接残余应力和结构应力耦合计算分析模型，构建焊接残余应力和车辆荷载耦合作用下平均应力、等效应力幅等疲劳参数计算方法，揭示钢桥面板顶板-纵肋焊接细节的焊接残余应力场和结构约束应力场的耦合机理，建立考虑残余应力影响的钢桥面板顶板应变疲劳分析方法；3）结合上述成果，提出考虑平均应力效应修正的全空间S-N曲线模型，揭示平均应力对典型焊接细节疲劳寿命的影响规律，建立考虑焊接残余应力影响的钢箱梁焊接细节疲劳寿命评估方法。项目成果有力地推动钢桥面板疲劳设计理论的发展，有利于揭示钢桥面板的疲劳损伤机理，对大跨桥梁防灾减灾科学以及全寿命设计理论和方法带来新的发展。