In order to quantitatively analyze the beam structural stiffness reliability at different life cycles, it is important to establish the accurate formula of degradation of physical property of beam under fatigue loads. According to influence of cumulative damage caused by fatigue loads on ultimate stress and using the relation of material strength and material elastic modulus, the formula of elastic modulus degradation was deduced based on residual strength degradation model. On this basis, the recursive formula of the beam structural elastic modulus degradation coefficient was given. The residual bending stiffness of beam with circular cross section was put forward. Adequate original data is necessary for probabilistic reliability model and fuzzy reliability model to analyze the structural reliability. To make use of the uncertain information of structures, the uncertain parameters such as initial elastic modulus, the load applied and so on were described as interval variables. Time-dependent non-probability reliability model of beam structural stiffness was established based on interval model. A numerical example has been used to illustrate the proposed method. The result shows that the proposed method is feasible and reasonable and practicable for the beam structural stiffness degradation analysis and the beam structural stiffness time-dependent reliability analysis.%为了定量分析在疲劳载荷作用下梁在不同寿命期内刚度的可靠性,建立梁结构物理性能退化的精确公式就十分重要.依据疲劳载荷造成的累积损伤对材料极限应力的影响,基于材料剩余强度模型,利用材料强度与弹性模量之间的关系,推导出结构弹性模量的退化表达式,并在此基础上,提出梁弹性模量退化系数的递推表达式,推导出圆截面梁剩余抗弯刚度的表达式.在对结构可靠性分析时,概率可靠性模型和模糊可靠性模型对于原始数据信息要求较高.为了充分利用结构的不确定性信息弥补原始数据的不足,将梁的初始弹性模量及所受的疲劳载荷等看作区间变量,利用区间模型建立基于刚度退化的梁刚度动态非概率可靠性模型.最后,结合工程实例的计算表明了该方法对梁的刚度退化分析及其刚度动态可靠性分析是可行、有效和合理的.
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