中文摘要：

针对石油井架使用过程中出现主梁应力集中，影响井架的安全性及可靠性的问题，以K型井架为例，将主梁强度的降低以及腐蚀磨损等效为主梁截面的减小，采用随机有限元方法进行了参数敏感性及可靠性分析。采用扩展有限元方法进行了主梁断裂缝面的扩展以及主梁结构强度的分析。结果表明：主梁缺陷的存在会明显降低井架的可靠度，导致井架主梁应力集中问题更加严重。裂纹尖端的应力集中是造成主梁裂纹面扩展的主要因素，而且裂缝面的存在会直接改变其周围的位移分布。根据研究结果，可以更好地预测主梁缺陷对于井架可靠度的影响，以及为主梁裂缝面扩展的评估提供依据，从而降低井架安全事故的发生。

英文摘要：

Aiming at the problem of the stress concentration of the girder and the safety and reliability of the derrick during the use of the oil derrick, taking the K-type derrick as an example, the reduction of the strength of the girder and the corrosion wear are equivalent to the decrease of sectional area, and stochastic finite element method is used to analyze the sensitivity and reliability of the parameters. The extended finite element method is applied to the extension of girder fracture surface and the analysis of girder structural strength. The results show that the girder defects can reduce the reliability of the derrick, leading to the problem of girder stress concentration is more serious. The stress concentration of crack tip is the main factor of crack propagation, and the fracture surface will affect the displacement distribution around it. According to the results, the model is beneficial to predict the influence of girder defects on derrick reliability, and it can provide the basis for the analysis of girder crack propagation and decreasing risk of derrick incidents.