弧长法在服役石油井架非线性全过程仿真中的应用研究

针对服役石油井架的结构特点,考虑几何和材料双重非线性因素,建立了非线性数学分析模型。采用弧长法对荷载-位移平衡路经进行了全过程跟踪研究;对服役井架提出了基于应力和模态进行模型修正、建立基准仿真模型的方法。以油田使用的两部石油井架为例进行仿真分析,结果表明:在屈服点以前,载荷位移曲线基本呈线性关系;载荷值达到临界点之后,位移值迅速增大,而载荷降低,井架结构失稳。应用该方法来跟踪结构非线性平衡路径的全过程可以实现其非线性全过程的仿真分析,能够确定井架的失稳状态、破坏形式、极限承载力,得到令人满意的结果,具有一定的实用价值,适合工程应用。

Applications of arc-length method to full range nonlinear simulation of derrick in-service

Aiming at structural features of oil derrick in-service,considering double factors of geometry nonlinearity and material nonlinearity,mathematic analytical model is established.The full load-displacement equilibrium path is theoretically investigated by using finite element approach in conjunction with arc-length method.By updating stress or updating mode of finite element model,baseline simulation model of derrick in-service is established.Simulation analysis was carried out for two derricks in-service of oil field.The results indicates that before the yield point,the load displacement curve is linear,but when load value reaches its critical point,the displacement value increases rapidly,while the load drops and the derrick structure becomes unstable.The nonlinear full range simulation analysis can be realized,the instability state,failure shape and ultimate bearing capacity of derrick can be obtained satisfactorily.This method has its practical value and is suitable for engineering applications.