Mechanical Behavior Analysis Of The Oil Derrick With Semi-Rigid Joint And Bar Damage

As an important bearing component for the exploration and development of oil field, the oil derrick has been indispensable to the drilling and exploitation of the oil. Especially when the construction involves the field operation, long-time rain, frost and wind vibration, the bump in the transport as well as the improper installation, it will pose a safety hazard to the normal use of the steel structure of oil derrick. Moreover, it will also threaten the safety of the equipment in the case of complicated load and work condition. Besides the extremely unfavorable operation environment, most of those in-service oil derricks are functioning longer than originally intended. Hence, the derrick structure has been damaged in different degrees. Once some important parts for connection are damaged, the damage may rapidly spread under the influence of the complicated and random load. In consequence, it may cause serious damage to the whole structure of the derrick, which will make it function in an unstable manner and thus result in an immeasurable loss. Therefore, it is of significantly realistic meaning to carry out the mechanical analysis of oil derrick by taking semi-rigid joints and rod damage into consideration.First of all, this paper will summarize the damage and defect in various oil derricks. Some equivalent treatments will be proposed to deal with the common damages of the derrick. To be more specific, the reference stress correction method has been utilized to realize the equivalent treatment of the section corrosion and initial bending of the derrick rod. The calculation component method has been adopted to classify the connecting joint of derrick column into several components, such as column lateral stress, column lateral tension, column lateral shear, pin axel shear and ear-plate wall tension. The rigidity of different components has been calculated to work out the overall rigidity of the joint. By taking JJ225/43-K oil derrick as an example, this paper will make a study of the moment-rotation property of the main column connection. The moment-rotation constitutive model will be also chosen for the analysis of the oil derrick. The influence of the section corrosion and initial bending on the moment-rotation feature of the joint will be also considered. Based on the finite element analysis, the sprint element has been added to the column joint. The moment-rotation relation influenced by the section corrosion and initial bending of the rod will be given to the spring element, thus building the overall model for the oil derrick. On the basis of the finite element model considering the influence of section corrosion and initial bending, this paper will also study the effect of the damage on the steel structure of the derrick from the perspective of static and dynamic characteristics.