Research On Load-bearing Capacity And Safety Evaluation Of Derrick With Variable Section Leg

Oil rigs derrick is the important component part of petroleum industry, it is a large scale load composition, is important to oil field production. Because of using many years, the different defects of strut and connect place influence directly the safety of drilling operation. At the moment, the general way of the safety assessment to oil derrick is that, testing derricks stress,displacement and structure dynamic characteristic, basing on testing data, making sure the bearing capacity of derricks by linear extrapolation. But only limited dangerous place can be tested in derrick load experiment, testing load is much lower than design load, so it is difficult to get comprehensive and reasonable assessment result. So, the study of oil derrick composition bearing capacity by limit element analysis, raising bearing capacity testing level and safety assessment level of oil derricks, that has the important theory significance and use value without doubt.The paper mainly carries on the safety assessment to the load capacity for variable cross-section leg derricks, firs taking in the using JJ225/43-K variable cross-section leg derrick as the example, carries on the statical analysis under the biggest load operating, makes sure the derrick's stress and displacement under the big hook load operating; Then the paper introduces the scene derrick test technique, and carries on the appearance examination,the static load experiment,dynamic load test and computer simulation, as the foundation for as follows safety assessment. Finally, the paper elaborates the equivalent processing method of derrick initial imperfection such as initial curvature,section corrosion, studies the safety assessment theory of oil derrick bearing capacity, and carries on the bearing capacity analysis and the safety appraisal to the variable cross-section leg derrick after equivalent processing.The paper unified project actual, carries on the bearing capacity analysis and the safety assessment to the variable cross-section leg derrick, uses the way which finite element analysis and the scene test, provides the reference to the using derrick and new derrick bearing capacity and reliable appraisal, will has the great significance to make the safety assessment system theory careful and thorough.