Damage Identification Of Derrick Base On Displacement Model

The carrying capacity of oil derrick will cannot match the original designcarrying capacity because of damage defect of oil derrick, as stated in nationalstandard that needs to detect it. However, stress testing belongs to samplinginspection so that stress testing will affect the judgement of the carryingcapacity of oil derrick.In order to study the stress state of oil derrick, the damage defect ofderrick must be identified. Based on the finite-element model of derrick whichhas damage defects, the carrying capacity of derrick is evaluated. This papersystematically describes the theory of structural damage identification basedon dynamic data.This paper establish finite-element model of HJJ450/47-T marine derrickand analyse stress state and dynamic parameters of the derrick by design load,stress state of the derrick by design load and wind load, stress state of thederrick by design load and wave load. Based on simulation of the marine derrick which has defects, displacement mode value is extracted and studiedthe impact of damage defects. The displacement mode difference and thecurvature mode difference are used for identifying damage.A HJJ450/47-T marine derrick model was established in the laboratory.Identify damage preliminarily by the curvature mode difference which basedon measuring with the laboratory model including some defects. This paperuses the finite-element optimization method and model updating technology tosimulate the laboratory model. The stress state of the model is calculated andcompared with the measured stress values, the relative error of less than5%,indicating that the higher accuracy of model modification. And this is a newmethod for the detection of carrying capacity of oil derrick.