Study Of The Safe Assessment Of In-Service Steel Gate

Our country has built a lot of large-scale and middle-scale hydraulic metal structures, the radial steel gates are used among them. However, many gates have already reached or will reach depreciation period soon, so the reliability of these gates are uncertain, there exist great hidden danger even. But because of such respects as actual need or fund etc, the gates are still continuing to use. The safe assessment of gates is already urgent, and which has very heavy social effect and economic benefits.The paper carries on the safe assessment to the in-service radial steel gate of a hydroelectric station. As a component of sluicing and lock water construction, the gate must be evaluated with the theory of structure reliability too. Radial steel gate is a kind of structure that has strong space effect; space finite element analysis technique is a modern calculation method, which can describe the entire work effect of the space structure. By using the ANSYS FEAS software, the calculation and analysis of a spillway radial steel gate are developed in this paper. The values of stresses of the gate in several load cases are presented. On the basis of reliability theory and the function character of hydraulic steel gate, this paper has essentially researched the distribution and statistics of the random variables of hydraulic steel gate, and on the basis of the intensity calculation of the gate's crucial points by three-dimensional finite element analysis method, has educed the limit state equation of all kinds of invalidation modes by stress coefficient method, and has obtained the reliability indices of the gate by JC method. Finally, on the basis of the analysis and comparison of the obtained results, the reliability of the gate is elementary estimated.The corrosion of the steel gates is a very general phenomenon. The corrosion makes the gates thin, and then causes the bearing capacity of the gates to fall; therefore corrosion measurement plays an important role to safe assessment of the gates. The paper has measureed the corrosion penetration of the gates. The results of the measurement show that the rate of the corrosion is of a normal range.The paper carries on nondestructive testing to the welding seams of the gates by ultrasonic wave in the end. The testing results show that there are welding flaws in the welding seams of the gates. On the basis of the finite element stress analysis of the gate, the paper establishes the limit state equations of cracks by probability rupture mechanics, and obtains the failure probability of the cracks. Finally, the failure probability of the cracks is elementary estimated.