Analysis Of Strength And Fatigue Performance Of Strengthening Steel Structures Using Externally Bonded Fiber-reinforced Polymers

In many engineering structures, the stress which is far less than intensity limit often results in destruction or deficient work of steel structures or steel members.By analysis and statistic, it is found that the fatigue failure is one of the main kinds. In this thesis, the author carries out some experiments on the steel members which are reinforced by Carbon Fiber Reinforced Polymers (CFRP for short) and have an obtuse angle welding line. It is shown that the CFRP can prominently enhance the fatigue life and fatigue intensity limit, meanwhile effectively decreases the stress concentrated on the welding line. Hence the present method that could remarkably improve the steel structure fatigue or steel members fatigue life has preferable applied value.In addition, there are some drawbacks in traditional Miner liner accumulated damage theory. Therefore, those drawbacks result in considerable errors in the prediction of fatigue life. In this paper the stress less than the fatigue limit is considered and it thinks over the actual "α" value that is not equal to "1". Based on these two factors, the fuzzy mathematics is introduced into establishing a new modified Miner accumulated damage theory. Compared with the two test results, the modified Miner theory improves the accuracy of fatigue life prediction and possesses potential application in engineering.