Safety Evaluation In Finished State Of Long-span Steel Box Girder Suspension Bridge Based On Quality Control Of Construction

China is a great country with a lot of great rivers, mountains and canyons. Long-span suspension bridge is one of the most suitable type of bridge under this condition. The are various components in suspension bridge, so high-level specialization of construction technology is required. Based on years of technology accumulation, China has taken the leading position in suspension bridge construction. However, quality variations, the deviation between construction quality and design requirements, inevitably exist in construction. These quality variation are usually not fatal problem, but absolutely effect the final state of bridge. Systematic research about types and degree of quality variation and their effects are rare so far. Taking the quality variability in construction for a new Angle of view, the safety degree of finished state is evaluated based on the effects that the quality variations work on bridge. Extend the evaluation from inspection of appearance and load test to quality control in construction.Based on the Puli bridge in Yunnan Province, which is a long-span steel box girder suspension bridge in mountain, by tracking its construction process, according to mass of data from linear measurement, internal force and stress test, the quality variation types, degree and reason of main towers, main cables, cable clips and hangers, anchorages, steel box stiffening girders are systematically researched. The results show that there are 14 types frequent construction quality variation.Through finite element analysis, the way the variability of construction quality influencing the safety state is analyzed, and the influence degree is quantitatively analyzed. Section stress variation in tower caused by the deviation of geometry size, and the main tower tilt. About main cable, the tension variation caused by position deviation, including horizontal and vertical deviation, on top of tower, cable shape deviation, effective area of cable section is discussed.Von-stress change caused by the angle deviation of tie rod in anchorage connecter, tension variation in main cable and hanger rod caused by the position deviation of cable clip, length deviation of hanger rod and weight deviation of steel box girders are analyzed. The effect of the maximum stress value including residual stress in welding line is discussed as well. Meanwhile the effect strength of each quality variation is discussed according to the result of sensitivity coefficient. At last, 9 major quality variation types are put forward.Then the concept of initial safety degree is put forward. Taking the compressive safety degree of main tower( Tt), the tensile safety degree of main tower(Tp), safety degree of main cable(C), safety degree of hanger rod(D), the safety degree of anchorage connecter rod(L), stess safety degree in steel box girder(G) as the evaluation indexes, the initial safety degree evaluation method for suspension bridge is creat based on PCA.The results show that the synthetic score value can reflect the real safety condition of suspension bridge. The state with higher synthetic score means high safety, otherwise, low safety. The application of PCA in the initial safety evaluation of suspension bridge is feasible and reliable.