Research On Reliability Of Half-through And Through Concrete-filled Steel Tube Arch Bridge System

In recent 30 years,concrete-filled steel tube arch bridge has developed rapidly at home and abroad because of its advantages of reasonable stress,convenient construction,economy etc.Design theory has received increasing attention on concrete-filled steel arch bridge,and structural reliability is an important part of the design theory.However,at present,there are few researches on the reliability of concrete-filled steel arch bridges and they mainly stay at the component level.There are few researches on the reliability of structural system,which leads to the serious lag of the structural design theory based on system reliability.The structural design method based on component reliability is often too conservative because it does not consider the structural redundancy.At the same time,it also makes the later maintenance and reinforcement of concrete-filled steel arch bridges lack the basis of reliability level,which limits the further promotion and application of concrete-filled steel arch bridge.Based on this,this paper combined with the existing reliability calculation theory and research results,aiming at the lack of reliability research of through and through concrete-filled steel arch bridge system with suspender,carried out research from the following aspects.(1)The structural reliability theory and the current research status of the reliability of the concrete-filled steel tube arch bridge system were summarized,and the main problems in the reliability evaluation of the concrete-filled steel tube arch bridge system were pointed out.Among them,the first-order second-moment method of structural system reliability calculation was emphasized.(2)Taking stability failure as the failure criterion,the calculation formula for the flexural bearing capacity of truss concrete-filled steel tube arch ribs was derived,and through the analysis of the random field characteristics of the arch rib material and geometric dimensions,a method considering the spatial variability and spatial correlation was proposed on truss concrete-filled steel tube arch ribs.(3)Based on the electrochemical corrosion theory of steel strands,combined with the corrosion characteristics of steel strands,resistance degradation models were established for the static and fatigue failure modes of the steel strand hangers of the mid-through and through concrete-filled steel tube arch bridges.At the same time,the suspender resistance,stress and time-varying stress amplitude were fully considered Characteristic,a model for calculating the time-varying reliability of a single suspender under the influence of corrosion was established.(4)According to the internal force transmission process of the most commonly used lattice girder bridge deck system for long-span concrete-filled steel tube arch bridges,it was proposed to simplify the reliability of the lattice beam bridge deck system to the reliability of multiple continuous beams,and then the reliability of the lattice beam bridge deck system was established by analyzing the failure modes of the continuous beams.(5)In view of the shortcomings of traditional algorithms that single suspension rod fracture was used as the failure criterion of the system,ANSYS was used to analyze the dynamic response of the remaining structure after the arch bridge suspension rod fractures,and the reliability index of the remaining structure in the dynamic response process under the failure condition of single or multiple booms was calculated.Based on this,the probability of continuous cable breakage of the arch bridge after a single suspension rod fracture and two adjacent suspension rods successively fractured was evaluated,and finally the failure mode of the arch bridge system considering the suspension rod fracture and its reliability calculation method were proposed.(6)Combining the above calculation methods of the reliability of each component and structural system and combining the principle of the series system,a universal calculation framework for the reliability of the mid-through and through concrete-filled steel tube arch bridge system was established.Then,it was applied to the world’s largest long-span arch bridge—Pingnan Third Bridge,and the time-varying law of the reliability of the bridge system and the influence law of various parameters were studied,which could provide a scientific basis for the later maintenance of the bridge.