Research On The Curved-pylons And Curved-girder Cable-stayed Bridge Without Back-stays

The curved-pylons and curved-girder cable-stayed bridge without back-stays is a kind of heteromorphosis cable-stayed bridge without back-stays, and its mechanical state is more complicated than the general cable-stayed bridge without back-stays.As its construction and research have just been started, mechanical performance analysis of the bridge will greatly promote research in the field of this new bridge style,and it is of great practical importance to guide production practices such as design and construction.In this paper, the object of study is principal design parameters of the curved-pylons and curved-girder cable-stayed bridge without back-stays.On the basis of exploring the interrelationship between various parameters and indexes representing mechanical properties,global and local mechanical properties of the bridge are investigated,so as to provide some references and recommendations to its design and construction.Relying on the Lichuan Bridge under construction in Dongguan, by means of theoretical study and parameter analysis based on the finite element model,three aspects including static performance, overall stability properties and dynamic characteristics of the bridge have been mainly researched.The main achievements of this paper are as follows:(1)The major structural features of the curved-pylons and curved-girder cable-stayed bridge without back-stays are proposed, as well as the conditions of static equilibrium between pylons and the girder of the bridge.(2) A finite element analysis method of this kind of bridge is proposed by giving principles and methods of modeling pylons,the girder, cables, prestressed tendons, isolation body for partial analysis in static finite element analysis and dynamic finite element analysis.(3)The Lichuan Bridge’s finite element model for static analysis is established by use of Midas/FEA finite element program.With the method of parameter analysis,the interrelationship between8main design parameters and11mechanical indexes is founded, meanwhile the qualitative and approximately quantitative relationship between them is summarized.It is pointed out and demonstrated that the static analysis results can provide some valuable references for the bridge’s design and research.(4) Based on the overall stability research of the Lichuan Bridge, the first2order buckling modes and corresponding stability factors of safety has been acquired. Comparative study of5main design parameters on overall stability of the bridge comes to a conclusion that weight and stiffness of pylons have the largest influences on overall stability, followed by stiffness of cables, while weight and stiffness of the girder have the minimal ones. According to this conclusion, an efficient measure to improve the stability of the bridge is proposed:using steel as the pylons’ material as much as possible.(5) Based on the study of the Lichuan Bridge’s dynamic characteristics, its first10order natural frequencies and mode shapes are obtained, and its main features of dynamic characteristics are summed up as follows:the pylons’ dominant modes live in an absolute majority; the10th vibration mode is a rare one whose in-plane vibration coupling with out-of-plane vibration; compared to Hongshan Bridge, the pylons’ dominant modes of Lichuan Bridge are a lot more, which to some extent reflects the deficiency on stiffness of the curved pylon. Based on comparative study of5main design parameters’ influences on dynamic characteristics, measures to improve dynamic characteristics of this kind of bridge are proposed:steel should be considerred as a part of the pylons’ material in design and the overweight of the pylons’ concrete should be prevented strictly during construction, the use of steel-concrete composite girder or steel girder should be considered, the way that improving stiffness of cables is not recommended.This paper provides effective ways for theoretical studies and structural analysis on the curved-pylons and curved-girder cable-stayed bridge without back-stays. The results are valuable references for design, construction and research of this kind of bridge.