關于斜拉橋的外文翻譯--高度超靜定斜拉橋的非線性分析研究

1、Study on nonlinear analysis of a highly redundant cable-stayed bridge1．AbstractA comparison on nonlinear analysis of a highly redundant cable-stayed bridge is performed in the study. The initial shapes including geometry

2、 and prestress distribution of the bridge are determined by using a two-loop iteration method, i.e., an equilibrium iteration loop and a shape iteration loop. For the initial shape analysis a linear and a nonlinear com

3、putation procedure are set up. In the former all nonlinearities of cable-stayed bridges are disregarded, and the shape iteration is carried out without considering equilibrium. In the latter all nonlinearities of the br

4、idges are taken into consideration and both the equilibrium and the shape iteration are carried out. Based on the convergent initial shapes determined by the different procedures, the natural frequencies and vibration m

5、odes are then examined in details. Numerical results show that a convergent initial shape can be found rapidly by the two-loop iteration method, a reasonable initial shape can be determined by using the linear computati

6、on procedure, and a lot of computation efforts can thus be saved. There are only small differences in geometry and prestress distribution between the results determined by linear and nonlinear computation procedures. Ho

7、wever, for the analysis of natural frequency and vibration modes, significant differences in the fundamental frequencies and vibration modes will occur, and the nonlinearities of the cable-stayed bridge response appear o

8、nly in the modes determined on basis of the initial shape found by the nonlinear computation.2. IntroductionRapid progress in the analysis and construction of cable-stayed bridges has been made over the last three decad

9、es. The progress is mainly due to developments in the fields of computer technology, high strength steel cables, orthotropic steel decks and construction technology. Since the first modern cable-stayed bridge was built i

10、n Sweden in 1955, their popularity has rapidly been increasing all over the world. Because of its aesthetic appeal, economic grounds and ease of erection, the cable- stayed bridge is considered as the most suitable cons

11、truction type for spans ranging from 200 to about 1000 m. The world’s longest cable-stayed bridge today is the Tatara bridge across the Seto Inland Sea, linking the main islands Honshu and Shikoku in Japan. The Tatara

12、cable-stayed bridge was opened in 1 May, 1999 and has a center span of 890m and a total length of 1480m. A cable-stayed bridge consists of three principal components, namely girders, towers and inclined cable stays. The

13、 girder is supported elastically at points along its length by inclined cable stays so that the girder can span a much longer distance without intermediate piers. The dead load and traffic load on the girders are trans

14、mitted to the towers by inclined cables. High tensile forces exist in cable-stays which induce high compression forces in towers and part of girders. The sources of nonlinearity in cable-stayed bridges mainly include th

15、e cable sag, beam-column and large deflection effects. Since high pretension force exists in inclined cables before live loads are applied, the initial geometry and the to reduce the deflection and to smooth the bendin

16、g moments in the girder and finally to find the correct initial shape. Such an iteration procedure is named here the ‘shape iteration’. For shape iteration, the element axial forces determined in the previous step will

17、be taken as initial element forces for the next iteration, and a new equilibrium configuration under the action of dead load and such initial forces will be determined again. During shape iteration, several control poin

18、ts (nodes intersected by the girder and the cable) will be chosen for checking the convergence tolerance. In each shape iteration the ratio of the vertical displacement at control points to the main span length will be

19、checked, i.e.,? ? | span main points control at nt displaceme vertical |The shape iteration will be repeated until the convergence toleranceε, say 10-4, is achieved. When the convergence tolerance is reached, the comp

20、utation will stop and the initial shape of the cable-stayed bridges is found. Numerical experiments show that the iteration converges monotonously and that all three nonlinearities have less influence on the final geome

21、try of the initial shape. Only the cable sag effect is significant for cable forces determined in the initial shape analysis, and the beam-column and large deflection effects become insignificant.The initial analysis can

22、 be performed in two different ways: a linear and a nonlinear computation procedure. 1. Linear computation procedure: To find the equilibrium configuration of the bridge, all nonlinearities of cable stayed bridges are n

23、eglected and only the linear elastic cable, beam-column elements and linear constant coordinate transformation coefficients are used. The shape iteration is carried out without considering the equilibrium iteration. A re

24、asonable convergent initial shape is found, and a lot of computation efforts can be saved.2. Nonlinear computation procedure: All nonlinearities of cable-stayed bridges are taken into consideration during the whole compu

25、tation process. The nonlinear cable element with sag effect and the beam-column element including stability coefficients and nonlinear coordinate transformation coefficients are used. Both the shape iteration and the eq

26、uilibrium iteration are carried out in the nonlinear computation. Newton–Raphson method is utilized here for equilibrium iteration. 4.2. Static deflection analysisBased on the determined initial shape, the nonlinear stat

27、ic deflection analysis of cable-stayed bridges under live load can be performed incrementwise or iterationwise. It is well known that the load increment method leads to large numerical errors. The iteration method woul

28、d be preferred for the nonlinear computation and a desired convergence tolerance can be achieved. Newton– Raphson iteration procedure is employed. For nonlinear analysis of large or complex structural systems, a ‘full’

29、iteration procedure (iteration performed for a single full load step) will often fail. An increment–iteration procedure is highly recommended, in which the load will be incremented, and the iteration will be carried out