Abstract
Large-span cable-stayed bridges design is impossible without a cable adjustment, which should be made in various stages of construction and for the finished structure as well. There may be many concepts of regulation – the creation of design geometry (mainly used for relatively small- span pedestrian bridges), the optimization of shear or moment diagrams in carriageway’s construction, the reduction of max tensile or compressive stresses in the load-bearing elements. Normally, the choice of mechanical and geometrical parameters for the main load bearing elements (cables, stiffness girder and pylons) which affect the flexibility of a bridge structure is an iterative process based on the structural engineering experience. The assumptions are to be tested by the Finite Element Method calculations and changed if necessary. This paper offers insight into the mathematical methods developed, based on the deformed shape of the cable-stayed bridge system. The method developed is demonstrated by example, where the system is optimized according to the type of cable-stayed bridge (“star” or “harp” design), geometrical parameters (lengths of stiffness beam sections, height of pylons) and the stiffness parameters (cross-section of cables, flexibility of the girder). This method allows analyzing the interactions between this data.
Highlights
A rapid development of cable systems for bridges is occurring in the recent decades (Ruiz-Teran 2010)
Perspective development of the method This paper shows a simplified example of the cable-stayed system of bridges
Behavior of a cable system under uniformly distributed load can be analyzed by studying deformations of their components
Summary
A rapid development of cable systems for bridges is occurring in the recent decades (Ruiz-Teran 2010). Authors of this paper are working on the analytically obtained interaction between the cables and stiffening girder of cable-stayed bridge (Straupe, Paeglitis 2011). These formulas show how mechanical and geometric characteristics impact the deformations and stresses in the system. Non-linear problem of finding forces in cables and answering the question how they affect the stiffening girder can be calculated by researching deformed shape of the system. It is to be found how a simple beam with elastic supports deforms under the uniformly distributed dead load (Fig. 1). Equation of the deformed shape of stiffening girder can be expressed:
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