In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.



Volume 8 No. 2 June 2002


Special issue on prestressed suspension structures

Preface; 67

Jüri Engelbrecht

Investigations of prestressed cable structures at Tallinn Technical University; 68–83

Valdek Kulbach

Abstract. The paper presents a summary of research activities of the Department of Structural Design at TTU in the field of suspension structures against the background of the world developments in this field.

Key words: cable, cable network, girder-stiffened structure, hanging roof, hypar-network.

Investigation and design of shallow wooden and composite shell-cable roofs; 84–100

Karl Õiger

Abstract. The paper gives a review of the investigations on the behaviour of shell roofs, carried out at the Tallinn Technical University. The roof structures examined consisted of a board shell or of a prestressed cable network and timber or steel cladding. Edge beams were made from blanks, glulam, or steel tube. Main attention is paid to the influence of the roof cladding (panels) on the behaviour of square and elliptical saddle-shaped suspension roofs.

Key words: suspension roof, shell-cable roof, hypar.

Analysis of saddle-shaped cable networks with different contour structures; 101–113

Valdek Kulbach, Juhan Idnurm, and Ivar Talvik

Abstract. Usually the cable network of a saddle-shaped roof is formed inside a contour of two inclined plane arches which are supported by massive counterforts at lower ends. In the present paper advantages of hypar-networks encircled by a spatial contour beam with elliptical layout and without any external horizontal supports have been presented. Both discrete and continuous calculation methods can be used for the analysis of the stress-strain state of those networks. A system of nondimensional parameters is used to study the effect of variable geometrical and stiffness properties on the behaviour of an elliptical roof structure. Comparison of the behaviour of cable networks with different contour beams is given.

Key words: cable structure, continuous analysis, discrete analysis, geometric nonlinearity, hanging roof, suspended roof, prestressed cable network, suspension structure.

Experimental investigation of the Saaremaa suspension bridge model; 114–120

Valdek Kulbach and Egon Kivi

Abstract. A model of the bridge across the Suur Strait between the Estonian mainland and Muhu Island has been erected and tested. The main problem by designing of a self-anchored bridge is evaluation of the stability of the bended and compressed stiffening girder. In spite of a very slender box girder the approximate analysis and experimental investigation demonstrated its sufficient stability. The investigation proved also some advantages of the model with unloaded anchor cables as compared to the model with the loaded ones.

Key words: suspension bridge, cable structure, box girder, bridge model, girder stability, self-anchored system.

Discrete and continuous modelling of suspension bridges; 121–133

Valdek Kulbach, Siim Idnurm, and Juhan Idnurm

Abstract. In the calculation of suspension bridges, the main problem is the geometrically non-linear behaviour of the cable. Linear methods of analysis are suitable only for very small spans. A geometrically non-linear continuous model is especially useful for classical loading cases as for the uniformly distributed load on the whole or half span. However, traffic generates both concentrated and uniformly distributed loads. The discrete model of a suspension bridge allows one to apply all kinds of loads, such as the distributed and the concentrated ones. In this paper, application of both discrete and continuous models for the calculation of the suspension bridges is considered. Linear elastic strain-stress dependence of the material and absence of the inclination of hangers is assumed. Hanger elongation may be taken into account. Some comparative numerical examples are presented.

Key words: suspension bridge, cable systems, continuous modelling, discrete modelling, geometric non-linearity, girder-stiffened structures.

Challenges for tensile stresses; 134–142

Jüri Engelbrecht

Abstract. This essay describes some interesting phenomena related to flexible (hanging) structures in nature and engineering. Despite of the seeming simplicity, the behaviour of such structures may be complicated due to non-linear effects.

Key words: tension, hanging structures, spider’s web.



Valdek Kulbach 75; 143