Abstract. Increased deformability can be considered as the basic disadvantage of suspension bridges. One of the ways to increase the rigidity of a suspension bridge is to transfer a part of stiffening girder rigidity to a suspension main cable. To give the suspension bridge more stable appearance, the authors propose to use the cables of varying bending stiffness. The main cables can be made of standard section shapes or have a composite section. The object of this work was to study a method for analyzing and determining the internal forces in the main cables and stiffening girder under static loading to provide recommendations for designing suspension bridges with stiffened cables. Simple formulas are presented for determining displacements, internal forces and stresses in the main cable and stiffening girder. Finite element modeling was performed. The final part of the paper discusses design procedures for such suspension systems. An example of a pedestrian suspension bridge is appended.

The present study focuses on a prediction of crack width and load-carrying capacity of flexural reinforced concrete (RC) elements strengthened with fibre-reinforced polymer (FRP) reinforcements. Most studies on cracking phenomena of FRP-strengthened RC structures are directed to empirical corrections of crack-spacing formula given by design norms. Contrary to the design norms, a crack model presented in this paper is based on fracture mechanics of solids and is applied for direct calculation of flexural crack parameters. At the ultimate stage of crack propagation, the load-carrying capacity of the element is achieved; therefore, it is assumed that the load-carrying capacity can be estimated according to the ultimate crack depth (directly measuring concrete's compressive zone height). An experimental program is presented to verify the accuracy of the proposed model, taking into account anchorage and initial strain effects. The proposed analytical crack model can be used for more precise predictions of flexural crack propagation and load-carrying capacity.

The paper presents a summary of numerical analysis on static behaviour of suspension bridges with varying rigidity of cables. The primary purpose of this study was to compare suspension systems with flexible and rigid cables and to determine the influence of varying rigidity of cables on the response of bridge members under the action of uniformly distributed symmetrical and unsymmetrical static loading. The finite element analysis of a three-dimensional bridge model was performed. In the first model, the cable is modelled as TRUSS3D element, in the second model as BEAM3D element. In both models, the hangers and backstays are TRUSS3D elements and stiffening girder as BEAM3D element. It is shown that a suitable increase of main cable's bending stiffness can effectively reduce the displacements, internal forces and stresses of suspension systems. Recommendations for appropriate stiffness are given.

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The article determines natural frequencies of vibration and the corresponding mode shapes of a suspension bridge with the varying bending stiffness of cables and examines variations that occur in these characteristics with respect to parametric changes in the bridge. A single span suspension steel footbridge with flexible cables has been selected as an initial model used for studying the dynamic characteristics of a suspension system. With the help of the finite elements (FE) method, parameter studies of the bridge model are presented in which vibration characteristics are studied as a function of structural and material parameters such as the flexural stiffness of the cable and the mass density of structural components. It has been generally found that the bending stiffness of the main cable contributes to a considerable effect on natural frequencies for this type of the suspension system. A simplified expression of predicting natural bending frequencies of the suspension bridge taking into account the bending stiffness of the cable has been developed for the application as the first step in the design process.