The aim of the article  was to discuss the application of steel-concrete composite structures in bridge engineering in the aspect of structural design, analysis and execution. It was pointed out that the concept of steel-concrete structural composition is far from exhausted and new solutions interesting from the engineering, scientific and aesthetic points of view of are constantly emerging. These latest trends are presented against the background of the solutions executed in Poland and abroad. Particular attention is focused on structures of double composition and steel-concrete structures. Concrete filled steel tubular (CFST) structures are highlighted.
The paper considers some results of creating load-carrying composite systems that have uprated strength, rigidity and safety, and therefore are called geometrically (self-) hardening systems. The optimization mathematic models of structures as discrete mechanical systems withstanding dead load, monotonic or low cyclic static and kinematic actions are proposed. To find limit parameters of these actions the extreme energetic principle is suggested what result in the bilevel mathematic programming problem statement. The limit parameters of load actions are found on the first level of optimization. On the second level the power of the constant load with equilibrium preloading is maximized and/or system cost is minimized. The examples of using the proposed methods are presented and geometrically hardening composite steel-concrete system are taken into account.
Taras Bobalo, Yaroslav Blikharskyy, Pavlo Krainskyi and Myhailo Volynets
The use of computers provides the opportunity to analyse and design complex structures, taking into account the geometric and physical nonlinearity of construction materials. In the article the study of stress-strain state of mixed steel-concrete beams, were presented. The results of this study showed that the method of calculation according to designe codes gave satisfactorily results of calculated strength compared with experiments. However, these methodes do not provide complete information of structural performance at all levels of load. For a more complete study of the stress-strain state and the physical nature of the processes occurring in steel-concrete structures reinforced with a mixed reinforcement, the calculation method using “Lira” software complex is proposed. The method of calculation is based on the finite element method. The calculation is made taking into account physical nonlinearity and real diagrams of σ-ε of materials using the nonlinear deformation law №14 of “Lira” software complex. The proposed method of calculation allows to determine the values of bearing capacity, the development of deformations and the beginning of crack formation, as well as stresses at all load levels.
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