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A developed mathematical model and calculation algorithm for steel frame cross-sectional optimisation taking into account inelastic strains and maintenance requirements are presented. An evaluation of dissipative features when employing inelastic steel strains results in a significant reduction of frame carrying capacity versus its elastic response. The maintenance requirements of structure involve not only strength but also the stiffness, stability and structural constraints. The latter ones define the minimum cross-sectional and slenderness values of members. The abovementioned factors restrict a free development of plastic strains, thus an optimal structure is in a state prior to plastic failure. The employed values of structural elastic response are functionally related to the optimised parameters, therefore the problem is solved iteratively. A strategy of choosing the limiting and that of starting parameters to handle iterative process ensures a successful problem convergence. A numerical experiment of 10-storey steel frame optimisation by standard profiles is presented. [ABSTRACT FROM AUTHOR]

A new strut-flamed beam steel structure is considered. This type structure is employed in reconstruction of pedestrian bridges. The proposed constructional design model allows replacing the two-span beam bridge by one span strut-framed beam. In this case the members of already existing carrying structure are employed and the service of the actual structure is not interrupted. A response of new structure to symmetric and asymmetric loadings is analysed. The analytical relations for distribution of internal forces are presented. The choice of parameters of strut-framed beam is investigated. An efficiency of suggested structural design model is illustrated via the performed numerical simulation of strut-framed beam. [ABSTRACT FROM AUTHOR]

The shakedown theory, which analyses elastic-plastic constructions, subjected by variable repeated load, enables treating moving load as a separate type of variable repeated load. The load is allowed to „move" at any part of the construction: from the middle of the bridge, to turn back, again move ahead -- in this manner loading history is universally evaluated and it is a crucial factor, considering stress-deformation state of structures under plastic deformations. This paper reveals a possibility to apply methods of shakedown theory for creation and solution of theoretical optimization mathematical models of trusses. The perfectly elastic-plastic loaded by moving load truss is considering. The mathematical models of the minimal volume truss or it acting load maximization problems are created. There are evaluating not only strength (shakedown) and rigidity restrictions, but also stability restriction in case of plastic state of truss in models. There is proposed new solution algorithms and introduced numerical examples of truss optimization in case of moving load. The results axe valid for the small displacement assumptions. [ABSTRACT FROM AUTHOR]