To solve the problem of predicting the service life of superstructures, this work proposes the basis and methodological developments of creep theory with increasing loads as well as regression analysis of the results of laboratory experiments. The main limitation in terms of reinforcement is corrosion in the concrete cracks, which was determined during laboratory experiments. Based on the results, the approximate analytical dependences concerning reinforcement corrosion depth change over time at a constant value of crack width were selected. The paper substantiates the validity of the analytical dependences as a result of regression analysis; it proposes formulae for determining the corrosion rate of rebars in reinforced concrete superstructures. The obtained analytical dependences allowed for the developing of a process for predicting changes to the state of the superstructure in light of operational changes.
Purpose. Determination of the stress-strain state of a typical continuous steel truss span by calculation according to national norms and computer simulation in the conditions of passage of high-speed passenger trains. Methodology. In this work, the stress-strain state of a continuous truss span of the typical project No. 3 501.2-166 for the possibility of its application in areas with perspective high-speed railway traffic was investigated. Calculation of the specified span structure for DBN V.2.3-14-2006 «Constructions of transport. Bridges and pipes. Design rules» for railroad loading С14 was executed. The cross-sections of the elements of a continuous truss span were calculated and the necessary checks performed. For the given span structure in the software complex a model was developed and the stress-strain state at various speeds of railway transport according to European and national norms was investigated. The acceleration and deflection of a continuous steel truss span were determined and their comparison with normative requirements was performed. Findings. As a result of simulation in the software complex for a continuous steel truss span, acceleration and deflection under the action of cargo and passenger load at different speeds of movement were determined. The cross-sections of the elements of a continuous steel truss span were calculated. Originality. The results of the study can be applied in the development of national regulatory documents on high-speed rail transport and in the design of bridge structures with continuous truss spans in areas with high and higher-speed railway traffic. Practical value. The obtained results of the research will allow to effectively use continuous steel truss spans of typical designs in areas with high– and higher-speed railway traffic.
Purpose. The purpose of the given work is to determine the most rational construction schemes during longitudinal thrust such that all of the construction stresses would be allowable. Methodology. As an object of study the work considers common continuous composite reinforced concrete span by the scheme 63+84+63 m made according to the model design of 3.503.9-62 series. For the purpose of research of the span’s stress state using software package “Midas civil” computer finite element models of different schemes of longitudinal thrust were created. Seven construction schemes were accepted for the calculation that include both longitudinal thrust of metal part of the span and the thrust of constructed composite reinforced concrete span. Findings. The calculation of composite reinforced concrete thrust has proved that during the first stages, when the structure reaches the half of the first span, the stress in the concrete slab exceeds designed tensile strength of the concrete. Because of this, given construction schemes can’t be used. On practice it is recommended to thrust the metal part first and then to lay blocks or concrete the solid deck, that is the rational scheme of longitudinal thrust for the given spans. Originality. The results of the stress-strain state research during the longitudinal thrust can be noted as a scientific novelty for the chosen scheme. Practical value. It was shown that the most rational method of construction is the longitudinal thrust when using either launching nose or a temporary support.
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