Local stability of concrete arch bridge based on Ritz method

In order to minimize the self-weight and prevent local buckling failure of thin-walled box concrete arch bridges at the same time, the limit values of width-thickness ratios are deduced based on Ritz method and equivalent strut theory of arch bridge. A new method of determining sectional forms based on the limit values of width-thickness ratios is put forward. Based on Mupeng bridge, the theoretical results are verified by finite element software ANSYS. Results show that the limits of width-thickness ratios are related to concrete grade, equivalent calculation length and radius of gyration, the allowable minimum thickness of Mupeng bridge is 15 cm to avoid local buckling. The limit values of width-thickness ratios deduced in this paper are reasonable and this new method of determining sectional forms is simple and rational to apply in engineering. A scientific engineering calculation method on arch ring design is put forward and it can provide a theoretical basis for the design of thin-walled box concrete arch bridges constructed by cantilever pouring.

LOAD-BEARING CAPACITY ANALYSIS FOR STRUCTURAL COLD-FORMED MEMBERS SUBJECTED TO CENTRAL COMPRESSION

The main purpose of the research was a deep analysis and verification of the consistency and completeness of the design code relating to calculation of load-bearing structural members made from cold-formed profiles. The work has been done in close connection with the implementation on the territory of Ukraine of this design code. The article has discussed and investigated the load-bearing capacity of structural members made of cold-formed profiles subjected to the action of central compression. A system of constraints has been presented, in which the strength and buckling constraints for thin-walled cold-formed column members are formulated, taking into account their possible post-buckling behavior, namely, the ability to resist external loads and effects even after the occurrence of the local buckling and/or distortional buckling phenomenon. The performed load-bearing capacity investigation has shown that for the mono-symmetric cold-formed profiles, the flexural-torsional buckling is determinative. For such cold-formed profiles, the effect of the overall dimensions ratio (flange width to web height) on the load-bearing capacity of cold-formed profiles has been estimated. It has been shown that for the same cross-sectional area the load-bearing capacity of a column structural member made from cold-formed profile and subjected to axial compression can be significantly increased by assigning an optimal ratio of flange width to web height. The paper also has presented the results of the load-bearing capacities for the structural cold-formed members subjected to central compression, calculated according to the design standard DSTU-N B EN 1993-1-3: 2012 and according to the design code DBN V.2.6-198: 2014. It has been shown that in some cases the difference in the assessment of the load-bearing capacity for such structural cold-formed members reached 25%. A comparison of the load-bearing capacities for the action of the central compression has been made for structural cold-formed members made from a C-shaped profile and with a composite section of two C-shaped profiles. It has been shown that the load-bearing capacity of the structural cold-formed member of the composite section exceeds the load-bearing capacity of the member with single C-shaped profile by more than 3 times, while cross-section areas of these structural members differ only doubly.