It is known that RC industrial structures are liable to the effects of crude oil products, which may have a disadvantageous influence on their exploitation and safety. Within this research, the influence of crude oil products on the physico-mechanical properties of mature concrete, as well as other possible mechanisms of RC progressive failure have been analysed. Crude oil products with a very low neutralisation number were found to be physico-chemical active agents affecting concrete. Experimental analysis undertaken in order to assess the compressive strength of concrete and its bond to reinforcements is described. Long term investigations were conducted in order to determine the effects of a group of crude oil products—mineral oils—on the properties of concrete and reinforced concrete samples. Detailed results of this research are included in the paper. Comparing the influence of different mineral oils on the compressive strength of concrete, leads to the conclusion that there are large differ...

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The influence of crude oil products on RC structure destruction

Measurement of strain on concrete using an ordinary digital camera

Time-dependent changes in the instantaneous stiffness of reinforced concrete beams

The paper presents method of calculation of eigenfrequencies of the cracked reinforced concrete beams including discreet model of crack. The described method is based on the stiff finite elements method. It was modified in such a way as to take into account local discontinuities – cracks. In addition, some theoretical studies as well as experimental tests of concrete mechanics based on discrete crack model were taken into consideration. The calculations were performed using the author's own numerical algorithm. Moreover, other calculation methods of dynamic reinforced concrete beams presented in standards and guidelines are discussed. Calculations performed by using different methods are compared with the results obtained in experimental tests.

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Eigenfrequencies of the reinforced concrete beams – methods of calculations

Complex method and Green's function method are used here to investigate the dynamic analysis for circular inclusion near interfacial crack impacted by SH-wave in bi-material half-space. Firstly, the displacement expression of the scattering wave was constructed which satisfied the free boundary conditions, then Green's function could be constructed, which was an essential solution to the displacement field for an elastic right-angle space with a circular inclusion impacted by out-plane harmonic line source loading at vertical surface. Secondly, crack was made out with “crack-division” technique. Meanwhile, the bi-material media was divided into two parts along the bi-material interface based on the idea of interface “conjunction”, and then the vertical surfaces of the two right-angle spaces were loaded with undetermined anti-plane forces in order to satisfy displacement continuity and stress continuity conditions at linking section. So a series of algebraic equations for determining the unknown forces could be set up through continuity conditions and the Green's function. Finally, some examples and results for dynamic stress concentration factor of the circular elastic inclusion were given. Numerical results show that they are influenced by interfacial crack, the incident wave number and the free boundary in some degree.

J. Pędziwiatr

Papers

Influence of internal cracks on bond in cracked concrete structures