Prestressed concrete sleepers are the most common type of the sleepers used on the railroad. They serve as rail supports and absorb loads induced by trains. Sleepers are important for the durability and safety of the railroad and are exposed to various loads and an agressive environment during exploitation. Therefore, different types of appearing damage can determine their reliability. The article briefly discusses possible causes of damage and the deterioration of prestressed concrete sleepers. End cracking and damage at the rail seat was determined during the inspection of used sleepers. Therefore, the strain state and cracking of the rail seat of the sleeper was analysed under static and dynamic loads. The paper provides the obtained results of experimental research of used and new sleepers.
The paper deals with experimental and theoretical investigations in reinforced concrete structures strengthened with carbon fibre sheets. Four stages in the behaviour of concrete structures strengthened with the carbon fibre reinforced polymer (CFRP) are distinguished. A method for calculating the deflections of such structures is presented. The design procedure for defining the strength of the structures evaluates the stiffness of the contact between the carbon fibre and the concrete. Experimental investigations with different fastening methods of the CFRP to the concrete were performed. In experimental investigations deflections of the strengthened members have been examined. Results of the calculations of deflections for experimental beams according to the proposed method are presented. A comparison of experimental and theoretical deflections is presented in the paper.
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