Investigations on rheological strains of compressed concrete elements strengthened with external composite reinforcement CFRP

The results of experimental studies on rheological strains of compressed concrete elements strengthened with surface CFRP materials are presented in this paper. The objective of the investigations was to estimate the influence of long-term load on strains and load-bearing capacity of compressed elements strengthened with CFRP materials. The studies were performed on specimens with various types of reinforcement. The specimens were strengthened with external composite reinforcement – longitudinal segments of CFRP strips and transverse confinement executed with CFRP sheets. The experimental studies were divided into two stages, in which specimens were subjected to long-term axial compression. The objects of the investigations were cylindrical specimens with a diameter of 113 mm and height of 350 mm. The plain concrete specimens were loaded with the level of about 1/3fcm,cyl (mean cylinder compressive strength of the concrete). After the period of initial loading the specimens were strengthened and the level of effort was increased to about 2/3fcm,cyl. The tests were conducted in constant thermal and moisture conditions. In the paper, the dependences of long-term strains increase in time are presented for the experimental elements. Additionally, theoretical studies connected with rheological model identification were performed.