| Abstract [eng] |
The aim of this work is to investigate the arrangement effect of bar reinforcement to deformations and cracking behaviour of concrete elements subjected to short-term loading. The study experimentally verifies the effective concrete area concept and analyses peculiarities of cracking process of reinforced concrete (RC) members with the emphasis on arrangement of the bar reinforcement. The test results of 9 beams and 119 ties with different reinforcement and loading layouts are reported. Results of the beam tests do not reveal a clear correlation between the crack widths and the crack spacing when the reinforcement layout changes, while the number of the reinforcement layers correlates with the flexural stiffness. An iterative procedure has been proposed for localizing the end effect in the ties. This procedure allows identifying the representative geometry for assessing the cracking parameters of RC ties. It was observed that scatter of the experimental outputs increases with the concrete cover. Specific equipment has been developed for tests of the ties with multiple reinforcement bar. The test results (maximum and average crack spacing) are practically independent of the reinforcement parameters, while the Eurocode 2 and the Model Code 2010 predictions of the maximum crack spacing are dependent on the ratio of the bar diameter to the reinforcement ratio. These results enable formulating a hypothesis that the crack parameters (spacing and width) are mainly dependent on the geometry of the concrete prism and, particularly, the cover depth. Deformation behaviour of the ties with multiple reinforcement bars was also modelled with nonlinear finite element software ATENA. The results of numerical simulations and physical tests indicate that the strain gradient in the concrete varies not only along the bar, but also within the cover. The outputs support a conclusion that the “effective area” concept has a limited application related with the loading conditions, stress-strain state, cover, and configuration of the unreinforced area. The thesis is composed of three chapters: literature survey, experimental programs, and discussion of the results. The literature survey is focused on the effects responsible for deformation and cracking performance of reinforced concrete members. The experimental study deals with deformations and cracking of flexural and tensile elements with different arrangement of the reinforcement in the tension zone. The last chapter discusses predominant characteristics of serviceability performance of flexural and tensile reinforced concrete members. The author have published 14 articles on the topic of the dissertation (five of them in the journals with an Impact Factor and three in the conference proceedings reffered by the Clarivate Analytics Web of Science). |
