Experimental investigation on cracking behavior of reinforced concrete tension ties

The safe design of modern structures against earthquake excitation is a matter that troubles consultant engineers worldwide. Given the random nature of crack formation, research into reinforced concrete members, in the context of cracking behavior, has proved difficult. Sometimes, depending on the crack width and spacing, cracking can affect general behavior and, specifically, the seismic behavior of reinforced concrete in multi-story buildings. Widely accepted methodologies for predicting crack characteristics, e.g. crack width and spacing and number of cracks, have not been developed yet. Furthermore, the phenomenon of cracking in highly-strained members, which takes place during earthquakes, needs to be investigated more. The characteristics of cracks affect the appearance of catastrophic phenomena, e.g. transverse buckling of reinforced concrete structural walls. In the context of the present work, the impact of the mechanical factors of tensile deformation is investigated, in terms of cracking behavior. Eight test specimens were divided into two groups according to their longitudinal reinforcement ratio (1.79% and 3.19%) and strained under uniaxial tensile loading. The degrees of elongation used were equal to 10‰, 20‰, 30‰ and 50‰. Extreme tensile strains were also used, e.g. 30‰ and 50‰, in order to take into account the cases of extreme seismic excitations. Apart from the investigation of the tensile strain factor, this work also examines the influence of the rebar content. The test results can be used to establish an experimental database, in order to develop an empirical equation that can forecast the quantity of cracks, their width and spacing. The experimental study is followed by an analytical investigation that aims to develop an empirical equation, predicting the average width of cracks. The results are basically given in terms of diagrams showing the development of cracking characteristics in relation to the tensile strain applied. Useful conclusions concerning cracking behavior are derived.