| Research Abstract |
1) In order to clarify the interrelation between artificial pre-crack induced in concrete member and shear crack caused by shear force, a series of experiments was performed. Under both monotonic and cyclic loading, the artificial pre-creak prevented propagation of new share crack and then the capacity and ductility of RC member increased. On the contrary, when the angle between pre-crack and new crack because less than 30 degree, the capacity of member was decreased owing to the new crack formed along the pre-crack.
2) Non-orthogonal smeared crack model of enhancing active crack method was adopted as a constitutive law to deal with non-orthogonal cracks with intersection. Comparinson with the experimental results verified that the proposed model could well predict the behavior of cracks with mutual interaction.
3) Shear behavior of concrete members with embedded plastic plates, as devices to emulate pre-cracks, was studied based on both experimental facts and analytical approach. As a result, proposed joint element had a beneficial effect on modeling consecutive plates.
4) The accuracy of the proposed non-orthogonal crack model was verified with experiments of RC plate structures under multi-directional loading. The result showed that active-crack method, which defined Intersection angle of 22.5 degrees as a threshold, could well predict interrelation between non-orthogonal cracks. In addition, the application of the model for structures that consist of high strength concrete and high strength reinforcing bars was proven.
5) Because thermal stress was assumed as an introduction source of pre-cracks, the tension-stiffness behavior of embedded steel in concrete under high temperature was clarified experimentally. The manifested characteristics were incorporated into the structural numerical analysis system.
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