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Date of Award
Restricted Access Dissertation
Doctor of Science (DSc)
An analytical model for local bond stress-slip relationship proposed in this paper was developed because of the need for a reliable bond stress-slip model to be used in predicting the bond behavior between steel bars and concrete in the well-confined zones of concrete structures under generalized excitations. Both experimental and analytical programs were carried out in this study to find out the influence of lug parameters on the shape of the monotonic bond stress-slip curve. The proposed analytical bond stress-slip model is based on a concept of the mechanical bond strength of the concrete key (concrete between steel lugs) which is a combination of strength and friction. All of the model's parameters are related to the bar's deformation pattern and can be quantified directly from the physical dimensions of the bar. A scaling factor was introduced in order to include the effect of concrete strength. A simple damage rule was derived based on the length of the undamaged portion of the concrete key and the developed friction. A hysteresis rule was developed based on the concept of reduced monotonic envelope. The model is successful in predicting both slip control and load control test results and for low and very high numbers of load cycles. The model is incomplete because it does not include a mode of failure that may occur if the lug depth to lug spacing ratio is relatively high. Both the experimental and analytical results show that bond strength under fatigue loading is very sensitive to the scale of the deformation pattern, that is a small increase in scale factor of the deformation pattern has a large increase in fatigue resistance. The results also show that bond stiffness is roughly independent of the scale of the deformation pattern. However, if the scale of the deformation pattern is small enough, bond resistance in terms of the bond stress at failure will decrease even under monotonic loading and the mode of bond failure will change from mechanical bearing to adhesion and friction.
Pochanart, Sakul, "A Quantifiable Model for Local Bond Stress-Slip Relationship under Generalized Excitations" (1987). Retrospective Theses and Dissertations. 51.