The research is focused on evaluating the average crack spacing of overlay-strengthened reinforced concrete (RC) beams. The current equations in different structural codes for predicting the average crack spacing of RC beam with multilayered-reinforcing bars is proved to be inapplicable for overlay-strengthened RC beam, although these two kinds of beams are both with reinforcement in multi-layers. Therefore, a simple, practical and new analytical model that is capable of predicting the average crack spacing of overlay-strengthened beams is developed. An overlay-strengthened beam element is analyzed based on equilibrium and compatibility equations to formulate the average stresses of concrete, overlay and tension reinforcement. A series of verification comparisons with the experimental investigations, which involved various types of beam elements, are performed to verify the validity and reliability of the model. The proposed model performs satisfactorily with respect to measured response from the experimental database.
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