Fracture Mechanics Approach for Failure of Concrete Shear Key. I: Theory

The objective of this paper is to develop a simple mechanical model for the analysis and design of plain or fiber-reinforced concrete shear key joints. The method makes use of well-known results of fracture mechanics and truss model theory, combined in a simple model. The analysis employs a single discrete crack model under wedging force and a smeared crack model under remote shear force. The proposed formulation identifies two main fracture mechanisms for shear-off failure of key joints: single curvilinear cracking and development of multiple diagonal cracks. Furthermore, as a first step in developing design aids for the shear strength of shear keys, a simple design formula is obtained. The procedures developed in this study would be useful in designing shear key joints according to the precast concrete segmental method of construction, which is becoming increasingly popular.

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