Stiffness and Crack Behavior of Unbonded Posttensioned Concrete Beam Strengthened with Aluminum Alloy Plate

Corrosion resistance of aluminum alloy plates externally bonded by magnesium phosphate cement provides the ability to strengthen inshore infrastructures in harsh environments subject to moisture and humidity. In this study, the aim is to study the stiffness and cracking behavior of concrete beams using this strengthening technique. Six damaged unbonded posttensioned concrete beams were repaired and strengthened and then subjected to monotonic load until failure. This technique improved the stiffness and limited the development of cracks. The formula of elastic-plastic stiffness coefficient related to the comprehensive reinforcement index was established. An influence coefficient δ considering the effect of aluminum alloy plates and unbonded tendons was introduced, and the crack expansion coefficient under short_term load was obtained by statistical analysis. Finally, some simplified methods were proposed to evaluate the stiffness and cracks of unbonded posttensioned concrete beams strengthened with aluminum alloy plates.

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