Flexural Behaviour of Unbonded Posttensioned Concrete Beam Strengthened with Aluminium Alloy Plates

摘要

Owing to their high corrosion resistance, aluminium alloy (AA) plates bonded with magnesium phosphate cement (MPC) are considered as a viable candidate for reinforcing inshore infrastructures that are subject to severe environmental conditions and vapor atmospheres. Therefore, the aim of this study is the evaluation of the flexural behaviour of simple beams that are strengthened using this technique. Six unbonded posttensioned concrete (UPC) beams with different reinforcement ratios are damaged by static loads and then repaired and strengthened using AA plates. The failures under two-point loading are then investigated. Thereafter, a simplified method is proposed for the evaluation of the flexural strength of a UPC beam strengthened by an AA plate with MPC. The flexural strengths of the six specimens increase by an average of 14%, and the displacement ductility factor decreases by an average of 34.14%. Moreover, the increase and decrease ratios are proportional and inversely proportional to the comprehensive reinforcement index, respectively. The influences of the three main factors on the flexural strength of the AA plate are determined: the increase in the stress of the unbonded tendons, stress at the midspan and slippage at the ends of the AA plate, and increase ratio of the flexural strength. It shows that the AA plates bonded with MPC can be used successfully in concrete strengthening.