ٍStrengthening of RC tunnels using externally bonded fiber sheets

Abstract

Strengthening of reinforced concrete members by externally bonded fiber-reinforced polymer, (FRP), sheets or plates has been increasing in recent years due to the beneficial characteristics of being non-corrosive and generally resistant to chemicals, high strength-to-weight ratio, and non-magnetic and non-conductivity of composite materials. The experimental results showed that better performance of the strengthened sections with FRP could be achieved in terms of ultimate load, crack control, and stiffness. Application of FRP to strengthen underground tunnels is one of the prime applications due to the severe environment, which the concrete is exposed to. Repair work of underground tunnels such as “Ahmed Hamdi Tunnel under Suez Canal or El-salam tunnel under Suez Canal” is carried out mainly to strengthen the primary lining of the tunnel due to any defects or cracks.

A computer model is developed for a concrete tunnel strengthened with glass and carbon FRP, (GFRP and CFRP), laminates to study the capacity enhancement and cracking behavior for arch concrete segments strengthened by single lining of FRP. An experimental program of arch concrete segments was carried out to verify the computer model. The nonlinear behavior of steel (elastic-plastic behavior with strain hardening) was considered in the computer model. The numerical investigation of the research work showed that the procedure described in this paper is stable, fast in convergence and effective for tunnels applications.