SERVICE LIFE PREDICTION AND RISK ANALYSIS OF REINFORCED CONCRETE GRAVITY FLOW PIPES USING RELIABILITY THEORY

Abstract

Reinforced concrete pipes are susceptible to different types of deteriorations that threaten their structural capacity and serviceability. Failure of these structures or losing parts of their operational capabilities may cause undesirable consequences that affect the surrounding environment, public health and the economy. The main objectives of this research are to estimate the service life, and to evaluate the level of risk of reinforced concrete sewer pipes (RCP) that are under persistent chemical deterioration caused by the sulfide attack that leads to excessive erosion along the pipe’s interior wall. In order to estimate the service life, reliability theory is used by implementing concrete cover limit state function, and the probability of exceedance is calculated as a time-dependent parameter. Herein, the predicted service life is defined as the time at which the probability of exceedance is equal to 10%, choosing this probability is based on engineering judgment. Regarding risk level, a simple product of the probability of exceedance and the consequences of failure is used; risk is considered in a qualitative context in this work. The proposed methodology has been applied to a sample of 30 RC pipes located in Arlington, Texas, USA. Pipes are in different conditions; some of these pipes have insignificant erosion and have expected service life greater than 120 years, however, other pipes are in severe condition and with a predicted service life of 60 years or less.