Reinforcement Analysis of a Water Tank Wall by External Prestressing

Abstract

Water storage structures age and deteriorate over time, which can make them vulnerable. There aremany reinforcement methods available to rehabilitate them. Our research focuses on a system for reinforcing thewall of a concrete tank, subjected to hydrostatic pressure, by additional external prestressing. The role of thelatter will be to relieve the wall of hydrostatic or even hydrodynamic tensile stresses, and allow it to return to anacceptable service state. This technique of adding external prestressing cables was initially introduced in thereinforcement and rehabilitation of civil engineering structures, mainly from the 1970s. In this study, adeterministic analysis is developed for the dimensioning of the external prestressing necessary to absorb part ofthe hydrostatic pressure exerted on the wall, taking into account the different instantaneous and deferred stresslosses. Additionally, the hydrodynamic effect is evaluated by the Westergaard method, to analyze the stress stateinduced by the fluid-structure interaction with respect to the seismic action. In a second step, a reliabilityanalysis is developed by considering three random variables, including the compressive strength of the concrete,the seismic intensity and the eccentricity of external prestressing cables. This reliability analysis is conductedusing a computer code developed with Matlab© software based on the Monte Carlo simulations method to assessthe probability of failure in tension of the circular wall for different seismic intensities. The developed approachwas applied, for a practical example, whose dimensions are realistic. Fragility curves are developed representingthe failure probability in the different levels of seismic acceleration