Damage detection in hyperbolic cooling towers using vibration based damage detection techniques

Hyperbolic cooling towers are large reinforced concrete shell structures used to cool the hot waste water from thermal power stations, nuclear power plants, coal fried plants, chemical plants and oil refineries. Hence, they are subjected to large temperature variations. This together with deterioration due to aging, environmental effects and random actions such as wind loading and earthquakes, can cause distress in these structures. Such a distress can go undetected as most part of the cooling tower especially its interior, is neither visible from the outside nor easily accessible. This distress can develop into a larger damage to trigger the failure or collapse of the cooling tower and disrupt the functioning of the entire facility or plant. All structures need to be monitored regularly to check whether they are safe to operate and capable of withstanding environmental impacts. In this context Structural Health Monitoring using vibration based damage detection techniques has emerged as a useful means to detect damage at the outset to enable appropriate retrofitting and minimize structural failure. The principle of these techniques is that the damage in a structure causes a change in its vibration properties and this change can be used to detect the damage in the structure. Vibration based damage detection techniques have been used to detect, locate and characterize the damage in many simple and some complex structures. This paper develops and applies vibration based damage indicators to detect and locate damage in hyperbolic cooling towers.