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

摘要

Hyperbolic cooling towers are large reinforced concrete shell structures built to have long service lives. Their primary task is to decrease the temperature of heated waste water generated from thermal power stations, nuclear power plants, coal fried plants, chemical plants and oil refineries. They are hence 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 and with time can trigger the collapse of the cooling tower. It is therefore necessary that cooling towers, and indeed all structures, be monitored regularly to check whether they are safe to operate and capable of withstanding environmental impacts. In this context vibration based structural health monitoring has emerged as a useful technique to detect damage at its onset to enable appropriate retrofitting and prevent failure of the structure. The principle of this techniques is that the damage in a structure changes its vibration properties and this change can be used to detect the damage in the structure. This technique has been used to detect, locate and characterize the damage in many simple and some complex structures. The present research aims to develop and apply a vibration based technique to detect and locate damage in hyperbolic cooling towers. The outcome of this research will enhance the safety of these critical structures whose failure can result in a shutdown of the facility. Some of the preliminary results will be presented and discussed in the conference.