Analysis On Cracks Control And Temperature (Shrinkage) Effect Of Over-long Frame Structure Of A Thermal Power Plant

The main building for thermal power plant usually adopts RC structural system, because it is more economic than adopting other structural system. However, in order to set equipment and production line, the length of the main building is usually more than 100m long. If the length of the building is too long, the effects, such as stress and crack in the structure, which are induced by the temperature and shrinkage, will become a big problem. The existing codes take the method to limit the length of structural units by setting expansion joint into the building to reduce the effects. However, the main building for thermal power plant become an over-long structure, because of in order to meet the necessary of setting equipments for production, it can not be allowed to set an expansion joint into the building. So, it is important to analyze the effects of the structure due to the temperature changing and shrinkage.In this paper, some models are built based on an under construction RC thermal power plant to analyze the effects of the temperature changing and shrinkage, and the total equivalent temperature changing was decided by referring other researches. After choosing the stress-strain relationship models for concrete and steel rebar, the linear and non-linear analysis of over-long structure under temperature changing and shrinkage were conducted. The paper also built a model to analyze the width of the cracks on serviceability limit state.The paper also took the vertical load as variable, investigated how the vertical load inference the stress and crack of the structure under the temperate and shrinkage.In Code for design of concrete structure, the maximum distance of two expansion joints in a RC building is 55m, and in Technical stipulation for the design of civil structure of thermal power plant, the maximum distance is 75m. In this paper, in order to investigate the rationality of the maximum distances decided by above Codes, three models were built respectively for 55m, 75m, 100m long structures based on an under construction power plant, and the linear and non-linear analysis were conducted.This paper also provided an anti-cracking method for over-long structure under the temperate and shrinkage, and investigated its validity through non-linear analysis of a 100m long power plant building.The analytical methods and the research results in this paper are useful for engineering practice.