The Numerical Analysis Of The Cracks Question With EPS Board Exterior Wall Insulation System

With the accelerated urbanization process and the improvement of the quality of resident life, the total building energy consumption in China is increasing year by year. The heating energy consumption per unit area is equivalent to 2 to 3 times of the developed countries with similar climatic conditions. Building energy conservation as one of ten energy conservation project is the key area of energy saving. The poor thermal insulating property of the exterior walls is one of the main reasons for building high energy consumption.In central China, especially Henan Province, EPS board exterior wall insulation system, with its many advantages, is more extensively applied in building energy efficiency, especially of existing buildings for energy saving. However, the material properties of EPS board exterior wall insulation system itself and the main structure are quite different. So they are likely to cracks or get off in the external negative factors and changing climatic conditions. Especially in summer sudden dropped heavy rain in high temperature and in winter freezing after heated, the probability of crack is larger near the hole of windows and doors under extreme conditions.In this paper, based on major public research projects in Henan(081100910400) and major science and technology projects in Zhengzhou(082SGZS32079), adopting the ways of finite element numerical simulation, to have a study of the cracks and get off phenomenon directed towards the EPS board thermal insulation system, to examine pre-crack temperature distribution, deformation and stress distribution, and puted forward measures and suggestions for cracking, the main work as follows:1)Selected a typical bay with a window hole of the external wall of a residential multi-storey masonry structure as the study object, seted up finite element model, calculated thickness of external insulation composite wall in accordance with the energy saving standard in Zhengzhou, then selected material properties, proposed basic assumptions, used coupling field unit to mesh.2)Simulated heat—structure coupling reaction of EPS board exterior wall thermal insulation system in summer rain environment after extreme high temperature, analyzed the temperature change, deformation and stress distribution, investigated the formation and rules of crack. The analysis founded that polystyrene board had a good insulation effect; and the maximum deformation was near windows, the material was contraction after the first expansion, if not adapted to such changes, it was prone to cracking; and finded the causes of vertical cracks, horizontal cracks and diagonal crack in the corners or windows.3) Simulated heat—structure coupling reaction of EPS board exterior wall thermal insulation system in winter frozen after heating, and compared with the result of the sudden drop in rainfall after high temperature in summer extreme environments, focusing on the windows nearby to analyze the temperature, deformation and stress. The analysis founded that, at the junction of polystyrene board layer and the mortar layer, the deformation uncoordinated, the value of stress was a mutation, it was easy to crack or even fall off; higher temperature produced press stress, lower temperature generated tensile stress, that tensile stress exceeded the tensile strength was the crack source; difference in temperature the greater, the deformation the greater, the greater the stress, so the environment frozen in winter was easily crack.4) Through the analysis, it concluded with EPS board exterior wall insulation system cracking measures and recommendations, and improved the questions of cracks and falling.