| In the project of energy saving of building,the insulation system is can't be ignored as an important link.There is an effective way to save energy by reducing energy consumption during using buildings.The building in cold areas usually chooses external insulation form as its thermal insulation layer.However,this kind of system also has problems like drums.cracks or even shedding before deadline.These problems can be caused by the change of temperature and humidity in the outdoor environment.In the current study,there is no comprehensive analysis of heat transfer and moisture transfer of external insulation system,and there are very few experiments to measure the strain of the exterior insulation structure.Therefore,this paper measures and simulates thermal displacements and moisture displacements focused on the external insulation structure of EPS in cold regionsIn this paper,the peripheral protection structure in Shenyang is firstly investigated.Forms of destruction of exterior layers are statisticed.And then the causes of damage and the location of damage in the wall are analyzed.It is shown in the study that transverse fractures are the common fractures and the rising of drum is easy to occur on the surface of veneer which is daubed on the buiding attached to the insulation layer.The paper also shows that the connection between the windows and floors is prone to rupture.The results of the research provide preliminary demonstration for the result of simulation.Then,the study simulates the external insulation system of EPS by the software named COMSOL.Outdoor conditions are used to select the temperature and humidity with hourly change of January and July in Shenyang.The energy of solar radiation is also added.Firstly,the simulation gets the change of internal heat transfer within a day and then obtains the thermal displacement and thermal stress of the wall.It is found that the stress generated by internal thermal expansion of wall reachs 105?106N while the thermal displacement is very small.This shows that the damage caused by heat is a constant process,and the wall follows the rule of heat expansion and contraction in both summer and winter.Secondly,the moisture transfer is simulated by using concentration instead of relative humidity.The simulation shows the change of concentration of water vapor in the wall and then obtains the stress of humidity by analyzing the infiltration expansion.It turns out that the stress of the humidity has not changed much in one day.Thirdly,a comprehensive analysis of the changes of heat and moisture in the wall is carried out.The result shows that the number of deformation by heat transfer is 10-4?10-5m and by moisture transfer is 10-7?10-8 m.It is concluded that thermal stress is the main reason for the crack of the exterior surface of the wall.And the number of thermal stress is an order of magnitude greater than moisture stress.Finally,the study measures the strain of exterior surface of one building in Shenyang by static strain gauge and strain gauge.It is found that there is a certain similarity between the strain rule of exterior surface and temperature variation,and this phenomenon can prove that temperature is the main reason for the displacement of wall surface.One the one hand,the result of measure can enrich the database of the actual measurement of external insulation system in China.On the other hand,the result supports the theory that Reducing the temperature change of the exterior surface layer is one of the methods to reduce the rupture.There is of great significance to improve the technology of external wall insulation system. |
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