Experimental Study On The Fatigue Of EPS External Wall Insulation System Under Variable Loa

With the wide application of external insulation system,more and more building walls appear cracking,hollow drum,fall off and other problems,the root cause is the lack of cohesiveness between the insulation board and the base,or under the action of wind load for a long time,leading to its fatigue damage and eventual destruction.Therefore,the research on the tensile capacity and fatigue performance of the insulation board in the external wall insulation system plays a vital role in improving the stability and reliability of the system.In this thesis,experimental research and numerical simulation are used to investigate the tensile capacity and fatigue performance of the insulation board in the external wall insulation system under constant amplitude and variable amplitude.The research focuses and conclusions are as follows:(1)The tensile strength test and constant amplitude and variable amplitude fatigue test of insulation board in EPS external insulation system are carried out.The stress loss of insulation board is studied according to Corten-Dolan cumulative damage criterion.The tensile properties of insulation board were studied by using the pasting method and pasting rate of insulation board as test variables.The fatigue performance of the thermal insulation board was studied by using pasting mode,pasting rate,constant amplitude and variable amplitude peak cyclic load as test variables.The results show that under the same construction conditions,the tensile capacity is in the order of full adhesion method > point adhesion method > strip adhesion method > cross adhesion method > point and frame adhesion method.The variation of constant amplitude fatigue frequency and variable amplitude fatigue frequency of thermal insulation board are consistent,which are positively correlated with the adhesion rate of thermal insulation board and negatively correlated with the peak cyclic load.Moreover,80% point adhesion method has the best resistance to variable amplitude fatigue,while the cross adhesion method has the worst.The initial cyclic load in the early stage will cause certain fatigue damage to the thermal insulation board,and the fatigue damage will increase with the increase of the initial cyclic load.In the primary and secondary amplitude variation tests,the maximum stress grade loss caused by the initial cyclic load can reach 0.25540 and 0.30274.(2)The durability of external insulation system of EPS insulation board was evaluated by the theory of fatigue damage.Through the frequency analysis of the actual wind speed in Jinan from 2016 to 2020,and considering the influence of building height change,the cumulative damage value of the building under different conditions was obtained,and the fatigue damage theory was used to evaluate the bond fatigue life of the insulation board.According to the fatigue life evaluation of the adhesion rate 40%,60%,80% point adhesive insulation board,the fatigue life of the adhesion rate 40%,60% point adhesive insulation board is short,respectively in 8years,18 years,not meet the design life of 25 years,should not only use mortar for bonding treatment in construction,should be treated in accordance with the design requirements of bonding anchor.To extend the service life of the external insulation system;The fatigue life of80% point adhesive insulation board is longer,about 31 years,which can meet the requirements of the design service life.(3)The stress variation and deformation of EPS external insulation system under ANSYS finite element software are analyzed.The model of EPS external insulation system was built with ANSYS finite element software,and the load simulation was carried out according to the size of wind load,and the stress variation law and deformation of the model was analyzed.According to the obtained data,under the same height wind load,the maximum shape variable and the maximum stress value of the point adhesive insulation board appear in the through cavity,and with the increase of the paste rate,the shape variable of the insulation board decreases and the stress distribution becomes more uniform.The deformation and stress of the full adhesive insulation board are obviously affected by wind load at different heights,and the distribution is mainly along the thickness direction,and the maximum value appears in the corners of the insulation board.In the actual construction,we should not only ensure the material strength of the insulation board itself in strict accordance with the specification requirements,but also strengthen the weak parts of the insulation board to reduce its deformation and stress.