Experimental Study On The Variable Amplitude Fatigue Performance Of The Anchor Bolt Of The Exterior Wall Thermal Insulation System

With the advancement of the dual carbon process,low-carbon sustainability in the construction industry is an inevitable trend.External wall insulation technology is currently the most commonly used energy-saving method for building operation,but the problem of cracking and detachment during use continues to emerge.Fatigue damage caused by wind load is one of the important reasons for its failure.The external insulation system was widely used in China in the late 1990 s and is currently approaching the 25 year service life required by the regulations.Therefore,evaluating the fatigue life of existing building external insulation systems and providing suggestions for the design and material selection of new building external insulation systems is an urgent problem to be solved.The main research and results of this article are as follows:(1)The tensile bearing capacity test was conducted with the anchor bolt anchoring depth and substrate strength as variables to explore the variation law of the anchor bolt tensile bearing capacity F.Then,under the premise of clear F,constant amplitude and variable amplitude fatigue tests were conducted with anchor depth and cyclic load as variables.Through comparative analysis,the mechanical performance differences of anchor bolts in different substrates under different anchor depths were obtained.The results show that the tensile bearing capacity of anchor bolts at different anchoring depths is positively correlated with the strength of the base layer;However,the constant amplitude fatigue performance of anchor bolts is influenced by factors such as anchor bolt failure form,substrate strength,cyclic load size,and anchoring depth.When the cyclic load is less than 320 N,the constant amplitude fatigue performance of anchor bolts in A3.5 block substrate is the best;The damage caused by the initial loading in the early stage to the fatigue performance of anchor bolts at various anchoring depths is directly proportional to the initial cyclic load value.The cumulative damage values of anchor bolts calculated by the Corten Dolan criterion are 0.01,0.15,0.19,0.32,and 0.41,respectively.(2)Based on the above experimental results,the S-N curve was obtained,and the durability of anchor bolts in the external wall insulation system was evaluated using Miner’s criterion and the actual wind speed in Jinan city.The results show that in the A3.5 block substrate,the fatigue life of anchor bolts at each anchoring depth meets the requirement of 25 years in the specification.In the same wind environment,the fatigue life of anchor bolts is mainly affected by the anchoring depth,with the maximum increase of 42.3% for the65mm-75 mm anchoring depth;The increase in anchor depth between 75 mm and 85 mm is only 2.9%.(3)Simulate and supplement the experiment using ABAQUS software with anchor bolt anchoring depth,anchor bolt diameter,and anchor spacing as parameters.The results show that the ABAQUS model is set correctly,with an error of about 10% between simulated and experimental values.The tensile bearing capacity of anchor bolts is positively correlated with the depth of anchoring,anchor bolt diameter,and anchor spacing.The anchor bolts quickly reach their ultimate bearing capacity in the early stage of loading,with displacement ranging from 3mm to 5mm.