| Bolt-ball grid structure is a high order statically indeterminate spatial grid structure that made up of multiple root bars and the bolt-ball nodes according to a certain grid form,it has the advantages of good appearance、lighter weight、stress reasonable、simple and applicable for large span,and it used in industrial and civil architecture widely.It is important to note that many bolt-ball grid structure engineering collapse has happened in recent years though the bolt net structure has developed more mature.It is necessary for us to analysis this kind of bolt-ball serious engineering accident carefully to find out the cause of the accident,summarize experience and lessons,promote the healthy and secure development of the bolt net structure in our country.In this paper,exampled by a certain factory building of shanxi bolt-ball rack collapse as the research background, we will study the area of collapse network frame through the methods of field observation、deformation measurement、fracture analysis and sampling test,and we will use the analysis software(MIDAS,ANSYS and FLUENT) to simulate and analyze the failure process of the network frame, find out the accident reason finally. Main job:(1) Find out the key clues of the accident through the field observation and measurement,including the measurement of component size、the inspection of construction quality、the analysis of fracture macroscopic and the photos, etc, and retain the component samples from the collapse area.(2) Conduct the material test of the component, including mechanical properties test and chemical composition test,find out the changes in composition and property ofter 13 years, then determine the bolt fracture type of the high strength bolt.(3) Using the finite element analysis software MIDAS to analyze the network frame model,verify the original design is reasonable, and analyze the force situation of each link and studies the cause of the bolt fatigue fracture appear; Dynamics analysis with finite element analysis software ANSYS, and study the damage reason of the false twist bolt that is pulled.(4) According to the census found in the process of high strength bolt phenomenon of false twist, conduct the high strength bolt’s false twist damage experiment, including 7 groups M30 high strength bolt,the depth of screw was controlled in 3 ring thread,the results with existing twist into the depth of 1.1 d of high strength bolt compare the test datato find out the degree of the influence.(5) Find out the reason of bolt-ball node network frame factory building collapse accident through studying, and put forward the proposal combined with the research content. |
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