Study On The Bending Performance Of Cuplock Steel Tubular Scaffolding Joints

Due to advantages of convenient installation and large carrying capacity,the cuplock steel tubular scaffolding has been widely used in practical engineering.But because of immaturity on design theory,construction safety technology and on-site management method,the collapse of scaffolding often occurred,causing serious loss of life and property.Since the study on mechanical properties of cuplock joints plays an important role in the mechanical property research of the overall scaffolding.Owing to the lack of particular conclusions about the semi-rigid characteristics of cuplock joints,this paper mainly investigates on the bending performance of the cuplock joint,and get relevant as follows:(1)The joint bending test of the cuplock scaffold was conducted.The research contents include the influence of the condition of members,the length of the standing tube and the direction of the bending moment on the M-? characteristic curve,the ultimate bearing capacity of the joint,the stress development of the bell shape cap and the bowl shape socket,the horizontal tube and the standing tube,and the vertical displacement change of the horizontal tube.(2)Comparision was conducted for various numerical models on M-? relationship of semi-rigid joints,and the teilinear model was selected to simulate the moment-rotation characteristic curve,which is concise and accurate.The simulation results show that the rotational rigidity of the joint decreases with the increase of the length of the standing tube.To overcome the initial relaxation and friction,the cuplock joint rotational rigidity reaches a reasonable value after certain rotation,under the positive bending moment: average rotational rigidity of new specimens can be as nigh as 52 kN·m/rad,which that of the old specimens is only 28kNm/rad;the curve slope of specimens under negative bending moment drops suddenly after yield,so it has little reference value to rotational rigidity.(3)The analogue simulation was conducted on stress and deformation of cuplock steel tubular scaffolding by using the finite element analysis software ANSYS,then the simulation data were campared with the test data,to verify the validity and feasibility of the finite element model establishment,and lay a foundation for the deeply understanding of the cuplock scaffolding joint bending resistance quality control standard.(4)By changing the tightening level on the bell shape cap in ANSYS,its influence on the flexural behavior of the cuplock joint was obtained: i.e,with the increase of bowl tightening level,the rotational stiffness of cuplock joint increases,and the vertical displacement of horizontal tube decreases,so it must be ensured that every bell shape cap of scaffolding is fully tightened.(5)By combining with the joint positive moment test data with the simulation results of the ANSYS,the cuplock scaffolding joint bending resistance quality control standard can be drawn as follow: The maximum rotation of the joint should not be more than 0.06 rad,and had better not more than 0.02 rad ~ 0.03 rad in normal service;when the load is less than 1.5 kN·m,the maximum vertical displacement of loading point on the cross tube is less than 27 mm,each member of the joint can not be destroyed nor largely deformed;the rotational for rigidity qualified standard of cuplock steel tube scaffolding joint should be at least 55 kN·m/ rad.