Study On The Bearing Capacity And Simi-rigid Node Of Steel Tubular Scaffold

The template support systems were the temporary bearing systems in the construction process of concrete structure,they play an irreplaceable role in ensuring the construction progress and security,so we should master their constructional performance to optimize the constructional design scheme,and play the preliminary analysis sufficientlly.Through the numerical analysis,experiment in lab and test in site on the steel fastener,bowl,pin and spigot-socket supporting systems,we mastered the application performance of different template support systems.As the researches on steel fastener,bowl and bolt supporting systems of their application performance are widely,this paper will carry out further study refer to the existed research methods and results.In this paper,we carried node test,plane frame test and whole aircraft on steel fastener scaffold,and unit frame test on spigot-socket scaffold to master the application performance of different template supporting systems.We obtained the ultimate bearing performance and failed modes of different frames,and defined the rigidity of the nodes.Made numerical analysis on different forms of supporting systems by the finite element software ANSYS,contrasted the difference between numerical results and experimental results,and determined the reasonable numerical analysis method.Get rid of the traditional construction methods with experience,and used interval number theory and convex analysis methods to quantify the rigidity degree of nodes,in order to quantify the node stiffness and to ensure the bearing capacity and stability in construction.Conducted several tests on different forms of support system,mastered their application performance in site under complicated conditions,provide certain guidance for the construction of the similar projects.Draw the following conclusions by the above studies:(1)We obtained the semi-rigid degree of the connection nodes by node experiment.We found that the node semi-rigid property is obvious;the initial stiffness values with different tighting stiffness were different by the analysis with MATLAB.And we knew that the node stiffness greatly affect the ultimate bearing capacity of the template support when it during 20 k N·m/rad ~ 60 k N·m/rad,while the influence of node stiffness to ultimate bearing capacity is not significant when it beyond the above range.(2)From the plane frame test on steel fastener scaffold,we knew that the parameters like the number of poles,the step pace,the bracings and the node stiffness can easily affect the lateral resistance bearing capacity,and the bracings was the most obvious factor in them.And we obtained a simple analysis model about node stiffness by utilizing the method of interval mathematics deals with convex method,and this provides a new way of thinking in the template support stiffness analysis.(3)Among the experiment of the whole steel fastener scaffold,the failed mode of each whole frame was buckling instability with no obvious signals in addition to condition 1.The main reason was that the overall stability of the frames with bracing is well,and the steel pipe adjacent to yield directly caused the damage of each scaffold.The bracing in scaffold improved the bearing capacity,changed the buckling mode,and limited the deformation of the scaffold.The scaffold with around vertical bracings becomes a closed body,and that greatly enhanced the overall stiffness,thus improved the bearing capacity of the supporting system.For example the bearing capacity of condition 3-2 is 2.3 times to that of condition 1.(4)As the widely use of new type of template supporting system,we should master their application performance.We master the mechanical performance of spigot-socket scaffold through the vitical bearing capacity test on unit frame.The vertical bearing capacity of unit frame with small horizontal spacing and large wedge tightness was larger than that with large horizontal spacing and small wedge tightness.Comparing the combination of wedge tightness and the horizontal spacing,we found that,the horizontal spacing was the main factor that affects the vitical bearing capacity,the larger the horizontal spacing the smaller vitical bearing capacity.And the wedge stiffness will surely affect the bearing capacity of the unit frame,but its influence degree depends onthe horizontal spacing,the larger the horizontal spacing the more significant impact of wedge stiffness to bearing capacity.(5)We draw some conclusions from the test in-site about the spigot-scoket mixed scaffold,steel fastener scaffold and the bowl-steel fastener mixed scaffold,that different site constructional conditions put forward different requirements to the template supporting system.The steel fastener scaffold is flexible in application,it is easier to set up all kinds of vertical and horizontal distance and interval pace,but the fasteners can easily lossed and led to waste.The elements in bowl scaffold and spigot-socket scaffold are standarded,their connection nodes between pole and bar are axial,the stress is more reasonable,and they are installate and dismantle quickly,so they have high construction efficiency.But the bowl scaffold and spigot-scoket scaffold can't meet the requirements of the special-shaped structure with their fixed elements.So we can mixed the bowl scaffold and spigot-scoket scaffold with steel fastener scaffold to meet the bearing capacity,stability and changing pole spacing flexble in construction,and this mixed scaffold include a basic frame by bowl scaffold or spigot-scoket scaffold,and a strengthen frame by steel fastener scaffold.