Experimental Research On The Stability Of Cross Pin-disk Type Steel Tube Supporting Frame Basic Unit And Spatial Expansion

The cross disc pin type steel pipe support is a.brand new temporary support system for construction.The support system is connected by the vertical bar,the cross bar,the inclined rod,the adjustable top support,the adjustable bottom support and the pin connecting parts to form the basic force element support of the structural geometric invariant system,It is very convenient to build up the whole support system by the horizontal and vertical expansion of the base of the basic force unit body through the joint of the disc pin and the upper and lower casing of the vertical rod.It is pointed out that the study of the structural performance of the basic force element of the disk pin type steel pipe support is the basis for mastering the overall structural performance of the support;Under the vertical load,the failure mode of the truss type support structure is reflected in the buckling instability of the element truss.In order to analyze and study the force performance of the basic force element of this type of steel pipe support,the method of combining the mechanical properties of the cross plate pin type steel bracket through indoor test and finite element numerical analysis.The influence of top cantilever length,step distance,span,span number,step number,whether the diagonal bar is installed and the way of diagonal bar erection on the bearing capacity of the basic stressed unit body are analyzed and discussed.The main research work is summarized as follows:(1)Carrying out the test of the force performance of the basic force unit body,The failure mode and bearing capacity of the basic force element are obtained.When the diagonal bar is not installed,the whole structure is torsional instability,and the vertical rod does not appear bending deformation.When the diagonal bar is arranged,the single vertical rod is bent and deformed.Whether the diagonal bar,the top cantilever length and the step distance have a great influence on the bearing capacity of the basic stress unit body,and the influence of the distance on the bearing capacity of the basic stress unit is relatively small.(2)The force performance test of the basic force element expansion bracket was carried out,and the failure mode and bearing capacity of the basic force element expansion bracket were obtained.The bearing capacity of the vertical expansion support decreases,and the instability form of the extended support is consistent with the instability form of the basic stress unit.That is to say,when the diagonal bar is installed,the buckling failure of the vertical pole is manifested,and the overall torsion failure is achieved without setting up a vertical bar.The ultimate bearing capacity of the lateral expansion bracket has not changed much.In the unstable shape,the lateral expansion bracket is the vertical buckling failure under the condition of setting the inclined rod and not setting the inclined rod.(3)Based on the theory of semi rigid base node,establish the basic model by force unit and its extension support the use of ABAQUS software,the basic mechanical unit and extended support loss displacement curve form of stability and load,and compared with the experimental results,to verify its accuracy.(4)ABAQUS software is applied to numerically analyze the influence of the parameters of the basic stress element on the mechanical performance of the unit,and the influence of top cantilever length,step distance,distance,span number and step number on the bearing capacity of the basic stress unit is obtained.The numerical analysis shows that:the top of the cantilever length is a key factor affecting the stability of the support,the cantilever length changes in the range of 300mm-700mm,the ultimate bearing capacity can be estimated by linear interpolation method;step influence on the stability of bracket,bearing capacity of step mumber on support should not control step should not be too large in in the process of construction,should try to use the method to increase the number of steps and reducing step improve the mechanical performance of the bracket;horizontal distance,horizontal expansion of a single vertical rod has little effect on the ultimate bearing capacity.(5)The experimental study and finite element analysis of diagonal basic mechanical unit building method,through analysis of the results of the inclined rod erection mode does not affect the basic unit instability forms,in the basic unit bracket erection parameters are the same,the symmetric diagonal set in to a certain extent,can improve the instability of the ultimate bearing capacity of basic unit.