Stability Analysis Of Slant Legged Frame System

Compared with the common straight leg frame(common frame),the slant leg frame has the characteristics and advantages of the force,and the force is transmitted by the bending of the bar.In addition to the bending force,there is a kind of "arch" transmission mode,so that the axial force of the leg frame is larger.The "arch" force,deformation of tilted frame stiffness than the ordinary frame,in the same load and section bar,tilted frame across space(span)or more,in the same span,bar section inclined leg frame can be made smaller.However,this will make the stability problem of the slant legged frame become prominent and important.The core of the stability problem is to evaluate and determine the critical force of the member or structure.For ordinary frame can be determined by the calculated length coefficient of frame column "appendix D standard" steel structure design,and the frame is not so lucky,in the common specification also did not see the relevant formulas or tables.It is impossible to derive and solve the stable critical equation for the specific structure in the project,because the critical equation is beyond the equation,no analytical solution,and must be solved iteratively.Although the software can be used to replace a large number of calculations,but the correctness of the results of the software needs to be tested,what to test,how to test?These are unavoidable problems.Therefore,engineering design is still in urgent need of some convenient and fast computing tools.This paper is aimed at this situation to carry out the work study of tilted frame stability,the critical equations are related,and then a solution and a large number of solution to obtain enough data to draw the nomogram can calculate the critical force of the frame column.The most valuable is the result of Schedule 1 to 3 in the nomogram nomogram for calculating the results of finite element calculation(ANSYS)test,the test results are correct and reliable,high precision.Since the stability problem is more complicated than the traditional one,it is necessary to consider the equilibrium of structural deformation,which belongs to the two order problem.The critical equation was deduced with the increase of the number of structural elements and nodes become difficult,so this paper only selected single span frame as the research object,but the research methods of this paper can be extended to the case of multi span.It is worth mentioning that in stable characteristics and rules of the tilted frame,the author found the right method,critical force parameters can be used to study the qualitative or quantitative and the frame is closely related(constraint and stiffness)influence,therefore introduced a new concept,namely the rigidity constraint,half rigidity constraint and zero stiffness constraint.These concepts include the knowledge of the structure of the column to the column to provide the size of the constraints,a very good help.It can also be a clear explanation of why the oblique leg frame is less critical than the straight leg frame of the same size.