Practical Calculation Methods For Whole Stability Of The Two Layer Frame

Due to the high strength of steel,steel frame can be done relatively thin and soft,so that the stability of the structure becomes prominent.The stability problem belongs to the two order problem,which needs to consider the deformation of the balance,and a strength of the traditional order is only considered before the deformation of the balance,so the stability problem is more complex than the first-order intensity,is a geometric nonlinear.The core of the stability problem is to calculate the bearing capacity of the member or structure(i.e,the critical force).It is not difficult to solve the critical force of a single member.but it is not easy to solve the critical force of the whole structure.In the current”code for design of steel structures”(GB50017-2003)has calculated length coefficient of solving frame form(see Appendix D),but the table implies some assumptions,which can only be used in the framework of rules(the column axial force,and the same)for irregular frame(the column axial force is no longer different)apply.In view of this situation this paper intends to start from the two layer framework,the overall stability of the critical Equation Derivation framework(transcendental equation),and then a solution,after solving thousands of times,get a lot of data,the nomogram made two frame column effective length coefficient.The calculated length coefficient of column calculated by these modes can be quickly nobel.Due to the instability of the whole frame,the critical force of each column is completely satisfied with the condition of instability at the same time.The most valuable is the natural results in table 4.2 and table 4.3 in the nomogram,correctness and reliability is verified by the nomogram of finite element calculation,and the calculation precision is very high.It is a good tool to quickly calculate the critical force of irregular frame columns.In the face of the "code for design of steel structures",there is no calculation form in this respect.Because the overall stability of solution,the number of unknowns increases with the increase in the number of layers to get the final critical equation of difficulty increases,so the only two storey single span frame,but also can be used for two layer multi span frame,the stiffness can be only included in the multi span frame beam.In this paper,a new method to solve the critical force is also discussed,such as the axial force area ratio method(fifth chapters),the critical force redistribution method(the sixth chapter),the deflection method(the seventh chapter)and so on.And some results are obtained.