Study On The Internal Force Of The Steel Frame With Oblique Plane Arrangemen

In steel frame buildings,some projects may have steel frame forms with oblique plane la yout due to the layout requirements of building design.However,the《Steel Structure Design Standard 》lack corresponding provisions for steel frames with oblique plane layout,which l eads to designers being unable to determine the effective length of columns by querying the s pecifications,causing certain difficulties in engineering applications.In addition,the new stee l standard has introduced the direct analysis method as a new method for steel structure analys is and stability design,which has not yet been truly applied.The operational process of direct analysis method in the analysis and design of steel frame structures with oblique arrangement,the comparison of analysis results with second-order and first-order analysis methods,as well as the scope of application and advantages and disadvantages,all need to be studied and expl ored.Therefore,conducting stable internal force analysis on steel frames with oblique plane a rrangements still has theoretical and practical value.Firstly,based on the elastic theory,the moment of inertia of the columns in the steel fram e structure with plane skew arrangement is derived,and the ratio of the linear stiffness of the beams and columns at different angles is obtained.Then,the elastic buckling equations of sin gle-story single-span and multi-story multi-span steel frames are obtained by displacement me thod and approximation method,and the effective length coefficients of H-shaped steel colum ns at different skew angles are obtained.Then,the finite element model is established,and the elastic buckling analysis is carried out to obtain the finite element results of the effective leng th coefficient at different angles.Finally,for the steel frame structure with spatial skew arrang ement,the first-order elastic analysis method,the second-order P-D elastic analysis method an d the direct analysis method are used to compare and analyze the structure,and the consistenc y and applicability of the three structural analysis and design methods are studied.Through research :(1)The theoretical value of the effective length coefficient of the single-layer single-spa n steel frame and the multi-layer multi-span oblique steel frame under different oblique angles is in good agreement with the finite element value.The skew angle has a great influence on t he effective length coefficient of the frame with lateral displacement,and has little influence o n the effective length coefficient of the frame without lateral displacement.(2)The specific operation process of the direct analysis method in the analysis of steel f rame structure,the introduction of the initial geometric defects of the structure and the compo nents,and the introduction of the overall initial geometric defects of the two structures are equ ivalent in the analysis results,but only the elastic analysis method of geometric nonlinearity is considered.At the same time,the direct analysis method considering the influence of material nonlinearity,geometric nonlinearity,joint stiffness and defects still has some difficulties in th e implementation of finite element software.(3)Three kinds of structural analysis method for oblique arrangement of steel frame str ucture analysis,the internal force results and displacement results are basically the same,but t he direct analysis method and the second order P-D elastic analysis results are larger than the first order analysis results.The internal force and displacement results obtained by the direct a nalysis method are more in line with the real stress state of the structure.