Analysis Of Warping Transfer Through I-section Beam-to-Column Joints

The torsion produces warping deformation of cross sections in thin-walled members. Through analytically solving torsion problem of thin-walled beam-to-column structure,the thesis found the torsion problem could be ultimately figured out supposing that the warping transfer through joints have been accurately deduced. The warping transfer at joints includes two relational expressions between two joint bimoments and two joint warping degrees of freedom,which are a couple of generalized force and generalized displacement about warping deformation of the joint.At present,in general finite element software,only one warping degree of feedom is adopted to describe warping of the cross section,as well as warping continuity at beam-to-column joints. This processing method can be applied to finite element analysis by modifying the coordinate transformation matrix, i.e. setting the value of coefficient corresponding to warping displacement as one in the matrix's diagonal position. The equivalent relationship concerning the ending bimoment and the ending warping displacement to the method mentioned above is revealed in the thesis. However, as is indicated by many research literature, the law of warping transfer through joints is not invariable,but dependent on the specific joint models. As a result,the treatment of the software is certainly not correct for not taking the distinction of joints into account.In this paper, three types of beam-to-column joint were treated and the expressions were obtained respectively.First,for the unstiffened joints, through a board-decomposing method,two simple relations between two joint bimoments and two joint warping degrees of freedom are found. Using the self-compiling finite program which modified by the educed two equations to calculate the model structure and comparing with solutions of finite element analysis using ANSYS Shell elements,partly agreements are achieved. At the same time,an anomalous distortion deformation caused by the warping torsion angle of the continuity of the inside and outside flange was detected in the web section while torsion take place in the beam-column structure with a small inclination of the beam,after studying the limitation of this suggested expressions.Secondly,for extended-flange stiffened joints,simple relationships between the warping displacements,which can be easily applied to finite elements analysis,was proved accurate and applicable for engineering practice. At last, some useful analysis methods for reference were introduced for three stiffened joints.