Vibration And Buckling Analysis Of Cold-formed Thin-walled Steel Members

With the development of technology and the engineering demands,more and more thin-walled structures are used in practical engineering.The instability and resonance of cold-formed steel(CFS)members have a significant effect on the structure during the service period.Taking the CFS section as example,the study of its distortional buckling and vibration behavior have been carried out.The main results achieved are as follows.Based on the plate and shell theory,a stiffened plate buckling model(SPBM)is improved to analyze the distortional buckling of CFS C-section with lateral restraint.The accuracy and rationality of the present model are verified by finite strip program.Based on the finite strip theory,the mass matrix of unit strip element is deduced.The finite strip program is designed to analyze the vibration behavior of common CFS sections and box bridge sections.The effects of different size ratios,lengths as well as lateral constraints on the vibration behavior of members are discussed.It is found that the increase of the length significantly reduces the value of frequency.The frequencies increase with increases in the section thickness.The effect of web height on the frequency of different type sections shows different rules.The frequency of the sections increse when the members become stiffer due to lateral restraint.Combined with the finite strip method with the Bolotin method,the parametric study of dynamic instability for C and Σ sections are carried out.It is found that the increase of C-section results in the movement of dynamic instability area to high frequency side,and the width of instability area increases.When the static load is included in the external load,the dynamic instability area of the beam will move to the low frequency side,and the width of the dynamic instability area will also expand.Based on finite strip theory,the MATLAB programs and visual interface for different cross sections have been developed.Meanwihle,the program is also suitable for vibration analysis of anisotropic thin-walled thin-walled structures,which may guide the vibration analysis of the structures in actual engineering.