Research On Mechanical Behavior And Design Method Of Cold-formed Steel Roof Trusses

This paper mainly presents detailed results on mechanical behavior and design method of cold-formed steel roof turss in low-rise residential structures by tests and nonlinear finite element analysis based on consulting a lot of documents.The bearing capacity of cold-formed steel roof turss about two different styles is tested in this paper. The trial device, test method and full test course as well as the analysis of test data are introduced in detail in this paper. Test results show that: the damage of test coupons happened on the supports, and the elements don't buckling, this illustrate that test coupous don't belong to the damage of strength, and the connection plays an important role.Nonlinear finite element analysis involving geometric large deformation and materials nonlinear is used to simulate test roof truss in this paper. Members are modeled as shell elements. The steel members are simply connected. The screws connecting of the chord to the web member are modeled through coupling methods. The equation resolution method is selected by ANSYS program automatically. The finite element analysis results are close to that of tests, so the finite element analysis method is correct. There are followed by a detailed parametric study using nonlinear finite element analyse, such as steel strength, section styles and steel thickness. The results of finite element analyse show that teel strength, section styles and steel thickness have great effect on bearing capacity of cold-formed roof truss.Based on the column deflection curve method (CDC method), the paper analysed the effect of semi-rigid connection to the effective length of compressed members in the cold-formed thin-walled steel truss. The results of CDC method show that:the influence factors of semi-rigid connection to the effective length of compressed members in the cold-formed steel truss are connection rotational stiffness, member rigidity and effective section. And the paper calculated the variety of column curve under the different M ?θcurve, at last, the suggestion value of effective length of compressed web members in cold-formed thin-walled steel truss were presented. The suggestion value of effective length of chord isμ= 1.0, The suggestion value of effective length of web member isμ= 0.9, The suggestion value of effective length of end strut and end web member isμ= 1.0.Finally, referencing above research achievements, current design codes or documents, simplified design method of cold-formed steel roof truss is done.