Research Spotlight: Characterization of Cold-Formed Steel Member Dimensions and Geometric Imperfecti
2017 Annual Stability Conference Presentation
Session SS1A: Technical Presentations: Stability of Thin-Walled Components and Assemblages Tuesday, March 21, 2017 1:40 pm
Characterization of Cold-Formed Steel Member Dimensions and Geometric Imperfections Based on 3D Laser Scanning
This paper briefly introduces the full-field laser-based imperfection measurement platform as well as the four-step post-processing toward measurement point clouds from the platform. The first three steps can lead to one application: variation of dimensions and correlation study of cold-formed steel members. The last step of post-processing enables another two applications, i.e., imperfection characterizations and finite shell-element analysis. The imperfections (deviation from perfect) may be characterized in geometric terms: bow, camber, twist, crown of a given flat plate, flare of a given element; or may be characterized in terms of their modal buckling content: fit to flexural modes, torsional mode, local mode, and distortional mode. In addition, the geometric imperfections may be transformed into the frequency domain and power spectrum of the imperfection magnitudes can be obtained. This 1D spectral approach provides a potentially novel means for generating realistic, but random geometric imperfections for use in shell finite element simulations. Shell finite element collapse analyses that compare the sensitivity in response to true, and various simulated imperfections are provided.The simulations indicate how simple modal imperfections are powerful for predicting strength conservatively, but the 1D spectral approach more closely approaches the results from the true (scanned) members. In the future larger Monte Carlo simulations should be performed to assess the reliability of cold-formed steel members using these results.
Xi Zhao and Benjamin W. Schafer, Johns Hopkins University, Baltimore, MD