Initial Geometric Imperfection Measurement and Characterization of Cold-Formed Steel C-Section Structural Members with 3D Non-Contact Measurement Techniques

摘要

Local flange and web imperfections, cross-sectional twist, and global sweep were measured for cold-formed steel C-section structural members (studs and joists) using non-contact measurement methods (photogrammetry and laser scanning) and a manual measurement method (dial gauges mounted on a precision rail). Cold-formed steel members acquire geometric imperfections from manufacturing, shipping, storage and construction, and these imperfections affect axial and flexural capacity. Photogrammetry and a newly constructed laser measurement method are demonstrated to be viable and accurate alternatives to manual measurements, producing 3D point clouds that allow detailed study of imperfections along a member. Measured imperfections provide an accurate geometry representation, which can be used in experimental comparisons and computational modeling. Each measured imperfection shape is characterized as a series of trigonometric functions along the member's length. This format allows researchers to reconstruct the member geometry and to understand the influence of imperfection shape on local, distortional, and global buckling deformations. The imperfection fields measured in this study, as well as past measurements from previous research, are organized with a common format in a new imperfections database hosted by the Cold-Formed Steel Research Consortium for communal access and future study.