Assessing Wind Effects on Low-rise Building Thin-Walled Structures

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In recent years, thin-walled cold-formed steel members have been widely used in low- and mid-rise buildings as primary and secondary structural elements. Individual cold-formed steel members are usually attached to cladding and sheathing materials to form the building envelope. During their life cycle, cold-formed members are acted upon by aerodynamic wind loads that fluctuate both spatially and temporally. Current analysis and design provisions fail to capture the true nature of wind effects on thin-walled cold-formed steel structures where elastic and collapse behaviors under wind loading are driven by the stability interaction of individual members and cladding systems. Furthermore, past studies generally focus on understanding the behavior of cold-formed members under uniform wind loading conditions that ignore the effects of spatial and temporal variation of wind. This research has the main objective of gaining a better understanding of the structural response of thin-walled members under realistic wind loading and use the finding to bridge the gap and improve the current analysis and design approaches. In particular, two types of structural systems were studied: (1) thin-walled panel purlin systems, and (2) thin-walled composite wall systems. The study leverages both conventional and innovative methodologies to achieve the main goal of the research. Based on the methodologies utilized for the evaluation of aerodynamic wind loads, this thesis is divided into two phases. In the first phase Computational Fluid Dynamics was used to generate wind pressure coefficients. In the second phase, aerodynamic wind loads were evaluated using wind tunnel measured pressure coefficients and the Database-Assisted Design (DAD), a realistic wind loading analysis and design technique based on aerodynamic database of wind tunnel tests. In both phases of the research, finite element analysis using ABAQUS was performed to examine the stability and strength behavior of thin-walled structural systems under the action of realistic wind loading. Finite element models of thin-walled panel purlin systems and thin-walled composite wall systems were developed that imitate the actual physical structural systems. Pressure coefficient data from the initially completed numerical simulations or wind tunnel tests were used to define the spatially varying wind loads on tested members. From the finite element analysis results, the critical wind pressure distributions and wind speeds associated with elastic buckling and collapse strength were evaluated. The unique buckling and collapse behaviors of thin-walled cold-formed steel structural systems were identified. The results also revealed the difference in performance of thin-walled cold-formed steel structural systems under realistic wind loads when compared with code specified wind loads. Finally, the research lays the groundwork for the development of database-oriented performance-based analysis and design method for thin-walled cold-formed steel members under the action of realistic wind loading. Keywords: Cold-Formed Steel, Computational Fluid Dynamics (CFD), Database-Assisted Design, Elastic Buckling, Nonlinear Collapse, Thin-Walled Steel Building Structures