Effective Lengths of Web Members in Trusses - an Experimental Investigation of Tension Effects
Date of Thesis
Throughout the truss and joist industry, research is constantly underway in an effort to determine ways to further minimize production costs and material use. In regard to structural stability, previous research has shown that the effective length factor, K, for web members may be overly conservative, leading to an overuse of material in the design. Currently, the top and bottom chords provide the only acknowledged flexural and torsional resistance for compression web members in trusses. This study presents an investigation into the restraining effects provided by tension members in trusses, which is in an effort to determine whether the tensioning effect is adequate to warrant the use of a smaller K-factor in routine design. Two different methods to explore the buckling mode of compression web members are performed for this research, including (1) the use of an experimental testing apparatus, and (2) computational analysis of compression web members within a modified Pratt truss. The results are presented and summarized based on the nature of the research method. Results of the experimental testing confirmed the presence of additional rotational restraint provided by tension members. Therefore, it was concluded that effective length factors for compression web members need not exceed a value of 1.0. The computational studies of a modified Pratt truss supported this conclusion and further suggest that a K-factor of less than 1.0 could be used in design, provided that sufficient resistance to out-of-plane translation is present along the bottom chord (via bracing or other means). Recommendations for future work, including full-scale testing and additional computational studies, are provided within this thesis.
compression web members, effective length method, K-factor
Bachelor of Science in Civil Engineering
Jean C. Batista Abreu
Partridge, Allison Louise, "Effective Lengths of Web Members in Trusses - an Experimental Investigation of Tension Effects" (2016). Honors Theses. 346.