Civil Engineering Study 98-3
PREFACE This report summarizes two studies related to the design of cold-formed steel connections. The study topics included the creation of a test standard for determining the strength of a screw, and the determination of the strength of a screw connection. A standard test protocol does not exist for determining the strength of a screw. Today, manufacturers use test protocols developed for their products. Thus, there is no consistency in defining the structural performance of a screw. A test standard has been developed. The standard used as its model the American Society of Testing and Material's F 606, Standard Test Methods for Determining the Mechanical Properties of Externally and Internally Threaded Fasteners and Rivets. Tests have been conducted to show the practicality of the proposed test standard. The connection strength equations in the AISI design specification are based primarily on tests of single- and double-screw connection tests. Also, design assumes that the connection strength is proportional to the number of screws. The connection strength study considered the variation of connection strength with the number of screws, the screw center-to-center spacing, and the location of the screws in the connection. This experimental study demonstrated that connection strength increased with additional screws in the connection, but the increase was at a rate less than a multiple of the single screw strength. Current design specifications do not account for the pattern formed by the screws in a connection. This study showed that the screw pattern has a minor effect on the structural performance, but may be neglected for the purposes of design. Finally, this experimental study determined that the connection strength decreased with a decrease in the center-to-center spacing of the screws. This report is based on a thesis submitted to the Faculty of the Graduate School of the University of Missouri-Rolla in partial fulfillment of the requirements for the degree of Masters of Science in Civil Engineering. Technical guidance for this investigation was provided by the American Iron and Steel Institute's Subcommittees on Test Procedures (S. R. Fox, Chairman) and Connections (M. Golvin, Chainnan). The Subcommittees' guidance is gratefully acknowledged. Thanks are also extended to H. H. Chen, D. F. Boring, and S. P. Bridgewater, AISI staff, for their assistance. Steel sheet used for the experimental phase of this study was provided by Dietrich Industries.
Civil, Architectural and Environmental Engineering
American Iron and Steel Institute
Wei-Wen Yu Center for Cold-Formed Steel Structures
Cold-Formed Steel Series
Missouri University of Science and Technology
© 1998 Missouri University of Science and Technology, All rights reserved.
Sokol, Marc Allen; LaBoube, Roger A.; and Yu, Wei-wen, "Determination of the tensile and shear strengths of screws and the effect of screw patterns on cold-formed steel connections" (1998). Center for Cold-Formed Steel Structures Library. 146.