Combined Tension and Bending Loading in Bottom Chord Splice Joints of Metal-Plate-Connected Wood Trusses

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Combined Tension and Bending Loading in Bottom Chord Splice Joints of Metal-Plate-Connected Wood Trusses by Philip J. O’Regan

Thesis submitted to the Faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in Biological Systems Engineering

APPROVED:

Frank E. Woeste, Chairman

Joseph R. Loferski

Audrey G. Zink

John V. Perumpral

May, 1997 Blacksburg, Virginia

Keywords: wood truss, combined loading, truss plate, splice joints, truss design

Combined Tension and Bending Loading in Bottom Chord Splice Joints of Metal-Plate-Connected Wood Trusses by Philip J. O’Regan Frank E. Woeste, Chair Biological Systems Engineering (ABSTRACT)

Metal-plate-connected (MPC) splice joints were tested in combined tension and bending to generate data that were used in the development of a design procedure for determining the steel net-section strength of bottom chord splice joints of MPC wood trusses. Several common wood truss splice joint configurations were tested at varying levels of combined tension and bending loading. The joint configurations were 2x4 lumber with 20-gauge truss plates, 2x6 lumber with 20-gauge truss plates, and 2x6 lumber with 16-gauge truss plates. All the joints tested failed in the steel net-section of the truss plates. The combined loading was achieved by applying an eccentric axial tension load to the ends of each splice joint specimen. Three structural models were developed to predict the ultimate strength of the steel net-section of the splice joints tested under combined tension and bending loading. The test data were fitted to each model, and the most accurate model was selected. Data from other published tests of splice joints were used to validate the accuracy of the selected model. A design procedure for determining the allowable design strength of the steel net-section of a splice joint subjected to combined tension and bending was developed based on the selected model. The new design procedure was compared with two existing design methods. The proposed design procedure is recommended for checking the safe capacity of the steel net-section of bottom chord splice joints of MPC wood trusses subjected to combined tension and bending.

Acknowledgments
I thank the members of my graduate committee for their guidance and assistance throughout my research. The committee members were Drs. Frank Woeste, Joe Loferski, and Audrey Zink. I especially thank Frank Woeste for all of his advice, encouragement, criticism, and support during my education at Virginia Tech. Frank played a key role in my decision to pursue a Master’s degree. He had confidence in my abilities, and for that I am grateful. I thank Dr. Perumpral and the Biological Systems Engineering Department for their financial assistance. This support made my graduate education possible. Special thanks go to Stuart Lewis, P.E., of Alpine Engineered Products, Inc., for providing invaluable technical advice, answers, and criticism. I appreciate the time and effort he gave to assist me with this research. Stu also provided truss plates for this study and test data on the mechanical properties of the steel coil used to manufacture the truss plates. The help of Steve Spradlin, Bob Carner, Butch Sizemore, Carlile Price, and Terry Platt is gratefully acknowledged. Steve fabricated several fixtures used in the testing that I conducted. Bob and Butch assisted with the use of the testing machine, and Bob also explained the data acquisition equipment. Carlile helped me find the tools and equipment I needed. I thank Terry for sharing his knowledge of the testing machine, and for adjusting his schedule so we both could use the test equipment. I thank my friends and fellow graduate students; their friendship and company will be missed long after I leave Blacksburg. Finally, I thank my sisters and parents for their support and encouragement.

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