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Design Considerations for Mortise and Tenon Connections

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Design Considerations for Mortise and Tenon Connections DESIGN CONSIDERATIONS FOR MORTISE AND TENON CONNECTIONS Richard J. Schmidt Christopher E. Daniels Department of Civil and Architectural Engineering University of Wyoming Laramie, WY 82071 A Report on Research Sponsored by the USDA NRI/CGP Washington, DC and Timber Frame Business Council Hanover, NH April 1999 1. REPORT NO. 2. 3. Recipient's Accession No. REPORT DOCUMENTATION PAGE 4. Title and Subtitle 5. Report Date Design Considerations for Mortise and Tenon Connections April 1999 6. 7. Author(s) 8. Performing Organization Report No. Richard J. Schmidt & Christopher E. Daniels 9. Performing Organization Name and Address 10. Project/Task/Work Unit No. Department of Civil and Architectural Engineering 11. Contract(C) or Grant(G) No. University of Wyoming (C) Laramie, WY 82071 (G) 12. Sponsoring Organization Name and Address 13. Type of Report & Period Covered USDA NRI/CGP Timber Frame Business Council interim CSREES PO Box B1161 Washington, DC 20250 Hanover, NH 03755 14. 15. Supplementary Notes USDA NRI/CGP Contract No. 9702896 16. Abstract (Limit: 200 words) The objective of this research is to determine the strength and stiffness characteristics of timber-frame connections in tension. Timber-frame connections use wood pegs to secure the tenon within the mortise. The design of these connections is currently beyond the scope of building codes, including the National Design Specification for Wood Construction (NDS). Full-size joints were tested to determine failure modes and to establish minimum edge and end distances that ensure peg failure. These end and edge distances were used to verify a design procedure for satisfying NDS spacing requirements. Peg failure was identified as the preferred failure mode because of the ductility exhibited prior to ultimate failure. Mechanical properties, which included peg bending strength, shear strength, and dowel bearing strength were also established. An efficient method for establishing dowel bearing capacities for combinations of base material (mortise/tenon) and pegs utilizing springs in series was also developed. 17. Document a. Descriptors traditional timber framing, heavy timber construction, structural analysis, wood peg fasteners, mortise and tenon connections, European yield model, joint testing, design standards. b. Identifiers/Open-Ended c. COSATI Field/Group 18. Availability Statement 19. Security Class (This Report) 21. No. of Pages Release unlimited. Unclassified. 98 20. Security Class (This Page) 22. Price Unclassified. OPTIONAL FORM 272 (4-77) (See ANSI-Z39.18) Department of Commerce Acknowledgments This report is based on the research conducted by Mr. Christopher E. Daniels, under the direction of Dr. Richard J. Schmidt, in partial fulfillment of the requirements for a Masters of Science Degree in Civil Engineering at the University of Wyoming. Primary funding for this research was provided by the USDA-NRI/CGP under contract #9702896. Additional funding was provided by the Timber Frame Business Council. Joint specimens were donated by Red Suspenders Timber Frames, Big Timberworks, Benson Woodworking, and Sunset Structures. Scott Northcott supplied the pegs. ii Table of Contents Page 1. INTRODUCTION............................................................................................................................................................................... 1 1.1 GENERAL OVERVIEW ...................................................................................................................................................................1 1.2 CURRENT PRACTICE OF TIMBER FRAMING...........................................................................................................................2 1.3 OBJECTIVES AND SCOPE...........................................................................................................................................................3 1.4 LITERATURE REVIEW ..................................................................................................................................................................4 2. MATERIAL TESTS............................................................................................................................................................................ 9 2.1 GENERAL PROCEDURES ..............................................................................................................................................................9 2.2 PEG BENDING..............................................................................................................................................................................11 2.2.1 Peg Bending Procedure ...................................................................................................................................................11 2.2.2 Peg Bending Results .........................................................................................................................................................12 2.3 PEG SHEAR..................................................................................................................................................................................13 2.3.1 Peg Shear Procedure........................................................................................................................................................13 2.3.2 Peg Shear Results..............................................................................................................................................................15 2.4 BEARING CONCEPT.............................................................................................................................................................18 2.4.1 Combined Tests..................................................................................................................................................................18 2.4.2 Base Material Dowel Bearing Procedure.....................................................................................................................19 2.4.3 Base Material Dowel Bearing Results...........................................................................................................................21 2.4.4 Peg Bearing Procedure....................................................................................................................................................28 2.4.5 Peg Bearing Results..........................................................................................................................................................29 3. JOINT TESTS...................................................................................................................................................................................31 3.1 INTRODUCTION..........................................................................................................................................................................31 3.2 GENERAL PROCEDURE..............................................................................................................................................................31 3.2.1 Southern Yellow Pine .......................................................................................................................................................32 3.2.2 Recycled Douglas Fir .......................................................................................................................................................34 3.2.3 Red Oak ...............................................................................................................................................................................34 3.3 FAILURE MODES .........................................................................................................................................................................34 3.4 SOUTHERN YELLOW PINE RESULTS ......................................................................................................................................35 3.5 RECYCLED DOUGLAS FIR RESULTS ......................................................................................................................................40 3.6 RED OAK RESULTS .....................................................................................................................................................................41 3.7 CYCLIC JOINT TESTS ...............................................................................................................................................................45 3.7.1 Method.................................................................................................................................................................................45 3.7.2 Cyclic Test Results.............................................................................................................................................................46 4. ANALYSIS AND RESULTS...........................................................................................................................................................51 4.1 SPRING THEORY........................................................................................................................................................................51 4.2 FAILURE MODES .........................................................................................................................................................................56
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