Investigation of Through-Tenon Keys on the Tensile Strength of Mortise and Tenon Joints

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dc.contributor.authorShields, Lance Daviden
dc.contributor.committeecochairHindman, Daniel P.en
dc.contributor.committeecochairRojiani, Kamal B.en
dc.contributor.committeememberLoferski, Joseph R.en
dc.contributor.departmentCivil Engineeringen
dc.date.accessioned2014-03-14T20:41:20Zen
dc.date.adate2011-08-19en
dc.date.available2014-03-14T20:41:20Zen
dc.date.issued2011-06-10en
dc.date.rdate2011-08-19en
dc.date.sdate2011-07-11en
dc.description.abstractA timber frame is a structural building system composed of heavy timber members connected using carpentry-style joinery that may include metal fasteners. A common variant of mortise-and-tenon joints are keyed (or wedged) through-tenon joints. No research on the behavior of wedged joints in timber frames is available. This research provides design knowledge of keyed through-tenon joints from experimental observations and comparisons between mathematical models and experimental measurement. Evaluation of through-tenon keyed mortise and tenon joints was performed by measuring tensile load and stiffness of white oak (Quercus alba) and Douglas-fir (Pseudotsuga menziesii) joints with four- and 11-inch tenons with one and two keys and comparing these results to mathematical models developed from the National Design Specification of Wood Construction (NDS), General Dowel Equations for Calculating Lateral Connection Values (TR-12), and engineering mechanics. Variables included joint species (white oak or Douglas-fir), protruding tenon length (four or 11 inches), and number of keys (one or two). Joints were tested to ultimate load, then model input specimens were cut from tested joints and additional key stock to generate inputs for joint load predictions that were compared to experimental joint load results for validation. Forty joints were tested with white oak keys and six of these joints were retested with ipe (Tabebuia) keys. Joints with four-inch tenons behaved in a brittle manner with tenon failures. Most joints with 11-inch tenons behaved in a ductile manner with key bending and crushing failures. Joint load and stiffness was similar between white oak and Douglas-fir joints. Joints with 11-inch tenons had greater load and stiffness than with four-inch tenons. Joints with two keys had greater load and stiffness than joints with one key, after normalizing joint load and stiffness responses on key width. Joints retested with ipe keys had greater load than joints originally tested with white oak keys. Tenon relish (row tear-out) failure was predicted for all joints with four-inch tenons. Horizontal key shearing was predicted for all joints with 11-inch tenons. Ratios of predicted ultimate joint load divided by experimental ultimate joints load (calculated/tested) or C/T ratios were used to validate the models chosen for load prediction. C/T ratios showed that ultimate load model predictions over predicted joint load which was due to occurrence of unpredicted tenon failures and simultaneously occurring key failures where models predicted key failures independently. Design safety factors (DSFs) were developed by dividing experimental ultimate joint load by governing allowable (design) load predictions. C/T ratios and DSFs were most similar between white oak and Douglas-fir joints and most different between joints with one and two keys. Alternative design values (ADVs) were developed for comparison to design load predictions. Comparisons between ADVs and DSFs showed that model predictions were most conservative for joints fastened with denser keys than joint members.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-07112011-100606en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-07112011-100606/en
dc.identifier.urihttp://hdl.handle.net/10919/33971en
dc.publisherVirginia Techen
dc.relation.haspartShields_LD_T_2011.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectTensile Strengthen
dc.subjectDouglas-firen
dc.subjectThrough-Tenonen
dc.subjectKeysen
dc.subjectWedgesen
dc.subjectWhite Oaken
dc.subjectTimber Frameen
dc.subjectJointsen
dc.subjectWood Connectionsen
dc.titleInvestigation of Through-Tenon Keys on the Tensile Strength of Mortise and Tenon Jointsen
dc.typeThesisen
thesis.degree.disciplineCivil Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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