Progress 10/01/01 to 10/01/06
Outputs
Results of tests on the bending moment capacity of rectangular mortise and tenon furniture joints indicated that a mortise and tenon joint becomes stiffer as either tenon length or tenon depth is increased. The results also indicate that tenon depth has a more significant effect on joint flexibility than tenon length. Furthermore, the presence of a shoulder on the rail member of a mortise and tenon joint substantially contributes to the stiffness of the joint. Semi rigid connection factor for a 2-inch deep by 1-inch long tenon on a 3-inch wide rail was found to be 4.321x10-6 radian/in-lb. Tests conducted to determine the effect of close-fitting shoulders on the bending moment capacity of round mortise and tenon joints indicate that close-fitting shoulders can substantially increase the strength of the joints and that useful estimates of the contribution of shoulders to the bending moment capacity of round mortise and tenon joints may be readily predicted by means of a
simple predictive expression. Simple working relationships between shifts in neutral axis, which result from the use of shoulders, and bending moment capacity were not found. Close fits can be obtained through the use of somewhat complex relationships, but these were not judged useful for practical design purposes. Tests conducted to compare the performance characteristics of school chairs constructed with pinned but unglued round mortise and tenon joints with those of chairs with glued but unpinned joints indicated that chairs with 0.125-inch cross pins in 0.723-inch diameter tenons developed over 90% of the strength of the chairs with glued tenons, whereas chairs with 0.313-inch diameter pins developed only 80%. Thus, results of the tests tend to indicate that chairs constructed with round mortise and tenon joints with small cross-pins should provide nearly the strength and durability of comparable chairs constructed with glued joints and therefore cross-pinning could be considered
as an alternative method of joint construction in areas of the world where adhesives are in short supply. Structural tests conducted to determine the strength and deflection characteristics of an 8 by 10 foot light-timber barn frame constructed with 3.5-inch square Douglas-fir members and round mortise and tenon joints indicated that the roof and frame system could withstand positive and negative roof loads of 10,000 lbs, or, 125 lb/ft2. Diagonal bracing or shear resistant siding likely would be needed to resist high lateral loads, however. Structural analyses of the frame conducted using finite element methods compared closely with predicted deflections after taking the semi-rigid behavior of the joints into account. Overall, results of the study indicate that high strength, ease and simplicity of construction, and the fact that members can be machined from small-diameter tree stems makes round mortise and tenon light timber frame construction well-suited for relieving both long and
short-term shelter problems, particularly in less-developed countries.
Impacts
Results of this study allow furniture designers and manufacturers to reliably estimate the bending moment capacity of rectangular mortise and tenon joints used in the construction of a wide variety of furniture. This study also demonstrates that added bending moment capacity may be obtained though the use of shoulders on the tenons in round mortise and tenon joint construction. This added capacity can substantially increase the strength and enhance the durability of furniture such as chairs. This study further demonstrates that school chairs constructed with cross-pinned tenons are nearly as durable as chairs constructed with glued tenons. Thus cross pinning may provide an alternative to the use of adhesives in areas of the world where adhesives are costly or in short supply. Finally, results of the study indicate that round mortise and tenon joints provide a means of constructing sturdy easy-to-assemble frames from a relatively few standardized part sizes. Since these
members can be machined from small diameter tree stems, these frames could provide an outlet for what is now a largely unused domestic wood resource. Furthermore, the ease and simplicity of construction of the frames coupled with the fact that the members can be machined from small rapid-growth tree stems makes this construction well-suited for relieving house, farm, and light industrial building frame needs in less developed regions. Finally, the simplicity of construction also makes this type of construction well-suited for relieving both long and short-term shelter problems in disaster areas.
Publications
- Eckelman, C.A., Y. Z. Erdil, and A. Kasal. 2005. Bending Moment Capacity of Rectangular Mortise and Tenon Furniture Joints. Forest Products Journal 55(12):209-213.
- Eckelman, C, Y. Erdil, E. Haviarova. 2006. Effect of shoulders on the bending moment capacity of round mortise and tenon Joints. Forest Products Journal 56(1):82-86.
- Eckelman, C.A., and Eva Haviarova. 2006. Performance tests of school chairs constructed with round mortise and tenon joints. Forest Products Journal 56(3):51-57.
- Eckelman, Carl A, Huseyin Akcay, and Eva Haviarova. 2006. Performance tests of small barn frame constructed with round mortise and tenon joints. Forest Products Journal 56(4):41-47.
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Progress 10/01/04 to 09/30/05
Outputs
Tests were conducted to determine the withdrawal capacities of both shrink fit and cross pinned round mortise and tenon joints. Joints with wooden cross-pins developed about one-third the capacity of comparable glued but unpinned tenons; joints with steel cross pins developed over one-half the capacity. Offsetting the cross-pins toward the root of the tenon increased withdrawal capacity, whereas offsetting the cross pin toward the tip of the tenon decreased capacity. Shrink-fit techniques were found to provide a simple means of producing uniformly tight fitting joints. Tests were also conducted to determine the effect of cross pinning the tenons of round mortise and tenon joints on the bending moment capacity of the joints. Cross pinning was found to reduce the bending moment capacity of red oak joints by 33% and the capacity of yellow-poplar joints by 38%. Smaller cross pins had less effect than larger cross pins, and offsetting the pins toward the tip of the tenon
also caused less reduction in bending moment capacity. Results also indicate that the shoulders on tenons significantly increase the bending moment capacity of a joint.. Tests were also undertaken to determine the withdrawal strengths of through-bolt with cross-pipe and nut connections in the ends of selected structural timbers. Results indicate that high strength end connections (25,000 pounds) can be obtained in structural timbers with these connectors, but surface checks and drying splits significantly reduced the strength of the joints and lead to major variations in strength. However, the weakening effect of major drying splits can be reduced by orienting the cross-pipe perpendicular to the plane of the split. Furthermore, average withdrawal strength is increased and variability in strength greatly reduced when the ends of the member are reinforced. Tests were also conducted to determine the withdrawal, lateral shear, and bending moment capacities of round mortise and tenon
timber framing joints containing substantial amounts of juvenile wood. Tenon diameters were 2-, 3-, and 4 inches. Tenon withdrawal capacities of joints with red oak cross pins were about 3,500, 5,000, and 10,000 lbs for 2-, 3-, and 4-inch tenons, respectively. Joints without shoulders had bending moment capacities of about 400, 1,400, and 3,750 ft-lbs for 2-, 3-, and 4-inch tenons and capacities of 700, 1,650, and 5,200 ft-lbs for comparable joints with shoulders. Lateral shear capacities of joints with tenons fully seated were about 3,500, 7,500, and 11,000 lbs for joints with 2-, 3-, and 4-inch tenons, respectively. Values for comparable joints with 3- and 4-inch tenons not fully seated were about 2,300 and 3,500 lbs, respectively. Results of the study suggest that the round mortise and tenon joints had sufficient withdrawal, shear, and bending moment capacity to justify their continued evaluation for use in light timber frames constructed from small-diameter timbers.
Impacts
The results of this study indicate that round mortise and tenon joints provide a means of utilizing small diameter timbers and squares cut from them in the construction of light timber frames. In additon, use of through bolt with cross pipe connections provides an additional means of constructing timber frames from small diameter timbers. Results of the furniture joint studies provide additional outlets for small diameter stems and otherwise waste wood materials. Information on the withdrawal capacity of cross-pinned round mortise and tenon joints will help manufacturers determine whether or not cross-pins may be used in place of adhesives in the construction of furniture.
Publications
- Eckelman, C., E. Haviarova, A. Tankut, N. Denizli, H. Akcay, Y. Erdil. 2004. Withdrawal Strength of Cross-Pinned Round Mortise and Tenon Furniture Joints. Forest Products Journal. 54(12):185-191.
- Eckelman, C., E. Haviarova, Y. Erdil, A. Tankut, H. Akcay, N. Denizli. 2004. Bending Moment Capacity of Round Mortise and Tenon Furniture Joints. Forest Products Journal 54(12):192-197.
- Eckelman, C. 2004. Exploratory Study of High-Strength Low-Cost Through-Bolt with Cross Pipe and Nut Construction for Roundwood and Squared Timber Frame Construction. Forest Products Journal 54(12): 29-37.
- Akcay, H., C. Eckelman, E. Haviarova. 2005. Withdrawal, lateral shear, and bending moment capacities of round mortise and tenon joints. Forest Products Journal 55(6):60-67.
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Progress 10/01/03 to 09/29/04
Outputs
Tests of a prototype light timber building frame constructed of low quality timber using round mortise and tenon joints indicate that such frames are able to resist large roof forces such as those caused by snow loads and wind uplift. Tests also show that these frames can resist substantial horizontal loads, but that cross bracing will be needed in areas of high winds unless shear resistant siding is used. Tests also indicate that a small cross bolt can be used to greatly increase the strength and durability of the critical tie beams used in such structures. Test results also indicate that a 2-inch tenon would be satisfactory in the critical corner post to rafter joints in structures up to 30 feet wide. Results also indicate that boring 2-inch diameter mortises into 3.5 inch square beams reduces the bending strength of the beams by only about 10%. However, cutting a 30 degree bevel on these members significantly reduces their strength. Use of pipe rather than wood
cross pins was found to significantly increase the withdrawal strength of the tenons from the mortises. Test results also indicate that when used as part of the frame, facia beams significantly increase the strength of the frame and reduce ridge deflections. The in-plane semi-rigid rotation coefficient for 2-inch tenons was found to be about 5 x 10-6 radians in-lb. Out-of-plane rotation was found to be about twice as great. Use of the semi-rigid rotation coefficients in the structural analysis of the building frame allowed deflections to be predicted with a maximum error of 15%. This result indicates that the performance of similar structures can be reliably estimated through structural analysis-provided the joints are treated as semi-rigid. Tests indicate that cross pins can reduce the bending moment capacity of round mortise and tenon joints such as those used in school chairs. However, performance tests of school chairs indicate that 0.125-inch cross pins reduce the strength of the
round mortise and tenon joints used in their construction by only 20%. Hence, cross pins may be considered as an alternative to adhesives in areas of the world where adhesive costs are excessive. It was also found that joint strength can be substantially increased when the shoulders on the tenons fit closely against the walls of the members in which the tenons are inserted.
Impacts
The use of round mortise and tenon joints in light timber frame construction provides the opportunity for the high speed processing of standardized components that can easily be assembled to form a wide variety of modular frame constructions with a multitude of potential end uses. These frames provide potential outlets for square timbers cut from small diameter tree stems or from rounds cut from small diameter stems and can thus lead to better utilization of underutilized timber resources. These frames also provide the means for constructing frames from local resources in less developed regions of the world and can thus lead to significant improvements in quality of life. In addition, the quick and easy assembly of these frames makes them potentially useful for disaster relief in many parts of the world.
Publications
- Gonzalez, Marvin, Gioconda Quesada, Federico Picado, and Carl Eckelman. 2004. Customer Satisfaction using QFD: An e-banking case. International Journal of Managing Service Quality 14(4):317-330.
- Erdil, Y., Haviarova, E., and C. Eckelmnan. 2004. Product Engineering and performance testing in relation to strength design of furniture. Wood and Fiber Science. Vo. 36, No.3, pp 411-416.
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Progress 10/01/02 to 09/30/03
Outputs
Tests show that through-bolt with cross-pipe and nut connectors provide a simple inexpensive manner of connecting timber frame members together. Tests also show that round mortise and tenon timber frame joints provide high levels of shear, bending, and withdrawal strength relative to the size of members joined together. Tests also show that use of cross pipes instead of wood pins or dowels greatly increases the withdrawal strength of round mortise and tenon joints at no increase in cost. Also, tests show that cross-pipes provide a means of constructing trusses from small-diameter round timber. Model tests also indicate that a wide variety of structures can be constructed from a relatively few modular parts. Thus round mortise and tenon joints together with through-bolt with cross-pipe and nut connections provide a simple low-cost method of producing strong dependable timber frames that form the basic structure for house, farm, and light industrial buildings along with
schools from small-diameter timber. Further research shows that shoulders on tenons contribute greatly to the bending moment capacity of round mortise and tenon joints. Cyclic tests also indicate that cross-pinned tenons may be used instead of glued tenons in school furniture in disadvantaged regions provided the tenons are cut on members with high shear strength. This allows expensive adhesives to be omitted while structural integrity is ensured when furniture is constructed in cottage industries in such areas.
Impacts
This research allows strong low cost hurricane and earthquake resistant building frames to be constructed from small-diameter timber with simple low cost equipment. This research also provides a means of ensuring the strength and durability of low cost school furniture constructed on the cottage industry level. This research, accordingly, both provides an outlet for small-diameter timber and also helps to solve schooling and housing problems in disadvantaged areas.
Publications
- Eckelman, C. A., and E. Haviarova. 2003. Buildings and Furniture Constructed with Round Mortise and Tenon Joints from Salvage Materials and Small Diameter Timber. Small Diameter Timber: Resource Management, Manufacturing, and Markets. MISC0509. Symposium Proc. Wash State Univ.pp 239-244.
- Tankut, Ali, C. Eckelman, and H. Gibson. 2002. Design and testing of bookcase frames constructed with round mortise and tenon joints. Forest Products Journal 53(7/8):80-86.
- Denizli-Tankut, Nurgul, C. Eckelman, and H. Gibson. 2003. Improving the deflection characteristics of shelves and sidewalls in panel-based cabinet furniture. Forest Products Journal 53(10):56-64.
- Eckelman, C.A., Hakcay, R. Leavitt, and E. Haviarova. 2002. Demonstration Building Constructed with Round Mortise and Tenon Joints and Salvage Material from Small-Diameter Tree Stems. Forest Products Journal 52(11/12):82-86.
- Eckelman, C.A., Y.Z. Erdil, and E. Haviarova. 2003. School chairs for Developing Countries: Designing for Strength and Durability, Simplicity, and Ease of Construction. Forest Products Journal 53(2):63-70.
- Erdil, Y.Z., J. Zhang, and C.A. Eckelman. 2003. Staple Holding Strength of Furniture Frame Joints Constructed of Plywood and Oriented Strand Board. Forest Products Journal 53(1):70-75.
- Erdil, Y.Z., Zhang, J., and C.A. Eckelman. 2003. Withdrawal and bending strength of dowel-nuts in plywood and oriented strand board. Forest Products Journal 53(6):54-57.
- Picado, Federico and Carl Eckelman. 2002. Mejoramiento de la calidad a traves del diseno robusto: aplicacion en la industria del mueble. Tecnologia en Marcha 15(1):84-87.
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Progress 10/01/01 to 09/30/02
Outputs
Results of tests indicated that the holding strength of screws in plywood and oriented strand board could be predicted by means of empirically developed expressions. Work also indicated that the lateral holding strength of dowels in these materials could also be estimated. Tests also indicated that the residual strength of furniture parts with cross holes could be estimated. Bending strength of round mortise and tenon joints is significantly reduced when cross pins are used to hold the tenons in place, but loss in strength is directly related to the diameter of the cross pin. Cyclic tests of school chairs indicate that sufficient strength is still obtained, however, to allow the use of cross pins in school furniture. Initial tests of joints constructed with 2, 3, and 4-inch diameter tenons indicate that round mortise and tenon joints have sufficient strength for use in timber frame construction. Further work indicates that a variety of timber frames can be constructed
from a relatively small set of standardized parts using round mortise and tenon joints. Construction of a small building timber frame building indicates that such frames can be rapidly erected from such standardized parts using simple tools and unskilled labor. Construction of one-fourth scale models also indicated that more complex "hip roof" type barns can also be constructed from relatively few standardized parts without the need to cut complex miter joints.
Impacts
Results of this work indicate that durable school furniture can be constructed in underdeveloped areas without the use of scarce glues. Results also indicate that small-diameter timber can be used in standardized timber frame construction including popular backyard barns and storage sheds through the use of round mortise and tenon joint construction.
Publications
- Erdil, Y.Z., J. Zhang, C. Eckelman. 2002. The Holding Strength of Screws in Plywood and Oriented Strand Board. Forest Products Journal 52(6):55-62.
- Eckelman, C.A., Y.Z. Erdil, and E. Haviarova. 2002. Effect of Cross Holes on the Bending Strength of Chair and Table Legs. Forest Products Journal 52(5):67-70.
- Zhang, Y.Z. Erdil, and C. A. Eckelman. 2002. Lateral Holding Strength of Dowel Joints Constructed of Plywood and Oriented Strand Board. Forest Products Journal 52(7/8):83-89.
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