Knee Braces for Bents Constructed with Round Mortise and Tenon Joints

Tests were conducted to determine the axial load capacities of knee braces suitable for use in light timber frames constructed with round mortise and tenon joints. To make the knee braces consistent with typical frame construction, the ends of the knee braces were tenoned and did not require machining equipment that was different or more complex than that used for a typical frame. Knee braces with tenons machined perpendicular to the faces of the ends of the braces satisfied these requirements. Three types of braces were investigated; specifically, braces with tenons centrally located on the end-faces of flush-fitting braces, braces with tenons located on the outer edge of the end-faces of flush-fitting braces, and finally, braces with the tenon centrally located on the end-faces of “housed braces,” i.e., braces with the end-faces housed in the sides of the connecting members. Results indicated that all three types of construction had sufficient load capacity to be useful in timber frames constructed with round mortise and tenon joints, but braces with tenons offset toward the outer edge of the end-faces had better structural characteristics than braces with flush ends and centrally located tenons. Finally, knee braces with centrally located tenons and housed ends had substantially greater load capacity than those with unhoused ends.