ABSTRACT
Humans have found shelter in timber-framed structures for millennia. These structures were built to resist gravity loads, and so rarely were any parts of the structure in tension. Timber's strength is greater parallel to the grain than perpendicular to it. Drying shrinkage cause cracks that reduce bending and shear strength, but these are less of a problem for tension members. The National Design Specification (NDS) reference design values incorporate a factor of safety to account for natural defects although these factors do not compensate for design errors. When we apply a tension force to our foam member, the circles deform and become elliptical–longer in the direction of tension. Connections are the biggest challenge in structural design. In historic structures, bottom chord and king-post connections were often dovetailed in, rather than the dubious tension capacity of mortise and tenon joints. Defining loads and determining a structural arrangement are fundamental for an efficient structural system.
