Compression
Wood can be subjected to compression parallel to grain, perpendicular to
grain, or at an angle to grain (Figure 3-12). When compression is applied
parallel to grain, it produces stress that deforms (shortens) the wood cells
along their longitudinal axis. Recalling the straw analogy discussed in
Section 3.2, each cell acts as an individual hollow column that receives
lateral support from adjacent cells and from its own internal structure. At
failure, large deformations occur from the internal crushing of the complex
cellular structure. The average strength of green, clear wood specimens
of coast Douglas-fir and loblolly pine in compression parallel to
grain is approximately 3,784 and 3,511 lb/in2
, respectively.