DETERMINATION OF YLINEN PARAMETER FOR PARALLEL-STRAND LUMBER

This study investigates the performance of 38 by 89 mm (1.5 by 3.5 in. ) parallel-strand lumber columns. Currently, the 1991 national design specification of the American Forest and Paper Association far columns includes a c factor that describes the interaction of columns between the pure crushing and stability failure modes. For wood material, c i s a combination of member straightness, material inhomogeneity, and st ress-strain plasticity. The objective of our study is to determine an appropriate c value for parallel-strand lumber. Columns of several len gths are axially loaded to failure. Based on the nonlinear least-squar es fit of column results, adjusted to a common moisture content, the m ost probable value of c for parallel-strand lumber is 0.86. This incre ased c value is attributed to the greater homogeneity and straightness of the manufactured columns.