The objective of this study was to develop the general theory for analysis of multi-layered built-up-beams, considering the effect of interlayer slip. The verification was also sought through an extensive experimental study. The theory was applied to the composite beams fastened wooden beams together with mechanical joints. And it described the behavior of the composite beam as superposition of two kinds of mechanism. One was the bending behavior of the parallel chord truss and the other was that of the solid beam. The experimental results showed good agreement with the theoretical calculations and the proposed theory was proved to be applicable in designing such constructions.
