This reserch focused on the composite beams assembled with timber beams and concrete slab at the interface. In vertically loaded condition, the previous theoretical model considering the load - deformation characteristics of the stud joints were applied. Assuming the slip disribution at the interlayer, useful approximation was proposed. In addition, previous model was modified to take into considerarion the shear deformation of wood. Series of experiments and FEM analyses showed good agreement with the presented calculations and veridity of the proposed method was comfirmed.