A structural design model for sofa seat frames equipped with sinusoidal-type springs

The design of seat systems for sofas that utilize sinusoidal-type springs i n the seat foundation is complicated by the fact that the springs apply for ces to the top edge of the rail in a direction perpendicular to the face of the rail. Thus the rail must be analyzed as a plate rather than as a simpl e beam. Finite element methods provide a means of treating rails, provided the material constants are known, but a simpler procedure is needed for pra ctical design purposes. One such procedure, which is demonstrated in this p aper, is to replace the solid wood front rail with a structurally equivalen t parallel chord truss. Furthermore, since stretchers provide significant s tructural support to front rails, they and the rails must be designed toget her as a structural unit. A procedure was developed, accordingly, that anal yzes the rail and stretcher system as they interact with one another. This procedure provides estimates of the deflection of the front rail that are f unctionally related to the stresses developed in the rails. Tests were carr ied out to verify the procedures developed. Good agreement was obtained in; the critical central areas of the rail with somewhat poorer agreement towar ds the ends of the rails where deflections were small.