| 摘要 |
Upper and lower flanges (3, 4) of the girder consist of solid wood and are connected to the web (6) by means of wedge-type finger jointing (11). The web (6) has to absorb essentially transverse forces and is therefore subjected principally to shear forces. Intersection of the stress trajectories in the central axis at 45 DEG takes place in webs which are subjected purely to compression. The shear strength of the webs is improved in that the wood-grain directions of each of the layers (7, 8, 9) of the webs do not run parallel and perpendicular to the longitudinal axis of the girder, but at 45 DEG . A possible variant is the arrangement of the central layer (9) at 45 DEG and of the two outer layers (7, 8) perpendicularly to the girder axis. A third variant, which is, however, not equivalent in terms of statics, consists in the central layer (9) being inclined by 45 DEG with respect to the longitudinal axis, while the two outer layers (7, 8) are arranged parallel to the longitudinal axis. In any case, even the advantage in terms of statics of this third variant is considerable with respect to the conventional web layers which are glued perpendicularly to one another. The wooden girder is simple and inexpensive to construct, and therefore to produce. It has a greater bending strength and flexural rigidity than the known wooden girders. <IMAGE>
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