| 摘要 |
<p>A longitudinal bar (4) as an upper girder, two longitudinal bars (2) as lower girders and an additional shorter bar (6) for each lower girder are assembled by means of struts (3), having preferably an undululated shape, into a lattice girder. The length and the arrangement of the shorter bar (6) are adapted to the moments curve. The shorter bar (6) is in direct contact with the longer bar (2) on its entire length and is integral therewith. All the bars of lower girder (2, 6) are in a single horizontal plane and are welded at each contact point of parallel bent portions (5) of the struts (3). The welded junctions thus obtained comprise weldings at the angles of a triangle or a trapezium, which is torsion resistant so that a complete force transmission is obtained. The bent portions (5) of the struts (3) form two rows of straight lines which are in line, preferably by pairs and arranged in a same plane and are alternately oblique with respect to the bars of lower girder (2, 6). Thus, the lower girder bars (2, 6) may remain smooth and do not require an adhering portion.</p> |
