A Text-Book on Roofs and Bridges Volume 2; Graphic Statics. 2. Ed (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1890 Excerpt: ...pounds. Total wind loads on the panels, .. 3.12, 2.44, 1.52, 0.54 tons. The dead load stress diagram is constructed in the same way as in previous examples, and is symmetrical with respect to a horizontal axis through k. As the snow apex loads are not uniform a separate diagram for stresses due to snow loads is required, and this one is also symmetrical with respect to a horizontal axis through k. The wind apex loads are next obtained by combining half of the wind loads on the panels adjacent to each apex as illustrated in Art. 19. On the truss diagram in Plate II the wind apex loads are drawn to double the scale of tons in order to determine their directions with greater precision. The reactions are then obtained by means of the equilibrium polygon (Arts. 6, 8, and 21). The ray ou', parallel to the closing side of the polygon, intersects the resultant of the wind loads au'a at the point u' giving an' and u'a as the reactions of the right and left supports if both ends of the truss were fixed, but as the right end is free its reaction ak is vertical and equal to the vertical component of au'. The load line for wind on the free side is obtained from that for wind on the fixed side by revolving it about a vertical axis, which operation may be conveniently performed by means of a piece of tracing paper. The point u" in this diagram is the same as u' in the preceding one, hence only one equilibrium polygon is required. The reaction ka of the right support is the vertical component of u"a. It is observed that when the wind blows on the free side of the truss, it causes compression in the lower chord from KH' to the left end. The stresses in the upper chord are also considerably less than for wind on the fixed side, and if the rise were-a little greater ...