The architects' and builders' pocket-book; a handbook for architects, structural engineers, builders and draughtmen

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. 1915 Excerpt: ...J horizontally at K and towards L as found from Diagram 3; A, the ares oi asj?=» 0.05062 in and //= 0.05062 + 0.00002562 = 1975, or, approximately, 000 lb. This shows that the span would lengthen about V20 in, if allowed free novement at one end; or, if fixed, there would be a Horizontal Force of 000 lb tending to push the supports out. In column 4 it is seen that the tresses per square inch arc only about one-tenth of those permissible. Assumng that the loads become 10 000 lb at each apex-joint, the Horizontal Df.flecIon becomes about Vt in, and the Horizontal Thrust becomes 20000 lb. rhis shows conclusively that a large excess of material must be employed in the cissoRS Truss, particularly in the members Em and Hu which contribute over ne-half the value of D as shown in column 7, if the Horizontal Deflection is 0 be made so small that its effect may be neglected. As stated before, if the russ is permitted to deflect horizontally until fully loaded, the walls or supports rill have sensibly no Horizontal Thrust to resist. The Hammer-Beam Truss. As usually constructed the Hammer-beam less is expected to exert more or less Horizontal Pressure at the supports; nd this is provided for by heavy walls and buttresses. The diagTam of such truss is shown in Fig. 27, in which the Curved Braces usually built in the riddle part of the truss are not shown, as they are considered to be purely ornamental and for vertical loading have no stresses. The brace OM is drawn as bough it were straight; but a curved brace may be used instead, without alterig the diagram. The stress in the curved piece is that found from the stressiagram, increased by the bending stress due to its curvature. To determine tresses in the members of this truss it is necessary to first find the Ho...