This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 edition. Excerpt: ...all the diagonals had the same slope, and multiplication of the chord index stresses by the ratio of horizontal to vertical ...
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 edition. Excerpt: ...all the diagonals had the same slope, and multiplication of the chord index stresses by the ratio of horizontal to vertical projection of the diagonal gave actual stresses. It is obvious that in order to follow this same method in the truss under consideration, some modification must be adopted. The simplest method in this case is to correct the index stresses in bars C/2L3 and 1/3/4, before writing chord index stresses. The best method of accomplishing this is to multiply Fig. 146.--Deal Panel Loads and Index Stresses. Single-Track Through Non-Parallel Chord Pratt Truss. the index stress in each of these bars by the ratio between its vertical projection and that of diagonal UiL2, that is, multiply the index stress in /2L3 by 'J, and that in U3Li by . The correctness of this method is illustrated by the following example: Let V, Vi and V3 be the vertical components in the diagonals of truss shown in Fig. 147, and //, . //, and //3 the stresses in the bottom chord. Evidently //, = K, x, The effect of this is to reduce the chord index stresses to the values they would have if all the diagonals had the same slope as la. The computation of the vertical components due to dead load in the inclined top chord members follows: V.C. Bar /it/2-Dead Load f 157.5X-45X = 38.6 So 3o/o0 V.C. Bar t/2tf3-Dead Load 157.5X-45X)=42.2. With these known, the vertical components in the web members may be written at once, beginning at the centre in the usual manner and obtaining a check at the end where the vertical component in the inclined end-post 1jqu is found to equal the net dead reaction. It will be noticed that the effect of the vertical component in U2U3 is to cause tension in bar U3L3. In a parallel chord truss this member, with the..."
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