On some common errors in iron bridge design
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. 1906 edition. Excerpt: ...case of trestle piers in page n. Here as there an adjusting device is most desirable and should be supplied. 19. Imperfect jointing of tension members.--The form of section and ratio of length to transverse dimension of a tension member are immaterial as regards strength, and so may be arranged according to convenience. The joints, however, are the points of vital consequence, and malformation of these often leads to serious loss of strength and efficiency. Of these joints there are two principal classes, riveted joints and eyebar and pin joints. The first of these is most usual in European, and the second in American bridge work. In riveted work, the metal is used as it comes from the rolling mill and the attempt to utilise the full section for strength is not made. A riveted joint, in other words, never claims perfect efficiency, but is always subject to some percentage of loss as compared with the pieces connected. To minimise this percentage of loss is the object in arranging the joint, and it is possible to reduce this to the proportion of area cut away by one rivet hole. Fig. 38 shows a properly riveted joint, which should fracture at the line AB, passing through the leading rivet and giving an efficiency less than unity by the fraction represented by the diameter of one rivet hole divided by the width of the bar. It will not fracture through the following pair of rivet holes, because the tension is too much reduced by the action of the first rivet to permit it, nor through the third row for a similar reason. All this has been verified by careful experiments at the Melbourne University and elsewhere. In contrast with this, Fig. 39 shows a tension member weakened by no less than three rivet holes in one leading row, and many similar cases...