Also by this method the purlin may be put in place and used as sup port for erection apparatus. In Plate 111, the additional pair of holes at panel points of the top chord arc for these clip angles.
After the draftsman has finished his drawing he should care fully check up all dimensions and bevels and inspect the drawing for errors in rivet clearances. The passing in of accurate detail drawings will soon result in a promotion to checker, a more pleasant position, but one with greater responsibilities attached.
Detailing of Plate Girder Spans. The information which the draftsman has to start with is in the form of the stress sheet. This may be as Plate V which is the latest and most approved form, or it will be like Plate VI. In both cases the number of rivets for the lateral connections are given, but on Plate V the rivet curve for the spacing in the flanges is given and also the curve of the total and dead load shears and moments.
As soon as a plate-girder stress sheet is turned over to the draftsman, he should lay it out at once and determine the exact location of the web splices, the stiffeners, and the cover plates and their lengths (if not given), should decide upon the lengths of the panels of the lateral bracing, and should also make layouts of the lateral plates, if possible, so that the material can be ordered at once if necessary. In making the above layout the following should be observed: (1) Be careful in locating splices to see that they come at a panel point of the lateral system.
(2) Locate all splices and stiffeners with a view of keeping the rivet spacing as regular as possible.
(3) Have the panels of the lateral systems equal if possible. If not, have a smaller one at the ends of the girder, the remainder being of equal length.
(4) Stiffeners to which cross-frames are attached should have fillers.
(5) The outstanding leg of stiffener angles should have a gauge of 21 inches or more. This will enable the cross-frames, or floor beams to be swung in during erection without spreading the girders.
(6) It is always best to use as few sizes as possible for stiffeners, connection plates, etc., and avoid all unnecessary cutting of plates and angles.
(7) Locate the end holes for laterals and diagonals so that they can be sheared by a single operation, see Fig. 70. This will, as a rule, throw the end rivet further back from the working point, and may increase the size of the con nection plate, but it is desirable.
(8) It is preferable to have an even number of panels in the lateral system since the girders can in most cases then be made symmetrical or nearly so about the center.
(9) The rivet spacing curve should be constructed if it is not given on the stress sheet.
In addition to the above the following rules which apply directly to the detailing should be followed. They are: (1) The second pair of stiffeners over the ends of the bed plate shall be so placed that the plate will extend not less than 1 inch beyond the outstanding leg.
(2) If spans are on a grade, unless otherwise specified, put the bevel in the bed plate or masonry plate and not in the base or sole plate, sometimes called the bearing plate.
(3) In short spans, 50 feet or less, put slotted holes for anchor bolts in both ends of the girder. This will usually be covered by a clause in the specifi cations.
(1) In square spans show only one-half, but give main dimensions such as "overall" and "center to center" and lengths of cover plates for the entire Span.
(5) The girder detailed is always the far girder and is looked at from the inside.
(6) If a span has no lower lateral bracing, only sufficient of the ends of the girder are to be shown in order that the detail of the base plate and its con nection to the flange may be shown.
(7) If the fillers become 12 to 15 inches wide, they become too heavy to be slipped in in the field and they should be riveted in place in the shop with at least two countersunk rivets.
(S) When the ends of two girders meet on the same pier the masonry plate should be made continuous, that is, one plate to extend under both spans. Never make the base plates continuous since they could not be riveted up in the field.