will not bear at all upon the lower and clear daylight may be seen between the two columns, while all the load is carried by the splices.

These conditions may be remedied in one of the following ways: (a) By shiming or wedging. Wedges of proper size may be driven in between the column ends. This, however, tends to concentrate the load at points instead of distributing it uniformly. Wedges should not be used in good work. (b) By providing the splice plates with sufficient rivets to safely carry the load, or by providing additional splice plates, as in Fig. 31. In this case first find from the Table of Loads or the Column Schedule for the particular structure under consideration, the load carried by the upper column. Then find out if the upper column bears partly on the lower column. For every square inch of full bearing allow 16,000 lbs. as per Building Code. The balance of the load must be taken up by additional rivets in shear. For instance: let the load on the upper column in Fig. 31a be 72 tons. By sticking the blade of a penknife in between the ends of the two columns it is found that the upper column bears only on the part shown in black in Fig. 31b. Let us say that this area is about 4 square inches. This will transmit in bearing at 16,000 lbs. per sq. in. 4×16,000 lbs., or 32 tons. The 16 rivets in the upper half of the splice will carry 16×2=32 tons in shear. We have so far accounted for 64 tons. Additional means must be provided for the remaining 8 tons up to 72 tons. Two 3/8 in. plates may be used, one on each side of the splice as shown on the inside of the column in Fig. 31a. This will place the new rivets in double shear, and carry easily the 8 additional tons. Instead of using inside fish plates as in this case, extra rivets may be provided in the original splice plates, and where the loads are heavy additional one. inch diam. rivets may be used in the splice plates instead of 34 in. rivets. (c) Where the columns are correctly milled and the holes in splice plates have been punched too high, the upper column may be lowered until it fully bears on top of the lower column. The operation requires careful manipulation. (d) When the gap between the two columns is uniform in width, a rectangular steel plate of sufficient thickness to fill the opening may be driven in between the two column ends, in such manner as to make both the upper and the lower column to come in full contact with this plate, as shown in Fig. 32a.

8. Butt Plates. Such plates are generally used in all cases where the column section changes, and are known as butt plates or bed plates. Following are common defects in butt plates:

a.

When the plates are shipped loose, some may get lost on the way, and shims may be substituted in order not to delay the erection work; or else the plates are left out. Both these methods should be condemned.

b. The plates may get mixed up. In this way plates slightly larger than necessary are driven with quite some trouble in some splices, while plates too small to cover the lower column section are used in other places, where the larger butt plates should have been used.

Butt plates should cover the lower column completely and should extend in between splice plates from splice to splice. In good jobs butt plates must not run shorter than 1/16 inch at either end. When the clearance between the edge of the butt plate and the splice plate is larger than 1/16 inch, the butt plate should be pulled out and replaced.

Most of the above defects can be easily avoided, and better work can be obtained in a shorter time, when the butt plates are shipped to the job bolted to the lower end of the column. This is shown in Fig. 32. The bottom view represents (Fig. 32b) the cross section of two H-Columns, the upper column being of smaller section than the lower one. Fig. 32a shows a butt plate between the two columns and two angles riveted to the web of the upper column and to the butt plate.

9. Filler Plates. When the depth of the upper column is less than the depth of the lower column, the difference in depth is made up by providing packing known as filler plates. These filler plates make possible tight riveting; they also stiffen the column splice, and when they are fairly thick and well riveted to the upper column, the fillers may be milled even on the bottom with the main column section and they will help distributing the load of the upper column upon the top of the lower column. Fig. 32a. shows two fillers FF between the upper column and the splice plate. There are four of these fillers in this splice, and the fillers do not bear upon the bed plate.

In good work instead of two such fillers like FF only one wide filler taking in the whole width of the upper column is used. Furthermore these fillers are milled to bear and they extend above the splice plate for about three inches, or enough to have the fillers riveted in the shop with a couple of rivets to the upper column. Where this is not done, the fillers are shipped bolted to the upper column, and very often they get lost on the way and are left out. This is bad practice and should not be allowed.

CHAPTER XII.

Beams and Girders.

USES. Beams and girders are used in steel structures in a great variety of forms for many purposes. We may distinguish several classes of beams:

(a) Wall Beams. These are beams carrying walls and are usually referred to as wall beams or wall girders. They may be single beams or Bethlehem H. sections, or they may be standard beams provided with a plate on top or on bottom to support the masonry. Many wall beams are made of double standard beams with separators in between them and bolted together. In some other cases plain built up girders or even box girders may be used to support brick walls.

(b) Floor Beams. These are used to carry floor arches and they usually frame either in between columns or in between other beams.

(c) Tie Beams are used mainly for the purpose of tieing in the columns to one another and to the walls. These beams generally carry no load and are often replaced by channels, angles, rods or plates.

Very often one beam belongs in the same time to two or more of these groups, and its connections at each end must be designed accordingly.

(d) Struts. All beams stiffen the structure. In tall buildings it is sometimes found necessary to figure some of the floor beams in between columns as struts. Such beams are made sufficiently heavy to take up wind pressure in addition to floor loads.

CONNECTIONS. Beam connections are generally figured for shear and for bearing; in special cases the connections are investigated for their resistance to bending caused by eccentricity, for crippling or tearing across in between rivets and for resistance to stresses caused by wind pressure. In order to reduce costs, it is customary to use the same type of a connection throughout a whole structure whenever possible. This establishes then a typical or standard set of connections. Some structural plants have their own standard connections and they employ same on all jobs, whenever possible. Any connection which is not standard should be drawn to a larger scale and filed with the plans for approval. The standard con

nections for steel beams framing into steel columns or girders are different from the standard connections of beams framing. into cast iron columns.

Standard Connections for Steel Beams to Steel Columns and Girders. While there is no such thing as a universal standard, the variations between different standard connections are small. The connections adopted by the Carnegie Steel Co. are in common use in this country and have been selected by the author as an illustration of standard connections.

These connections are figured allowing a working unit stress of 20,000 lbs. per square inch for bearing, and 10,000 lbs. per square inch for shear. In most cases it will be found that the number of rivets provided is ample. There are rare instances, however, where the standard connections are not sufficiently strong, as in the case of beams on short spans loaded to their full capacity. The following table gives the minimum spans of I-Beams and Channels for which standard connection angles may be safely used, with the beams loaded to their full capacity. The same connections may be used for all greater spans. For spans shorter than given in this table, and for beams fully loaded, additional rivets may be found necessary.

TABLE OF MINIMUM SPANS.

For which standard connections may be safely used with beams uniformly loaded to their full capacity, figured with an allowable fibre stress of 16,000 lbs. per sq. in. in the beams.

The minimum spans given in the above table may be

found approximately by the following rules:

22

2224

4

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루리

-

2- 1 6 x 4 x 3/8 - 0 - 21g. For 3in.and 4 in. Is and E 2-156x4x8-0-31g. 2-1 6 x 4 x 1⁄2" — 0-5′′ lg. For 5in.and 6 in. Isand E For Tin-8in-9in-10in Isand 22 2 24

2¥24

2-15 6 x 4 x % -0- 7 lg. 2-1564x72"—0′-10′′lg.

For 12in. Is and E.

For 15in. Is and E.

2-14 x 4x-1-3 lg. 2-15 4 x 4 x 8"- 1-6" Lg.

For 18 in.and 20in. Is.

Fig.

For 24 in. Is

33.-Standard Connections for Steel. All shop rivets 4 in. diam.

All holes for field rivets 13-16 in. diam.