Building Design and Construction Handbook - Merritt - Ventech!

7.114 SECTION SEVEN
FIGURE 7.55 Welded beam splices.
For one reason or another it is sometimes
expedient to make a long beam
from two short lengths. A welded joint
usually is selected, because the beams
can be joined together without splice
plates and without loss of section because
of bolt holes. Also, from the viewpoint
of appearance, the welded joint is
hardly discernible.
Usually, the joint must be 100% efficient,
to develop the full section. Figure
7.55 illustrates such a detail. The back side of the initial weld is gouged or
chipped out; access holes in the beam webs facilitate proper edge preparation and
depositing of the weld metal in the flange area in line with the web. Such holes
are usually left open, because plugs would add undesirable residual stresses to the
joint.
7.37 COLUMN SPLICES
Column-to-column connections are usually determined by the change in section. In
general, a change is made at every second floor level, where a shop or field splice
is located. From an erection viewpoint, as well as for fabrication and shipment,
splices at every third floor may be more economical because of the reduced number
of pieces to handle. This advantage is partly offset by extra weight of column
material, because the column size is determined by loads on the lowest story of
each tier, there being an excess of section for the story or two above.
Splices are located just above floor-beam connections, usually about 2 to 3 ft
above the floor. Because column stresses are transferred from column to column
by bearing, the splice plates are of nominal size, commensurate with the need for
safe erection and bending moments the joint may be subjected to during erection.
From the viewpoint of moment resistance, a conventional column splice develops
perhaps 20% of the moment capacity of the column.
Figure 7.56 illustrates the common types of column splices made with high
strength bolts. In Fig. 7.56a and b, the upper column bears directly on the lower
column; filler plates are supplied in (b) when the differences in depth of the two
columns are greater than can be absorbed by erection clearance.
As a rule, some erection clearance should be provided. When columns of the
same nominal depth are spliced, it is customary to supply a 1 ⁄8-in fill under each
splice plate on the lower column, or, as an alternate, to leave the bolt holes open
on the top gage line below the finished joint until the upper shaft is erected. The
latter procedure permits the erector to spring the plates apart to facilitate entry of
the upper column.
When the upper column is of such dimension that its finished end does not
wholly bear on the lower column, one of two methods must be followed: In Fig.
7.56c, stresses in a portion of the upper column not bearing on the lower column
are transferred by means of flange plates that are finished to bear on the lower
column. These bearing plates must be attached with sufficient single-shear bolts to
develop the load transmitted through bearing on the finished surface.
When the difference in column size is pronounced, the practice is to use a
horizontal bearing plate as shown in Fig. 7.56d. These plates, known as butt plates,