ments is described in detail in Ueda et al. (1984)
building levels the "free" end), the bending
and will be briefly reviewed here.
moments along each column are calculated in
Initially, a survey of all sway bolts is taken,
two directions. Axial loads are obtained from the
and unloaded sway bolts are backed off so as not
previously described calculations. Axial and
to interfere with the measurement of the loaded
bending stresses are then determined. Finally,
bolts. At this time, an attempt is made to alleviate
the combined stress factor is obtained (AISI,
all pinching or spreading loads caused by oppos-
1980) from
ing loaded sway bolts at each collar. Pinching
fa /Fa + fbx/Fb + fby/Fb ≤ 1.0
loads occur when opposing end or side sway
(1)
bolts in different column halves are transmitting
forces, whereas spreading loads occur when
where fa = axial stress (kPa) (from Table 2)
opposing center bolts are loaded (ref., Fig. 8b).
fbx = bending stress in x-direction (kPa)
Any pinching loads on a single column half are
(from stress measurements)
relieved by backing off the least loaded sway
fby = bending stress in y-direction (kPa)
bolt.
(from stress measurements)
After completion of the initial survey, the
Fa = axial stress permitted if no bending
force on each loaded sway bolt is measured
stresses exist (kPa) (from Table 2)
using a hydraulic jack and ram and a dial indica-
Fb = bending stress permitted if no axial
tor. The ram is placed between the collar and col-
stresses exist (kPa).
umn, adjacent to the sway bolt being checked.
The dial indicator is then mounted via a mag-
This dimensionless equation applies only
netic stand between the column and collar on the
when the axial stress is 15% or less of the allow-
able with no bending present (i.e., when fa/Fa <
side directly opposite the ram. The angular ori-
entation of the sway bolt is marked, and pressure
0.15). The sum of the three quotients results in
is applied to the ram to unload the sway bolt so it
the combined stress factor, which indicates the
can be backed off. This causes a small horizontal
supporting framework's structural integrity.
displacement between the column and collar
From the above equation, the combined stress
that is displayed on the dial indicator. Ram pres-
factors can be seen to incorporate the axial load
sure is reduced until the dial indicator once again
on the column as well as forces in the two hori-
zontal directions.
reads zero. This is the pressure required for the
The results of the stress measurement surveys
ram to assume the original sway bolt load. The
are depicted in Appendix B. These graphs give
force can then be easily calculated by multiply-
the combined stress factors for each collar level
ing the ram pressure by the piston area.
as well as at the base for the years 1983 to 1988.
Ram pressure is then increased and the sway
Only the building level measurements were
bolt returned to its original position. The sway
completed in 1983, so stress factors are not cor-
bolt resumes the load when the ram pressure is
rect except at level 1. An average of the overall
released. The dial indicator is checked to see if it
system is included for reference. A combined
has rezeroed. The loaded sway bolts are checked
stress factor of 1.00 indicates the column has
individually and the pressures recorded. When
reached the accepted design load. A combined
all the loaded sway bolts have been measured,
stress factor in excess of 1.60 indicates that the
the bolts loosened during the initial survey are
loads and moments exceed safe design limits
lightly tightened against the columns, thus
(yield point). Figure 12 depicts the combined
returning the truss system to its original configu-
stress factors for the base level (at the column
ration.
footing) for all five years for which complete
Lateral forces can now be determined from
data are available. Comparisons of the bar
the sway bolt pressure measurements. If all the
graphs for the combined stress factors in this fig-
lateral forces on each column except those at the
ure show great variability in both the columns
base are known, the base force can be calculated
for any given year and the factors for any given
from equilibrium conditions (the forces must
column from year to year. Inspection of the data,
balance). Free body diagrams of each column can
however, indicates that a load pattern develops
now be made in two perpendicular directions:
over time.
across and along the column rows.
In 1984, after the building was moved and
Next, treating each column as a cantilever
raised, stress levels were relatively uniform and
beam (using the base as the ground point and the
8
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