A3, N3, and N4, we can see how this happens. As
A3, N3 and N4 settle respective to A4, the build-
FPO
ing and truss also settle with respect to A4 at those
locations. From Figure 14, the direction and mag-
nitude of the footing tilts averages approximately
300 and 0.014 radians, respectively. The highest
loads in the building and truss levels should then
be at A4 with intermediate loads at A3 and N4
and the lowest loads at N3. The horizontal loads
should be greatest where the settlement is least.
Data taken during the 1988 field work confirm
both conditions. This also applies to the forward
truss.
It is interesting to note that after the 1987 mini-
Figure 15. Flooding of footing N1, August 1988.
life-extension and plumbing operation, the base
level moments decreased on average about 36%
The settlement of the footings will have an ef-
(Fig. 12) and the stresses were redistributed. Some
fect on the horizontal forces experienced by the
of this may be due to the releveling of the trusses.
trusses and supporting columns in two ways.
The distribution of the base level stresses are sim-
The first is through uneven loading of the col-
ilar in 1986 and 1988, when stresses were high.
umns. Graduated settlement, as seen at DYE-2,
However, they do not correlate as well for 1985
results in the structure leaning in the direction of
and do not correlate at all for 1984, which is the
the lowest footings. This will cause column tilt
year following the last major lifting and leveling
and nonaxial loading of the columns. The result
operation. The pattern is clear, though. When the
is the generation of large moments at the column
building and trusses were releveled, the stresses
bases, which will be discussed in more detail in
were reduced and redistributed. As the footings
the next section.
continue to settle, a loading pattern starts to de-
The second factor is horizontal loads on the
velop within the two truss systems and the corre-
columns caused by canting of the truss system. If
sponding building sections. Both truss systems
we look at the rear truss which joins columns A4,
eventually become highly loaded in their north-
Table 4. Footing tilts and resultants.
Footing
Attribute
1982
1983
1984
1985
1986
1987
1988
A1
Resultant
0.00062
0.0019
0.00522
0.00685
0.00894
0.01023
0.01244
Direction
105.8
357.0
347.7
336.1
330.6
326.9
322.8
A2
Resultant
0.00167
0.00441
0.00735
0.00973
0.01195
0.01378
0.01739
Direction
226.0
226.1
287.4
291.7
294.3
294.9
293.8
A3
Resultant
0.00265
0.00408
0.00540
0.00770
0.00983
0.01153
0.01418
Direction
190.0
234.0
272.4
283.9
287.8
290.0
291.6
A4
Resultant
0.00096
0.00150
0.00378
0.00584
0.00793
0.00968
0.01112
Direction
252.5
266.2
293.6
299.8
303.7
305.0
306.1
N1
Resultant
0.00130
0.00408
0.00615
0.00841
0.00982
0.01105
0.01314
Direction
84.7
17.1
356.1
352.8
343.1
336.6
335.3
N2
Resultant
0.00103
0.00281
0.00517
0.00743
0.00921
0.01122
0.01345
Direction
80.5
355.9
336.9
331.0
326.2
325.2
323.6
N3
Resultant
0.00233
0.00789
0.01102
0.01349
0.0153
0.01782
0.02106
Direction
336.7
377.6
343.0
339.4
336.4
335.5
336.0
N4
Resultant
0.00075
0.00474
0.00899
0.01254
0.01549
0.01863
0.02363
Direction
292.8
332.4
325.7
322.6
321.8
320.5
320.8
Average Resultant
0.00141
0.00393
0.00664
0.00900
0.01106
0.01299
0.01580
Direction
196.1
270.8
320.4
319.7
318.0
316.8
316.3
Notes: Resultants in radians from center of footings.
Coefficient of linearity of averages for resultants is 0.9974.
Direction is clockwise from line parallel to direction from N4 to A4 (see diagram).
12
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