Civil Engineering Reference
In-Depth Information
The observed trend of sensor
EL
-
BNW
continued with the remaining
temperature cycles causing a cumulative increase in tilt in the direction away from
the retained soil mass, resulting in a steep trend in angle-change when compared
to the temperature trend. At the last recorded temperature cycle, the measured tilt
corresponding to the installation temperature of 15.5ºC was nearly -4 minutes.
It is consequently apparent that the presence of the retained soil mass behind
the northern wall of building PG-1 resulted in the modification of the expansive
and contractive movement of the structure. Without the soil restraint present on
only one side of the building, the volumetric strains induced by temperature
variations of the rigid frame would be expected to be equal in magnitude at
corresponding temperatures, and repetitive with repeating temperature cycles. In
the case of sensor
EL
-
BNW
, the measured tilts were not equal at corresponding
temperatures, although they were fairly repetitive within individual temperature
cycles.
Examination of the data of the center sensor (
EL
-
BNC
) reveals a behavior
largely similar to that of the western sensor, with a few exceptions. The range of
movements of
EL
-
BNC
(approximately
0.5
to -2.25 minutes) was smaller than
BNW
(approximately 0 to -6.2 minutes), which can be noted as well for the center and
western sensors installed at the basement level. Moreover,
EL
-
BNC
virtually
reverted to its initial position during the second temperature cycle with a
corresponding installation temperature of 15.5ºC. Nevertheless, the sensor
subsequently recorded a permanent increase in tilt during the remaining
temperature cycles, and in general, the measurements of sensor
EL
-
BNC
illustrate a
tilt trend rather steeper than the constant temperature trend, and a cumulative
movement of the northern wall away from the retained soil mass.
Contrasting with the western and center sensors data, the tilt measured by the
eastern sensor (
EL
-
BNE
) demonstrate a relatively stronger relationship between
temperature and tilt, roughly similar to the sensors installed at the basement level.
The range of movement of
EL
-
BNE
(approximately 1 to -2.5 minutes) was smaller
than
BNW
(approximately 0 to -6.2 minutes), and larger than
BNC
(approximately
0.5
to -2.25 minutes), which can similarly be noted for the sensors installed at the
basement level. The comparable difference in the range of tilts recorded by the
western, center and eastern sensors on both levels A and B could be attributed to
several factors, including (1) a difference in stiffness within the soil mass, (2) the
fact that at the western side of the wall, the soil mass is retained in part by the
northern wall of an underground walkway leading to the basement of the adjacent
apartment building, and terminates in a stable slope extending into the excavated
cellar of the latter building, thus resulting in less confinement of the soil mass at
the western end of the PG-1, (3) the presence of reinforced concrete walls acting
as shear walls at the eastern end of PG-1 on levels A and B, running the entire
length of PG-1, and (4) the stiffness distribution of the lateral load resisting
elements of PG-1.
