Civil Engineering Reference
In-Depth Information
Chapter 4 is correlated to earth pressure, according to the following methodology.
First, measured movements were corrected for thermal expansion and contraction
of the structure, to obtain lateral displacement due to earth pressure only. Next,
the resulting lateral displacement due to earth pressure only was correlated to
earth pressure using the calibrated closed form expressions derived in Chapter 3.
The results confirm the strong dependence of earth pressure on temperature for
rigidly framed earth retaining structures.
5.2 Building Description
The structure, shown in Fig. 4.1-4.2 and labeled PG-1, is a four-story parking gar-
age including a full basement, with a rectangular footprint measuring 172 ft by
234 ft. The building's structural system consists of reinforced concrete waffle
slabs supported by rectangular reinforced-concrete columns. The north side of the
building is a reinforced concrete retaining wall cast against earth at full height
with a thickness of 16 in at the base tapering down to 12 in on top. On the south-
ern side, a one-story high, 12 in thick, cast-in-place concrete wall provides enclo-
sure for the basement. Resistance to lateral loads is provided by (1) the retaining
walls, (2) irregularly placed concrete shear-walls, and (3) the flexural resistance of
the concrete columns. The building is open on three sides and is subject to large
temperature variations.
At the beginning of the project, an optical survey revealed that PG-1 underwent
a maximum lateral drift of 3 in. in the north-south direction, and a drift of 1 inch
in the east-west direction, at the roof level, during its 25 years of service assuming
that PG-1 was built square and plumb.
Adjacent to building PG-1 is another four-story parking-structure (PG-2) of
similar construction, but different footprint. The two buildings are separated by an
expansion joint along their lengths. PG-2 was not subject to earth pressure at the
northern side due to the presence of a multi-story building with an excavated
basement at its northern edge. No signs of structural distress or lateral movements
were observed in PG-2.
5.3 Geotechnical Properties of the Retained Soil
The soil retained by PG-1 had been filled as part of the site development, but the
surface profile prior to the building construction was unknown. A subsurface
soil investigation was conducted in an effort to obtain the properties for the back-
fill soil for use with this analysis. Boreholes taken behind the northern wall of
PG-1, by an independent testing agency, indicated that the top 20-28 ft of soil re-
tained behind the northern wall of the building consist of miscellaneous uncon-
trolled fill composed of shot rock intermixed with brown medium to fine sand
