Civil Engineering Reference
In-Depth Information
It can therefore be concluded that for RFERS with lateral frame stiffness per
foot of width of structure less than nearly 5000 kip/ft/ft calculated based on
equation 7.3, the classical Coulomb active earth pressure theory may reasonably
predict the lateral earth pressure developed in the backfill soil at the end of the
backfill stage.
On the other hand, for RFERS with lateral frame stiffness per foot of width
larger than 5000 kip/ft/ft, the lateral earth pressure is better predicted based on the
provisions of ASCE 7-98.
7.2.2.3 Effect of Staged Construction Calculation on the Mobilizations of
Active Earth Pressure
To examine the effect of the staged construction calculation used to analyze the
rigid frames for the development of lateral earth pressure at the backfill stage,
frames F1 through F12 are reanalyzed with the elimination of the staged
construction step. In other words, the RFERS and the backfill soil are assumed to
be present simultaneously,
i.e.
“wished in place.” In the latter case, the analysis is
initiated with the calculation of the in-situ state of stress of the soil mass, followed
by the analysis of the full soil-structure problem.
10
σ
hn1
σ
hn3
σ
hn6
σ
hn10
σ
hn15
σ
hn20
Coulomb
ASCE 7-98
BOCA, SBC, IBC
K
0
8
6
L
b
= 10 ft
φ
4
= 30
o
Staged Construction Not Included
2
S
c
/S
b
= 1
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
σ
h
, kips/ft
2
Fig. 7.6
Lateral Earth Pressure for Single Story Frames - Staged Construction not included
Fig.7.6 presents the lateral earth pressure resulting from the analysis of frames
F1 through F7. The figure indicates that the lateral earth pressures developed in
the retained soil mass when staged construction is not included in the numerical
simulation are substantially larger than their counterparts obtained from
simulating a backfill stage. The earth pressures predicted using Coulomb's active
earth pressure theory, along with the loads stipulated by the major building codes,
all tend to underestimate the lateral earth pressure developed behind the stiffer
rigid frames, namely frames F3 through F7. The pressure distribution is such that
active pressure conditions prevail for the top half of the structure, followed by a
