Civil Engineering Reference
In-Depth Information
20
σ
hn1
σ
hn3
σ
hn6
σ
hn10
σ
hn15
σ
hn20
Coulomb
ASCE 7-98
BOCA, SBC, IBC
15
10
L
b
= 10 ft
φ
K
0
= 30
o
5
S
c
/S
b
= 1
0
20
σ
hn1
σ
hn3
σ
hn6
σ
hn10
σ
hn15
σ
hn20
Coulomb
15
ASCE 7-98
BOCA, SBC, IBC
K
0
10
L
b
= 10 ft
φ
= 30
o
5
S
c
/S
b
= 4
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
σ
h
, kips/ft
2
Fig. 7.9
Lateral Earth Pressure behind Two Story Frames (
L
b
= 10 ft, φ = 30º)
Fig.7.9 indicates that the lateral earth pressures developed behind the top group
of frames are a close match to the magnitude and distribution of earth pressures
determined using Coulomb's active earth pressure theory. The soil loads stipulated
by BOCA, SBC and IBC are also a close match to the earth pressure loads found
from the analysis, whereas the soil loads specified by ASCE 7-98 seem to
overestimate the lateral pressure. Moreover, the magnitude of the earth pressure
developed behind the frames is notably smaller than the lateral earth pressure at
rest.
For the second group of substantially stiffer frames, however, where the
column to beam stiffness is increased four times, the lateral earth pressures
developed behind the frames with 10, 15 and 20 bays seem to be closely
correlated with the lateral loads prescribed by ASCE 7-98, and are about 20% to
25% larger than the earth pressures developed behind the same frames with the
smaller column to beam stiffness ratio. Nevertheless, the largest earth pressure
found from the analysis remains notably smaller in magnitude than the lateral
earth pressure at rest.
Fig.7.10 illustrates the analysis results for earth pressures behind frames with
20-ft bay length. The results shown in said figure are reasonably comparable to
those presented in the previous figure. The lateral earth pressures developed
