Civil Engineering Reference
In-Depth Information
the analysis, and the magnitude of the lateral earth pressure at rest is also
significantly larger.
The second graphic in Fig.7.11 indicates that lateral earth pressure behind
stiffer rigid frames, such as those with 10, 15 and 20 bays, and with a column to
beam stiffness ratio of 4, is notably larger than the same group of frames with
lower column to beam stiffness ratio. The lateral earth pressure distribution behind
the stiffer frames is such that Coulomb's active earth pressure conditions prevail
for top half of the height of the structure, increasing subsequently to reach the
magnitude of ASCE 7-98 soil load and finally the magnitude of the lateral earth
pressure at rest.
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
= 40
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
10
L
b
= 10 ft
φ
K
0
= 40
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. 7.11
Lateral Earth Pressure behind Two Story Frames (
L
b
= 10 ft, φ = 40º)
Fig.7.12 illustrates the analysis results for two story frames with bay length of
20 feet retaining the backfill soil. The top graphic in said figure indicates that the
lateral earth pressure developed behind the frames with the lower stiffness is
reasonably comparable to the lateral pressure determined using the classical
Coulomb active pressure theory. The lateral soil loads stipulated in the major
national building codes seem to overestimate the lateral earth pressure with
increasing degrees of magnitude.
