Civil Engineering Reference
In-Depth Information
member stiffness were performed using the commercial finite element analysis
software
Plaxis
. The structural members composing the rigid frames were
modeled using an elastic material model, while the backfill soil was modeled
using an elastic-plastic Mohr Coulomb model with varying parameters. The
individual structural frames were assumed to have beam stiffness and column
stiffness that are respectively equal throughout the structure. The structural wall
retaining the backfill was assumed to be of concrete construction. The structures
were assumed to have infinitely rigid foundation strata.
To accommodate the plane strain limitations of the finite element model, the
cross sectional properties of the structural elements were determined by dividing
the column and beam properties by the tributary width of the frame selected as 10
feet, and by utilizing the equivalent area and moment of inertia per foot of length
of the floor slab. Given that gravity loads on the structural elements are not of
concern, this method of resolving the cross sectional properties of the rigid frame
elements allows an adequate modeling of the lateral stiffness of the rigid frame
under plane strain conditions.
Table 8.1
Finite Element Analysis Parameters (Single Story RFERS)
Parameter
Variation
Number of Bays for Structural Frames, n
1, 3, 6, 10, 15 and 20
Bay Lengths for Structural Frames, L
b
(ft)
10 and 20
Number of Stories for Structural Frames, s
1
Story Height, h (ft)
10
Structural Beam Properties
Cross Sectional Area, A
b
(in
2
)
144
Moment of Inertia, I
b
(in
4
)
2073 and 1036
Structural Columns Properties
Cross Sectional Area, A
c
(in
2
)
144 and 432
Moment of Inertia, I
c
(in
4
)
2073 and 41460
Structural Wall Properties
Cross Sectional Area, A
w
(in
2
/ft)
144
Moment of Inertia, I
w
(in
4
/ft)
2073
Modulus of Elasticity of Structural Members, E
s
(ksi)
3150
Poisson Ratio of Structural Members,
ν
s
0.25
Density of Structural Members,
γ
s
(pcf)
150
Backfill Soil Properties
Internal Friction Angle, φ (Degrees)
Dilatency Angle (Degrees
Cohesion, c (psi)
Modulus of Elasticity, E (ksi)
Density,
30 and 40
0 and 10
0
41500 and 144000
100 and 120
0.75
(pcf)
Strength Reduction for Interfaces
γ
