partition, ft-kips/ft (kNm/m)

DESIGN OF SLABS-ON-GROUND 360R-37
portion of the superstructure dead and live loads that
frame into exterior wall. P does not include any
portion of foundation concrete, lb/ft (N/m)
P
e
= effective prestress force after losses due to elastic
shortening, creep, and shrinkage of concrete, and
steel relaxation, lb (N)
PI = plasticity index
P
i 
= prestress force immediately after stressing and
anchoring tendons, kips (kN)
P
r
= resultant prestress force after all losses (including
those due to subgrade friction), kips (kN), see 
9.8.1
and 
9.8.6
P
r
= post-tensioning force required to overcome
subgrade friction, lb/ft (N/m), see 
9.5.2
q
allow 
= allowable soil-bearing pressure, lb/ft
2
(N/m
2
)
q
u
= unconfined compressive strength of soil, lb/ft
2
(N/m
2
)
RE = prestress loss due to steel relaxation, kips (kN)
r
1 
= area ratio
S
= interior stiffening beam spacing, ft (m) If beam
spacings vary, average spacing may be used if ratio
between largest and smallest spacing does not
exceed 1.5. If ratio between largest and smallest
spacing exceeds 1.5, use S = 0.85 × (largest spacing);
S
b 
= section modulus with respect to bottom fiber, in.
3
(mm
3
)
SG = prestress loss due to subgrade friction, kips (kN)
SH = prestress loss due to concrete shrinkage, kips (kN)
S
t 
= section modulus with respect to top fiber, in.
3
(mm
3
)
S
ten
= tendon spacing, ft (m)
t
= slab thickness in a ribbed (stiffened) foundation, in.
(mm)
V
= controlling service load shear force, larger of V
S
or
V
L
, lb/ft (N/m)
V
cs
= maximum service load shear force in slab on
compressible soil, kips/ft (kN/m)
V
L
= maximum service load shear force in long direction
from either center lift or edge lift swelling condition,
kips/ft (kN/m)
V
ns
= service load shear force in no-swell condition, kips/ft
(kN/m)
V
S
= maximum service load shear force in the short
direction from either center lift or edge lift swelling
condition, kips/ft (kN/m)
v = service load shear stress, psi (MPa)
v
c 
= allowable concrete shear stress, psi (MPa)
W
= foundation width (or width of design rectangle) in
direction being considered (short or long), perpen-
dicular to L, ft (m), see 
9.8.3
 and 
9.8.4
W
= slab strip width, 12 in./ft (1000mm/m), see 
9.5.2
;
W
slab 
= foundation weight, lb (kg)
W
slab 
= self-weight of the foundation slab, lb/ft
2
(N/m), see
9.5.2
y
m
= maximum differential soil movement or swell, in.
(mm)
α = slope of tangent to tendon, radians
β = relative stiffness length, approximate distance from
edge of slab to point of maximum moment, ft (m)
Δ = expected service load differential deflection of slab,
including correction for prestressing, in. (mm)
Δ
allow
= allowable differential deflection of slab, in. (mm)
Δ
cs
= differential deflection in slab on compressible soil,
in. (mm)
Δ
ns
= differential deflection in no-swell condition, in.
(mm)
Δ
o
= expected service load differential deflection of slab
(without deflection caused by prestressing), in.
(mm)
Δ
p
= deflection caused by prestressing, in. (mm)
δ = expected settlement, reported by geotechnical
engineer, occurring in compressive soil due to total
load expressed as uniform load, in. (mm)
μ = coefficient of friction between slab and subgrade

tải về 2.35 Mb.

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