DESIGN OF SLABS-ON-GROUND 360R-67
APPENDIX 4—SLAB DESIGN USING
POST-TENSIONING
This chapter includes:
• Design example: residential slabs on expansive soil;
• Design example: using post-tensioning to minimize
cracking; and
• Design example: equivalent tensile stress design.
A4.1—Design example: Residential slabs on
expansive soil
This design example is a three-story apartment house in
Houston, Tex., with plan dimensions of 120 x 58 ft. It is built
on expansive soil. Construction is stucco exterior, sheetrock
interior, and gable truss roof. Design
calculations are worked
out as outlined in
Section 9.7
:
•
Design soil values are provided by the geotechnical
engineer;
•
Design for the edge lift condition; and
•
Design for center lift condition.
A4.1.1 Design data including design soil values
A. Loading
1)Perimeter loading = 2280 lb/ft
2) Live load = 40 lb/ft
2
B. Materials
1) Concrete:
f
c
′ = 3000 psi
2) Concrete creep modulus of elasticity:
E
c
= 1,500,000 psi
3) Prestressing steel: 270k 1/2 in. seven-wire strand
C.
Design soil values
1) PI = 40
2) Edge moisture variation distance
e
m
= 4.0 ft (center lift)
e
m
= 5.0 ft (edge lift)
3) Differential swell
Y
m
= 0.384 in. (center lift)
Y
m
= 0.338 in. (edge lift)
Chia sẻ với bạn bè của bạn: 
