MatakuliahMatakuliah : S2094 / Rekayasa Pondasi: S2094 / Rekayasa PondasiTahunTahun : 2005: 2005VersiVersi : 1.1: 1.1
Pertemuan 07Pertemuan 07Daya Dukung Pondasi DangkalDaya Dukung Pondasi Dangkal
Shallow FoundationsShallow Foundations
• Shallow Foundations versus Deep Shallow Foundations versus Deep FoundationsFoundations
Shallow FoundationsShallow Foundations
• Usually the more economical optionUsually the more economical option• As a general rule, consider deep As a general rule, consider deep
foundations only when shallow foundations only when shallow foundations do not give satisfactory foundations do not give satisfactory designdesign
• Types of Shallow foundationsTypes of Shallow foundations• Spread footings (square, circular, Spread footings (square, circular,
rectangular)rectangular)• Combined FootingsCombined Footings• Continuous Footings Continuous Footings • Mat or Raft Foundations Mat or Raft Foundations
Combined/Strap FootingCombined/Strap Footing
Construction MethodsConstruction Methods
• Excavation; Backhoe followed by Excavation; Backhoe followed by handworkhandworko Neat footing-no formwork usedNeat footing-no formwork usedo Formed footingFormed footing
Mat (or Raft) FoundationMat (or Raft) Foundation
Computation of Bearing Computation of Bearing PressurePressure
Bearing PressureBearing Pressure– Gross Bearing Pressure (q)Gross Bearing Pressure (q)– Net Bearing Pressure(qNet Bearing Pressure(q´)´)Bearing CapacityBearing Capacity– Ultimate Bearing Capacity (qUltimate Bearing Capacity (qultult))– Allowable Bearing Capacity (qAllowable Bearing Capacity (qa)a)
Computation of Bearing Computation of Bearing PressurePressure
Column Load (Ex 5.1)Column Load (Ex 5.1)
Wall Load (Ex 5.2)Wall Load (Ex 5.2)D
f uAWP
q
D
f
uB
bW
bP
q
Net Bearing PressureNet Bearing PressureNet Bearing Pressure (qNet Bearing Pressure (q´) ´)
Floating FoundationFloating Foundation– When qWhen q´ = 0´ = 0– ExampleExample: Student Center Building at MIT: Student Center Building at MIT
Estimated without floatation settlement = 1.0ft Estimated without floatation settlement = 1.0ft and settlement with partial floatation was 2-3 and settlement with partial floatation was 2-3 inchesinches
zoqq
Eccentric Loads or MomentsEccentric Loads or Moments
Eccentric Loads or MomentsEccentric Loads or Moments
Eccentric Loads or MomentsEccentric Loads or Moments
Beu
AWP
q Df 61min
Beu
AWP
q Df 61max
Two-way Eccentric Loads or Two-way Eccentric Loads or MomentsMoments
Eccentric Loads or MomentsEccentric Loads or Moments
Le
Beu
AWP
q LBD
f 661
For contact pressure to remain (+) ve everywhere,
0.166
Le
Be LB
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