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Peter Sheffield & Associates Ltd. Micropile Bearing Plates: Are they Necessary? Presented by: Nadir Ansari, P.Eng.
Peter Sheffield & Associates Ltd.
Micropile Bearing Plates:
Are they Necessary?
Presented by: Nadir Ansari, P.Eng.
Peter Sheffield & Associates Ltd.
The Art Gallery of Ontario
Peter Sheffield & Associates Ltd.
Post-Transformation – Frank Gehry
Peter Sheffield & Associates Ltd.
Royal Ontario Museum
Peter Sheffield & Associates Ltd.
Post-Transformation - Daniel Libeskind
Peter Sheffield & Associates Ltd.
-Reasons for Test-Test set up-Instrumentation-Our Findings
Outline
Peter Sheffield & Associates Ltd.
Reasons for Test and Analysis Program
- Cost- Time/ Schedule impact- Difficult to ensure plate to grout contact- Plates impede concrete placement beneath- Plates provide smooth interface where
cracks may propagate - Tests by the Ohio DOT in 1947, suggest
large plates may weaken pile caps
Peter Sheffield & Associates Ltd.
Test Set Up
Dial Gauges
Air Pocket10
00 m
m
1800 mm
800 mm
1200 mm
Area of micropile Is 0.0294 m^2
Peter Sheffield & Associates Ltd.
Test Set up
Dial Gauges
Peter Sheffield & Associates Ltd.
Test Set UpConcrete Strain
Gauge
Rebar with Strain
Gauges
Compressible Material
Peter Sheffield & Associates Ltd.
Test Set Up
Cylinders30 MPa Concrete
Peter Sheffield & Associates Ltd.
Cyclic Loading for One MicropileLT1- Micropile Compression Test
0
500
1000
1500
2000
2500
3000
3500
4000
4500
0 5 10 15 20 25 30 35 40 45 50 55
Movement (mm)
Load
(kN
)
-8050 kN ultimate load on cap-50 mm movement -136 MPa based on MP area
-2.33 Design Load
Peter Sheffield & Associates Ltd.
Results - Actual Cracking Pattern
Peter Sheffield & Associates Ltd.
Actual CrackingPattern
Peter Sheffield & Associates Ltd.
CrackingPattern in
one quarter of the cap
Column Base Plate
Peter Sheffield & Associates Ltd.
Strut and Tie Model Used to Determine Required Reinforcement
Compression Strut
Tension Tie
A1
A2
Peter Sheffield & Associates Ltd.
Vertical Stress
Peter Sheffield & Associates Ltd.
Vertical Stress
Peter Sheffield & Associates Ltd.
Horizontal Stress in Reinforcement Plane
Peter Sheffield & Associates Ltd.
Results-Rebar Stress
-30
-25
-20
-15
-10
-5
0
5
0 1 2 3 4 5 6 7 8 9 10Load (1000 kN)
Stre
ss (M
Pa)
TestAnalytical
Peter Sheffield & Associates Ltd.
Our Findings
-Bearing plates were not necessary
-Based on area the bearing strength was 4.5 times the concrete compressive strength much higher than allowed by codes
-Class A analysis predicted failure within 5%
-The concrete strut was parabolic, not linear
Peter Sheffield & Associates Ltd.
Findings Continued
-Longitudinal rebar was in Compression in the middle of the pile cap
-Rebar can be spaced evenly across pile cap
-Further research for other geometries is necessary
Peter Sheffield & Associates Ltd.
Ontario College of Art and Design
