statnamic load testing development, interpretation of results, advantages
TRANSCRIPT
STATNAMIC LOAD TESTINGDevelopment, Interpretation of Results,
Advantages
Presentation Outline• Pile Load Testing - background• Brief Statnamic Introduction• Recent activities in the US• Statnamic Theory and Analysis• Recent activities in Taiwan
– 20MN testing at the TFC project, Taiwan– other notable jobs
• Standardisation of “RAPID” Load Testing• Q&A and Discussion
Quick Statnamic Facts• 21 Statnamic devices world-wide• 12 Statnamic testing companies• Over 1200 contract Statnamic load tests
performed in 16 countries - more than one test every day, somewhere in the world!
• Over 80 published papers, including papers from 2 International Statnamic Seminars
• More than 10 Universities currently researching Statnamic (USA - Auburn, USF, BYU, Umass, John Hopkins, plus others)
• Acceptance by 16 State DOT’s in the US, US Army Corps of Engineers, FHWA, and Japanese Geotechnical Society
Pile Load Testing
Background
5
20MN Static Load Test
STATIC TEST - Reaction piles
Advantages Disadvantages- Static behaviour- Maintained load- Cyclic loading- No pile damage- Direct load measurement (calibrated load cell)- Direct displacement measurement
- Expensive- Time consuming- Different procedures
Features of STATIC Load Tests
7
Dynamic Load Test
DISPLACEMENT [mm]
6
Features of DYNAMIC Load TestsAdvantages Disadvantages
- Economic- Quick
- Indirect load measurements strain transducers : F = E.A. concrete piles : E variable bored piles: E and A variable
- Indirect displacement measurements accelerometers, u = a.dt
- Calibration to static load test- Experienced high level educated engineers- Chance on pile damage- In many cases capacity not mobilised
Statnamic
14
Introduction to Statnamic
strainacceleration
loaddisplacement
loaddisplacement
The Idea
LOAD
TIME
DLT STNStatnamic
Note: The JGS defines a Rapid Load Test as 5 < tr < 500, where tr is the number of times a stress wave will travel up and down the pile during the loading event
This type of test was clearly different from a Dynamic Load Test
A NEW WORD WAS REQUIRED!!
• Inertial Load Testing (Bermingham - 1987)
• STATNAMIC (Middendorp - (1989))
• Pseudo-static (Fundex PS PLT - early 1990’s)
• Kinetic (Holeyman - 1992)
• Rapid Load Test (Japanese Study Group - 1995)
• Transient Long-period (Janes -1997)
• Slow dynamic (Goble, Rausche - 2000)
• others - impulse, kinematic, push, etc.
...a global perspective...
In March of 2000, the Japanese Geotechnical Society added “Rapid Load Testing” to their national standard for pile testing.
In the year 2000, it is estimated that there will be more than 500 Statnamic Load Tests on foundations around the world.
STN Joint development
Berminghammer- Statnamic device- Pyrotechnics & ignition system- Catch mechanism
TNO- Electronics & data acquisition - Analysis software- Soil dynamics & theoretical and applied research- Development
Statnamic is a joint development of TNO from theNetherlands and Berminghammer from Canada
Statnamic Schematic
Gravel container
GravelReaction massesSilencerCylinder
Laser
Laser beam
Pile to be tested
Piston
Laser sensorPlatform
Load cell
GravelContainer
Masses
Pile
Laser
Gravel
Newark Airport - 3,500 ton Statnamic Test
1800 tons Japan
Test Pile as Support Pile
300 ton Statnamic Testing in Holland
500 ton Testing at JFK Airport, New York, N.Y.
Mechanical Catching Mechanism (2000)
1800 ton
Test Pile as Support Pile
Mechanical Catching
Mechanism
Recent Activities in the USA
Use of Water as Reaction Mass
Concept
Experiments at Berminghammer’s Yard in Canada, ‘98
First Contract Test - Lake Charles, Louisiana
Statnamic Hammer (in development)
Recent Activities in the USA
Lateral Load Testing
400 ton Lateral Testing - Auburn, Alabama
800 ton Lateral Testing - Mississippi
Lateral Test Programs in the US
• New Bern, North Carolina DOT (50 tons)
• Brigham Young University - (200 tons) Utah DOT &
CALTRANS
• Auburn University, Alabama - (250 tons) (FHWA)
• Pascagoula, Mississippi DOT (800 tons, over-water)
• Providence, Rhode Island DOT (400 tons, over-water)
• San Juan, Puerto Rico Trans Authority (400 tons)
• New Bern, North Carolina DOT (1200 tons, over-water)
“Statnamic” Earthquake Generator(John Hopkins University & FHWA)
• Drilled Shafts– tested up to 3500 tons– laterally and axially
• Driven Piles (all types)• Pile Groups
– tested laterally and axially• Stone Columns• Auger-Cast Piles
– conventional and ‘displacement’ types• Spread Footings and Plates• Other types of “Ground Modification”
Foundation Types Tested in the USA Using Statnamic
BackgroundStatnamic Theory and Analysis
• GOAL:– to derive the STATIC load
displacement behavior from a STATNAMIC load test
– (usual goal for axial compression testing)
Fm mF
F = ku
(Static)
F = ma + cv + ku
(Statnamic)
u u
k k
Static Dynamic
Structural Analogy
Physical Model
c
m
k
F
u
EQUATION OF MOTION:
This equation describes the equilibrium between some forcing function and the 3 forces:
Inertia (mass x acceleration)
Damping (damping coefficient x velocity)
Stiffness (stiffness coefficient x displ.)
This equation forms the basis for describing the motion of any single degree of freedom system.
F = ma + cv + ku
Analysis
Assuming that stress-waves can be ignored, the analysis of a Statnamic Load Test is greatly simplified in comparison to a dynamic load test.
Although stress-waves may be ignored, the ‘dynamic’ effects of INERTIA and DAMPING CANNOT!
Result: a detailed model, which includes pile and soil properties IS NOT NEEDED.A simple physical model can be used to remove the effects of damping and inertia from the measured signals - no information about the soil is needed, and subjective judgement is minimized.
0
20
40
60
80
0.0 2.0 4.0 6.0 8.0
LOAD (MN)D
ISP
LAC
EM
EN
T (
mm
)
”Derived Static” from Statnamic
Measured Statnamic
Derived Static
0
20
40
60
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120
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0
LOAD (MN)D
ISP
LAC
EM
EN
T (m
m)
14 m Driven Concrete Pile in Sand
Static - 3 cycles
Statnamic
0
5
10
15
20
25
30
0 100 200 300Load (kN)
Se
ttle
me
nt (
mm
)
STN Derived Static
Static with holds removed
Recent Activities in Taiwan
2000 ton Testing at the
Taipei FinancialCenter
STATIC TEST - Reaction piles
0
5
10
15
20
25
30
0 500 1000 1500 2000 2500 3000 3500
Load (tonnes)D
isp
lace
me
nt
(mm
) Derived Static Load-Displacement
Measured Static Load-Displacement
0
2
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0 500 1000 1500 2000 2500
Load (tonnes)D
ispl
acem
ent
(mm
)
Derived Static Load-Displacement from Measured StatnamicPile 241Measured Static
Load-DisplacementASTM Quick Test, Pile 241
02468
101214161820
0 500 1000 1500 2000 2500
Load (tonnes)D
isp
lace
me
nt
(mm
)
Derived Static Load-Displacement
Quick Static Load-Displacement
Notable Projects from Around the World
Library of Alexandria, Egypt
Quay West Apartments, Melbourne, Australia
Hanshin Expressway, Kobe, Japan
Standards
Standardisation of RAPID Load Testing
• Recommendations on STN testing of PILES in soil and rock (FHWA)
• Japanese Geotechnical Society, Standard for Rapid Load Testing (2000)
• ASTM - Standard for Rapid Axial Compressive Load (2008)
• Florida LRFD Design Guidelines
