STATNAMIC LOAD TESTING Development, Interpretation of Results, Advantages

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

80

100

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

4

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8

10

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20

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

mjustason@berminghammer.com

www.berminghammer.com

The End.