Presentation on theme: "STATNAMIC LOAD TESTING"— Presentation transcript:
1 STATNAMIC LOAD TESTING Development, Interpretation of Results, Advantages
2 Presentation Outline Pile Load Testing - background Brief Statnamic IntroductionRecent activities in the USStatnamic Theory and AnalysisRecent activities in Taiwan20MN testing at the TFC project, Taiwanother notable jobsStandardisation of “RAPID” Load TestingQ&A and Discussion
3 Quick Statnamic Facts 21 Statnamic devices world-wide 12 Statnamic testing companiesOver 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 SeminarsMore 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
12 The IdeaStatnamicNote: 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
13 Inertial Load Testing (Bermingham - 1987) This type of test was clearly different from a Dynamic Load Test A NEW WORD WAS REQUIRED!!Inertial Load Testing (Bermingham )STATNAMIC (Middendorp - (1989))Pseudo-static (Fundex PS PLT - early 1990’s)Kinetic (Holeyman )Rapid Load Test (Japanese Study Group )Transient Long-period (Janes -1997)Slow dynamic (Goble, Rausche )others - impulse, kinematic, push, etc.
14 ...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.
40 Lateral Test Programs in the US New Bern, North Carolina DOT (50 tons)Brigham Young University - (200 tons) Utah DOT & CALTRANSAuburn 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)
41 “Statnamic” Earthquake Generator (John Hopkins University & FHWA)
42 Foundation Types Tested in the USA Using Statnamic Drilled Shaftstested up to 3500 tonslaterally and axiallyDriven Piles (all types)Pile Groupstested laterally and axiallyStone ColumnsAuger-Cast Pilesconventional and ‘displacement’ typesSpread Footings and PlatesOther types of “Ground Modification”
43 Background Statnamic Theory and Analysis GOAL:to derive the STATIC load displacement behavior from a STATNAMIC load test(usual goal for axial compression testing)
44 Supporting evidence…stress waves? Pile ToeApplied Force (RLT)Pile Head
45 Supporting evidence…stress waves? Pile HeadPile Toe
46 Supporting evidence…stress waves? Pile HeadPile Toe
47 Physical Model m c k F u In a STATNAMIC LOAD TEST: F = Applied force from the Statnamic device (measured by a load cell)m = Pile mass (easy to calculate)c = pile/soil damping (UNKNOWN)k = pile and soil stiffness (the term we need to find)u, v, a = measured by an optical sensor and/or accelerometer
48 Physical Model F = ma + cv + ku GENERAL LIMITATIONS: This equation makes the following assumptions:1. Inertia (mass x acceleration) - assumes that a single value of ‘m’ (the pile mass) represents all of the moving mass in the system2. Damping (damping coefficient x velocity) - assumes that a single value of ‘c’ is valid throughout the entire load test, and that the damping force is directly proportional to velocity3. Stiffness (stiffness coefficient x displ.) - the calculated stiffness is the stiffness of the pile and soil system under a RAPID load - no correction is made for long-term, time-dependent pile behavior, which includes effects such as changes in pore-pressure and creepF = ma + cv + ku
49 Structural Analogy F = ku (Static) F = ma + cv + ku (Statnamic) Static DynamicmFF = ku(Static)F = ma + cv + ku(Statnamic)ukF
50 Physical Model F = ma + cv + ku 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
51 AnalysisAssuming 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.
52 ”Derived Static” from Statnamic Measured StatnamicDerived Static”Derived Static” from Statnamic
53 Statnamic Force, Inertia Force, & Damping Force (ms)Statnamic Force, Inertia Force, & Damping Force
54 Statnamic & Derived Static Force (ms)Statnamic & Derived Static Force
55 14 m Driven Concrete Pile in Sand Static - 3 cyclesStatnamic14 m Driven Concrete Pile in Sand
79 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
80 firstname.lastname@example.org www.berminghammer.com The End.