AFT STATNAMIC Load Testing of High Capacity Marine Foundations By: Mike Muchard, P.E. Applied Foundation Testing, Inc.
Outline St. George Island Project Description Instrumentation of Cylinder Piles STATNAMIC, Static and Dynamic Testing Class A Comparison of Test Methods
St. George Island Bridge Boh Bros. Construction Co. Inc, Sverdrup Civil, Inc. 4.1 Miles 54” Cylinder Piles 750 to 900 Ton Factored Design Loads. Weathered Limestone Bearing Material
St. George Island Bridge Load Test Program 6 Non-Production Test Piles All Test Piles Instrumented with multiple levels of Strain Gages 6 STATNAMIC Tests 4 Static Tests Dynamic Testing on Test Piles and 50 Production Piles Static and Dynamic Tests Performed by Geo Consultant
Pile Instrumentation
Post Tensioning Strains
Post Tensioning Stress
Post Tension Measurements 54” Cyclinder Pile Eccentricity Non-Uniform Contact Between Segements Arching 760 to 1,010 psi Pre-stress Composite Modulus of Elasticity 5,725 ksi Back Calculated f’c over 10,000 psi
Pile Driving and Dynamic Testing (PDA)
Soil and Foundation Conditions
Driving Measurements
Measurements During Driving Stresswave Propagation. Maximum Tension Occurs Near Pile Top. Toe Remains In Compression. Resistance Not Mobilized Simultaneous. Therefore, Modeling Required for Distribution.
1,600 Ton Static Load Testing
2,000 Ton STATNAMIC Device
Statnamic Test Description
Stages of a STATNAMIC Test Before Test The Test After Test Load Produced F = ma
Instrumentation
Load Cell Calibrated Full Scale Laser Projector & Capacitive Accelerometers
Data Acquisition
STATNAMIC Analysis
STATNAMIC Load Distribution
Three Loading Characteristics
STATNAMIC Has Similarities to Each Test Method Load Duration Precludes Stresswaves Pile displaces as a unit (like a static test) Much Simpler Analysis Not an Impact Rapid Translation, Inertia and Damping must be Subtracted Rate of Loading Must Also be Considered Via Rate Factor (Mullins, NCHRP, 2005)
Test Pile 1 - Composite
Test Pile 2 - Composite
Test Pile 3 - Composite
Test Pile 5 - Composite
Pile No. CAPWAP Total (kips) Static STATNAMIC LT-1 1950 2136 2166 LT-2 2016 3109 3052 LT-3 1820 3060 3113 LT-5 2028 2889 2631 CAPWAP – 14 day Re-strike STATNAMIC performed 2 days After Static Test LT-5
CAPWAP / Static
STATNAMIC / Static
Friction Comparison
End Bearing Comparison
Conclusions Class A Test Method Comparison. Instrumentation Allowed Measurement of Pre-stress, and Load Distribution During Testing. Dynamic Testing Under-predicted Capacity 9% to 41%. CAPWAP Skin Friction and End Bearing Predictions had Large Disagreement. STATNAMIC within 2% of Static Capacity on Three Piles and 9% Below in the Fourth Pile.
Thank You Any Questions? AFT Applied Foundation Testing, Inc.