StatNamic Load Testing

The StatNamic Load Test is a type of test for assessing the load-carrying capacity of deep foundations which is faster and less expensive than a Static Load Test. StatNamic is like StatRapid one of the methods for performing Rapid Load Testing: powerful quasi static test methods for determining the static load capacity of piles in compliance with ASTM D7383 and EuroCode 22477-10

Key Characteristics

Fast method for high strain pile testing
Embodies advantages of SLT and DLT and eliminates disadvantages of these
Direct measurement of force and displacements
Load-settlement diagram as direct output without a stress wave analysis (no signal matching)
Test execution user independent
High accuracy, reliability and reproducible
Fully compliant with international standards (ASTM, EuroCode, etc)

StatRapid is one of the methods of Rapid Load Testing

StatNamic Load Test on the 2nd Penang Bridge

Rapid Load Testing is a method were a pile is loaded in a short moment, giving a gentle push on the pile top. This method is much faster than static load testing. The duration of the load is much longer than during a Dynamic Load Test (DLT), High Strain Dynamic Test or PDA. Due to the long duration of the load, no stress waves phenomena are involved. When the requirements of the quasi static situation are fulfilled, the interpretation of the Rapid Load Test results are straightforward, without stress wave analysis and without Signal Matching. As a result, the results of Rapid Load Tests are more accurate, reliable, and man-independent.

Rapid Load Testing has two major test methods: StatNamic and StatRapid.

Want to know more about Rapid Load Testing? Contact Joost Bakker at bakker@allnamics.com

StatNamic

StatNamic is the quasi static, high strain test method for determination of the bearing capacity of foundation piles.

StatNamic testing works by accelerating a mass upward that in turn imparts a load onto the foundation pile below the StatNamic device. The load is applied and removed smoothly resulting in load application of 100 to 200 milliseconds. This is 30 to 40 times the duration of dynamic pile load testing. As the duration of the loading is relatively long, piles less than 40 m in length remain in compression throughout, resulting in negligible stress wave effects and potentially simpler analysis. For foundation design it is necessary to derive the equivalent static load-settlement curve from the Statnamic data. The simplest form of StatNamic analysis used to obtain equivalent static pile response is known as the unloading point method (UPM). The UPM analysis method was conceived to be simple and based on measured results alone (Middendorp et al., 1992).

The StatNamic test applies a force to the pile head over a typical duration of 120 milliseconds by the controlled venting of high-pressure gas. The gas is the product of the combustion of a fast-burning fuel within a piston (fuel chamber). At the top of the piston are vent holes that are sealed by the load hanger retaining the reaction mass. At some point the pressure within the piston is of such a magnitude to force the load hanger arrangement upward at accelerations in order of 20g. This process applies a load downwards on the test pile.

During the loading sequence the load applied to the test pile is monitored by a calibrated load cell incorporated in the base of the combustion piston. Pile settlement is measured using the Allnamics Reyca optical suystem. Data capture is undertaken using the PDR data acquisition system connected to a field computer.

StatNamic

THE STATNAMIC TEST DEVICE

The StatNamic weight packs usually consist of steel or concrete rings placed over the StatNamic silencer. As the device does not rely on gravity to apply loads as in static or drop weight testing it can be used vertically, horizontally and inclined to test raked piles. The ability to test horizontally has led to the method being used for lateral load testing of piles and simulation of ship impacts on mooring bodies.

In order to improve the flexibility of the device and minimise transportation costs for offshore works, a device has also been tested that can apply up to 14 MN using water as a reaction mass. This is achieved in over-water pile tests by connecting the StatNamic device to a vessel full of water below the water body’s surface, thus removing the need for heavy reaction weights.

The only significant difference between the smaller and larger testing devices is the method of catching the reaction mass. The catching method for larger tests uses gravel. This is achieved by placing the StatNamic device on the test pile and lowering the reaction mass onto its hanger. A large containing container is then placed around the assembly and filled with gravel. As the StatNamic weights move upwards the gravel moves to fill the void left and support the weights once movement has ceased. Due to the time required to place and remove the gravel after testing this method is reserved for tests above 16 MN. Smaller rigs utilise a hydraulic catching mechanism that allows the mass to be caught within the frame of the device. This allows up to ten individual piles to be tested in a day or multiple cycles on a single pile at 15-minute intervals.

ALLWAVE-RLT

Relationship between the StatNamic mass en amount of fuel and the test load will be determined prior to the tests, using AllWave-RLT. This program, as part of the AllWave Software Package, simulates the StatNamic Load Tests, incorporating all possible influences from pile, soil and testing setup. With AllWave-RLT an efficient StatNamic test can be prepared.

MONITORING SENSORS

The monitoring system of the Rapid Load Testing (StatNamic, StatRapid) consists of the PDR data acquisition unit and sensors recording the following quantities at the pile top:

The load, measured with load cells
Displacements with the Allnamics Reyca optical system with reflector on the pile
Accelerations

Direct measurements of loads and settlements gives direct measured load-settlement diagrams. By analyzing the results with the Unloading Point Method, according to ASTM and EuroCodes (and other codes), the static load diagram is obtained.

SPECIFICATIONS AND CODES

The tests of the Rapid Load Testing are in compliance with a.o. ASTM D7383, and EuroCode EN ISO-22477-10, as well as other national codes (i.e. Dutch CUR-230). StatNamic Load Testing is routinely used as an alternative to ASTM D1143 (compression tests), ASTM D3689 (Tension pile test or anchors), ASTM D3966 (for lateral pile testing) and ASTM D1194 (plate load test).

According to these codes:

Test data analysis based on user-independent principles,
No signal matching is required.
Taking into account loading rate dependencies of the soil (as for DLT and PDA)

ADVANTAGES

Test data analysis based on user-independent principles,
No signal matching is required.
Taking into account loading rate dependencies of the soil (as for DLT and PDA)

STATNAMIC LOAD TESTING ON YOUTUBE

See also our YouTube Allnamics channel and YouKu Allnamics channel

StatNamic test for Taipei 101; highrise building of 508 m height

Product informatie (PDF)

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