Influence of Stress Wave Phenomena during Statnamic Load Testing"
P. Middendorp, Profound
B. Daniels, TNO Building and Construction
International Conference on the Application of Stress-Wave Theory To Piles,
Orlando, Florida, 1996
Because of its advantages
compared to static and dynamic load testing, especially for bored piles, the
application of Statnamic load testing has increased considerably. The
Unloading Point Method (UPM) has become a standard tool for the analysis of
Statnamic (STN) load testing signals. The method is based on the assumption
that the pile can be modelled as a concentrated mass and springs. Modelling
is only valid when stress waves phenomena are minimal. In case of long piles
or short duration STN testing, stress wave phenomena are not negligible.
The sensitivity of STN to stress wave phenomena can be characterised by the
wave number which is determined by the duration of the STN load, the stress
wave velocity and the pile length. With the stress wave program TNOWAVE
simulations have been made for piles with the same ultimate capacity but
different wave numbers. Conclusions are drawn from these results as to what
wave number UPM can be applied reliably to predict ultimate load capacity.
Some measures to correct for stress wave phenomena, when they occur, are