Abstract:
Short rigid piles are widely used to support structures such as wind turbines, traffic
signals, jetties, transmission towers, highway overhead signs and water front
structures.
In order to assess the effect of L/D ratio and strain on short piles subjected to
horizontal sinusoidal vibrations. Four RCC short piles of diameter 20cm, 30cm,
40cm and 50cm each having a length of 2m were cast The important part of this
dynamic analysis is to calculate the stiffness and the damping ratio. For a better
understanding of the site geotechnical properties of the site were also evaluated.
To generate horizontal sinusoidal vibrations a motor-oscillator assembly was used.
Four foundation bolts were cast into the pile cap to enable the mounting of a motoroscillator
assembly. Three acceleration transducers were suitably mounted on the
vertical face of the pile cap to monitor the induced accelerations. These piles have
been tested for four different force level i.e. eccentricity setting of motor-oscillator
assembly
For each pile and eccentricity setting, acceleration-frequency records were analysed
to obtain resonant frequency of the soil-pile system and shear strain at ground level.
Using this data, a procedure has been developed to obtain damping ratio and stiffness
of the soil-pile system. Conclusions have been drawn relating (i) Exciting force level
and resonant frequency, (ii) Soil-pile stiffness and strain level and (iii) System
damping and strain level, considering each pile individually. The influence of L/D
ratio on the dynamic response of the soil-pile system has also been demonstrated.
