PDA, SPTCan piezoelectric (PE) accelerometers be used on steel piles, and can piezoresistive (PR) accelerometers be used on concrete or timber piles?
PR accelerometers may be used on any kind of pile under any circumstance. PE accelerometers may be used in any case EXCEPT when there is steel-to-steel impact, for example with some hammers whose driving system does not have a hammer cushion or on SPT rods. In those cases the use of PE accelerometers may result in unacceptable velocity traces (lack of proportionality with the force trace and/or excessive high frequency components), which means that the accuracy of the measurement may not be within 3% as required by American Society for Testing and Materials (ASTM). The use of PE accelerometers on steel piles when there is direct impact between the ram and the helmet or the top of the pile should therefore be avoided; the use of those accelerometers in other cases with steel piles is possible and will result in sufficient accuracy, provided that the distance between the top of the pile and the sensors is kept within the recommended limit (preferably more than 2 times the diameter).
