PRESTRESS FORCE EFFECT ON VIBRATION FREQUENCY OF CONCRETE BRIDGES. TECHNICAL NOTE

When examining the condition of an existing prestressed concrete bridge, one unknown parameter has been prestress force. The primary objective of the study presented in this technical note is to quantify the effect of the existing prestress force on stiffness, based on the measured vibration frequency of prestressed concrete bridges. Field and laboratory tests were conducted. Results indicate that, for practical ranges of prestress force, the change in natural frequencies of prestressed concrete members is very small, leading investigators to the conclusion that the use of vibration data to determine the actual prestress losses is inappropriate.