ABSTRACT
ABSTRACT: One of the important causes that result in cracking in webs of prestressed concrete bridge is that the prestress of many finely rolled thread steel bars do not meet the design requirements. Theoretical analysis and experimental tests of vibration behavior of the exposed segments of vertical prestressing bars showed that the values of effective tensions affect their vibration frequencies. The exposed segment was modeled as a cantilever beam with an elastically confined end, and the vibration frequency formula is deduced. Furthermore, influences of some factors such as diameter, linear density of the bar, mass of the sensor, confining rigidity of rotation are analyzed. The length of the exposed segment is modified to consider the influence of anchoring screws. Experimental results proved that there was a stable relationship between the confining rigidity of rotation and the effective tension force. Hence the effective prestress can be predicted from the measured vibration frequency.
