An Experimental Study to Estimate Loss of Prestress and Determining Fundamental Natural Frequecny of Prestressed Concrete Bridge

Prestressed Concrete (PSC) structures especially bridges are being largely used all over the world due to their multifarious advantages in terms of structural behaviour, economy as well as aesthetical aspects. However, many PSC structures deteriorate with time due to several factors which may lead to certain loss in their initial applied prestress. This loss may affect the structure’s behaviour and its service life adversely and need to be checked. Such loss of prestress results in degradation of stiffness of the structure. A precise determination of prestress losses in prestressed concrete members is a complicated problem because the rate of loss due to one factor, such as relaxation of tendons, is continually being altered by changes in stress due to other factors, such as creep of concrete, fatigue, etc. It has been known that any change in the stiffness of the structure will change its natural frequency also. Hence, it may be possible to ascertain the loss by measurement of natural frequency at regular intervals. In this study, an effort has been made to know the natural frequency of a PSC structure by Vibration Method and determining the existing prestressing force to ascertain the loss of prestress.