Experimental investigation of dynamic behavior of prestressed girders with internal tendons

Abstract

In this study, the dynamic behavior of internally prestressed concrete beam is extensively investigated using the scaled experimental specimens to identify the influence of prestressing force on the natural frequency because there are inconsistent analytical theories in the relationship between natural frequency and prestressing force of internally prestressed concrete beam. Three experimental specimens, i.e., the straight line of tendon with and without eccentricity and parabolic tendon profile are considered to investigate the dynamic behavior of internally prestressed concrete beam. Based on the experimental results, it is observed that the natural frequency is increased as tensile force of tendon is increased in the specimen with eccentricity, however, no meaningful relationship between natural frequency and tensile force could be found in the specimen without eccentricity. These results are related not only to the tensile force itself but also to the camber of the beam introduced by the tensile force. Therefore, it is difficult to establish the distinct relationship between natural frequency and tensile force. Instead, this relationship may be explained as dual effects of tendon on the natural frequency of beam, i.e., stiffening and softening effects. Therefore it is important to consider not only tensile force but also many other parameters such as tendon profile, camber of beam, boundary conditions, ratio of stiffness of concrete and tendon, and etc. for estimating the natural frequency or tensile force of the internally prestressed concrete beam.