Changes of natural frequencies of a short-span concrete skew bridge during construction

Abstract

This paper demonstrates the changes of natural frequencies and modes of a PC bridge with a skew angle of 30 degrees throughout all the construction stages from production of a PC box-beam at factory to completion of asphalt pavement work by using a portable vibration measurement system with hammering excitation. This paper clarifies as follows: The first mode of vibration and first predominant frequencies of 14 individual PC beams are closed to the first natural frequency and mode of a simply supported beam. The bridge behaves as a plate after shear key development followed by transverse post-tensioning for integration of single beams. We experimentally confirmed that its first natural mode is longitudinally bending and its second mode is torsional. The largest increase of the first natural frequency occurred after integration, however remarkable decrease observed after asphalt pavement.