Abstract. An investigation was carried out to determine dynamic characteristic of reinforced concrete (RC) bridges by using ambient vibration test (AVT). The ambient vibration sources on bridges may come from traffic, wind, wave motion and seismic events. AVT describes the dynamic characteristics of the bridge and ground by measuring the natural frequencies using highly sensitive seismometer sensor. This test is beneficial due to light weight equipment and smaller number of operator required, cheap and easy to be handled. It is able to give a true picture of the bridge dynamic behavior without any artificial force excitation when vibration data is recorded. A three-span reinforced concrete bridge located in Sri Medan, Batu Pahat, Johor was measured by using microtremor equipment consist of three units of 1 Hz eigenfrequency passive sensors used in this test was performed in normal operating condition without excitation required from any active sources or short period noise perturbations. Ten measurements were conducted on the bridge deck and ten measurements on the ground surface in order to identify the natural frequencies of the bridge. Several peak frequencies were identified from three components of Fourier Amplitude Spectra (FAS) in transverse (NorthSouth), longitudinal (East-West) and vertical (Up-Down) direction as well as squared average Horizontal to Vertical Spectral Ratio (HVSR) of ground response, computed by using Geopsy software. From the result, it was expected the bridge have five vibration modes frequencies in the range of 1.0 Hz and 7.0 Hz with the first two modes in the transverse and longitudinal direction having a frequency 1.0 Hz, the third mode is 2.2 Hz in transverse direction, fourth and fifth mode is 5.8 Hz and 7.0 Hz. For ground natural frequencies are in range 1.0 Hz to 1.3 Hz for North-South direction and 1.0 Hz to 1.6 Hz for East-West direction. Finally the results are compared with several empirical formulas for simple verification.

Abstracts. Bridge is one of the important facilities use in daily life as a bridge is built to span physical obstacles such as a body of water, valley or road for the purpose of providing passage over the obstacle. Various testing conducted on the bridge in order to know the dynamic characteristics of the bridges. One of populartesting use isan ambient vibration test. Ambient vibration is a nondestructive test conducted using highly sensitive sensor. This testing iseasy to conduct with less labour, time and also cost. This paper aim to provide up to date literature review on ambient vibration test on bridge includes sources of ambient vibration, procedure of conducting the measurement and results from the ambient vibration test.It is important to known the dynamic characteristics of the bridge especially to determine the dynamic response of the structure and also as dynamic information for seismic design.