Influence Of The Temperature To The Evolvement Of Dynamic Characteriscs Of Concrete Girder Bridge

It is unavoidable for the bridges to be damaged by the effect of environment, natural disaster, long-term load and so on during the operation period, so mastering the evolvement of nature vibration characteriscs of concrete bridge accurately is very important for the safety and health assessment, damage detection and strengthening conservation of the bridges. Most of the researches indicate that environmental effect, especially the temperature, has a significant impact on the dynamic characteristics of the bridges, which usually covers the change of dynamic characteristics caused by damage. Therefore, the mechanical property of concrete material and the dynamic property of structure under different temperatures need to be studied necessarily.In this paper, two grades of concrete specimens and 3 concrete test beams were made. The elastic modulus of the concrete specimens and the natural vibration characteristics of the test beams under different temperatures were tested and analyzed. And the influences of the temperature to the evolvement of the dynamic characteriscs of concrete girder bridge were discussed through the natural vibration characteristics test of an exising concrete girder bridge. The main conclusions obtained through the above research are as follows:(1) The elastic modulus of concrete has negative relation with temperature. The elastic modulus of concrete decreases with the increase of the temperature. The change rate of the low-strength elastic modulus of concrete with temperature is greater than high-strength concrete. The elastic modulus of concrete grows with the ages in the range of 0-200 days. Since the load process can cause some damage to the concrete, the elastic modulus of concrete decreases.(2) The natural frequency of the concrete test beams has negative relation with temperature. The natural frequency of the concrete test beams decreases with the increase of the temperature. The inner temperature of the test beams lags obviously behind the environmental temperature. The time is about two hours.(3) The evolvement of natural vibration characteriscs of concrete girder bridge with temperature is closely related to the change of the modulus of concrete. Thus the influence of the temperature should be considered in the dynamic characteristic test and performance evaluation of the actual bridge.