Evolvement Of Nature Vibration Characteriscs Of Concrete Girder Bridge Considering Environmental Temperature And Time-depended Performance Of Concrete

Concrete girder bridge is widely used in the highway and railway engineering of China. Its natural vibration characteristics are constantly changing by the effects of environmental temperature and time-depended performance of concrete. Therefore, it is important to research the bridge natural vibration characteristics change under environmental temperature and time-depended performance of concrete.This paper made lots of concrete blocks and six concrete test beams(three steel bearing, three rubber bearing), experimental analysis the change of concrete elastic modulus with time, experimental analysis the change of concrete simply supported bridge nature frequency under environmental temperature and materials properties development, experimental analysis the natural frequency change of concrete simply supported bridge in different bearing of24hours. Analysis the influence of environment temperature and material long-term performance on nature frequency of concrete simply supported bridge, and combined two bridges to experimental and analysis. Through the above research can draw the following main conclusions:(1) Concrete strength and modulus of elasticity grow fast in curing28days-50days, and the growth trend obviously reduced after50days.(2)The natural frequency of concrete girder bridge change with time and environmental temperature. The natural frequency of bridge is growing with time. For an ideal simply supported bridge, the natural frequency has negative relation with environment temperature. When the temperature between0℃or so, the change of natural frequency of bridge is lag behind with the environment temperature and humidity change.(3)Environmental factors influence on bridge natural frequency are various, environmental temperature, the change of concrete elastic modulus, bearing performance, constraint changes must be taken into account comprehensively. The change of bridge natural frequency should consider the actual bridge forms and constraint when the bridge expansion joint can not work normally.