Effect Analysis Of Temperature On Static And Dynamic Characteristics Of Long Span PC Box-girder Bridge

Temperature research has always been a hot issue and difficult problem in the field of bridge engineering. The action of the sun will lead to nonlinear temperature field in the beam and large temperature stresses in the structure for the prestressed concrete box-girder bridges, which may lead the structure’s cracks, and seriously affect the bridge’s safety and durability.Temperature not only has effect on bridge structure’s static characteristics, but also has effect on bridge structure’s dynamic characteristics, which performances significantly in many cases. What’s more, it may surpass many changes caused by structural damages. Hence, how to get accurate dynamic characteristic for structure in one project seems very crucial.This paper took one PC single box single room continuous bridge, which superstructure is64.8m+120m+64.8m, as the engineering background. It analyzed the influence of temperature on structure’s static and dynamic characteristic. The main contents of this paper are as follows:1. Systematically summarized domestic and overseas research status, pointed out shortcomings of those researches.2. Analysed temperature field of section of the example bridge girder with numerical simulation approach by ANSYS, Got approximately similar measured values&calculated values. Meanwhile,concluded vertical temperature gradient for box-girder was Ty-17e-4y3. Reviewed temperature effect calculation principle, the finite element model was modeled to analyse structure’s static characteristic under the temperature gradient, the following conclusions were drawn:(1) The longitudinal temperature stresses and the vertical deformations caused by the temperature gradient ruled by Highway Bridge Regulation were unreliable by the fitting curve of temperature gradient, while the transverse temperature stresses were reliable.(2) The temperature gradient mode that was regardless of the bottom slab temperature difference distribution was unreliable.(3) The longitudinal and transverse temperature stresses of concrete box-girder section were sensitive to different vertical temperature gradient.(4) In terms of calculation results of the transverse temperature stresses caused by section parameters, the box-girder design should first focus on roof thickness, then the beam’s depth and floor thinkness.4. Summarized the influence mechanism of the structure dynamic characteristics under temperature effect, then, deduced the theoretical formula of structural frequency under the temperature effect, and analysed the influence of the structural dynamic behavior (frequencies and vibrational modes) by numerical simulation under seasonal temperature,temperature gradient and bearing temperature, Came to the conclusion that the seasonal temperature and bearing temperature chang had great effects on the structure frequencies, while changed little caused by the temperature gradient.Whether seasonal temperature changes or the influence of the temperature gradient, the effect of vibrational modes of structure was not obvious.