Study On Solar Radiation Thermal Field And Thermal Effects On Concrete Box Girders Strengthened With CFRP

Due to the advantages of Carbon Fiber Reinforced Polymer(CFRP), the reinforced technology with CFRP has became a trend in engineering field of reinforcing the concrete box girders. Box cross-section reinforced with CFRP has been widely used in domestic bridge structure due to its good structural performance. But under the action of solar radiation temperature conditions is very complicated. The temperature field of concrete box girder reinforced with CFRP are greatly affected by meteorological parameter such as solar radiation intensity,environment temperature and the wind speed and so on. so reinforced CFRP would change the original concrete box girder temperature field, besides, when the temperature changes, the stress performance of the concrete box girders reinforced with CFRP will also have a change.At present, the assumption of plane cross section will be only fit for the engineering design, and not for concrete box girders with the spatial mechanical behavior, So considering the shear lag effect on a box girder, it will be necessary for us to research the distribution formula of the thermal self-restrained stress and interfacial shear stress. it is very important to deduce the distribution formula of the thermal self-restrained strss and interfacial shear stress under the action of the solar radiation.This paper studies on the Basis of fruitful achieved test results. For the research on solar radiation thermal field and thermal effects on concrete box girders reinforced with CFRP, which are systematically studied through theoretical analysis combined numerical simulation, The mail work and achievements are as follows:(1) We are establishing the main factors which affect the temperature field by analyzing the characteristics of various parameters on solar radiation initial condition, boundary condition and thermodynamic, Based on these factors, and the method is advanced that BP neural network technology is employed to analyse the transient the data for the solar radiation thermal fields on concrete box girders reinforced with CFRP. Then the prediction data and experimental data were analyzed comparatively.(2) Considering theory of the thin-walled box girder, combined with the theories of thermal elasticity and strength of composite materials, the differential equation about the thermal self-restrained stress and interfacial shear stress of reinforced concrete box girder with CFRP under solar radiation thermal loads has been established on the basis of the energy-variational principle, the thermal self-restrained stress and interfacial shear stress formula has been derived. At last, the results were compared with the numerical simulation results.(3) Based on the temperature gradient in vertical direction in our country bridges design code, We has carried on the nonlinear computation using the ANSYS finite element software by using different modeling ways to simulate concrete box girders reinforced with CFRP. We got the distribution rule of the thermal self-restrained stress, interfacial shear stress and their shear lag effect.The results on the paper shows: By inputing meteorological parameter such as solar radiation intensity, environment temperature and the wind speed and so on, BP neural network technology model has a prediction with satisfaction and convenience on the temperature field of concrete box girder reinforced with CFRP. and The prediction solution are in good agreement with the measured data, The maximum is only 3.6%. By analyzing the thermal self-restrained stress, interfacial shear stress and their shear lag effect only under the temperature gradient in vertical direction, It is shown that the new analytical solutions in this article are in good agreement with the numerical simulation results, and the both variation is similar. Maximum stress location of the three materials is not uniform near the region of the interface, the edge for concrete, the center of bonded ends for CFRP and edges of bonding end for interfacial shear stress. from the perspective of shear lag effect, by contrast, reinforced technology with CFRP is beneficial to make vertical stress more uniform.