Calculation methods for boundary conditions of relative humidity on steel bridge surface
The surface relative humidity is an important factor determining the corrosion rate of steel bridges,and the key to accurately calculate surface relative humidity is selecting appropriate boundary conditions of temperature field.Therefore,the relative humidity tests on the arch rib model was conducted,the finite element analysis software ABAQUS with the DFLUX and UVARM subroutines was used to calculate the surface relative humidity of the steel bridge.A comparative analysis was conducted on the effects of different solar radiation,radiative heat transfer,and convective heat transfer calculation methods on the surface relative humidity of the steel bridge.The results show that the influence of solar radiation intensity on surface relative humidity is mainly concentrated during sunrise and sunset periods.The daily total solar radiation tends to overestimate using the calculation method of Hottle model,leading to lower surface relative humidity.It is recommended to calculate the solar radiation heat flux density based on the measured solar radiation data.The effects of radiation heat transfer with sky and ground on the surface relative humidity should not be ignored.Substituting simple radiation heat transfer with atmospheric for radiation heat transfer with sky and ground will lead to an increase in heat absorption by the structure and a significant decrease in surface relative humidity.It is recommended to consider the effects of sky temperature and ground temperature when calculating the heat flux density of radiative heat transfer.During the day,convective heat transfer has a cooling effect on the structure,causing the surface relative humidity to increase.At night,convective heat transfer has a warming effect on the structure,causing the surface relative humidity to decrease.Currently,the studies on calculation methods of convective heat transfer coefficient are mostly based on concrete structures.It is suggested to conduct research on convective heat transfer coefficients suitable for calculating the surface relative humidity of steel bridges in the future.
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维普
