Fire Resistance and Influencing Factor of Composite Box Girder with Corrugated Steel Web and Steel Bottom
In order to study the deflection variance rule and fire resistance of composite box girder with corrugated steel web and steel bottom under fire,taking a test beam as the study background,and using finite element software ANSYS to establish a numerical model of composite box girder with corrugated steel web and bottom for carrying out thermal and mechanical coupling analysis.The the influences of different temperature curve,fire area,load ratio and height span ratio on fire resistance are studied.The result shows that(1)the temperature gradient of steel web and concrete roof of composite box girder is obvious along the beam height direction,and the temperature gradient becomes more obvious with longer fire time;(2)the mid-span deflection time history curve of the composite box girder with corrugated steel web and steel bottom plate is mainly divided into 2 stages,the early stage is a slow growth stage with an average growth rate of 1.5 mm/min,and the late stage is a rapid growth stage with an average growth rate of 5 mm/min;(3)the fire resistance of the composite box girder under HC fire is the shortest,and the fire resistance of the composite box girder under the influence of standard ISO834 heating curve under the same load ratio decreases by 71.8%;(4)the larger the fire area is,the smaller the fire resistance is,the closer the fire area is to the mid-span section,and the smaller the fire-resistance is;(5)the load ratio has great influence on the fire resistance of the composite box girder when the load ratio increases from 0.2 to 0.4,and the fire-resistance of the composite box girder decreases by 40.4%;(6)although the fire resistant performance of the composite box girder with a larger high-span ratio is improved in the early stage of fire obviously,the fire-resistant limit is smaller than that of the composite box girder with a smaller high-span ratio as the temperature continues to rise in the later stage,and the fire-resistant limit decreases by 23.1%as the high-span ratio of the composite box girder increases from 0.088 to 0.147.The study result can provide reference for the fire protection design of composite box girder with corrugated steel web and steel bottom.
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