Research And Application Of Fire Resistance Of Concrete Box Girder Based On Fire Retardant Coating

The probability of bridge fire is small,with randomness and uncertainty,but often due to uncertainty,it is easy to cause hidden dangers of bridge fire safety.Spraying fire retardant coatings on the surface of bridges is one of the main methods of fire prevention of bridges.By delaying the heat transfer to concrete,the fire retardant performance of concrete structures can be improved.In this paper,concrete box girder as the basic analysis object,fire performance of concrete box girder under fire,including the establishment of ANSYS finite element analysis model to analyze its fire temperature field,while the expansion of fire retardant coatings and non-expansion of fire retardant coatings fire performance of experimental analysis,and finally concrete box girder Application of fire prevention construction.The main conclusions are as follows:1)the protective layer prevents the transmission of temperature.The greater the thickness of the protective layer is,the more beneficial it is to the reinforcement.Therefore,in the actual fire protection design,we can consider increasing the thickness of the protective layer.In the box girder without fire-proof coating,the temperature at the bottom and web of the box girder increases gradually with the increase of fire time.The nearer the web is,the higher the temperature is;the nearer the web is,the higher the temperature is.2)the greater the thickness of the fire retardant coating,the better the fire performance of the box girder.In case of fire prevention,the thickness of fire retardant coating should be appropriately increased for non intumescent fire retardant coatings.When the thermal conductivity of the fire retardant coating changes,the inner temperature of the fire retardant coating with thermal conductivity of 0.09 W /(m.)is very small.The fire retardant coating Temperature should be chosen with small thermal conductivity of fire retardant coating.3)the existence of the optimum thickness of 5mm fire retardant coating can make the compressive strength of test block unchanged.When the thickness of the brush is 5mm,the high temperature compressive strength of the test block is basically unchanged.When the thickness of non-expansive fire-retardant coating is less than 10 mm,its fire-retardant performance is limited,and the optimum thickness of fire-retardant coating is 10 mm.With the increase of axial compression ratio,the fire resistance value of concrete gradually decreases.Load eccentricity has a great influence on the fire resistance limit of concrete specimens.It is necessary to select concrete specimens with small eccentricity for fire resistance.The fire resistance value of components with larger section size is greatly improved.4)Fire-proof construction of expansive fire-proof material of box girder concrete has the characteristics of simple construction,economical cost and strong applicability.Its fire-proof construction passes fire-proof acceptance once and for all,which fully meets the requirements of bridge fire-proof construction.