Study On Fire Resistance Of Reinforced Concrete Beam Strengthened With Anti-fire Coatings

Strengthening concrete structures with steel and carbon fiber is a common method in the construction industry,but in the event of fire,these reinforcement materials will lose their bearing capacity quickly,which seriously threatens the safety of the building structure.At present,cement mortar is applied to the surface of concrete structure to prevent fire.The research shows that the thickness of cement mortar and the effect of fire prevention need to be further explored.At present,2011 edition of Guangdong Province,"Technical Specification for Refractory Design of Building concrete structures",gives the fire resistance limit time of reinforced concrete beams and columns strengthened with CFRP sheets with different thickness and thickness protected by fire resistant coatings.but the thick type is required to meet the fire resistance limit time required by the code.The thickness of fire coating is large,so it is not convenient for practical construction.At the same time,the high temperature performance of thin fire resistant coating is better than that of thick fire proof coating,but it is difficult to be used in strengthening concrete structure alone for various reasons.Therefore,this paper attempts to study the fire resistance of reinforced concrete structure under the protection of thick and thin fire proof coating.In this study,taking the flexural failure strengthening concrete simply supported beam as an example,four beam specimens were made,two of which were strengthened with steel plate and the other two were strengthened with carbon fiber sheet.The beam specimens of the same reinforcement material are coated with cement mortar and thick and thin fire proof coating.Then two specimens of reinforced concrete beams strengthened by shear are added to study the fire resistance of reinforced concrete beams strengthened with thick and thin fire resistant coatings.Six specimens were put into high temperature furnace for fire-resistance test under predetermined conditions.The displacement of each measuring point and the temperature change of each thermocouple were recorded during the test.After the test,the failure shape and appearance of each specimen were described.The test results showed that the failure modes and fire limits of each girder meet the expectations before the test.The corresponding temperature field is obtained by the finite element software ABAQUSsimulation,and the relative data obtained from the test are compared and fitted.On this basis,the theoretical bearing capacity of each strengthened beam at high temperature is calculated by using the 500 ? isotherm method in the code and compared with the actual loading value,and the fire resistance of reinforced concrete beams coated with different fire-proof protective layers is obtained.The reinforcement effect of reinforced concrete beam specimens at high temperature is also discussed.An hour high temperature simulation of the flexural reinforcement beams with different fire protection layers was carried out,and the effect of the thickness and type of the fire protection layer on the fire resistance of the reinforced beam was obtained.Finally,the ultimate bearing capacity of the area of the fireproof coating and the cement mortar area of the shear reinforcement beams after two hours of high temperature is also compared.It is concluded that the failure area of the shear reinforcement beam in the fire may be transferred from the end to the middle.This phenomenon should be paid enough attention by the engineering designers.