Study On The Performance Of Concrete Box Girder Of PSC Structure In Fire

In recent years, with the rapid increase in traffic as well as diversity, bridges’ fire occursfrequently with increasing number of vehicles in transporting flammable substances. Trafficaccidents and man-made causes fire accidents on bridge become a new threat to thetransportation infrastructure. Accidental fire as a bridge load causes incalculable damage tothe structure, the light is bound to affect the quality of traffic, causing personal injury andeconomic loss, the severe can cause permanent damage to the bridge and its collapse. Currentresearch of bridge fire mainly focuses on overall and local structural fire resistance ofstructural under fire of the prestressed concrete (hereinafter referred to as "PSC") structureand reinforced concrete (hereinafter referred to as "RC"), research less involves overall andlocal structural fire resistance of structural after fire and the PSC structure in fire resistanceresearch is less than the former.This paper takes the National Natural Science Foundation"Research analysis ofprestressed concrete bridge decay mechanism and effective carrying capacity under fire(51308056)"; Ministry of Transport and Communications Construction Technology Project"under the bridge structure fire disaster mechanism and safety evaluation and reinforcementtechnology research (2011318812970) as the basis for the overall fire resistance ofprestressed concrete box girder bridge, studied on the model test and numerical simulation.The main research work are:Based on survey data on criterion and abroad, to collate prestressed concrete materials,elastic modulus and constitutive relation after the high temperature strength and analyzecomputational models, and the use of high computational model selected by the line instages, distribution fitting each mechanical properties of concrete materials (strength, elasticmodulus and constitutive relation) model fitting method to obtain high temperature afterprestressing.Three beam (contrast beam PSB-1, no fire protection coating beam PSB-2, fireproofcoating beam PSB-3) are tested research model under fire and after fire. Based on the testbeam temperature field under fire, when the displacement process and prestressing losses ofdata analysis, the protective coating to reveal the extent of the impact on the fire resistance ofstructural PSC. Test beam displacement, strain and stiffness, frequency-based data analysisafter the fire, given the remaining carrying capacity and dynamic characteristics of thesituation after the PSC structure fire. By measuring the compressive strength of concrete block after high temperature,comparing concrete blocks without high temperature and study on different thicknessintumescent fire protective coatings of concrete structures and give the empirical formula ofstrength reduction. Through the fire from the bottom to the top of the beam and by burningmethod to determine the depth of the concrete strength, concrete strength values calculated toreveal the changes in the law after the concrete strength by the fire burning along the beamheight and depth of the subject.Study and analyse the EUROCODE, ASTM-E119, JIS A1304and ISO834computational fire model, a clear warming on models and theoretical calculation methodsused in the analysis of fire, fire process by comparing the temperature field trial datastructures, revealing the structure of temperature field from the outside to the inside of theheat conduction law, and the use of large general-purpose finite element software model fornonlinear analysis of temperature field, by comparison with the measured values to verify thecorrectness of the model.The use of large-scale finite element analysis software for three test beams to simulatethe material by setting different constitutive relations and finite element model of the test inaccordance with the boundary conditions, the simulation test beam deflection under load,the concrete strain and ultimate bearing capacity of the test beams, natural frequency, etc.,by comparing the measured values, and the validity of the model.