Review of assessment and repair of fire-damaged RChighway bridgesAbstract ：This paper presents a review of the progress of the research and engineering practice of assessment and repair of fire-damaged RC highway bridge，s based on which existing and pressing problems of the evaluation method are pointed outAt last，Prospect for the development of assessment and repair of fire-damaged highway bridges is also proposedKey words ：fire damage；assessmen；t repair techniques；RC structure；bridge1 PrefaceFires can cause great structural damage to bridges and major disruption to highway operationsThese incidents stem primarily from vehicle accident (often oil tanker) fires， bridges might also be damaged by fires in adjacent facilities and from other causesQuite a few of them， though rarely happened， lead to severe structural damage or collapse and casualtyOn June 2，2008，fire disaster broke out under the 18th span of Nanjing Yangtze River Bridge and lasted for approximate 75min During the fire s development andextinguishment， the structure experienced the sharp rise and fall in temperature causing severe damage to fire- stricken segmentsOn April 29，2007，a gasoline tanker overturned on the connector from Interstate 8O to Interstate 880 in California The intense heat from the subsequent fuel spill and fire weakened the stee1 underbelly of the elevated roadway ,collapsing approximately 165 feet of this elevated roadway onto a section of I880belowOn March 25， 2004，Connecticut，United States， a tanker truck carrying fuel swerved to avoid a car and overturned，dumping 8000 gallons of home heating oil onto the Howard Avenue overpass The consequent towering inferno melted the bridge structure and caused the southbound lanes to sag several feetUndocumented number of bridge fires occurring throughout the world each year cause varying degrees of disruption，repair actions，and maintenance cost Although fires caused damage to the bridge structures ,some bridges continue to function after proper repair and retrofit Still in some situations they have to be repaired for the cause of traffic pressure even though supposed to be dismantled and reconstructed However ,in other cases， structures are severely damaged in the fire disaster and fail to function even after repair，or the costs of repair and retrofit overweigh their reconstruction costs overwhelmingly even if they are repairable， under which situation reconstruction serves as a preferable optionTherefore in situ investigation and necessary tests and analyses should be conducted to make comprehensive assessment of the residual mechanical properties and working statuses after fire and to evaluate the degrees of damage of members and structures , in reference to which decisions are made to determine whether Fire damaged structures should be repaired or dismantled and reconstructedUrgent need from engineering practice highlighted the necessity to understand the susceptibility and severity of these incidents as wel1 as to review available information on mitigation strategie，s damage assessment，s and repair techniques.2 Progress in Research and Engineering Practice2.1 Processes of Assessment and Repair of Fire damaged Bridge StructureIn China and most countries in the world， most highway bridges are built in RC structureAnd the practice of the assessment and repair techniques of bridge structure after fire directly refer to that of RC structure，which ，to date， domestic and foreign scholars have made great amount of research on，with their theories and practices being increasingly mature .As for the assessment and repair of fire-damaged reinforced concrete structures， there are two mainstream assessmentprocessesin worldCountries including United States， United Kingdom and Japan adopt the assessment process stipulated by The British Concrete Society .This process grates the severity of fire damage of concrete structure into four degrees according to the deflection， damage depth，cracking width, color， and loading capacity variation of fire-damaged structures and adopt four corresponding strategies (including demolis，h strengthen after safety measure，s strengthen. and strengthen in damaged segments) to deal with them accordingly In general，this process is a qualitative method and considered，however， not quantity enough.In Chinese Mainland and Taiwan ， the prevailing as assessmentand repair process of fire damaged incorporates following steps：In comparison this process is more detailed(1) Conduct In-situ inspections， measurements， and tests including color observation， concrete observation，degree of rebar exposure observatio，n cracking measuremen，t deflection measuremen，t various destructive and nondestructive test methods as grounds for assessment of fire damaged structuresIn assessment of the post -fire mechanical properties of fire damaged structures， historical highest temperature and temperature distribution of structure during the fire