Fire Resistance Mechanism Research On Building Seismic Rubber Bearing With Fire Protection Measures

China is an earthquake-prone country with a shallow earthquake source.About half of the cities are located in areas with a basic intensity of 7 degrees or more.In recent years,China has been developing seismic isolation buildings vigorously.Seismic isolation technology with soft grams achieve the "three protections" of the building: structure itself,non-structural components and internal facilities in order to ensure safe of the structure without repairing.But the major material of the isolation device is rubber which has great fire risk.And there are few related researches at home and abroad.Therefore,it is necessary to systematically study the fire risk of isolation building and the corresponding fire protection measures.The project originated from the National Twelfth Five-Year National Science and Technology Support Plan Project “High-rise and Large-span Building Partition Seismic Reduction Technology”(No.2012BAJ07B02),in which the research and development of high-performance bearings,in addition to high mechanical properties of seismic rubber bearings,such as the ultimate shear strain of more than 400%,but there is highlighted the problem about fire resistance and fireproof.In order to effectively improve the safety of earthquake-isolation buildings,development of high-performance bearings also should include research of fire resistance and fire protection devices.This research uses the background of the “Twelfth Five Year Plan” National Science and Technology Support Program project as a starting point to study the following aspects:1)Analyze the fire hazard of seismic isolation buildings: classify the location and function of the isolated floor;analyze and calculate the fire performance of the seismic isolation building,and analyze the fire growth rate,maximum heat release rate,and fire scenes.The most unfavorable fire temperature development rule of the isolated floor is obtained.2)Research on the fire-resistant ultimate temperature(guaranteed basic mechanical performance)of the main constituent material rubber in the seismic isolation bearing of the seismic isolation building.The high-temperature temperature at which the rubber material decomposes is determined by means of a thermogravimetric test at a high temperature;Different temperatures are selected and divided between normal temperature and decomposition temperature for heating test,and mechanical properties at normal temperature and high temperature are tested and studied.The lower thermal weight and guarantee the fire-resistant ultimate temperature of the basic mechanical properties are obtained after different high temperatures.3)Research on the fire-resistant limit of isolation rubber bearings,the fire resistance of three types of fire protection structures and the related factors that affect the fireresistance limit.Through the test method,10 full-scale seismic isolation devices and connection structures comply with GB9978.1-2008 "Fire-resistance tests——Elements of building construction Part 1: General Requirements" and GB9978.7-2008 "Fire-resistance tests——Elements of building construction——Part 7" : Special requirements for columns for large-scale fire tests,summarizing the fireresistance limits of seismic rubber bearings,the three types of fire protection construction,and the related factors affecting the fire-resistance limit.4)The temperature field at the high temperature of the seismic rubber bearings is studied by the parameter analysis and the derivation of the heat transfer formula.Through numerical calculation methods,Abaqus finite element software is used to perform numerical calculations on the above 10 tests and repeatedly adjust relevant parameters for comparison and analysis to determine the numerical calculation model of the relevant seismic isolation device;through parameterization analysis and theoretical derivation,the seismic isolation device was subjected to high temperature field calculation formula.It provides a reference for engineering applications.5)The engineering application of the research results is analyzed and summarized.Firstly,the source of the project and the overview of the demonstration project at the Beijing New Airport will be elaborated.Then through the summary of engineering application,the fire protection design process and design method of the isolation device and the construction process flow that meets the actual project are obtained.In the design and calculation of the fire protection of seismic rubber bearings for key nodes in isolated buildings,the use of tests,theoretical derivation formulas,and numerical calculation methods can well resolve the isolation support.The seismic isolation function also satisfies the problem of corresponding fire resistance,and the reasonable optimization of the device performance and economic investment in isolated buildings.Except the Beijing New Airport,there are no fire protection projects in various types of isolated buildings in China.Therefore,the design and construction method of fire protection for isolated rubber bearings based on heat conduction theory is provided to fill the blank of the fire protection design of old isolation bearings.It has practical significance for the fire safety design of isolated buildings.