Behavior And Acoustics Emission Characteristics Of Two-way Slabs Of Full-scale Structures Under Fire

Nowadays, the influence of building fire to our life is more and more serious.Experts from many countries pay much more attention to the subject of fire-resistant instructures, while the existing studies are mainly focused on the tests of singlecomponent or numerical simulation, tests considering the collaborative work ofdifferent components in the overall structure are not enough. This paper researched thecomponents’ behavior and audio emission properties under fire, based on the full-scalestructure test.The subject structure is a3-storey steel frame civil building, in which4pieces ofreinforced concrete slabs with different boundary conditions were subjected to fire inthe test, each floor was equipped with a constant load. There were4steel beamsexposed to the fire while the column was protected from fire in the center of the fourslabs. During the test, displacements of the surface of the concrete plates, steel beamand column were measured, the temperature of the gas in the furnace, the section of theslabs, steel beams and column were also collected. Finally, the temperature distributionlaw, the relationship among displacement of the components, time and furnacetemperature were acquired, and compared the behavior of the concrete slabs withdifferent boundary conditions under fire. Through data analysis, the sensitivetemperature of deformation of concrete slabs is between450℃and550℃, water in theconcrete puts off the temperature rising; concrete slabs with the high temperature andexternal load generated cracks to redistributes stress during the test; integral pouringconcrete slabs have a better fire-resistant capacity, they wouldn’t collapse suddenly inthe test; the boundary constraints have a large influence on the deformation of theconcrete slabs.The test also recorded the acoustic emission signals of slabs, including the largestamplitude, duration, energy of single signal and the total number of the events.Parameters of acoustic emission signals were researched, total number of events foreach channel, the energy rate and b value were obtained, and the parameters distributionlaw and change characteristics were summarized in this paper. Through data analysis,total number of events was the reflection of the severe degree of cracks developmentand friction of material, which reflected slab activity in the fire, when the furnacetemperature got to550℃, slab has the highest activity; signal energy reflected thestrength of the event, higher energy rate can be used to recognize the occurrence ofcracks or large scale destruction; acoustic emission b value showed the stress state in thematerial, b value will smoothly progress or slowly rise in the process of strain accumulation, and b value decreased substantially or fluctuating violently, when bigcracks or a wide range of destruction appeared.