Concrete Composite Box Beam (black Box) Net Floor Fire Test And Analysis

Composite box net beam ceiling is box section ribbed floor, made of prefabricated laminated member" superimposed box" and after pouring rib beams as beam, plate and an overall, has a bottom level, big cavity honeycomb structure, spatial characteristics of force. Concrete composite box net beam ceiling has been widely applied in various engineering.In recent years, more and more building fires which caused a serious threat to people’s lives and property were frequently happened. In fire, Concrete composite box net beam ceiling not only act as the role of bearing, but also assum the role of cutting off fire, which are the most serious destroyed elments.So it is necessary to learn the behavior of the Concrete composite box net beam ceiling under fire.In order to board in the fire behavior, this article on concrete composite box (concealed box) net beam ceiling in the fire behavior were studied, and the test results are analyzed, are as follows:According to the test requirements of the fire test furnace transformation; through the simulation of concrete composite box (concealed box) network slab simply-supported boundary conditions, in accordance with the ISO834 international standard temperature curve, were under dead load of concrete composite box (concealed box) net beam ceiling in the real fire experiment under the condition of test plate; section temperature, steel temperature, composite box inner cavity, inside and outside the plane displacement, plate edge angle, monitoring and acquisition, and contact test macro phenomenon to deal with the experimental data, obtained by simply supported composite box (concealed box) net beam ceiling by fire after the injury mechanism, the fire board temperature distribution and displacement as a function of time and temperature variation.This paper summarizes the concrete composite box (concealed box) net beam ceiling on fire in the mechanical properties of general rules and conclusions, as follows:(1) Composite box net beam ceiling fire effect, superimposed box bottom plate subjected to temperature increases due to the plane generated by the internal pressure and the gas expansion cavity outside the plane stress interaction, first generation blowout" instability", concrete abscission, rib beam not burst phenomenon.(2) As a result of composite box bottom under the condition of high temperature cracking, concrete composite box net beam ceiling structure by hollow floor structure transforms into similar to well-shaped beam floor structure, and internal force redistribution, floor around the rib beam subjected to torsion effect; as the combustion time of growth and temperature increased, peripheral rib beam torque gradually, resulting in crack, may cause torsional failure.(3) Along with the superimposed box floor burst, floor stiffness reduction rate significantly increased. When the majority of plate after the burst, stiffness reduction rate slows, the stiffness decreases mainly by the action of high temperature properties of materials change cause.(4) Superimposed box bottom plate after the burst, rib beam at the three face under fire condition, but as a result of composite box side plate for ribbed beam has a certain protective function, slowing the rib beam internal heat transfer, improves the rib beam floor fire resistance and fire resistance limit.(5) From time of fire and destruction form, concrete composite box (concealed box) net beam ceiling fire resistant capacity more concrete composite box (unconcealed box) net beam ceiling.(6) The damage occurred in the plate after the ceasefire.