Study On Burning Behavior Of Textile Membrane And Overall Stability Analysis Of Air-supported Membrane Structure Under Fire Condition

As a kind of novel architectural form, membrane structures has received praises from people because of its artistic quality, economy, self-cleaning and other advantages. The development membrane structures is relatively late in China, as a result, textile membranes with substrate of polyester fiber and flame-retardant coating of PVC or PVDF still dominate the Chinese architectural membrane market. However, with the growing number of permanent membrane structures, textile membrane materials are not only structural components but also the potential combustible materials contributing to fire accidents, the burning behaviors of them have critical influence on the safety and stability for the whole building. At the same time, because of the large span of Air-supported enclosed membrane structure, fire rescue difficulties grow dramatically, and the temperature field might be different from general structures. Therefore, it is significant to conduct fire studies and overall stability analysis for the designing, construction and management of membrane structure.Based on the fire hazard of membrane structure, a series of theoretical, experimental and numerical simulation researches have been conducted from two perspectives, burning behavior of textile membrane and stability analysis of air-supported structure under fire condition. Firstly, on the basis of theoretical analysis, combustion process and evaluation indicator of combustion performance have been summarized. Utilizing the radiation ignition experiments of membrane materials, their combustion characteristics including HRR, MLR, ignition time and critical ignition heat flux have been comparative analysed according to different perspects, such as types, welding position, heating situation and external heat flux. Then theoretical model of upward flame spread for double-side emptied thermally-thin materials has been established, which has been discussed with the results of small-scale flame spread experiments. Simplifying the fire model of air-supported structure to obtain the critical instability pressure and failure temperature is applyed for overall stability analysis with utilization of FDS in different fire scenarios.From radiation ignition experiments, S6101 with the fire retardant additive shows the lowest HRR and longest ignition time; while, S6003 and S6013 have intenser burning behavior. Under different external heat flux, S6101 and S6003 are sensitive to the heat flux, but X1400 shows the lowest TRP value, which could be attributed the knife coating process. Most combustion evaluation indicators of materials are higher when heated with adiabatic backside, which illustrate more fire harzard compared with double-side emptied condition obviously. However, Welding region and heated surface have limited effects on the combustion behavior of textile membrane samples.According to the classical theory of flame spread and the characteristcs of thermally-thin materials, the theoretical model of upward flame spread for double-side emptied thermally-thin materials has been established with consideration of double-side flame and burnout. From small-scale flame spread experiments of 4 kinds of textile membranes, the flame propagation ability were evaluated, which indicated that S6101 and X1400 could self-extinguish when away from fire, by contrast, S6003 and S6013 have strong flame propagation ability. With the analysis of relationship of length, time and temperature field, the pyrolysis region and the flame heating region of textile membrane spread in a linear trend, which is used to discuss the non-uniform heat flux to the surface for the correction of theoretical model.After overall stability analysis of air-supported membrane structure, three kinds of results for different fire scenarios could be obtained. When the fire source is set away from the membrane roof, no failure would be occured. When the fire source is closer to the membrane and lead to small burning through area, the pressure would decline slightly and then began to level off, which could not cause the complete collapse of the structure. When the flame is near the membrane to burn through a large area, inside pressure would drop dramatically and the overall stability of structure could not maintain any longer.