# Theoretical and Numerical Simulation Research on Fire of Large-Span Spatial Structures
## 5 Conclusions  
At present, the large-span spherical dome steel structure is widely used, but there are few studies on the fire of large space spherical dome buildings with smoke exhaust at the top. At the same time, all the large space two-region prediction models do not consider the distribution of temperature. Therefore, examining the effects of varying natural air inlet  
Figure 34: Calculation process. Figure 35: Modified temperature curves with height (80 m span). areas on the fire temperature field and smoke flow within a 60 m-span large-span spatial structure equipped with natural smoke exhaust, this study employs the two-zone model to analyze smoke flow and heat transfer during a fire in structures with top openings. The traditional plume model's velocity formula is enhanced, and a method is proposed for theoretically determining the maximum temperature attainable in such structures during a fire by simplifying the spatial temperature field distribution. Consequently, a logarithmic curve model is derived innovatively, correlating the maximum post-fire temperature with vertical height, which accurately predicts the maximum temperature within the structure. (1) In large-span spatial structures with top openings, the top opening and air supply outlet significantly influence the internal temperature field distribution, which can be segmented into areas within and outside the flame zone. The equilibrium temperature value primarily dictates the fire temperature rise curve's maximum difference. An increase in the air supply outlet area boosts the smoke exhaust volume, effectively reducing the temperature and thickness of the smoke layer. (2) During fire heat transfer in large-span spatial structures with top openings, the total heat release rate of the fire source is partitioned into convective and radiant heat flows, with a substantial portion being carried away by the gas exiting through the opening. The temperature within the flame zone diminishes with height, while the central velocity of the fire plume initially increases and then decreases with height. A fitting formula is proposed for the central velocity of the fire plume, adapted from the traditional plume model, which is well-suited for spherical dome space structures with top openings, demonstrating a satisfactory fit. (3) The temperature field distribution beyond the flame zone exhibits uniformity in the horizontal direction and primarily vertical non-uniformity. Based on these characteristics, a regional model is established within the structure for the fire environment post-quasi-steady state. This model, preliminarily formulated using the average, maximum, and initial temperatures of the smoke layer, accurately delineates the temperature variation within the structure in relation to height during a fire. Under real fire conditions, the ambient wind and the structure will have a great impact on the natural smoke exhaust flow and the air temperature field in the space, making the occurrence of fire random. However, this paper does not analyze the temperature field of building fire under the coupling of wind and fire, nor does it consider the impact of real structures and the issues of reinforcement after fire. Numerical simulation may be relatively idealistic and may not take into account precise boundary conditions. In the future, the influence of external wind on the fire temperature field of large-span spatial structures should be studied, and calculations should be conducted on real structures. Further, after conducting extensive numerical simulation analyses, experimental validation will be carried out to verify the accuracy of the computational model so as to provide a scientific basis for the fire protection design of large-span spatial structures or for the reinforcement issues after fire, as well as the assessment of the fire scale that such structures may encounter. Conceptualization, G.S. and J.W. ; methodology, X.Z. ; software, X.Z. ; validation, G.S., S.X. ([PERSON]) and S.X. ([PERSON]); formal analysis, S.X. ([PERSON]); investigation, S.X.