# Large-Scale 3D Multi-Story Enterprise Layout Design in a New Type of Industrial Park in China
## 3 Problem Description
### Association Safety Risks
New-type industrial parks typically contain multiple multistory buildings, and fires spread rapidly in high-rise buildings. Furthermore, some enterprises have pressure vessels, which increases the risk of explosion. Therefore, risk enterprises were classified according to the most severe dangerous events categories: (1) fire risk enterprises, (2) explosion risk enterprises, and (3) other types of risk enterprises. This study only calculates the fire and explosion risks separately and does not consider situations in which both occur simultaneously. (2) Step 2: Assessment of association risk with neighboring enterprises  
Many studies have conducted quantitative assessments of risk for fixed-location enterprises. [PERSON] [51] proposed a QRA method that combines a risk matrix, fault tree, and fishbone diagram model. First, the two enterprises to be evaluated are considered adjacent. The probability of a primary risk event occurring can be calculated based on a fault tree. The domino effect extension probability model [25] can be used to calculate the probability of accidents caused by other enterprises. The consequences of an accident can be analyzed using the Dao chemical index method. The risk matrix method can determine the probability and severity of the consequences. Finally, based on Equation (1), the associated safety risk when enterprises are adjacent is obtained. This method determines accident probability among enterprises by merely considering the occurrence of the most severe risk event. This moderately simplified approach aims to reduce the magnitude of computing complexity without losing the rationality of the enterprise layouts. (3) Step 3: Risk diffusion coefficient function  
The risk diffusion coefficient function identifies the degree to which the risk value decreases with an increase in distance from the risk event flashpoint and is a function of distance. The layout points used in this study were fixed. Thus, the distances are discrete and can be approximated as floor differences. (i) Fire risk enterprisesAccidents that cause fires can generally be divided into pool fires, jet fires, fireballs, and flash fires, and the main hazard is thermal radiation [28]. The point source model is simple, easy to manage, and widely used to calculate fire thermal radiation. [PERSON] [52] first hypothesized that the fire source was a point heat source and used the square ratio theorem to calculate the thermal radiation intensity at any target point around the flame. However, they did not construct a perfect mathematical calculation model. [PERSON] [53] set the location of the point heat source at half the height of the flame above the flame centerline based on their predecessors and derived a mathematical calculation model of the single point heat source model through theoretical derivation. [PERSON] [54] proposed a method for estimating the total radiant output of turbulent jet flames by measuring the radiative heat flux at a single location. This study examined the impact of enterprises that are distant and suitable for applying point source models. The general formula for the application of the single-point source model to thermal radiation in pool fires is  
\[I_{p}=\frac{Qt_{c}}{4\pi x^{2}} \tag{2}\]  
where \(I_{p}\) is the intensity of the thermal radiation at the target point, \(Q\) is the total thermal radiation of the pool fire, \(t_{c}\) is the thermal conductivity, and \(x\) is the distance from the target point to the center of the flame. The point source model reduces the flame to a radiant emission point in a spherical shape that radiates heat into the surrounding space based on the inverse ratio of the intensity of the thermal radiation to the square of the distance to the radiation source. The point source model is shown in Figure 2. Referring to the point source model, the fire risk diffusion coefficient function is defined as follows:  
\[\gamma^{f}\big{(}D_{ij}\big{)}=