# Large-Scale 3D Multi-Story Enterprise Layout Design in a New Type of Industrial Park in China
## 3 Problem Description
### Association Safety Risks  
The new-type clustered industrial park is a complex system in which enterprises are risk-related. This risk correlation can partially be explained by the domino effect. The occurrence of the domino effect is only possible when the energy of the initial accident is sufficiently large to affect other enterprises within the range. It is generally believed that the spread of an initial accident must at least cause a secondary accident to happen [25]. The association safety risk of Enterprise A to Enterprise B is the size of the risk faced by Enterprise B from Enterprise A. Unlike the domino effect risk, the association safety risk also includes the possibility that Enterprise A did not cause a secondary accident in Enterprise B but only led to harm Enterprise B. The impact of an accident in Enterprise A on Enterprise B is illustrated in Figure 1. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Article** & **Main Problem** &
\begin{tabular}{c} **Multi-Story** \\ **Layout** \\ \end{tabular} & **Risk** & **Profit** & **Cost \({}^{*}\)** & **Hierarchy** & **Approach** \\ \hline [PERSON] [4] & Industrial park layout & No & Yes & No & Yes & Single & Heuristic \\ [PERSON] [6] & Facility layout & No & No & No & Yes & Single & Heuristic \\ [PERSON] [24] & Process plant layout & Yes & Yes & No & Yes & Single & Exact \\
**This study** & **Industrial park layout** & **Yes** & **Yes** & **Yes** & **No** & **Multiple** & **Heuristic** \\ \hline \hline \end{tabular}  
* \({}^{*}\) does not include costs related to safety and risk but only the actual economic outlay.  
\end{table} 
Table 1: _Cont._  
Figure 1: Impact of an accident in Enterprise A on Enterprise B. Where \(P_{A}\) is the probability of an accident in Enterprise A, \(P_{AB}\) is the probability that an accident in Enterprise A causes a secondary accident in Enterprise B, \(C_{B}\) is the loss caused by the secondary accident in Enterprise B, and \(C_{AB}\) is the loss in Enterprise B caused by an accident in Enterprise A. It should be noted that \(C_{AB}\) may be 0. That is, an accident at Enterprise A will not affect Enterprise B. Risk can be expressed as a function of probability and consequence [50]. The association safety risk \(R_{AB}\) of Enterprises A to B can be calculated by  
\[R_{AB}=P_{A}P_{AB}(C_{B}+C_{AB})+P_{A}\overline{P_{AB}}C_{AB} \tag{1}\]  
From engineering experience and previous research, it has been found that the farther away locations are from the flashpoint of risk events, the less they are affected. However, the distance between multiple enterprises is unknown before the layout is implemented, and the specific location of the dangerous equipment is unknown. This article takes the enterprise as the smallest layout unit. The actual association risk assessment steps between enterprises were simplified to reduce the calculation scale and improve the feasibility of the layout model. The specific steps are as follows: (a) classify enterprises according to the category of the most severe risk event; (b) consider only the most severe risk event and assess the association risk when two enterprises are adjacent; (c) determine the diffusion coefficient functions for different risk events; (d) determine the association risk change between enterprises when the distance changes according to the risk diffusion coefficient function. The specific steps are as follows:  
(1) Step 1: Risk enterprise classification  
There are many types of enterprises in the new-type industrial parks, and accidents that may occur include fires, explosions, object strikes, electric shocks, and mechanical injuries. This study examines the interactions between enterprises. The domino effect is caused by the following physical effects: fire heat radiation, overpressure of an explosion shock wave, and propellant fragments. Accidents causing the domino effect can be divided into fires and explosions [25]. These two types of accidents are also the focus of our work.