# Large-Scale 3D Multi-Story Enterprise Layout Design in a New Type of Industrial Park in China
## 7 Conclusions  
This study investigated the layout problem of enterprises in a new-type clustered industrial park. First, the association risk was defined, and the calculation formulas were given in combination with the QRA method and domino effect. Risk enterprises were divided into three types: fire risk enterprises, explosion risk enterprises, and other types. Subsequently, a BLINLP model was proposed to formulate the large-scale 3 DMSELD problem. In the proposed model, minimizing the total association risk was the upper-level goal. The lower-level goal was to maximize the rental profit of the park. However, the proposed model was difficult to get a global optimum as the problem size was large. In this sense, the decision variables were first transformed to reduce the problem scale. Then, an improved GA was applied. Finally, a case study of the Shunde Industry Park was conducted to validate the proposed model and approach. Two different scenarios were implemented, and critical parameters were tested to provide valuable management insights. Several insights on the theory and practice of the large-scale 3 DMSELD problem considering risk and profit are obtained based on the results in Section 6. First, the bi-level optimization theory represents the hierarchical relationship between layout objectives, which is rarely considered in the existing literature. This model prioritizes enterprise association risk affected by distance: the farther the distance, the smaller the association risk. Secondly, the strategy we propose solves the problem that it is difficult to obtain an optimal solution for nonlinear models built for large-scale problems. It can be seen from the tracking plots (e.g., Figure 9) that the optimal objective value change curve converges well, and the change amplitude is large. In practice, the proposed model and approach are suitable for modeling such problems. Optimal layout results can be obtained that greatly dramatically reduces the total association risk and improves the rental profit. From the layout results, it is found that it is imperative to consider the association risks in the actual layout problem. When laying out considering rental profit only, the risk increased from 350.6 to 2048.2, which validates the effectiveness of the proposed model. In particular, the model considers the impact of existing layouts that often appear in real-world scenarios. It can be seen from the simulation results that a unified layout for all enterprises is more conducive to reducing the overall association risk of the park. In addition, the number of risk enterprises and the size of the park have a significant impact on the total association risk, which is in line with our engineering experience. Finally, the rental profit to the park manager from non/low-risk enterprises is significantly affected by the layout results of the risk enterprises. As can be seen from the sensitivity analysis, rental profit fluctuates but does not change significantly. However, the lower-level layout can still improve rental profit (see Figure 4b). Despite these contributions and novelties, our study has several potential directions that can be further investigated. The layout results identify the floor on which the enterprise is located, but detailed explanations and constraints on single-floor layouts are lacking. Our work mainly focuses on the risks of fire and explosion, and there is a shortage of investigation on other risks. In addition, our study only considered the current risk level of the enterprise to be laid out; however, risk changes over its lifespan. Therefore, potential future work can be done to (a) add a single-floor specific location layout and form a multi-stage layout framework to solve the large-scale 3 DMSELD problem; (b) include other factors in the analysis, such as emergency facilities of risk enterprises and toxic and harmful gas leakage; and (c) study the risk changes during the lease period of enterprises and improve the layout model. Conceptualization, X.L. and X.G. ; methodology, X.L. and X.G.