**1. Introduction**

Bridges are an important part of modern city construction. Once a fire hazard occurs, it will cause great losses. On 31 August 2004, a car burst into flames on a double-deck road bridge in Imphal in northeast India, causing an explosion that paralyzed the surrounding road system and caused extensive damage. In a fire event, the mechanical properties of the bridge decrease rapidly as the temperature increases. Therefore, it is vital to study the temperature variation characteristic of bridges under fire hazard.

The influence of fire hazards on bridges has been previously discussed by scholars. Garlock et al. [1] presented a detailed review of actual fire incidents, case studies related to fire hazards, and post-fire assessment and repair strategies for bridges. Their study pointed out that the number of damaged bridges caused by fire is nearly 3 times more than that caused by earthquakes. Peris-Sayol [2] analyzed information related to 154 cases of bridge fire, proposed classifying the damage levels suffered by a bridge during fire, and established the main factors involved in bridge fire damage. Mendes [3] and Fernando [4] et al. conducted a numerical simulation of a ship fire after the cable pylon of the Vasco da Gama bridge was hit by ships and obtained the temperature field and fire resistance time of the main beam section of the cable-stayed bridge under such a fire scenario. Bennetts

**Citation:** An, W.; Shi, L.; Wang, H.; Zhang, T. Study on the Effect of Bridge Deck Spacing on Characteristics of Smoke Temperature Field in a Bridge Fire. *Fire* **2022**, *5*, 114. https://doi.org/ 10.3390/fire5040114

Academic Editors: Chuangang Fan and Dahai Qi

Received: 26 July 2022 Accepted: 8 August 2022 Published: 12 August 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). *fire*

et al. [5] conducted a simulation analysis on three fire scenarios for cable-stayed bridges without fire prevention design of the main tower, providing the actual time when the main tower was subjected to different ratios of ultimate load with or without fire prevention. Smith et al. [6] conducted a risk and vulnerability assessment (RVA) during the design and construction of four cable-stayed bridges in the United States by considering main tower protection, bridge deck stability, cable loss, fire prevention, and other factors, and put forward different mitigation decisions. Although the current design guidelines lack specific suggestions on how to deal with different security-related risks, designers need to ensure that the risk assessment level is enough. Ataei et al. [7] adopted the nonlinear finite element modeling and analysis method to study the influence of hypothetical fire and temperature gradient propagation along a cable and studied the influence of fire intensity and fire duration on cable strength loss by using the finite element method.

Accordingly, although many scholars have studied bridge fire, most research focuses on the influence of high-temperature fire on mechanical properties. For steel bridges, however, the critical buckling stress of the bridge is reduced greatly due to the rapid increase in temperature. This study focuses on a steel bridge in Guangzhou, China, i.e., the Shiziyang bridge, which is in the design stage. Fire Dynamics Simulator (FDS) is used to simulate the smoke temperature field of this double-deck bridge during fire to study the temperature variation of the ceiling and truss. On the one hand, the variation rule of the smoke temperature field with the change of bridge deck spacing is obtained in this paper. It is helpful for designers to choose the best bridge deck spacing for the Shiziyang bridge to achieve a balance between fire safety and economy. The temperature field of different components and different positions of the bridge is also obtained, which provides guidance for the Shiziyang bridge to adopt a zoning fire resistance scheme, i.e., different fire resistance strategies for different zones. On the other hand, there is no relevant code concerning bridge fire protection in China. There is also no basis for fire detection, fire resistance design, and safe evacuation, which are closely related to the smoke temperature field. Therefore, this study can provide basic theories and data for the establishment of bridge fire codes.
