PSI - Issue 48

Arifin Nurcholis et al. / Procedia Structural Integrity 48 (2023) 33 – 40 Nurcholis et al. / Structural Integrity Procedia 00 (2023) 000–000

34 2

1. Introduction Ships and offshore buildings are structures that are significantly at risk of experiencing a fire, and it will be tough to predict structural failure due to various loadings [Cao et al., 2016; Prabowo et al., 2017; 2018; 2019a,b; 2020; 2022; Smaradhana et al., 2021; Alwan et al., 2022; Ansori et al., 2022; Do et al., 2022; Nubli et al., 2022; Carvalho et al., 2023; Faqih et al., 2023; Pratama et al., 2023]. One of them is fire because many conditions are connected by fire triangles (oxygen, heat, and fuel) that exist in several critical locations/compartments during the operations of ships and offshore structures. [Gillie, 2009; Imran et al., 2015; Gravit and Dmitriev, 2021]. In the cases of offshore and shipbuilding, fires are the worst case that occurs in sea transportation which causes ships to disappear, cargo to be lost, endangered safety, and very likely cause human death [Luo and Shin, 2019; Wang et al., 2021]. Therefore, when a fire occurs, the structure of the ship and offshore buildings must withstand the load and at least it can give time for the users to be evacuated. Each system usually has standardized fire resistance; one example is using a standard fire resistance test [Zhang et al., 2016]. The frame is the main structure that holds the heaviest loads in offshore ship and building construction. Most offshore building frames and ship structures are composed of iron, an excellent heat-conducting material. Iron is a material that will experience a decrease in mechanical properties as the temperature increases [Qiang et al., 2013; Zhang et al., 2013; Tepperneg et al., 2016]. The structural response to fire heat can be tested using a standard fire test [Zhang et al., 2015; Gillie, 2009]. However, structural response testing using the traditional fire test method has received a lot of attention from structural engineers and fire dynamics engineers; from a structural point of view, the standard fire test is considered to oversimplify the problem because it thinks the temperature of the fire during a fire to be linear, so the conditions are very unrealistic. In structural fire engineering, three things must be considered: modeling fire exposure, modeling thermal insulation, and modeling structures' response to fire exposure [MacIyntre, 2022a]. Currently, 16 fire standards use a calculation basis, making it possible to analyze the structural response to fire using the FEM method. To determine the response of a structure to fire, the analysis can use direct modeling or a time-equivalent approach. Modeling directly is complex and challenging to do [MacIyntre, 2022b]. Therefore, this paper uses the equal time approach, simplifying the structure by involving forces acting on other structural components. The main focus of this paper is to determine the response of structural pieces from offshore buildings and ships to exposure to fire. 2. An example problem 2.1. Idealized structure geometry and loading A simple bar, 1000 mm long and having a cross-sectional area of 35 mm x 35 mm, as presented in Figure 1, bears a distributed load of 4250 N/m. Because the rod is a piece of structure and has axial flexibility, the ends of the rod are supported by pinned supports, and the rod has an axial stiffness of 190181250 N/m.

Figure 1. Beam dead-load scenario.

2.2. Fire scenario and material properties

In the case of a fire accident, the structure undergoes a process of heating, then cooling so that the system will experience expansion and shrinkage again; the shrinkage experienced by the structure depends on the maximum temperature of the structure when a fire occurs [MacIyntre, 2022a].