# Response of Seismically Damaged Steel Reduced Beam Section Joints under Fire
## 1 Introduction  
Fire after a major earthquake is an extreme event that has occurred many times with devastating effects [1; 2]. Steel structures are generally sensitive to fire due to the intrinsic limited thermal inertia, and their fire resistance can be significantly reduced if seismically damaged, as also shown by [1; 2; 3]. In fact, steel moment-resisting frames (MRFs) can dramatically lose their lateral rigidity and resistance following major earthquakes if plastic hinges form in the columns. Nowadays, capacity design rules are widely used to enforce the plastic deformations at the ends of the beams of MRFs, provided that the beam-to-column joints guarantee adequate ductility [4; 5; 6]. Many types of beam-to-column joints have been studied, verified and used in many applications [7]. Among them, dog-bone or reduced beam section (RBS) moment-resisting joints are brilliant solutions to decrease the demand on the column and optimize the design of the structures and their seismic response [8; 9; 10; 11]. Therefore, RBS have been largely used to guarantee strong column-weak beam behaviour, and many studies have been carried out to investigate their seismic behaviour [12; 13; 14; 15]. In order to enhance the capacity of the welded connection and the ductility of the RBS joints, rib stiffeners have been also studied by the authors of [15; 16], who verified the enhanced seismic performance of such stiffened RBS joints. [PERSON] and [PERSON] [17] also studied the seismic response of RBS joints with bolted web attachment and provided effective design criteria to promote a ductile response under seismic loading. [PERSON] and [PERSON] [18] tested twoRBS joints with extended endplate beam-to-column connection and European profiles, thus demonstrating the effectiveness of RBS application with European connections and steel profiles. [PERSON] et al. [19] proposed an optimization design procedure of RBS joints using genetic algorithms. More recently, [PERSON] and [PERSON] [20] performed a numerical study to investigate the seismic performance of novel replaceable RBS joints for steel moment-resisting frames. The concept of replaceable RBS joints also allows considering such detail as an alternative type of flexural damper for the mitigation of seismic effects in buildings that can be combined with other passive systems [21; 22].  
As it can be easily recognized, a large number of studies have been carried out to investigate the seismic performance and design of RBS joints. However, the response of seismically damaged RBS joints subjected to elevated temperature (e.g., the case of fire after an earthquake) has not been widely investigated, especially in the framework of Eurocode 8-compliant steel MRFs. Therefore, parametric finite element (FE) simulations have been carried to investigate such an open issue. In particular, a building archetype with perimetric steel MRFs was designed with welded and stiffened RBS joints according to Eurocodes and considered as reference case study. Both external and internal beam-to-column assemblies were sub-structured from the reference archetype. In particular, since no corner moment resisting bay was adopted, the external joints have a moment-resisting joint on one side of the column and a gravity load-resisting joint on the other side. Flush end-plate bolted connection was used for the gravity load-resisting joint. Different levels of seismic damage were imposed and three fire scenarios were considered.  
This study is summarised in the present paper, which is organized as follows: (1) the first part describes the reference archetype and the considered loading scenarios; (2) modelling assumptions and their validation are given in the second part; (3) the results of FE simulations are summarised and discussed in the third part.