Numerical investigation of the effect of thermal stresses on the behavior of reinforced concrete wide beam-column connections

Fire is one of the risks that the study of its effects on different structures is essential. Fire can lead to extensive social and economic damage. Furthermore, knowing the extent of damage to concrete under heat can also help designers in the strengthening of structures. Connections are one of the most sensitive areas in all structural frames, steel and concrete, affected by large forces during earthquakes and their performance has a very important effect on the structurechr(chr('39')39chr('39'))s response. For this purpose, it is important to study the behavior of different types of beam-column joints in different environmental conditions. However, experimental and numerical data on the behavior of RC beam-column joints under high temperature are not available. In addition, due to the special feature of beam-column joints, ie passing part of the longitudinal reinforcements of the beam outside the connection spring, in this study, the behavior of beam-column reinforced concrete joints under the influence of thermal stresses has been investigated. In this research, 9 numerical models of wide beam-column joints under post-earthquake fire were investigated. After validation of modeled specimens, parametric study was conducted. Parameters such as wide beam height, beam reinforcement area, concrete grade and percentage of passing bars through the column core were studied. Results showed that with increasing the height of the beam, the fire resistance of the structure increases. Also, with increasing rebar area and concrete strength, the structurechr(chr('39')39chr('39'))s fire resistance increases. In addition, by reducing the rebar passing through the column core, the fire resistance of the structure is reduced. There is one thing in common in all these matters; all joints begin to form plastic joints at a temperature of about 450°C, and this temperature in the joints is formed about 200 minutes after the start of the fire.