Abstract

At the beginning of 2023, the world was shocked by a catastrophic earthquake that occurred in Turkey and Syria. A huge number of victims and tens of thousands more injured as a result of large-scale destruction of buildings. At the same time, the destruction of houses occurred in many cities and in vast areas. We have seen all this from numerous news feeds in the media. However, it is enough to watch 3-5 videos to come to the conclusion that a large number of dead and injured is the result of the lack of reinforcement of buildings or the use of reinforcing bars of an inappropriate strength class and low quality. There are colorful examples (video from surveillance cameras) when houses simply crumbled and folded, as if they lacked reinforcement. At the same time, in the photo of the consequences of the earthquake, you can see that among the many collapsed buildings nearby are the surviving buildings. The latter indicates that the development was carried out according to different building codes using reinforcement of various strength and quality classes, or even its absence. All of the above suggests that, in the light of what happened, it is necessary to rethink the requirements for rebar for construction in seismically active regions, approaches to its production, application and control of mechanical properties.

Modern requirements for rebar to reinforcing bars are set out in national and interstate regulatory documents of various countries [1,2], which regulate the chemical composition of the steel used and the level of mechanical properties. The main characteristics that determine the applicability of reinforcing bars in construction are strength indicators-tensile strength (σin) and yield strength (σ0.2), and deformability-relative uniform elongation (δ_p) or total relative elongation at maximum load (δ_max). The level of the last characteristic is differentiated into three groups [1], which determines the applicability of rein-forcing bars for critical structures, depending on climatic and seismic conditions. For reinforcing bars with a strength of 400-600MPa, there are three categories of deformability-standard (δ_max≥2.5%), increased (δ_max≥5.0%) and high (δ_max≥7.5%). This article is the author’s private response to the consequences of a specific event of world significance-an earthquake in Turkey and Syria that occurred in February 2023. The practice of using reinforcing bars in structures for special purposes, or construction in different climatic regions, takes into account the use of bars with different levels of deformability (plasticity). Rolled products with plasticity δmax≥7.5% (high category of deformability) are considered the most reliable and are used for construction in regions with increased seismic activity. Achieving a high category of deformability is ensured by the chemical composition of steel and the technology for the production of rebar.

Keywords:Earthquake; Deformability; Carbonitride; Cold resistance