Improvement of the mathematical model of the diagram of deformation of the compressed composite steel and concrete structures

Department of reinforced concrete and stone structures, Kharkiv National University of Civil Engineering and Architecture, 61002, Kharkiv, 40, Sumskaya Str., Ukraine

^* Corresponding author: sfomin@ukr.net

Abstract

The mathematical model of the stress-strain ratio of compressed concrete at elevated temperatures for composite structures described in Eurocode EN 1994-1-2:2005 Eurocode 4 divided in two stages: Stage 1 - represents the ascending branch and is defined by two parameters: compressive strength f_{c, θ} and corresponding deformations ε_cu,θ, stage II - the descending branch which is accepted for numerical methods. The design practice showed deficiencies in the provisions on models of deformation diagrams given in Eurocode 2. Part 1-2 General provisions. Structural Fire Design. (EN 1992-1-2:2004), (ENV 1992-1-2:1995), which were reflected in the national standards in the process of harmonization. A technique for determining the refined diagrams “σ_c,θ – ε_c,θ” was developed for the design of composite reinforced concrete structures in case of fire. Diagram parameter values were adjusted for concretes based on silicate filler at high temperatures, the mathematical stress-strain model of the concrete under compression and high temperatures was specified.