Influence of loading ratio on flat slab connections at elevated temperature: A numerical study

Abstract

For reinforced concrete members subjected to high temperature, the degree of in-service loading, commonly expressed as the loading ratio, can be highly influential on the structural behaviour. In particular, the loading ratio may be pivotal in relation to the phenomenon of load-induced thermal strain. Despite its potentially pivotal role, to date, the influence of the loading ratio on both material and structural behaviour has not been explored in detail. In practice, real structures experience variation in imposed loading during their service life and it is important to understand the likely response at elevated temperatures across the loading envelope. In this paper, the effect of the loading ratio is numerically investigated at both material and structural level using a validated finite element model.The model incorporates a proposed constitutive model accounting for load-induced thermal strain and this is shown to outperform the existing Eurocode 2 model in terms of accuracy. Using the validated model, the specific case of flats slabs and the associated connections to supporting columns at various loading ratios are explored. For the cases examined, a marked difference in the structural behaviour including displacement direction was captured from low to high loading ratios consistent with experimental observations.

Bond behaviour of rebar in concrete at elevated temperatures: A soft computing approach

“…10 The failure mechanism of a RC member, including the bond between the concrete and steel, is affected by heat application; this is in part due to the concrete's temperature gradient. 10,11 Since there is a difference in heat conductivity between concrete and steel, this property can be influential during a fire because significant temperature gradients within the structural element can emerge. The resulting temperature change directly affects the compressive strength of the concrete due to the dehydration of the C-S-H gel and can induce thermal spalling.…”

“…The resulting temperature change directly affects the compressive strength of the concrete due to the dehydration of the C-S-H gel and can induce thermal spalling. The following factors have been identified as causes of thermal spalling: the heating rate that the concrete experiences, 12 the incompatibility of thermal strains of components (cement paste, aggregates, steel) or layers with various temperatures and coefficients of thermal expansion, 11,[13][14][15][16][17] and the pore pressure build-up induced by steam ejected during the dehydration of the C-S-H gel and portlandite 12 as well as CO 2 expelled during the calcination of limestone aggregates (in cases where limestone aggregates predominate). 18 When steel fibres are added to the concrete mix, the steel fibre content influences the temperature gradient as steel fibres, being distributed throughout the concrete section, distribute the heat much faster within the concrete.…”

“…Nevertheless, the bond between steel and concrete at high temperatures remains one of the least studied phenomena in concrete research 10 . The failure mechanism of a RC member, including the bond between the concrete and steel, is affected by heat application; this is in part due to the concrete's temperature gradient 10,11 . Since there is a difference in heat conductivity between concrete and steel, this property can be influential during a fire because significant temperature gradients within the structural element can emerge.…”

Vibrational Analysis of a Metallic Column Submitted to Mechanical Axial Load and Fire Exposure

“…Structural behavior under temperature change has been of number of analytical, computational and experimental studies performed by several researchers (Aditya 2021;Al-Hamd 2020;Yaobing 2018;Kingsley 2018;Abbas 2016;Harshad 2016;Feng 2012;Nubissie 2011;Mourão 2007;Liu 2006;Ribeiro 2005;Buchanan 2001;Rotter 2000). Mechanical machines often operate under diverse temperature conditions (Nubissie 2011).…”