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Advanced Modelling
(2019)
Engineering Modelling
(2019)
This chapter presents the most commonly used approach to analyse the
thermo-mechanical behaviour of concrete structures subjected to high temperatures as in the case of fire loading. Prescriptions of the Eurocode are detailed for the thermal as well as the mechanical analysis. Finally, recommendations from two national (Austrian and German) guidelines give some improvements for Underground infrastructure.
Although concrete in general is a non-combustible material, the fire resistance of concrete structures depends, to a large extent, on the mechanical material behaviour. Fire tests have shown that SCC is often susceptible to explosive spalling due to fire exposure, in a similar manner to HPC. But there are hardly any studies available that report properties of specimens at high temperatures.
This chapter report the most recent experimental results on mechanical behaviour at high temperature of high-performance concretes. After a short introduction, subsection 5.2 describes the main testing methods that were used in the analysed studies.
Sub-section 5.3 collects and compares; the temperature-dependency of the compressive strength and modulus of elastici1ty of many experimental studies. The influence of parameters such as the initial compressive strength, the type of aggregate, the presence of additions, the W/C ratio, the moishrre content and the way the mechanical test was performed is analysed. Sub-section 5.4 presents the experimental results obtained under a constant temperature, i.e. creep tests at high temperature.
Sub-section 5.5 presents experimental results obtained under increasing temperahrre.
These results allow assessing the free thennal strain of concrete (when no mechanical load is applied) and the so-called "transient the1mal strain". Finally, subsection 5.6 collects and analyses the few results conceming the temperature-dependency of the tensile strength of high-perfo1mance concretes.