Numerical modelling of slab-column concrete connections at elevated temperatures

Abstract

<p>Flat slab-column concrete frames are an economical type of concrete building. The main advantages of this type of frame structure are that they are easy to construct, relatively cheap to build and offer flexible column arrangement. However, they are susceptible to a type of failure known as “punching shear”, where columns “punch” through slabs. This is a particularly dangerous type of failure as it occurs suddenly. Punching shear occurring at high temperatures, such as in fire, is an obvious concern. This condition has been studied experimentally, but to date, there has been a very little numerical investigation of the topic. This paper presents a numerical study of the mechanics of punching shear failure at elevated temperatures, with a focus on the role of load induced thermal strain (LITS), which is shown to explain apparently anomalous experimental results.</p>

Novel shearhead reinforcement for slab-column connections subject to eccentric load and fire

“…Where; ε is the total strain, ε is the mechanical strain resulting from the mechanical load, ε is the thermal strain due to the material expansion, ε is the load-induced thermal strain resulting from the concrete shrinking under a high level of mechanical loading and ε is the creep strain that develops in the material due to external loading over time. The modelling approach adopted by Al Hamd et al [41,42] gives good results showing a close comparison with experimental data for ambient and elevated temperatures validation (further details on the model can be found in [41,42]). The same approach was applied to the models with shearhead reinforcement described in the previous section to examine the effect of the shearhead presence in the connection.…”

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

“…al. [9,10] which demonstrated more realistic results in capturing the structural behaviour of the slab-column connection. Although some limited experimental work has been conducted to examine the effect of loading ratio, no numerical study incorporating accurate capture of LITS has been carried out to date in this particular application.…”

“…Al-Hamd et al [9,10] put forward an explanation for the unexpected behaviour reported in the experimental tests conducted by [5][6][7][8] for the slab-column connections. The main reason for this behaviour is found to be the activation of one of the strain components (LITS) of the heated concrete generated under combined heating and high levels of loading conditions.…”

“…The modelling approach developed by Al-Hamd et al [9,10,30] steel rebar is assumed [30]. Whilst this is a simplification of reality, the approach was implemented by [30] for the specific case of punching shear and was shown to have a good agreement with corresponding test results within the level of accuracy of (0.73-8.14%).…”

“…away from the heating source rather than towards it. A recent study by Al-Hamd et al [9,10] concluded that the phenomenon of load-induced thermal strain (LITS), which is seen in heated concrete, explains the observed behaviour.…”