Fire resistance of timber-concrete composite slabs

Abstract

The paper presents a simplified method for calculation of resistance of a TCC slab in fire conditions.Within the method the tensile and the compressive failure criteria in the outermost fibres of the cross-section are checked. The influence of the fire is applied through one-dimensional charring of the timber part of the cross-section in accordance with current standards on reduction of properties of materials. The concrete-timber connection is assumed to be ideal during the determination of resistant moment of the TCC cross-section. On the other hand, the calculation of the deflection of the TCC slab is conducted with the reduction of the connection's rigidity. The ineffective zone of the timber as well as the cracked tensile zone of concrete part do not contribute to the effective stiffness of the TCC slab. The method is validated against the results of full sized fire tests of one way spanning TCC slabs form literature. Calculated and experimentally determined midspan deflections and failure times of the TCC slabs are compared and their considerable agreement is observed. Due to its convenience and accuracy, the present simplified method represents a useful tool for designers of TCC structures in fire conditions.

Timber-Concrete Composite Structural Elements

“…Another approach includes a crude simplification and completely disregards slip in the connection. Thus, Bernoulli hypothesis can be applied and stress distribution over TCC cross-section in ULS (due to exceeded tensile or compressive bearing capacity) can be determined, see e.g., [21,27]). The advantage of this method in comparison with the gamma method is in possibility to consider cracking of concrete as a result of exceeded tensile strength.…”

“…Thus far, behaviour of TCC structural elements in fire has been extensively experimentally investigated [20] and both analytical simplified methods and numerical methods for fire safe design have been developed, see for example [19,21,22], respectively. However, the variety of designs and complexity of behaviour of TCC structural elements in fire conditions calls for further research.…”

Variations of moisture content in manufacturing CLT-concrete composite slab using wet construction method

“…This structure is a promising and feasible solution that can compete with steel and reinforced concrete structures in some applications. In particular, the TCC floor system has a higher fire performance than the only timber floor system, and the studies on such improvement in fire performance and fire conditions play a part in increasing mass timber buildings (Frangi et al 2010;Ogrin and Hozjan 2020). Therefore, the construction of eco-friendly high-rise buildings using CLT-concrete composite (CCC) slabs is increasing worldwide (Harte 2017;Mai et al 2018;Timmers and Jacobs 2018).…”