SUMMARYA research project was carried out at the Swiss Federal Institute of Technology (ETH) to study the fire behaviour of hollow core timber slabs and timber-concrete composite slabs. This paper describes the main results of the basic fire behaviour of timber measured in the study. The first part of the analysis looks at the charring rate of timber. In the second part a new calculation model for the temperature development in wood members exposed to the standard ISO-fire is presented and compared with the fire test results.

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In recent years the refurbishment of old buildings with timber floors has drawn attention to an efficient type of floor system, the timber-concrete composite slab, which consists of timber members in the tensile zone, a thin concrete layer in the compression zone and the connection between timber and concrete. Besides the beam type floors ( Fig. 1 right), slab type floors as shown in Fig. 1 (left) are common. Compared to timber floors, the main advantages of this type of composite structure are increased strength and stiffness, improved sound insulation and fire resistance.The structural behavior of timber-concrete composite members is governed by the shear connection between timber and concrete. If the action effects on the connection remain within the linear elastic range until the timber members fail, a linear-elastic behavior of the composite structures may be assumed. If, on the other hand, the connectors reach their load carrying capacity, the outer connectors deform plastically and a non-linear behavior of the composite structures should be considered.Bending tests demonstrated that nonlinearities certainly influence the structural behavior of the tested timber-concrete composite beams at higher load levels. For this reason the linear-elastic model g-method according to Eurocode 5 [1] will not give an accurate prediction of the load-bearing capacity of the tested timber-concrete composite beams. Therefore, a new elasto-plastic model was developed, taking into account the ductility of the connectors. The new elasto-plastic model considers the behavior of the connection by assuming of a rigid-perfectly plastic load-slip relationship of the connectors making the calculation easier for the designer.The first part of the paper looks at the elastic behavior and modeling of timber-concrete composite beams, in the second part the elasto-plastic calculation method for timber-concrete composite members is presented and compared to test results. SummaryThis paper describes an elasto-plastic model for timber-concrete composite beams with ductile connection. The first part looks at the elastic behavior and modeling of timber-concrete composite beams, in the second part an elasto-plastic method for timber-concrete composite beams with ductile connection is presented and compared to test results.

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Cross-laminated solid timber panels represent an interesting technical and economical product for modern timber structures. The use of large prefabricated cross-laminated solid timber panels for load-bearing wall and floor assemblies has become increasingly popular in particular for residential timber buildings. The fire behaviour of cross-laminated solid timber panels has been experimentally and numerically studied during two different ongoing research projects carried out at the Institute of Structural Engineering of ETH Zurich, Switzerland and the Trees and Timber Institute CNR-IVALSA in Trento, Italy. The paper presents the main results of the experimental and numerical analyses. Particular attention is given to the comparison of the fire behaviour of cross-laminated solid timber panels with homogeneous timber panels.The results of the analysis have shown that the fire behaviour of cross-laminated solid timber panels depends on the behaviour of the single layers. If the charred layers fall off, an increased charring rate needs to be taken into account. The same effect is observed for initially protected timber members after the fire protection has fallen off. Thus the fire behaviour of cross-laminated solid timber panels can be strongly influenced by the thickness and the number of layers. Further vertical structural members (walls) may show a better fire behaviour in comparison to horizontal members (slabs).