Timber/steel composite members in multi-storey buildings under standard fire test loadings

Multi-storey buildings can be designed using vertical and horizontal tying elements to limit disproportionate collapse, however there is a concern in relation to potential brittle and/or early failure of timber post and beam... [ view full abstract ]

Multi-storey buildings can be designed using vertical and horizontal tying elements to limit disproportionate collapse, however there is a concern in relation to potential brittle and/or early failure of timber post and beam buildings. This paper sets out to assess the potential benefits of incorporating steel sections into timber gluelaminated members used in beam and post structures. The investigation involved identifying the tensile capacity of the members, intended as tying members in an accidental event involving a standard fire. Laboratory testing of these composite Sitka spruce/steel beams was undertaken using the ISO 834 standard fire curve. Three-dimensional, thermo-mechanicals models were also developed to identify the time timber and the timber/steel composite members could sustain the required tensile load in a fire condition. The finite element software package ANSYS was used to model the members and the results obtained compared to the laboratory tests carried out. It was found that the duration the composite members sustained the tensile load was significantly longer than pure timber members, as well as providing ductility into the structural system. The inclusion of a steel core within an insulating timber beam would also allow for more secure end connections at the column locations.