Fire Safety Science Digital Archive

Timber, one of the oldest structural materials, was used extensively in the construction of buildings before the development of other materials such as concrete and steel. Due to its combustible nature there have been frequent doubts concerning its performance in case of fire but experience has shown that large size timber sections are capable of giving a good performance. Conflagrations such as the Great Fire of London led to restrictions being placed on its free use but recently a more enlightened attitude is being taken. Despite its combustibility its use in buildings of certain types, particularly those intended for domestic occupancies, is permitted provided the design of the elements enables a speoified degree of fire resistance to be obtained. Over the last twenty years investigations have been undertaken on the fire resistance of timber elements, with the major emphasis on floors, beams and walls. Very little work appears to have been carried out on columns, with the exception of a few tests on solid sections 300 mm square by the Underwriter's Laboratories in U.S.A. Test data are also available on beams and floors for domestic purposes from investigations undertaken at Boreham Wood. One of the reasons for the lack of interest for a systematic study on timber elements, particularly columns, may have been the difficulty of obtaining sections without flaws, such as knots, shakes etc. and being able to specify their structural properties closely. Recently developed techniques of laminating sections, commonly termed 'glue-lam', have enabled larger sections of specified properties to be produced by permitting the use of selected grades of the material. Tests have been carried out by laboratories in Scandinavia and Germany on the performance of laminated beams which have indicated that the material is capable of giving a good performance under fire conditions. Laminated columns did not receive much attention in the course of these investigations; a few tests in France indicated that, when suitably designed, their fire resistance was similar to that expected from solid structures. As a result of discussions between the Joint Fire Research Organization and the Timber Research and Development Association (TRADA) a co-operative research programme on the fire resistance of laminated timber columns was formulated. In addition to providing basic data on the performance of columns, it was expected that information would be available for inclusion in the British Standard Code of Practice No. 112, which at present does not provide any data on the fire resistance of timber structures.