Journal of Emerging Trends in Engineering and Applied Sciences: Research Areas

Article Title: Analytical and Experimental Comparison of Deflection in Timber Double Chord Truss System
by Ezeagu C.A; Umenwaliri S.N. And Aginam C. H

Abstract:
This work first reviewed the use of timber in Nigeria construction industry and highlighted the great use of timber world wide. A comparison indicates that advances, enhancements and innovations have been made in countries like United Kingdom, Germany, India and France, in area of generic (improved) timber products - the structural composites, like laminated Veneer Lumber, Glue Laminated Lumber, complete concealed connections, plywood and plywood web beams, long span timber beam and trusses and that timber has been misunderstood, undervalued, underutilized and less appreciated in Nigeria. This work examined a total of five existing trusses: three trusses at a workshop found to have been 10 years in service and two trusses at existing classroom building found to have been 20 years in service. These roof trusses were specially designed on a double chord system mode to ascertain the serviceability of the trusses in terms of long span deflection and deformation which had occurred after 10 years and 20 years life cycle span. Furthermore, similitude models were developed using two computer aided soft wares (RISA-2D and Q-frame) packages and a manual calculation. The models results show that the maximum possible deflection of 0.016mm, 0.06mm and 0.0516mm are obtained in the three models are very negligible and within the permissible deflection limits of 0.4m (L/30) as stipulated in BS 5268 part 2 (structural use of timber 1996 code of practice) for permissible stress design and this agreed with the observed visual and experimental zero deflection of the existing trusses. This agreement helps to recommend the use and suggests the replacement of any existing mono trusses timber trusses with double chord systems and the special use of a termite resistant species (Ekhimi).

Keywords: comparison, deflection; model, timber and trusses

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