Analysis of Pre-fabricated Timber Roof Truss

Abstract

Pre-fabricated timber roof truss made of glued laminated timber (glulam) may deem more efficient in supporting the load compared to similar truss made of solid timber. An analysis was conducted on single and double Fink trusses made of solid and glulam timber from selected Malaysian tropical timber with similar configurations. For solid timber truss, the timber used was Kempas from strength grouping SG2 whilst glulam, Mengkulang from SG5 was used since the glulam technology enhanced the strength properties of solid timber into two grades higher. Comparisons were made on the optimum sections designed for the trusses to support similar loadings. Various load patterns were also applied to the trusses to observe the worst-case scenario that resulted in the selection of the optimum sizes of each truss elements. The different combinations of load patterns, namely load applied on member and on node, with and without wind loads, and, symmetric and asymmetric loadings were analyzed. Two significant findings were observed in this analysis. First, glulam truss from a lower stress grade material can be of comparable structural performance to a solid truss from a higher-grade material. This can provide a cost-effective measure as alternative to solid truss since the differences in volume are small. Second, the worst-case scenario of load pattern for the truss for designed consideration is when the truss is symmetrically loaded on both nodes and members of the top chords and without the inclusion of wind load.

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