INSPECTION, CHARACTERIZATION AND STRUCTURAL ANALYSIS OF TIMBER ROOF TRUSSES: A CASE STUDY IN URUGUAY

5^th International Conference on Structural Health Assessment of Timber Structures. SHATIS´2019. 25-27 September 2019, Guimarães, Portugal

Abstract

Introduction: Maintenance is an essential task to extend the service life of buildings; and yet, not well attended in Uruguay. This fact has led to the development of timber structures with assorted problems related to humidity. The warehouse presented in this paper was built at the beginning of the 20th century. Its roof is supported by trusses, made of sawn timber pieces joined by traditional woodworking joints. Due to some roof leaks and a reform project that modified the structural loads, the owners requested us a roof inspection and rehabilitation proposal. To fulfill this, we set three objectives: first, to inspect the trusses; second, to characterize the timber —since no records of the original project were founded—; and third, to analyze the structure with the new loads.

Developments: We started visually inspecting the trusses to detect the damage caused by biotic agents and to propose its reparation. Then, we estimated the timber mechanical properties destructively (by longitudinal compression tests of small-scale wood specimens) and non-destructively (by wave propagation testing techniques). Finally, we analyzed and checked the trusses in both the ultimate and serviceability limit states, after placing the projected new covering.

Remarks and Conclusion: Since some of the encounters between the trusses and the walls showed active attacks of fungal rot (brown rot), we recommended the elimination of the damaged areas and the reinforcement of the corresponding joints. Based on the destructive and non-destructive tests, we estimated the mechanical properties of the timber to be those of a C24 strength class —though denser (610 kg/m³). Regarding the structural analysis, we observed that the new roof covering (new loads configuration) and the stresses fluctuation due to suction wind could critically affect the structural behavior of both the woodworking joints and the trusses elements.