A. O. Feio

Non-Destructive Evaluation of the Mechanical Behavior of Chestnut Wood in Tension and Compression Parallel to Grain

This article addresses the evaluation of the strength and stiffness of chestnut wood, in tension and compression parallel to the grain, using different non-destructive techniques (ultrasounds, Resistograph® and Pilodyn 6J). Approximately 200 timber specimens (divided into compression and tension tests) were tested up to failure, comprising recently sawn timber (which is now available on the market for structural purposes) and what was called old wood, obtained from structural elements belonging to ancient buildings. The possibility of predicting wood properties by application of non-destructive techniques is discussed based on simple linear regression models. Extrapolation of regression models obtained from recent cut wooden material to that obtained from old timber beams is analyzed. The results show reasonable correlations between mechanical elastic properties and non-destructive techniques (ultrasounds, Resistograph® and Pilodyn 6J). New and old wood mechanical data exhibited a scattered cloud of points, implying in terms of assessment of properties of timber elements in service by regression models that these models should not be supported only on data from recently sawn wood. Therefore, models combining information from new and old wood specimens are proposed based on lower 95% confidence limits of regression lines.

Selected solutions for rehabilitation of wooden structures : some portuguese case studies

Timber is one of the most used materials in the roofs and floors of monumental constructions in Portugal. The geometry is defined by elements that occupy a limited and well defined part of the tri-dimensional space, with a clear evidence of the hierarchy of the components. Timber elements are often visible, which allows easier conservation, identification of the wood species, characterization of details and evaluation of deterioration. Complex timber structures, such as those belonging to the roofs of large monuments, are often not easy to understand in a expedite way. As the coverings of monuments as cathedrals, public buildings, mansions or villas show very complicate features, not easy to be understood during the first inspection. This is not only due to the fact that the system is very elaborate and to the large number of members but also due to continuous changes and repair past works, mostly with additional stiffening or propping. The typical result of the history of the construction is the increase in the number and the heterogeneity of the members, together with a multiplicity of connections and diversity of supports. This means that the original must be distinguished from the additions and the replacements. This complexity makes the field of conservation of historical timber structures not only a challenge but a field much in need of modern research. The objective of this paper is to present some of the Portuguese experience in this field, showing how the rehabilitation solutions can be supported by the inspection techniques and by an extensive knowledge about the constituent material from which the structure was made, both from the mechanical point of view and from the physical point of view. A number of case studies will be presented to illustrate common conservation problems, and design problems as well as the possibilities and limitations of several solutions and to discuss the suitability of several intervention methods.

Feasibility of Creosote Treatment for Glued-Laminated Pine-Timber Railway Sleepers

This article studies the possibility of using market available glued-laminated timber (GLT) based on melamine-urea-formaldehyde (MUF) adhesives as an alternative to traditional solid timber sleepers. The study comprised an examination of the effect of creosote treatment on the short-term and durability after accelerated aging of the glue lines (delamination and shear strength) and the potential for full sapwood penetration by the creosote. Creosote treatment showed a negative effect on shear strength and delamination, more severe in the nonstructural than the structural GLT specimens tested. Full penetration of creosote into the sapwood was not achieved. GLT elements based on MUF adhesives can be considered an alternative to solid wood sleepers if specific grading of lamellas, proper treatment schedule, and highly controlled factory production are implemented.