Timber engineering has advanced over recent decades to offer an alternative to traditional materials and methods. The bonding of fibre reinforced plastics (FRP) with adhesives to timber structures for repair and strengthening has many advantages. However, the lack of established design rules has strongly restrained the use of FRP strengthening in many situations, where these could be a preferable option to most traditional techniques. A significant body of research has been carried out in recent years on the performance of FRP reinforced timber and engineered wood products. This paper gives a State of the Art summary of material formulations, application areas, design approaches and quality control issues for practical engineers to introduce on-site bonding of FRP to timber as a new way in design for structural repair and rehabilitation.

No abstract

This paper deals with the development of models for twist in structural timber. Twist was measured on 240 studs of Norway spruce (Picea abies). Several material parameters were also measured, such as spiral grain angle, shrinkage in all three directions, annual ring width and density. Twist in the studs was measured at four different times at different moisture contents. The amount of twist correlated well with the moisture content and was reversible throughout several moisture changes. When the moisture content decreased, the twist increased and vice versa. About 50% of the variation in twist could be explained by a single parameter, i.e. the average growth ring curvature. All studs with severe twist were cut with its centroid within a radius of 75 mm from the pith. A statistical analysis of the data shows that growth ring curvature and spiral grain angle together explained about 70% of the variation in twist. Other parameters, such as shrinkage strains, density and ring width, did not increase predictability. When using a model developed by Stevens and Johnston (1960), about 66% of the variation in twist could be explained. The model also explained twist quantitatively well. The model included curvature of the growth ring, spiral grain angle and the tangential shrinkage strain. Verwerfung von Fichtenschnittholz. Teil 2. Simulation der Verdrehung Diese Arbeit behandalt dia Entwicklung von Modellon fu Èr die Verdrehung in Schnittholz. Die Verdrehung wurde gemessen an 240 Fichtenkantho Èlzern (Picea abies). Mehrere Materialeigenschaften wurden ebenfalls gemessen, und zwar: Faserwinkel, Schwinden in drei Richtungen, Jahrringbreite und Dichte. Die Verdrehung der Kantho Èlzer wurde zu vier verschiedenen Zeitpunkten bei unterschiedlichen Feuchtegraden gemessen. Das Ausmaû der Verdrehung war gut korreliert mit der Feuchte. Mit abnehmender Feuchte stieg die Verdrehung und umgekehrt. Rund 50% der Verdrehungswerte sind durch einen einzigen Parameter erkla Èrt, na Èmlich die Jahrringkru Èmmung. Bei allen Kantho Èlzern mit starker Verdrehung lag die Mittelachse innerhalb eines Abstandes von 75 mm von der Markro Èhre. Die statistische Analyse ergab, daû Jahrringkru Èmmung und Faserwinkel zusammen ca. 70% der Variation der Verdrehung erkla Èren. Andere Parameter wie Schwindspannungen, Dichte und Jahrringbreite erho Èhten die Vorhersagbarkeit nicht. Mit Hilfe des Modells von Stevens und Johnson (1960) konnten rund 66% der Verdrehung erkla Èrt werden. Dieses Modell lieferte auch zufriedenstellende quantitative Ergebnisse. Beru Ècksichtigt werden dabei Jahrringkru Èmmung, Faserwinkel und tangentiale Schwindspannung.

No abstract

No abstract

No abstract

Stringer-to-floor-beam connections in riveted railway bridges have in many cases shown to be critical details with respect to fatigue. These connections, while generally designed with respect to shear forces alone, are often subjected to repeated outof-plane distortion as a result of their rotational stiffness. The behavior of double-angle stringer-to-floor-beam connections in riveted railway bridges is examined using finite element analysis. A series of static and fatigue tests was performed on three full-scale bridge parts taken from an old riveted railway bridge in order to study the response of these connections under the action of bending moment. The results of the analysis show that these double-angle "shear" connections are capable of developing appreciable moment due to the restraint they exert on the rotation of stringer ends associated with bending. The resulting bending and axial stresses in the angles and the rivets of the connection might consequently be considerable. High stress concentrations are also present in these components, which further increases their fatigue-damage susceptibility.

The mechanical and physical properties of modified wood were assessed experimentally. Timber studs with a cross-section of 45 mm×70 mm were modified on a semi-industrial scale by four different methods: 1) acetylation (AC) with acetic anhydride; 2) modification with methylated melamine formaldehyde resin (MMF); 3) heat treatment in vegetable oil (HT); and 4) furfurylation (FA). Sapwood of Scots pine (Pinus sylvestris) with test specimen dimensions of 10×10×200 mm3 was investigated. A total of 2449 specimens were included in the study. The following properties and their correlations were studied: density, modulus of elasticity (MOEdyn) measured dynamically, equilibrium moisture content (EMC), and swelling behaviour. The properties were measured at humidity levels of 30%, 65%, and 90% RH, while the temperature was kept constant at 23°C. Significant changes in material properties took place. AC increased the density and reduced MOEdyn, EMC and swelling strain. FA increased the density and the swelling coefficient and reduced EMC and swelling strain. HT reduced the EMC, while MMF modification increased it.