Glued-in rods have been used for a number of years in several of the EU Member States which are active in timber engineering. They are an economically, architecturally and industrially attractive means of transferring forces within a structure, and of providing local reinforcement to critical zones of timber members. They also provide an important technology for the repair and upgrading of historically important timber structures which exist throughout Europe. Not withstanding their importance, internatonally acknowledged design rules for glued-in rods do not exist. The lack of standards and design rules within the field of glued-in rods lead to this project being initiated.

In this paper, bending creep test results from high-temperature (HT) dried Norway Spruce timber are presented. The results are compared with creep tests of conventional low-temperature (LT) dried timber. The HT drying was performed at 115°C and the LT drying was performed at 70°C. The creep tests were performed in a varying climate with 20°C and 30–90% relative humidity. A total number of 24 specimens, 45 × 70 × 1100 mm, were loaded in bending during approximately 240 days. Both the HT-dried and the LT-dried material were cut from the same four trees to have as equal raw material as possible for the two drying methods. The results show smaller bending creep deformations of HT-dried timber (approximately 30%) as compared to the LT-dried timber. The variation in magnitude of creep for HT-dried timber was equal to or smaller than for LT-dried timber. Additionally, the variation in deformation between the moisture cycles was smaller for HT-dried timber. These observations indicate a less pronounced mechano-sorptive effect for HT-dried timber. The free shrinkage in the grain direction was significantly smaller for the HT-dried material than for the LT-dried material.

Pine (Pinus sylvestris) and spruce (Picea abies) of Swedish origin has been heat-treated according to a process intended for above-ground end-uses. Tests have been carried out in order to study and evaluate the durability of the heat-treated material against decay and discolouring micro-organisms as well as technical and other properties, such as bending strength, stiffness, delamination of glulam, withdrawal load for fasteners and chemical emissions. The tests have shown that the bending strength has been reduced by approximately 50 % whereas the stiffness has been much less affected. Thus, the use of heat-treated wood where the strength is a decisive property should be carefully considered. There is an indication that the withdrawal load for fasteners for heat-treated wood is lower than for untreated wood. Gluing of heat-treated wood needs particular consideration, and PVAc adhesives seems to be unsuitable for gluing heat-treated wood. Chemical emissions (VOCs) were very low and will not be any major problem, providing proper conditioning is carried out after treatment. Heat-treated wood seems to be less susceptible to attack by discolouring micro-organisms than untreated wood. The decay tests in the laboratory and in the field have not yet given an unambiguous answer concerning the performance in various end-uses. However, the use of heat-treated wood in ground contact should be avoided.

Vinterns takras och andra händelser under det senaste decenniet, däribland problemen med de enstegstätade putsade regelväggarna, motiverar rubriken. Tillsynen i byggandet måste förbättras och det är dags att rusta upp den byggtekniska forskninger, skriver Carl-Johan Johansson och Ingemar Samuelson, SP Sveriges Tekniska Forskningsinstitut.

Det är inte bara den gångna vinterns takras som motiverar rubriken utan ytterligare ett antal händelser som inträffat under det senaste decenniet, däribland problemen med de enstegstätade putsade regelväggarna. Takrasen beror inte på att det kommit för mycket snö. I stället är det så att snön avslöjar slarv och okunskap. Tillsynen i byggandet måste förbättras och det är dags att rusta upp den byggtekniska forskningen.

Moisture content profiles with high spatial pixel resolution, 21 µm, were measured in Scots pine heartwood while drying from wet conditions to near equilibrium in the surface layer, (0–300 µm). The measuring technique used was Magnetic Resonance Imaging. In order to obtain magnetic resonance profiles with a high pixel resolution at both high and low moisture contents, a highg-radient permanent magnet was used. The results presented show one-dimensional moisture content profiles and mean moisture content development in the surface layer. In Scots pine heartwood, almost flat moisture content profiles were observed when the moisture content was above the fibre saturation level. When the mean moisture content in the surface layer decreases to the fibre saturation level, gradients start to build up from the surface towards the bulk of the sample although the bulk moisture content is far above the fibre saturation. Furthermore, the results presented in this study imply that a dry shell forms in the surface layer shortly after drying has begun. This dry shell controls the drying rate until the mean moisture content in the bulk decreases to the fibre saturation level.

Environmental-SvepElektronMikroskop, ESEM, har använts för att undersöka mikroautoradiogram av furusplint (Pinus silvestris L.) målad med en grundolja innehållande 14C-märkt alkyd. Mikroautoradiografi är en fotografisk metod som visar var ämnen märkta med radioaktiva isotoper finns i det undersökta materialet. De fotografiskt framkallade silverkornen i mikroautoradiogrammet visar var det märkta ämnet finns. Ej preparerade mikroautoradiogram undersöktes med ESEM, konventionella prepareringstekniker är tidsödande och kan orsaka oönskade artefakter. Det är bevisat att trästrukturen syns tydligt under den i huvudsak transparenta fotografiska filmen i mikroautoradiogrammet. Bilder framtagna med backscatter-detektorn hade hög kvalitet, silverkorn och trästruktur är synliga samtidigt och bilderna har nästan inga artefakter p g a uppladdningar, vilket inte är möjligt att uppnå med ett konventionellt SEM. Inträngning i trä undersökt med mikroautoradiografi kan sålunda enkelt utvärderas med ESEM.