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Diagnosis of failures in wood beams from historical house in Banská Štiavnica – Relations between ultrasonic measurements and bending properties
2010 - IRG/WP 10-20437
Various degrees of rot and other damages in ceiling beams with dimensions of 6500-8800 x 160-200 x 240-310 mm (length x height x width) situated in one historical bourgeois house in the UNESCO town Banská Štiavnica, Slovakia were determined visually and by the PUNDIT-plus ultrasonic device. Subsequently, for seventeen of the most bio-damaged fir (Abies alba Mill.) beams chosen for exchange were carried out other ultrasonic tests and also “in vitro” ultrasonic and bending tests on small specimens (300x20x20 mm). “In situ” measurements have shown that the lowest velocity of ultrasonic waves is usually in the ends of beams, i.e. in their direct contact with walls it was only 300-400 m/s, while 0.5-1 m from their ends it was usually higher from 700 to 1100 m/s. “In vitro” measurements (the modulus of elasticity determined either by ultrasonic test – Ed, or by bending test – E; the bending strength “modulus of rupture” – fm) depended significantly on the density of tested fir specimens. High correlations were observed also between values of the dynamic and static modulus of elasticity, and between values of the modulus of elasticity and values of the bending strength. Achieved “in situ” and “in vitro” results could help at evaluation of bio-damages in other wooden heritage structures, as well.
L Reinprecht, M Pánek


Fumigation as a remedial treatment: A review of North American literature
1983 - IRG/WP 3253
The development of the use of fumigants for eliminating decay in timber and roundwood in North America is reviewed. Initial experiments on oak wilt identified volatile chemicals which eradicated decay in roundwood. Subsequently, extensive experimentation on Douglas-fir poles in service showed that treatment with chloropicrin eliminated internal decay for more than ten years. Vorlex was also quite effective, but Vapam appeared to be much less effective, with decay fungi becoming re-established within ten years of treatment. Studies on other wood species indicated that fumigation could be successfully used to treat resistant species such as western red cedar. Fumigation of glulaminated beams and large timbers with chloropicrin, showed that internal decay could also be eliminated in these products, although wrapping the beam in polyethylene was beneficial for optimization of the treatment. Bioassay techniques have been reported for successful monitoring of fumigant vapor concentrations in treated poles.
J N R Ruddick


Diffusion of bifluorides and borates from preservative rods in laminated beams
1991 - IRG/WP 3644
Laminated beams from spruce, pine and larch were treated with two preservative rods, based on bifluorides and octaborate respectively. After 3 and 6 months placed in different climates (65% r.h., 100% r.h., water) the diffusion of the active ingredient was measured. After the 6 months period, the diffusion of the bifluorides was, in all species, ca. 5 times larger than the diffusion from octaborate rods. The bifluorides were not hindered by the glue-lines. The diffusion of the borate was poor, mainly perpendicular to the grain and was hindered by the glue-line.
H Militz


A laboratory evaluation of the susceptibility to biological attack of glued laminated pine timber
1991 - IRG/WP 2387
In the scope of a research programme concerning the use of maritime pine (Pinus pinaster) to produce glued laminated timber structures in Portugal, the natural durability of this material was checked by using laboratory test methods. An European standard, EN 113, was used to test durability against basidiomycetes and a test method developed at LNEC for termites was adapted for this purpose. From the results obtained, it seems that the existence of glue layers does not influence the natural durability of the material under basidiomycetes attack. As for termites the method used indicates that they are unable to cross the glue layers though this effect would hardly be of importance for practical uses.
L Nunes, H Cruz


A deflection test for monitoring decay in miniature beams
1986 - IRG/WP 2269
A laboratory apparatus for assessing decay in small stakes is described. It involves the measurement of deflection in a static bending apparatus using a displacement transducer linked to a microcomputer. Measurements are non-destructive, rapid, accurate and automatic and decay can be assessed repeatedly over long time periods.
S M Gray


Essais de collage de bois traités pour la réalisation d'éléments de charpente lamellées. (+ abstract dated September 1971, Influence du traitement de préservation sur le collage d'éléments de charpente lamellés collés et efficacité vis-a-vis de larves néonates)
1971 - IRG/WP 203
Le but du travail est de vérifier les propriétés générales d'une poutre lamellée collée après traitement des éléments la composant au moyen de formulations insecticides et fongicides commerciales à solvant clair dans les conditions les plus usuelles de fabrication. Les essences utilisées ont été: Epicéa - Pin sylvestre - Sapin de Douglas en planches rabotées de 80 cm de long, 14 cm de large et 20 mm d'é-paisseur, à environ 12% d'humidité, collées après traitement avec une colle de type résorcine - formol du commerce à raison de 6 éléments pour former une poutre expérimentale. Les produits de traitement ont été au nombre de 4, commercialisés -couramment utilisés sur le marché français. Ces produits seront appelés A - B - C - D. Ils appartiennent tous au type organochloré en solution dans un solvant organique, les adjuvants et solvants pouvant être différents. En général, les planches utilisées étaient débitées sur faux-quartier et comportaient essentiellement du bois parfait, la proportion d'aubier en bord état souvent peu importante. Une première mesure sommaire de l'absorption de chaque planche en produit de préservation a été effectuée par pesée. Les essais suivants ont été poursuivis après collage: Résistance à la délamination - Résistance de cisaillement en compression et pourcentage d'adhérence. Les essais biologiques ont porté sur la mise en présence des zones externes des poutres (zones aubieuses pour les essences à aubier distinct et attaquable) avec des larves néonates de Capricorne des Maisons. Les premiers résultats dépouillés permettent de penser qu'aux faibles doses utilisées les propriétés mécaniques des poutres restent satisfaisantes. Après observation du comportement des larves néonates, des dosages chimiques vont être effectués afin d'établir le seuil d'efficacité des quatre produits.
J Guillemain-Thévenot


Borate diffusion in wood from rods and liquid product. Application to laminated beams
1988 - IRG/WP 3482
In the aim to use borate preservatives (fused rods and boracol) in fields of building construction other than external joineries, tests of diffusion of borate rods and secondary boracol, were carried out on different species of woods exposed to different moisture conditions. Tests were also applied on laminated beams very often subjected to high moisture contents and thus decay of rot fungi. Diffusion was tested in different conditions and in relation, the action of these products was tried with stains and resins for improving strength properties. Diffusion tests on several species of wood confirm the proportionality already observed between moisture content and diffusion of borates in wood for all species. In a short time, test of diffusion on laminated wood showed a good diffusion in two lamella along the glue line leading to another way of boring. There is no problems between these borate products and stains or resins.
D Dirol


Laboratory evaluation of termite resistance of five lesser-known Malaysian hardwoods used for roof and ceiling construction
2001 - IRG/WP 01-10398
The general laboratory procedure of AWPA E1-97 was used to evaluate the termite resistance of 5 lesser- known species (LKT) of Malaysian hardwoods: Kekatong (Cynometra sp.), Kelat (Eugenia spp.), Mempening (Lithocarpus spp.), Perah (Elateriospermum tapos) and Pauh Kijang (Irvingia malayana) against the subterranean termite Coptotermes curvignathus over 28 days. Kempas (Koompassia malaccensis) and Rubberwood (Hevea brasiliensis) were included for comparison with these LKT. Employing the AWPA five-point visual rating scale of termite resistance of wood material, Rubberwood and to an extent Mempening, were the least resistant (rating 4-7), Kekatong was virtually immune (rating 9) to the Coptotermes species, while Kempas, Kelat, Pauh Kijang and Perah sustained between light-to- moderate attack (rating 7-9). There was a tendency for higher final wood moisture content, higher mass loss or reduced termite mortality to correspond with the lower visual ratings (low termite resistance) generally. In-ground natural durability test results did not correlate with mass loss or visual rating data from the laboratory test.
A A H Wong, Kee Suan Cheok, J K Grace


Influence of preservative treatment on the glueing of the members of glued laminated frames and effectiveness with respect to newly hatched larvae of the house longhorn beetl
1971 - IRG/WP 203 E
The object of the work is to check the general properties of a glued laminated beam after treatment of the members composing it by means of commercial insecticidal and fungicidal formulations in clear solvent under the most common conditions of manufacture. The species used have been spruce, redwood and Douglas fir in planed boards of 80 cm long, 14 cm wide and 20 mm thickness at about 12% moisture content, glued after treatment with a commercial glue of the resorcinol-formaldehyde type at the rate of 6 laminates to make one experimental beam. The treatment products have been 4 in number, commercialized and readily available on the French market. These products will be called A-B-C-D. They all belong to the organochlorine type in solution in an organic solvent, the other material and solvents being allowed to be different. In general, the boards used were composite cut and comprised essentially of heartwood, the proportion of sapwood at the edge being often of little importance. A preliminary initial measurement of the absorption of the preservative product by each board was made by weighing. The following tests have been persued after gluing. Resistance to delamination - Resistance to shearing in compression and percentage of adhesion. The biological tests have been carried out by exposing newly hatched larvae of the house longhorn beetle on the external zones of beams (sappy zones for the species with sapwood distinct and susceptible to attack). The first results scrutinized permit us to think that with the weak amounts used the mechanical properties of the beams will remain satisfactory. After observation of the behaviour of the newly hatched 1arvae, chemical quantitative analyses are going to be undertaken in order to establish the threshold of effectiveness of the four products.
J Guillemain-Thévenot


Bending strength of heat-treated spruce and pine timber
2002 - IRG/WP 02-40242
Heat-treatment of spruce (Picea abies) and pine (Pinus sylvestris) beams (45 x 145 mm) gave a reduction in bending strength of approximately 50%. The bending stiffness (modulus of elasticity) only decreased by 3.5%. Tests were carried out according to EN 408. Another effect of the heat-treatment was increased variation in bending strength. The 5th percentile value of the bending strength, the so called characteristic value, decreased by 66% for spruce and by 55% for pine after heat-treatment. The study consisted of 200 spruce beams and 200 pine beams of Swedish origin. Half of the material was heat-treated and the other half was used as controls. The heat-treatment was carried out in a steam chamber in Finland at a maximum temperature of 220°C. The level of treatment was assumed suitable for above ground end uses. When storing the material in a climate that was approximately 20°C/65% relative humidity the heat-treated material reached an equilibrium moisture content of 3-3.5%. For the untreated material corresponding figure was 12-12.5%. The dry density for the heat-treated material decreased by approximately 7.5% compared to the untreated material.
C Bengtsson, J Jermer, F Brem


Preservation of coppice wood for the fabrication of glued beams or panels
1987 - IRG/WP 3427
In this survey we will examine the specific problems concerning the conservation and the preservation of timber (issued from trunks of small diameter corresponding to products of clearings or coppices) destined for the fabrication of solid reconstituted elements. Thus for six metropolitan species of wood, we first characterized the biological deteriorations which occur after felling and their kinetics with respect to the exploitation period. We then defined two methods of treatment adapted to coppice timber, i.e. methods which are efficient and compatible with gluing and finishings. The efficiency of the treatments (applied to damp timbers) was verified by determining the penetration of the preservatives in the wood, by chemical analysis and biological assessment. These treatments (with CCA and CCB salts applied by vacuum and pressure) confer a permanent and high degree of protection to the timber from the first cut of the saw, dispense with the need for a temporary treatment of newly sawn timber and can be easily integrated into an industrial manufacturing process. The degree of protection conferred to the species does not appear to be affected by the humidity of the wood at the time of treatment.
G R Y Déon, R Schwartz


Decay rates and strength and stiffness loss in foundation beams
1992 - IRG/WP 92-1563
The TNO Centre for Timber Research has executed an extensive research programme into the rate of decay in foundation beams, as a result of lowering of ground water tables. The aim of the research was to develop a method, predicting the decrease in strength and stiffness in beams, due to wood decay during drytime of foundation beams. With the calculated extremes in decay, the damage caused by local settlements of the foundation can be estimated. Though this research deals with untreated timber only, the results yield information which may be used for methods of testing treated timber in ground contact. From 1987 to 1989 literature studies and field inspections have been evaluated, and the most important influencing factors were described. In the following laboratory research the aim was, to quantify the influence of these factors (wood species, dimensions, age, soil wetness, temperature, fluctuation of water) on the decay rate. The rate of decay was measured by mass loss after one year of exposure in a wet but aerated soil, using pine and spruce in different dimensions. For part of the specimens, decrease in strength properties was also measured. Results indicate, that for timber with high moisture contents (over 80%), the decay type is dominated by softrot (95%) and is mainly determined by the surface/volume ratio. The relation between mass loss and loss of strength and stiffness was determined. These results will be used for calculating the deformation of foundation.
P Esser, H S Buitenkamp


Moisture distribution in glulam beams with natural cracks observed with CT Scanning before and after rain
2013 - IRG/WP 13-20534
The way cracks in outdoor wooden constructions affect durability is an interesting topic, since a certain amount of cracks can always be found naturally in wood and glued laminated wood. The question in this was, can cracks lead water into the wood and thereby increase the risk for decay and reduce strength and service life. Moisture balance, i.e., water absorption and water distribution were studied in two 2-meter-long glulam beams after exposure to rain. For the experiment, computer tomography and image processing were used. The beams were X-ray scanned on four occasions during one year: August (CT1), September (CT2), June (CT3) and the following August (CT4). One red-painted spruce beam 215 x 315 mm and one oiled pressure-treated pine beam 140 x 315 mm were studied. The study shows that water can enter a crack for many millimeters by capillary forces, but that this does not necessarily occur. How and to what extent water enters into a crack or delamination depends on material, surface treatment, position and size of the crack or delamination and the quantity of rain and wind. The sizes of the cracks depend on the climate, that is, moisture and temperature variation over time. Some of the cracks become invisible during this movement, and the variation can be as much as 2.5 mm over a 36-hour period. Under certain conditions, small cracks disappear as the woods swells.
K Sandberg


Decay resistance of beams made from thermally modified Scots pine and Norway spruce after 6 years’ exposure in ground contact
2017 - IRG/WP 17-40806
In the present study the resistance of beams treated by ThermoWood® process was studied in ground contact and the results given are based on a “modified” EN 252 test. After six years’ exposure clear differences were found between untreated Scots pine and Norway spruce beams and treated ones. In all cases thermal modification improved the performance. Thermally modified pine heartwood showed the best performance, where only partial decay was found in the outer part of glue-laminated beams s. Decay was more accelerated in Scots pine sapwood, and especially within untreated pine sapwood posts, severe decay was found.
S Metsä-Kortelainen, H Viitanen