Your search resulted in 234 documents. Displaying 25 entries per page.
Modelling of moisture content in timber bridge details
2017 - IRG/WP 17-20613
The design of details is an important aspect in durability design of timber bridges. Details are often considered the weakest points in bridges due to their tendency to trap and accumulate moisture and thus facilitate decay. When designing maintenance plans and inspection intervals, it is important to know how design choices will come to influence the service life. Moreover, service life and wood moisture content are closely related. Therefore, the aim of the present study was to develop a method that can be used to estimate the moisture content in typical timber bridge details. This was done by considering the moisture content in details as the sum of two components: a reference moisture content (ideal drying conditions) and an amplified moisture content response (due to actual drying conditions). The focus of the present paper was on the latter component. The proposed approach consists of a set of simple equations and a detail-specific parameter, kdry, which describes the detail-specific drying conditions. The detail-specific parameter was fitted to four time-series from two different data sets. In all cases, the estimated moisture content time-series exhibited the same behaviour as the measured data. In all three wood-to-wood details, the best fit was obtained for kdry=1/10 which indicates some level of consistency. Although the approach was only tested against a few time-series, it has so far shown some promising features. More data will be added in future work.
J Niklewski, C Brischke, E Frühwald Hansson, L Meyer-Veltrup
Performance of wood decking after 5 years of exposure: verification of the combined effect of wetting ability and durability
2019 - IRG/WP 19-20647
Wood is one of the most important construction materials and its use in building applications has further expanded in recent decades. In order to enable even more extensive and reliable use of wood, factors affecting wood’s service life need to be understood. More recently, a new concept to characterize the durability of wood-based materials and to predict the service lives of wood was proposed, based on the material-inherent protective properties, the moisture performance, and the climate and design induced exposure dose of wooden structures. This approach was validated on the decking of a model house in Ljubljana that was constructed in October 2013. Decay and moisture content of decking elements was regularly monitored. In addition, the resistance dose DRd, as the product of the critical dose Dcrit and two factors taking into account the wetting ability of wood (kwa) and its inherent durability (kinh) was determined in the laboratory. DRd was well correlated with the decay rates of the decking of the model house. Furthermore, the positive effect of thermal modification and water repellent treatments on the outdoor performance of the examined materials became evident as well as synergistic effects between moisture performance and inherent durability
M Humar, D Krzisnik, B Lesar, C Brischke
A comparison of soft rot, white rot and brown rot in CCA, CCP, CCF, CCB, TCMTB and benzalkonium chloride treated Pinus radiata IUFRO stakes, after 9-15 years exposure at five test sites in New Zealand
1991 - IRG/WP 1485
The aim of this study was to determine if decay type varies significantly between five field trial test sites of different soil type, aspect and climate in 9-15 year old, replicate CCA, CCF, CCP. CCB, TCMTB and AAC treated IUFRO stakes. A visual on-site assessment of decay type on every test stake was made and observations confirmed by microscopical examination. Regression analyses were used to determine significant differences of percentage frequency of occurrence of each rot type between sites and preservatives. Large differences in percentage frequency of occurrence of rot type were evident between sites. One site was dominated by brown rot (85%) and two were dominated by soft rot (99 and 91%). The fourth site had intermediate proportions of brown rot (40%) and soft rot (71%) but had the second highest occurrence of white rot (32%) (highest = 37%; lowest = 11%). The fifth site was distinct in that a large proportion of stakes (69%) had both well established brown rot and soft rot. Stakes at the other four sites tended to have only one rot type. Some highly significant preservative effects were also found. Possible causes of these differences are discussed in terms of inter-site soil type, climate and other differences.
R N Wakeling
Ultra-structural observations on the degradation of wood surfaces during weathering
1987 - IRG/WP 2280
Radiata pine (Pinus radiata D. Don) sapwood was converted into blocks with a transverse face about 5 mm square and measuring 8 mm longitudinally. Transverse (T.S.), Radial (R.L.S.) and Tangential (T.L.S.) surfaces were prepared and specimens exposed to the weather inclined at 45° facing equatorially for periods of between 20-60 days. After 30 days exposure erosion of the middle lamella was observed followed after 40 days exposure by extensive separation of individual fibres at the interface of the middle lamella and secondary wall. Degradation of the S2 layer of the cell wall revealed corrugations orientated parallel to the fibre axis suggesting preferential removal of cell wall components. Further degradation proceeded by progressive delamination and checking of the S2 and erosion of the S3 cell wall layer. In addition to the above changes preferential degradation of the rays was observed in radial (R.L.S.) and tangential (T.L.S.) longitudinal surfaces.
P D Evans, S Thein
Co-operative research project on L-joint testing. Sampling after 8 months exposure
1983 - IRG/WP 2208
It was anticipated in Document No IRG/WP/2192 that exposure of L-joints by the European co-operators would take place on 1 April 1983. Where L-joints were exposed at this time, sampling after 8 months exposure is due on 1 December 1983. The present document draws attention to relevant previous documents which describe the sampling methods to be adopted. It also provides Tables for recording the results.
J K Carey, A F Bravery
In-ground performance of two formulations of chlorothalonil after five years of exposure at three test sites in Australia
1996 - IRG/WP 96-30101
Sapwood specimens of Pinus radiata D. Don and Eucalyptus regnans F. Muell. were each treated to three retentions of each of two preservative formulations (chlorothalonil in oil; chlorothalonil plus chlorpyrifos in oil) and installed in-ground at three field test sites in Australia. Specimens were treated with each formulation to achieve 3.2, 6.4 and 12.8 kg/m³ of chlorothalonil a.i. and 3.2 + 0.2, 6.4 + 0.4 and 12.8 + 0.8 kg/m³ of chlorothalonil plus chlorpyrifos a.i. For comparison, specimens of each timber species, treated to a commercial in-ground retention of a copper-chromium-arsenic (CCA) formulation, were also installed. Treated specimens (including controls) have been rated for their condition annually for attack by subterranean termites and fungal decay using a scale ranging from 4 (sound) down to 0 (failed). After five years of exposure, mean termite and decay scores for replicate test specimens at each site reveal that the performance of all three retentions of each formulation, particularly the two highest retentions, is comparable to CCA.
J W Creffield, T L Woods, N Chew
Modélisation sur maquette du rejet accidentel d'un gaz toxique et inflammable dans l'atmosphere - Emission de type "bouffée d'oxyde d'éthyléne [Water model simulation of toxic and flammable gases in the environment on industrial sites - Puff of ethylen oxide]
1990 - IRG/WP 3576
Soft rot cavity widening - A consideration of the kinetics
1984 - IRG/WP 1227
Studies on the micromorphology of soft rot cavity formation by Phialophora hoffmannii in birch using time-lapse cinemicrography are briefly outlined. A mathematical model is constructed to describe the cavity widening process, particularly changes in the surface area of a hypothetical cavity during enlargement. On comparison with observed data it is concluded that the rate of cavity widening is determined by wood cell wall characteristics.
M D C Hale, R A Eaton
Surveillance médicale des personnels exposés aux produits de préservation du bois
1990 - IRG/WP 3588
Exposure trial at tropical marine sites of pyrethroid/creosote mixtures as wood preservatives: Preliminary results
1989 - IRG/WP 4155
Pinus sylvestris sapwood blocks measuring 25 x 25 x 200 mm³, impregnated using a Lowry or Rüping pressure treatment cycle with solutions of permethrin, cypermethrin or deltamethrin in BS144 creosote, have been exposed at marine sites in Australia, Papua New Guinea, the U.K. and Singapore. The effectiveness of these solutions in preventing marine borer attack is being compared with the efficacy of creosote alone, creosote/CCA double treatment, pyrethroids alone and no treatment. Blocks at the tropical sites have been installed in the intertidal zone in areas where the crustacean borer, Sphaeroma is active. Teredinids (shipworms) of several species are very numerous at these sites and the bivalve borer, Martesia, is present. Limnona colonies were found in untreated blocks at the sites in Papua New Guinea and Australia. The results of inspections after exposure periods of up to 26 months at the tropical sites are summarised in this report. Untreated sample blocks failed rapidly to borers, particularly teredinids. Pyrethroids alone reduced the level of crustacean borer attack and to a lesser extent, teredinid attack. All blocks treated with creosote-containing solutions have so far not been attacked by borers or degraded significantly by micro-organisms. Soft-rot and bacterial degradation occurred in untreated blocks and blocks treated with pyrethroids alone. Settlement by barnacles and serpulid worms appears to be inhibited by the creosote/CCA double treatment, but there is no evidence of long-term inhibition of barnacle or serpulid settlement by pyrethroid-containing solutions, whether with creosote or without. Samples at the site in the UK are exposed to teredinid attack. No inspections have yet been carried out at this site.
S M Cragg
Vertical distribution of fouling and wood-boring organisms in the Trondheimsfjord (Western Norway)
1981 - IRG/WP 467
Results of a detailed study on the vertical distribution of fouling and wood-boring organisms of Trondheimsfjord at an interval of 3 m from intertidal level to a depth of 30 m, has been presented, based on data collected from two series of panels, exposed from 15 March 1977 to 15 July 1977 (Series I) and from 22 July 1977 to 13 March 1978 (Series II). The intensity of fouling generally decreased with increasing depth. Quantitatively, fouling was heavy on panels of Series I more than on Series II, although species-wise it was more heterogenous on panels of Series II. The bulk of the fouling was constituted by Balanus crenatus, Laomedia sp., Mytilus sp., Modiolus sp. and Hiatella arctica. Incidence of borers and the resultant destruction of timber were heavier on panels of Series II than on those of Series I. The influence of the period of exposure on the above pattern of infestation by foulers and borers has been discussed. Psiloteredo megotara concentrated at the upper levels up to a depth of 15 m, with more settlement between 3 m to 9 m depth. Although Xylophaga dorsalis was present on panels from 3 m to 30 m depth, their intensity abruptly changed from 9 m onwards and continued to increase with increasing depth, with a maximum number near the mud level at 30 m. Attack of Limnoria lignorum also was heavy at the mud level. On the same panel, while Psiloteredo megotara preferred to settle in more numbers on the lower surface, Xylophaga dorsalis did so on the upper silted surface. The importance of such selective vertical incidence of different borers and their co-operation in the destructive activity have been stressed from the point of wood destruction in the Tronheimsfjord. The rate of growth of Balanus crenatus, Laomedia sp., Psiloteredo megotara, Xylophaga dorsalis, and Xylophaga praestans in relation to depth has been presented. For Balanus crenatus rate of growth decreased with increasing depth, while for Laomedia the same increas with depth up to 12 m and declined thereafter. In accordance with its depth preference, Psiloteredo megotara registered faster growth between 3 to 15 m depth. In the case of Xylophaga dorsalis, the size of the shell valve and burrow increased with increasing depth up to 24 to 27 m and then showed a slight decline at 30 m. Factors influencing the growth-rate at different levels have been discussed. The results on the vertical zonation and rate of growth of the wood-infesting organisms encountered, have been compared with relevant literature published earlier.
L N Santhakumaran
Questionnaire pour la préparation de fiches monographiques pour les champignons lignivores
1972 - IRG/WP 103 F
Performance of untreated French Guianan piling in marine exposure
1992 - IRG/WP 92-4173
Round piling of seven French Guianan species, greenheart, and preservativ-treated Southern Pine were installed as fender piling in Key West, FL. After 12½ years, none of the tropical hardwoods performed as well as dual-treated Southern Pine. Of the hardwoods, kouata patou and maho noir were the most resistant to decay and marine borers.
B R Johnson
Depletion of wood preservatives after four years' marine exposure in Mt. Maunganui harbour, NZ
1994 - IRG/WP 94-50036
This paper reports on chemical analysis of marine test samples exposed in Mt. Maunganui harbour, New Zealand from 1977 to 1981. Depletion data for a Class II CCA, a CCA-A formulation, acid copper chromate and ammoniacal copper arsenate are presented. The results suggest differences in the rate of loss of individual preservative components among the four formulations and redistribution of individual preservative components within the wood.
K J Archer, A F Preston, C M Chittenden, D R Page
Model questionnaire for preparation of monographic cards for wood-destroying fungi
1972 - IRG/WP 103
What information can we glean from field testing
1995 - IRG/WP 95-20057
To mathematically compare the performance of preservatives in a field test, equations were formulated to describe the relation between log score and time and between rate of decay and retention. By combining these equations, a model was derived for the performance of a number of waterborne preservatives. Some relations between the estimated parameters for different preservatives were noted and these were used to develop a universal model to encompass a variety of patterns of deterioration. An attempt was then made to relate these common parameters to the factors known to affect preservative performance. As a result it may be possible to distinguish and quantify parameters specific to the efficacy of the preservative, the aggressiveness of the test site and the characteristics of the wood substrate.
P I Morris, S Rae
Corrosion of fasteners in heat-treated wood – progress report after two years’ exposure outdoors
2005 - IRG/WP 05-40296
The corrosion of common fastener materials now in use - mild steel, zinc-coated steel, aluminium and Sanbond Z-coated steel – has been evaluated after two years’ exposure outdoors in untreated and heat-treated spruce (Picea abies) respectively. Spruce from South-western Sweden was used. The heat-treatment was carried out in Finland according to the ThermoWood process at a maximum temperature of 220 °C for five hours. The results so far show that the corrosion of fasteners in heat-treated wood according to the particular specification is more severe than in untreated wood. Mild steel and zinc-coated steel has been most susceptible. Stainless steel is hardly attacked at all.
J Jermer, B-L Andersson
An in-ground natural durability field test of Australian timbers and exotic reference species. Part 2: Progress report after approximately 13 years' exposure
1983 - IRG/WP 1189
The condition of heartwood specimens of Australian and exotic timber species after approximately 13 years' in-ground exposure is given. Four of the 5 test sites have a termite hazard in addition to the hazard from a range of decay fungi. Values for specimen life are given only where all replicates of a timber species have become unserviceable. Results give evidence leading to doubt about the accuracy of the tentative durability ratings previously ascribed to at least some of the species under test.
J D Thornton, G C Johnson, I W Saunders
Evaluation of wood treated with copper-based preservatives for Cu loss during exposure to heat and copper-tolerant Bacillus licheniformis
1999 - IRG/WP 99-20155
Copper-based wood preservatives need to be effective against exposure to all types of microorganisms. Wood treated with six copper-based preservatives was exposed to 121°C and 20 psi pressure for 15 minutes under standard autoclave conditions and the copper-tolerant bacterium, Bacillus licheniformis CC01, for 10 d at 28°C and 150 rpm. Sixteen to 37 percent of the copper was released from the wood during autoclaving, with copper citrate demonstrating the highest percent loss. Forty-four to 82 percent of the copper remaining in the samples following autoclaving was removed during exposure to the bacterium in liquid culture; copper naphthenate in oil and ACQ-D had losses of eighty percent or greater of the remaining copper. The bacterium removed as much or more total copper in 4 of 6 gas-sterilized samples (85-94%) than the cumulative effects of steam-sterilization and the bacterium on treated samples. Copper loss from in-service treated wood compromises the efficacy of copper-based wood preservatives.
D M Crawford, C A Clausen
Short term preconditioning of preservative-treated wood in soil contact in relation to performance in field trials
2000 - IRG/WP 00-20185
The effect of pre-exposure to primary colonising micro-organisms on preservative-treated wood, prior to a basidiomycete decay test, was determined by preconditioning in two soil types. Scots pine EN 113 blocks treated with 3 model systems (a triazole, a copper quaternary compound and a copper boron triazole) were leached according to EN 84 and subjected to 6 weeks and 8 weeks burial in either John Innes no. 2 (a loam-based horticultural compost) or soil from the Simlångsdalen field site in Sweden. The samples were then tested according to the method described in EN 113. Selective isolations were also performed after soil exposure and compared with those from a longer term field trial. Preconditioning lowered the effectiveness of the 2 copper containing preservatives. Some effect of soil pre-exposure could be noted with the triazole but this was limited. The fungal isolations from preconditioned EN 113 blocks and field exposed stakes were a similar mixture of soft rot and mould fungi. Bacteria were commonly isolated from the preconditioned wood. The role of these micro-organisms in the modification of the preservatives is currently being investigated.
S Molnar, D J Dickinson
Final draft of a monographic card for Pole Fungus A, L Harmsen, Rigidoporus vitreus (Fr.) Donk according to the 'Model Questionnaire for preparation of monographic cards for wood-destroying fungi'
1978 - IRG/WP 178
Soil-bed studies (Part 3): A cause of failure of multisalt preservatives following soil-bed exposure
1983 - IRG/WP 3261
P Vinden, J F Levy, D J Dickinson
Monographic information on Serpula (Merulius) lacrymans (Schum. ex Fr.) S. F. Gray according to the "Model Questionnaire forpreparation of monographic cards for wood-destroying fungi"
1975 - IRG/WP 133
J Segmüller, O Wälchli
Exposure monitoring of creosote vapors
1989 - IRG/WP 3511
Creosote oils contain hundreds of compounds. During impregnation and handling of treated wood the main component in the vapors released in air is naphthalene. Other main components are alkyl naphthalenes, indene, phenol and its methyl derivatives, benzothiophene, diphenyl, acenaphthalene and fluorene. In the measurement of creosote vapors, naphthalene can be used as an indicator agent. One of the major urinary metabolites of naphthalene is 1-naphthol. To explore the relation between naphthalene concentration in the air and 1-naphthol in the urine of exposed workers we monitored air concentrations and collected urine samples from six men over a working week. 1-Naphthol concentrations in urine samples were analyzed by GC as a pentafluorobenzylbromide derivative. The average concentration of 1-naphthol in the Monday morning samples was 0.1 mg/l, in the Monday afternoon 3.1 mg/l, in the Friday morning 0.4 mg/l and in the Friday afternoon 2.9 mg/l.
P Heikkilä, M Loutamo, V Riihimäki, M Romo
Sequential exposure of borate treated Douglas-fir to multiple Formosan subterranean termite colonies in a 40-week field test
1993 - IRG/WP 93-10006
Douglas-fir boards (ca. 74.5 g) pressure-treated with disodium octaborate tetrahydrate (DOT) retentions of 0 (controls), 0.88, 1.23, 1.60, or 2.10% (weight/weight) DOT were sequentially exposed to four active field colonies of Formosan subterranean termites, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), in an above-ground field test. Samples were placed in contact with each colony for 10 weeks, with oven-dry weight losses determined between exposures, for a total termi exposure period of 40 weeks. Feeding activity differed among termite colonies, with the control wood samples having mean weight losses of 1.3-15.1% of their initial weight during each individual 10-week termite exposure. The two lower borate retentions (0.88 and 1.23% DOT) were virtually equal efficacy, with mean wood weight losses during each individual 10-week exposure ranging from 1.2-4.6%. Feeding was negligible at the two higher borate retentions, with mean wood weight losses from termite feeding during each 10-week period ranging from 0.7-1.3% with 1.60% DOT, and 0.3-0.9% with 2.10% DOT. Total cumulative wood weight losses over the 40 week exposure were: 10.2% (0.88% DOT), 8.7% (1.23% DOT), 3.6% (1.60% DOT), and 2.4% (2.10% DOT).
J K Grace, R T Yamamoto