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Evaluation of timber bridges with special consideration of detail design
2017 - IRG/WP 17-40781
Since 1997 the use of wood in bridge construction has been increasingly criticized by the Hamburg federal state authority supposedly because of shortened service life due to decay. With regard to wood research, however, it is often suggested that use of timber is suitable for weathered structures as long as constructive protection measures will be observed. In order to unravel the reasons for the shortened service life in Hamburg, several bridges were examined by visual assessment focussing on decay and especially on design. Thus, details of design which affect the durability of individual bridge components and favour damage propagation as well as subsequent decay were primarily detected. In this respect, faulty planning measures and insufficient wood protection is consequently considered as the main cause of the short service life in Hamburg. Giving examples of pedestrian timber bridges, this practical report illustrates several essential faults of protective design which are still being made in planning and construction of naturally weathered timber structures. However, proven solutions are already available and emphasis is placed on constructive solutions with a positive influence on structure durability.
K Robbers, J Fromm, E Melcher


Extending the useful life of creosoted electricity distribution poles in service
1993 - IRG/WP 93-50001-16
Creosoted transmission poles have provided good service over many decades in a whole range of environments. The use of save biocides for secondary treatments has the potential to extend the life of such poles. These techniques, together with a full understanding of the modes of failure, make it possible to establish new strategies to further improve the environmental benefits of treated wooden poles.
D J Dickinson, B Calver


Some observations on causes of failure of preservative treated natural round transmission poles in Nigeria
1977 - IRG/WP 291
Treated natural round transmission poles in Nigeria have been discovered to be attacked underground as early as two years after planting. Termites and rot fungi attack the inner tissues and leave a pattern characteristic for the species of the pole. Tectona grandis, Nauclea diderrichii and Wide Pore pine, the major species for transmission poles in Nigeria show these attacks. A form of termite shield to protect the butt end surface of the pole is advocated.
M A Odeyinde


Observations on the failure of anti-sapstain treated timber under non-drying conditions
1990 - IRG/WP 1437
A range of bacteria and yeasts were isolated from antisapstain treated timber and fresh sawdust. Solution samples containing 100 ppm of TCMTB in a nutrient medium were inoculated with these organisms and incubated at 25°C for 5 days. The levels of TCMTB remaining in solution were determined by HPLC analysis after this time. Results indicated high losses of active ingredient for a range of organisms. These results suggest that active biodetoxification of organic biocides could occur in a short period of time during storage of antisapstain treated timber under favourable conditions. The implications of these results are discussed.
G R Williams


Conservation of wooden cultural property
1994 - IRG/WP 94-30038
A survey of the conservation of wooden archtitectual monuments, art objects and archaeological finds is presented. Each of the three areas has typical conservation problems which reqire the use of selected wood preservatives and consolidation agents. Furthermore specific protection and consolidation methods are necessary. A precise damage diagnosis with non-destructive testing methods is the first step in a careful conservation work.
A Unger, W Unger


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


Polyflavonoid tannins - From a cause of CCA soft-rot failure to the "missing link" between lignin and microdistribution theories
1986 - IRG/WP 3359
Polyflavonoid tannins are proven to be fast-reacting with CCA solutions and hence, to be strong competitors of the structural wood constituents for fixation of CCA preservatives. The consequence of this effect is that even relatively small amounts of tannin cause severe undertreatment of the structural wood constituents which in turn badly affects the long term durability of CCA-treated timber. The effect is compounded by heavy disproportionation between tannins and structural wood constituents of Cu, Cr and As. This leads to the well-known high susceptibility to soft-rot attack in Eucalyptus species and in vineyard posts even experienced with some susceptible softwoods. Relationships found by other authors between soft-rot incidence and lignin content in CCA-treated timber are shown here to be only part of the total failure mechanism. The total mechanism of resistance and failure is due to the balance of distribution of reactions among the various proportions of highly reactive tannins and more abundant but less reactive lignin and carbohydrates present in any wood. As a consequence of the clarification of these mechanisms the liability of different woods to soft-rot attack may then be determined. Solutions to the problem are presented and discussed. Lignin and microdistribution theories are shown to be both correct and different facets of a single unified theory. Better-performing CCA formulations for tannin-containing softwoods are proposed and proved to be effective. Directions under investigations for better performing CCA formulations for hardwoods are discussed. Inorganic waterborne preservatives formulations "precipitating", not "fixing", such as simple CrIII arsenates or ammoniacal copper arsenites, can be deduced to be better suited for Eucalyptus preservation than CCA itself.
A Pizzi, W E Conradie, M Bariska


HCB - a new preservative combination for wood pole maintenance
1996 - IRG/WP 96-30122
New combination of heavy creosoted boron (HCB) applied on hardwood and softwood logs at different moisture content revealed successful diffusion of boron in all sapwoods within 7 days and in all sapwoods plus hardwoods within 15 days. The new cost effective paste sterilizes wood through diffusion and suitable for pole maintenance at groundline and above groundline e.g. cut ends, drilled holes, woodpecker's holes etc.
A K Lahiry


Analysis of volatile emissions as an aid in the diagnosis of dry rot
1992 - IRG/WP 92-2393
The dry rot fungus, Serpula lacrymans was grown in pure culture on malt extract and on sapwood of pine. The volatile compounds emitted from the cultures were determined by diffusion sampling on tubes filled with Tenax TA, thermal desorption and gas-chromatography-mass-spectrometry in order to find markers for attack of the fungus.
J Bjurman, J Kristensson


The possible significance of the lignin content and lignin type on the performance of CCA-treated timber in ground contact
1988 - IRG/WP 1357
The lignin in wood samples of Alstonia scholaris, Octomeles sumatrana and a Simaruba species have been analysed. These timbers are characterised by a high lignin content and low syringyl:guaiacyl ratios. Decay tests with two soft rot fungi showed that the timbers were less susceptible than timbers with a low lignin content and higher syringyl:guaiacyl ratios. Numerous data for field performance of Alstonia and limited information on treated Octomeles and Simaruba suggest that timbers with a high lignin content and low syringyl:guaiacyl ratios will perform well in ground contact when treated with CCA.
T Nilsson, J R Obst, G F Daniel


Morphological and Molecular Diagnosis of Leptographium spp. in Canadian Softwoods
2003 - IRG/WP 03-10479
Sapstaining fungi that affect commercially important softwood species mainly belong to the genera Ceratocystis, Ophiostoma and Leptographium. Our 1997-1999 fungal surveys confirmed that this is the case in Canada. The work reported here addresses identifying the morphologically plastic Leptographium at the species level, which is difficult using conventional methods. We assessed the morphological and physiological characteristic of survey isolates grown on artificial media and wood, and then compared them with reference cultures. The morphological data obtained from isolates grown on wood were less variable and, therefore, more conclusive, than those grown on artificial media. Microscopic observation of isolates grown on wood, differentiated them into three known Leptographium groups: aureum, clavigerum, and abietinum. Preliminary DNA sequence data for the ITS2 rDNA and β-tubulin genes confirmed the identity of the three species, but also indicated two additional groups. Ongoing biological work and sequencing of other genes will clarify the relationships between these species and discrepancies between morphological and molecular data.
S Alamouti, Jae-Jin Kim, A Uzunovic, C Breuil


Inadequacies in preservative retention and formulation as contributory causes of premature failure of CCA-treated vineyard posts
1984 - IRG/WP 3280
Analyses of severely decayed or failed vineyard posts and examination of stake test data on effectiveness of copper-chrome-arsenate (CCA) preservatives have suggested two contributory causes of premature failure of vineyard posts: 1. Preservative retentions in posts are such that after 15 years' exposure some decay is inevitable. 2. The high arsenic, low chrome formulations with which the posts were treated are less effective in controlling decay than low arsenic high chrome formulations previously used in New Zealand, on the performance of which many concepts of CCA effectiveness are based.
M E Hedley


Biostatic film as a primary treatment against pole failure in soil
1995 - IRG/WP 95-40053
Field liners of low density polyethylene (LDPE) film applied as primary treatment of soil-contact surfaces of creosote-treated poles prevented their detoxification and premature failure by establishing hurdles against microbiological colonisation. These hurdles include low water activity, low oxygen tension and nutrient limitations. Moreover, under conditions of high soil moisture, field trials showed that the hurdle of toxicity provided by creosote is maintained by LDPE films which prevent it from leaching. However, such liners must remain intact to confer sustained protection. Susceptibility of LDPE to termite damage and to possible microbiological damage in the long term led to the development of materials resistant to biodeterioration. A dry film preservative (DFP) was incorporated with masterbatch for use in LDPE manufacture. Laboratory tests showed the masterbatch granules to be biocidal against soil microorganisms, confirming that neither the moulding temperature nor the immobilisation of the DFP in the masterbatch had neutralised the antimicrobial properties of the DFP. The masterbatch was then used to produce LDPE film which, with unpreserved control film, was applied as liners to surfaces of untreated Eucalyptus grandis posts. All posts were placed under flood-irrigation in termite-infested soil in Natal for eight months. Preserved liners remained intact and the wood under these was uncolonised by microorganisms or termites. Some control films, and the wood under them, had been destroyed by termites, and wood surfaces under the other control films which appeared intact were visibly colonised by fungi.
A A W Baecker, M Behr


Premature failure of treated timber in wharfs in Papua New Guinea, attributed to defects in design
1991 - IRG/WP 4158
The performance of timber in wharfs in Papua New Guinea has been monitored for a number of years. Premature failure of wharf structures was found in many cases to be due to defects in design rather than ineffective preservative treatment. Above-water timbers were found to be prone to severe checking followed by decay. Protection for the end grain of pile tops and the limiting of radial checking in them was found to be vital. Removable metal caps and stout metal bands sized to give a snug fit around the circumference of the pile were found to give the best protection. Major areas of decay or marine borer attack were most common where other structures were attached to the piles in such a fashion that the "envelope" of treated sapwood was breached. In order for treated timber to perform satisfactorily in wharfs, care has to be taken at the design stage. Any post-treatment machining should be undertaken with suitable tools and remedial treatment or protective measures will be required. A list of recommendations for the use of treated timber in wharfs in the tropics is given, relating to the preparation of wood, the construction of the wharf and the protection of vulnerable parts of the installed wharf. The question of good and bad design, and its effect on service life of wharf timbers requires further investigation. The author requests colleagues with information relating to this to contact him.
S M Cragg


Cellular and fractural failure after supercritical fluid impregnation of four wood species
2004 - IRG/WP 04-10503
Supercritical fluids (SCFs) have been investigated for delivering biocides into sawn wood. Pressure differentials during treatment may exceed the compressive or tensile strength perpendicular to grain, creating a potential for transverse deformations that exceed elastic strain limits. Wood treated by SCF processing with CO2, a potential biocide carrier, was inspected macroscopically and microscopically. Both cell wall damage and smooth fracture surfaces appeared in the cellular structure. Damage was related to the rates of pressurization and venting and appeared to be species-specific. Cell walls were damaged during pressurization, whereas fracture damage occurred during venting. Specimen dimensions, permeability and anatomical structure are critical variables in developing SCF processes for biocide treatment of wood and wood-based products.
M E Anderson, R J Leichti, J J Morrell


A non-pressure method of protection based on hurdle theory to control the spectrum of internal environmental factors which affect the decay of poles in soil contact
1993 - IRG/WP 93-20005
A field trial was conducted to establish whether superficial barrier linings on poles in soil contact could function as environmental hurdles against the growth of biological agents and thus provide preventative methodology to preclude premature failure of vineyard poles under flood-irrigation. Assessment after 52 weeks exposure to the prevailing conditions and sub-tropical environment showed that open-ended cylindrical linings of biologically inert heat-shrink polyethylene applied to the vertical soil-contact surfaces of Eucalyptus grandis poles unequivocally prevented termite-induced failure of untreated poles, basidiomycete decay of creosote-treated poles and fungal colonisation of CCA-treated poles. The success of the liners in prevention of incipient decay of these poles was explainable on the basis of hurdle theory and was therefore attributed to the ability of the former to control essential growth factors and create internal conditions inimical to the proliferation of decay agents in the poles. Consequently, sub-optimal conditions of Aw, Eh, and nitrogen content were considered to have arisen to function as environmental hurdles which decay agents could not overcome at wood-soil interfaces.
A A W Baecker


Premature failure of CCA treated vineyard posts from brown rot
1993 - IRG/WP 93-10016
A survey of CCA (AWPA Type C) treated posts used as grape vine trellis supports, to determine the extent and type of decay was carried out at a terraced vineyard in the Hawkes Bay region of the North Island of New Zealand. Of 357 posts examined out of a total of 970 in the vineyard, 47% had moderate to severe decay or had failed, 20% had established decay, 10% had a trace of decay and 23% had no sign of decay. The posts were less than three years old at the time of the survey and it was predicted that the average life of the posts would be 5 years. Atomic absorption spectroscopy showed that the average above and below ground CCA retention for 13 failed posts were 17.32 and 14.80 kg/m³ of salt respecitively. Light and transmission electron microscopy showed that brown rot was the only cause of decay. The rapid rate of decay was in part attributed to a high inoculum potential for brown rot in the soil caused by the presence of a large volume of decaying wood. It seemed likely that this high inoculum potential conferred a high degree of tolerance to CCA by the brown rot fungus or fungi. Leucogyrophana was consistently isolated from soil but certain observations relating to the morphology of fungal hyphae and the presence of Chlamydospores in decayed wood suggested that another fungus may have been responsible.
R N Wakeling, A P Singh


Failure of overhead power transmission and telecommunication poles in Tanzania: Causes, preventive and remedial measures
1988 - IRG/WP 3465
Unless measures are considered urgently to combat massive pole failures occuring in service, it is likely that wooden poles may soon become unpopular. Consequently, pole users may be forced to use costlier alternatives such as underground cables and concrete or steel poles. In trying to countercheck this trend, this paper names the main agents of pole failure, discusses different models of pole failure and suggests possible control measures for each.
K K Murira


Adequate preservative treatment of kiln dried Eucalyptus camaldulensis and Acacia mangium for tropical and subtropical wood poles
1996 - IRG/WP 96-40075
The Eucalyptus camaldulensis and Acacia mangium round timbers kiln-dried at EMC and full cell pressure treated with CCA-C ensured requisite penetration and adequate dry retention (30 kg/m³ or 4% w/w). The sufficient inherent strength, seasoning property, treatability of sapwood and heartwood equivalent to 44% of radius, natural durability of heartwood, and field investigation on service performance of similar hardwood poles treated with CCA-C, pentachlorophenol and creosote ensured their longterm use as tropical and subtropical poles.
A K Lahiry


rDNA-ITS sequence of Serpula lacrymans and other important indoor rot fungi and taxon-specific priming PCR for their detection
1999 - IRG/WP 99-10298
Taxon-specific priming polymerase chain reaction (TSPP) is a powerful molecular tool for fungal diagnosis. For its application to indoor rot fungi, the internal transcribed spacer (ITS) of the ribosomal DNA (rDNA) of the main fungal species causing wood rot in European buildings was amplified with the polymerase chain reaction (PCR). The ITS region was sequenced. The complete sequences are presented. From base sequence divergency among the fungi, species-specific oligonucleotide primers were designed for TSPP. These marker molecules were suitable for the differential diagnosis of the dry rot fungus, Serpula lacrymans, the wild merulius, S. himantioides, the oak polypore, Donkioporia expansa, the brown cellar fungus, Coniophora puteana, the broad-spored white polypore, Antrodia vaillantii, the sap polypore, Tyromyces placenta, and the yellow-red gill polypore, Gloeophyllum sepiarium. Each specific marker identified isolates of its respective target species. Cross reaction with 'foreign' fungi was the exception. Species identification from unknown field samples from rot damage in buildings is also possible, because DNA from contaminating organisms does not response to the specific primers. Our variant of the technique is fast, because no preceding fungal pure cultures, no special DNA extraction/purification, and no restriction by endonucleases are necessary.
O Schmidt, U Moreth


Colonisation of painted wood by Aureobasidium pullulans - Analysis of features and consequences for failure in service
1996 - IRG/WP 96-10144
Wooden blocks of spruce were painted with different paint formulations. Water- and solvent-borne model and commercial paints were used. The painted wooden blocks were inoculated with a spore suspension of Aureobasidium pullulans (de Bary) Berkg. and placed in an environment of high humidity for 14 months. Different colonisation and growth patterns were observed on the different paint surfaces. The susceptibility to staining and/or degradation of tested painted wood blocks are discussed. The commercial paints with and without a fungicide became heavily stained. Model paints were not as susceptible to blue stain as the commercial paints tested. Estimation of degree of staining was done with digital image analysis. Further observations were done with a stereo microscope and scanning electron microscopy.
S L Bardage


Treatment groups and remedies for CCA treated hardwood and softwood poles
1999 - IRG/WP 99-40142
Different hardwood and softwood species from Bangladesh and Bhutan was investigated regarding density, green fiber stress, natural durability of heartwood and CCA treated sapwood, CCA treatability grades, sapwood thickness, and kiln-drying properties for long term use as electric poles. These properties along with the past service records for nineteen years, separated ten heardwood and five softwood species into four treatment groups. The treatment groups are very specific for specific timber species and adequate for equivalent requisite service life for tropical and subtropical climatic conditions without premature failure like in the past.
A K Lahiry


Quantification of creosote migration down wooden poles and the prevention of its depletion during flood irrigation
1994 - IRG/WP 94-50032
Polyethylene field liners heat-shrunk onto soil-contact surfaces prevented decay of creosote-treated Eucalyptus grandis vineyard poles under flood-irrigation. The present work quantified losses of creosote from these poles after six and 24 months' service. After six months' service the mean creosote retention of unlined poles above the ground line was 12.62% (m/m dry wood), with sample retentions decreasing progressively to 4-6% at the ground line and 2-3% throughout their sub-soil profiles. These values remained similar after 24 months' service. The mean creosote retention above the ground line of lined poles after six months' service was 13.06%, however sample retentions did not decrease towards the ground line, and these remained between 13-17% throughout the sub-soil profile. After 24 months' service the mean creosote retention above the ground line of the lined poles had fallen somewhat, but sample retentions remained over 12% at, and below, the ground line. The results showed that, while slight creosote evaporation from wood above ground may have ocurred, the major phenomena affecting creosote retentions in unlined poles in soil were gravitational migration and leaching to soil, and it seemed that these factors were coupled. Primarily, the results confirmed that creosote was lost from poles by leaching to soil, and that such loss was prevented by the application of the field liners.
M Behr, A A W Baecker


The effect of oil-borne preservative treatments on the shear strength of FRP/wood composite adhesive bonds
2003 - IRG/WP 03-40265
Reinforcement of structural wood components with Fiber Reinforced Polymer (FRP) will enhance the beam’s strength, but actual data on long-term durability is sparse, not well documented or not readily accessible. In this study, bond properties of FRP-wood composite materials were investigated following treatment with creosote or copper naphthenate preservatives. The properties investigated included stress and the percentage of wood failure experienced in shear (ASTM 1998). When tested in a wet condition (following a vacuum/pressure soak), creosote-treatment adversely affected the wood failure values associated with specimens fabricated with a pultruded FRP composite sheet (E-glass fiber, bonded with urethane). When these tests were conducted with samples under ambient conditions, the shear strength of this material was also adversely affected by creosote. In addition, both creosote- and copper napthenate-treatment adversely affected the shear strength of a SCRIMP™ fabricated FRP material (carbon fiber, vinyl ester matrix).
B Herzog, B Goodell, R Lopez-Anido


Continuous moisture measurement (CMM) to detect failure of moisture resistance
2009 - IRG/WP 09-20422
A wood coating system will fail to perform properly after a certain time of weathering. From that moment, the substrate is especially prone to fungal attack. Moisture plays a key role on weathering performance, wood protection efficacy and decay susceptibility of wood. Therefore, knowledge of the moisture dynamics of the applied wood protection is of significant importance in the prediction of the service life of the wood coating system. Furthermore, weather action (abiotic) and biological factors (biotic) change the impact of moisture on the wood coating system. In this regard, this research focused on detailed monitoring of the moisture fluctuations of eight wood coating systems during outdoor weathering using a CMM (Continuous Moisture Measurement) set-up. Simultaneously, weather data were recorded. Data processing comprised correlation analysis, PCA (Principal Component Analysis) and cluster analysis on the functional moisture content data. In addition a laboratory evaluation combining artificial weathering with a floating test is discussed to determine moisture characteristics in a reliable way. Finally, these techniques are evaluated as a tool for the estimation of service life.
I De Windt, J Van den Bulcke, J Van Acker


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