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Utilization of Pressure Treated Lumber in Cross Laminated Timber Manufacture and its Impact on Bondline
2022 - IRG/WP 22-40953
Mass timber building construction is increasing dramatically across North America which presents challenges to these structures not seen in Northern Europe. Large parts of the United States harbor termites and existing mass timber building technologies that rely solely on moisture exclusion to increase durability are insufficient in these areas. The successful expansion of mass timber construction in the United States will require the incorporation of pressure treatments into panel fabrication, but chemical presence introduces difficulties with resin compatibility. This work examines the impact of preservative treatment on cross laminated timber (CLT) bondline integrity by constructing small-scale panels using treated lumber or treating panels after layup. Douglas-fir 2 x 6-inch lumber or untreated CLT panel sections were treated with one of three different preservative systems, pressure treatment with borates, pressure treatment with propiconazole, tebuconazole, imidacloprid, permethrin and iodopropyl butyl carbamate (PTIP+IPBC), or dip treatment with propiconazole, tebuconazole and imidacloprid + borate (PTI). Panels were made with one of two resins, melamine formaldehyde (MF) or Polyurethane (PUR). Delamination, block shear and wood failure were tested according to the PRG-320 standard. The all-organic preservative treatment passed delamination test standards when pressure treated lumber was used to layup panels, while utilizing borate-treated lumber for panel manufacture resulted in failure. Bondline characterization was done microscopically to measure depth of resin impregnation into the cross section of CLT laminae. This work provides useful information on preservative-resin compatibility for CLT manufacture and can help improve the durability of mass timber structures.
G Presley, C Wainscott, J Valenti, S Noble

A new approach to the maintenance problems of wooden railway sleepers
1986 - IRG/WP 3392
The microenvironment of wooden railway sleepers is being investigated to assess their condition to determine the necessary treatment, repair and replacement criteria. The research work involves the development of an integrity tester to determine the condition of sleepers, a remedial treatment of sleepers by selective application of boric acid and a synthetic repair system.
W Beauford, P I Morris.

Impact of decay and blue stain causing fungi on the structural integrity of wood
2009 - IRG/WP 09-10699
The potential influence of diverse decay patterns caused by different brown rot provoking basidiomycetes on the structural integrity of wood was investigated. Additionally the potential impact of blue stain on the structural integrity was examined. Therefore decayed Norway spruce (Picea abies Karst.) specimens representing a wide range of mass loss, caused by four different brown-rot fungi and one white-rot fungus, were applied to a high-energy multiple impact (HEMI) -test series. The relationship between the resistance to impact milling (RIM) and the mass loss by fungal decay could be subdivided in three areas: 1. Prior to measurable mass loss a strength reduction was detectable due to the depolymerisation of wood cell wall components. 2. Between 0 and 25-30% mass loss RIM decreased with increasing mass loss. 3. Above 30% mass loss RIM increased again due to gluing effects of the fungal mycelium. The influence of the different brown rot fungi on the structural integrity of the wood differed slightly, but partly significantly. According to preliminary results blue stain caused by Aureobasidium pullulans and Sydowia polyspora was found to have no significant impact on RIM.
C Brischke, C Welzbacher, T Huckfeldt, F Schuh

Influence of heat treatment intensity on the structural integrity of 14 timber species
2012 - IRG/WP 12-40586
Thermally modified timber (TMT) is characterized by improved durability and dimensionally stability, but strength properties, especially the dynamic ones, are compromised at the same time. Because dynamic standard tests require high efforts and time, the high-energy multiple impact (HEMI) –test was developed for the fast and reliable characterisation of the structural integrity of TMT, showing a strong correlation of decreasing structural integrity with rising treatment intensity. Since the number of wood species subjected to this test method was limited up to now, 14 soft- and hardwoods were heat treated by ten different treatments at 180 and 220°C and used for determination of the structural integrity. The results showed temperature dependent strong correlations of decreasing structural integrity with increasing intensity for all species tested, pointing to the general applicability of the destructive HEMI-test in the frame of the post production quality control of TMT. In addition, the structural integrity is not affected by density, anatomical macro-defects like drying cracks, growth ring and fibre deflection or weathering impacts, which confirms its usage for implementation within a reliable factory production control to ensure constant product qualities.
C R Welzbacher, C Brischke, G Maier

The effect of preservative treatment on mechanical strength and structural integrity of wood
2015 - IRG/WP 15-30667
The use of wood for demanding construction applications is increasing in Europe. Wooden constructions are frequently designed of susceptible conifer wood, which is endangered by wood decay fungi in wet applications. Therefore in many cases treating wood with preservatives is unavoidable to ensure the desired service life. However, chemical treatment of wood can result in changes of its mechanical properties. There are contradictory results published in literature regarding the influence of the various impregnation agents on relevant mechanical properties. In order to elucidate mechanical properties of impregnated wood, Scots pine (Pinus sylvestris) sapwood and Norway spruce (Picea abies) wood were impregnated with a copper-ethanolamine based system, an aqueous solution of boric acid and a solvent based wood preservative. For comparison, wood samples were impregnated with deionised water. After conditioning, half of the samples were artificially aged according to the EN 84 leaching procedure. Afterwards, samples were oven dried, and their bending and compressive strength in axial and radial direction was determined. In parallel, structural integrity of the samples was determined in High-Energy Multiple Impact (HEMI) tests. The results clearly showed that treatment with wood preservatives does not have significant influence on the mechanical properties, with exception of non-aged copper-ethanolamine and boric acid treated wood that exhibited significantly lower structural integrity of wood. The negative effect on strength and structural integrity was found to be reversible through exposure to liquid water or high relative humidity.
M Humar, D Kržišnik, C Brischke

Underground timber constructions from the First World War are well preserved after 100 years
2017 - IRG/WP 17-10897
During the Great War or World War I many underground constructions have been built for protection from shelling. They were an important part of the trench warfare as they were used as an area to rest and carry out other activities such as eating. They would usually range in size from smaller constructions that could hold several men to larger entities that could hold thousands of soldiers. In the context of tunnel warfare the construction of underground facilities was very extensive. About 180 dugout sites have been located in the Ypres Salient and since the 1990s some of them were entered (Doyle et al. 2002, 2005). During use these dugouts which are typically timber based tunnels were kept dry, however got fully submerged when no longer in use. These wooden constructions remained under groundwater level and are very well preserved after approximately 100 years. Several of these constructions have been documented and one specific one is very much highlighted in 2017. As the ‘Zonnebeke Church Dugout’ is intended to open up for the public for some months and this construction was checked on different parameters. Wood species identification confirmed the considerable presence of wood from overseas origin, here Jack pine (Pinus banksiana). Although several low durability wood species have been used the decay rate found on the material is minimal and structural integrity analysis allows to ensure safe passage for visitors to the dugout.
J Van Acker, I De Windt, K Haneca, H Beeckman, F Claeys, S Vandenbussche, J Vandewalle, N Robeyst, A Willems

Thermal performance and fire safety properties of traditional circumferential log-cabin walls
2019 - IRG/WP 19-40872
The paper describes the experiment of fire resistance of a circumferential log-cabin wall fragment using various structural modification of the gap between two log members. The influence of the gap structural modification on the criterion of fire resistance E (envelop integrity) and I (insulation) is evaluated. The evaluating criteria are represented by the development of temperatures measured in various gap setups and photo documentation from the experiment. The experiment is supplemented by the theoretical calculation of the temperatures during a fire on the unexposed fragment side in two cases: according to the average temperatures on the specimen surface from the radiation panel and for the standardised fire temperature 1,000°C. The reason for the calculation is the verification of the I criterion (insulation) in connection with the U-value of the construction, i.e. heat transfer affecting the flashpoint temperature on the unexposed side of the log-cabin wall.
S Jochim, L Makovicka Osvaldova, M Zachar, Z Danihelova