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The effect of biodeterioration on the structural connection performance of timber for conventional framing and mass timber has been investigated recently, but there is a need for additional data as well as for the development of analytical models to utilize these data. An empirical material model (seismic analysis of wood frame shear walls) was fitted to cyclic connection test data of four species of cross-laminated timber at different levels of biodeterioration by two brown-rot fungi. These model inputs were then analyzed to account for trends between wood species and fungal species. Weak trends were most prominent for initial stiffness, intercept load, and displacement at peak force. Correlations were poor with postyield and postpeak stiffness modifiers. These relationships were consistent both as a function of time and as a function of mass loss, but additional data are needed to more accurately predict the effects. The limited relationships likely reflect the variations in fungal decay across the test members., One of the most used materials in the shift to mass timber construction has been cross-laminated timber (CLT). Substantial research has gone into structural characterization and design with CLT, ranging [...]

Cross laminated timber (CLT) is a mass timber product that is gaining popularity in construction within North America. CLT is made up of wood, a building material of biological origin. Therefore, these materials are at a risk of decay upon intrusion of moisture, a situation that could lead to loss of confidence in the material. Ensuring durability and optimum performance of building elements throughout their expected service life will require an understanding of the potential for decay and the possible consequences. This paper reviews the various possibilities of moisture intrusion in CLT, their potential effects on the physical and mechanical properties of CLT, and ultimately the associated biological decay risks. The paper concludes by enumerating variables that are critical and should be evaluated to completely understand decay in CLT panels, stemming from a thorough review of previous studies and methods used to evaluate decay in mass timber., Timber construction is one of humankind's earliest methods of building. Woods (2016) suggested that many homes built over 10,000 years ago were constructed with timber as the primary construction material. [...]

The effect of pretreatment with either boron or glycerol followed by thermal modification on the durability of Douglas-fir heartwood was evaluated in an American Wood Protection Association ground proximity test in Hilo, Hawaii. Non-thermally modified samples were generally more heavily decayed than any of the modified woods, but there was no consistent effect of different thermal modification conditions on decay resistance. Thermally modified woods tended to perform better than untreated timbers but not as well as copper azole-treated Douglas-fir heartwood lumber in test at the same site. The results are discussed in relation to how the extreme site conditions might have made it difficult for thermally modified materials to perform., Thernial modification is a long-established method for altering the resistance of timber to moisture uptake, thereby resulting in conditions that are presumably less conducive to fungal attack (Esteves and Pereira [...]

Rapid Ohia Death is a major concern for the viability of ohia (Metrosideros polymorpha) in Hawaii and has led to restrictions on log movement. The potential for using disodium octaborate tetrahydrate (DOT) and didecyl dimethyl ammonium chloride (DDAC) dip diffusion treatments to control the two causal fungi (Ceratocyslis lukuohia and Ceratocystis huliohia) was investigated. A 10 percent boric acid equivalent dip diffusion treatment killed the pathogens in 0.5-cm-thick disks obtained from 4.0- to 5.0-cm-diameter limbs of naturally colonized trees. DOT tended to diffuse more consistently in 50- to 60-cm-long bolts of small (4.0 to 9.0 cm) and large (9.1 to 17.0 cm) diameter healthy ohia compared with those bolts naturally infected by C. lukuohia. Diffusion periods longer than 6 weeks resulted in deeper penetration. Immersion (24 h) of logs (1.3 m long; 9 to 17 cm diameter) from C. lukuohia artificially inoculated trees in two forest locations in a 15 percent DOT/1 percent DDAC solution and storage for 10 weeks before evaluation resulted in incomplete elimination of the pathogen and lower boron concentrations in the inner sapwood than outer. Further investigations are needed to explore using either higher boron concentrations or longer diffusion periods to deliver fungicidal concentrations of boron deeper within the wood matrix., The Hawaiian keystone tree ohia (Metrosideros polymorpha Gaudich.) is under attack by two newly discovered fungal pathogens, Ceratocystis lukuohia I. Barnes, T.C. Harrin, and L.M. Keith and Ceratocystis huliohia I. [...]

Wooden crossarms play a major role in supporting electric distribution lines in North America, but relatively few data exist on their condition as they age. The residual capacity of Douglas-fir crossarms in service in western Oregon for 45 to 60 years was investigated. Arms were sampled for residual preservative retention, the presence of visible decay fungi, and residual flexural properties; these results were then compared with three nondestructive tools. A majority of the arms tested had preservative levels well below those required for new arms, but only one decay fungus was isolated, and only five arms removed and dissected had any evidence of visible internal decay. Moduli of rupture for the arms were generally below the minimum levels required by national standards, but most still retained at least 67 percent of this value. Nondestructive evaluation tools were generally poorly correlated with flexural properties, possibly because of the heavily weathered and checked exterior condition., Crossarms are widely used on electric utility poles in North America to support the wires and create separation between the electrical phases. Although a variety of materials can be used [...]

The performance of several wood surface treatments as well as a silica treatment claiming to provide protection against fungal decay and termite attack in aboveground applications were examined in termite, ground proximity, and sandwich tests at a subtropical site near Hilo, Hawaii. In general, the surface treatments performed similarly to untreated controls and provided little or no protection against fungal or insect attack. The silicate treatment provided some termite and decay protection, but fungal decay resulted in rapid declines in condition after 50 to 54 months of exposure. Copper azole--treated lumber provided the best performance against both termites and fungal attack, illustrating the benefits of pressure treatment over surface treatments in highdecay-hazard environments. These results also illustrate the importance of rigorous testing and standardization protocols for any product that makes durability claims before it enters the market to ensure that it will perform as expected., Wood exposed aboveground in exterior applications is invariably subjected to wetting that creates conditions conducive to fungal attack. Extending the useful life of timber requires either using naturally durable heartwood [...]