Australian Timber Pole Resources for Energy Networks. A review

More than 5 million timber utility poles are currently in-service throughout Australia’s energy networks. Most were produced from select native forest-grown hardwood species having the required structural characteristics and naturally-durable heartwood. Anecdotal evidence suggests that up to 70% of the timber poles that are currently in-service were installed over the 20 years following the end of World War Two, and these poles are likely to require replacement or remedial maintenance over the next decade. The purposes of this review were to clarify the supply and demand situation for traditional timber poles, and to investigate alternatives in terms of their potential availability and suitability.

Behaviour of stress wave propagation in utility timber pole

Non-destructive testing has been used for many years to evaluate the in situ condition of timber piles. Longitudinal impact is usually applied on the top of piles to induce longitudinal wave to detect faults in piles due to the fact that the longitudinalwave has less dispersive nature at lowfrequency. On the other hand,when it comes to evaluation of poles in situ, it is different as poles are partly embedded in soil and it is more practical to produce bending waves, as the top of the pole is not easily accessible. However, bending wave is known for its highly dispersive nature; especially in the low frequency range which is usually induced in low strain integrity testing. As bending wave can be considered as a hybrid of longitudinal and shear waves, it will be helpful, if it could detect the component of these twowaves separately.To do so, components of displacements or accelerations along radial and longitudinal directions need to be determined. By applying Fast Fourier Transform (FFT) on the signals, the dominant frequencies can be obtained. It has been found that, the longitudinal component decreases along radial direction which indicates the presence of bending wave component and this finding allows to the application of ContinuousWavelet Transform (CWT) on the longitudinal component of wave signals in order to obtain phase velocity. Phase velocities at different frequencies are then determined to draw the dispersive curve and compare with analytical phase velocity curve. The dispersion curve matched well with the analytical curve. © 2013 Taylor & Francis Group.

Reducing the effect of wave dispersion in a timber pole based on transversely isotropic material modelling

Round timbers are used for telecommunication and power distribution networks, jetties, piles, short span bridges etc. To assess the condition of these cylindrical shape timber structures, bulk and elementary wave theory are usually used. Even though guided wave can represents the actual wave behaviour, a great deal complexity exists to model stress wave propagation within an orthotropic media, such as timber. In this paper, timber is modelled as transversely isotropic material without compromising the accuracy to a great extent. Dispersion curves and mode shapes are used to propose an experimental set up in terms of the input frequency and bandwidth of the signal, the orientation of the sensor and the distance between the sensors in order to reduce the effect of the dispersion in the output signal. Some example based on the simulated signal is also discussed to evaluate the proposed experimental set up.

Determinations of stress wave velocity in a timber pole using wavelet transform

This paper presents an application of Wavelet Transfonn (WT) for determination of stress wave velocity for Non-destructive Testing of timber utility poles in service. For surface Non-destructive Testing (NDT), the hammer impact, which produces generally broadband frequency excitation, is used to generate stress wave. Moreover, due to practicality the impact location for field testing of a utility pole is on the side of the pole and 1.5 m above ground level. And the geometry of utility pole could not guarantee non-dispersive longitudinal wave. All of these issues have resulted in lack of accuracy and reliability of results from surface NDT in field testing. In recognition of such problem, this research explores methods to reliably calculate desired wave velocity by isolating wave mode and studying dispersive nature of utility pole. Fast Fourier Transfonn (FFT) is firstly conducted to determine the suitable frequency from a stress wave data. Then WT is applied on the wave data mentioned to perfonn time-frequency analysis. Velocity can be detennined by time history data of desired frequency from WT results which will be compared with the available analytical solution for longitudinal wave velocity. The results of the investigation showed that wavelet transfonn analysis can be a reliable signal processing tool for non-destructive testing in tenns of velocity detennination, which in tum also helps to detennine the embedded length of the timber pole.

A study of guided wave propagation in timber pole using spectral finite element method

Timber is one of the most widely used structural material all over the world. Round timbers can be seen as a structural component in historical buildings, jetties, short span bridges and also as piles for foundation and poles for electrical and power distribution. To evaluate the current condition of these cylindrical type timber structures, guided wave has a great potential. However, the difficulties associated with the guided wave propagation in timber materials includes orthotropic behaviour of wood, moisture contents, temperature, grain direction, etc. In addition, the effect of fully or partially filled surrounding media, such as soil, water, etc. causes attenuation on the generated stress wave. In order to investigate the effects of these parameters on guided wave propagation, extensive numerical simulation is required to conduct parametric studies. Moreover, due to the presence of multi modes in guided wave propagation, dispersion curves are of great importance. Even though conventional finite element method (FEM) can determine dispersion curves along with wave propagation in time domain, it is highly computationally expensive. Furthermore, incorporating orthotropic behaviour and surrounding media to model a thick cylindrical wave (large diameter cylindrical structures) make conventional FEM inefficient for this purpose. In contrast, spectral finite element method (SFEM) is a semi analytical method to model the guided wave propagation which does not need fine meshes compared to the other methods, such as FEM or finite difference method (FDM). Also, even distribution of mass and stiffness of structures can be obtained with very few elements using SFEM. In this paper, the suitability of SFEM is investigated to model guided wave propagation through an orthotropic cylindrical waveguide with the presence of surrounding soil. Both the frequency domain analysis (dispersion curves) and time domain reconstruction for a multi-mode generated input signal are presented under different loading location. The dispersion curves obtained from SFEM are compared against analytical solution to verify its accuracy. Lastly, different numerical issues to solve for the dispersion curves and time domain results using SFEM are also discussed.

A comparative study of guided wave propagation in timber poles with isotropic and transversely isotropic material models

Guided wave (GW) has been used for many years in non-destructive testing (NDT). There are various ways to generate the guided wave, including impact or impulse either manually or using devices. Although the method of impact or impulse is considered to be simple and practical in guided wave generation, it produces waves with broadband frequencies, which often make analysis much more difficult. The frequency bandwidth produced by manual impacts is usually at the low end, and is therefore justified when dealing with one dimensional wave propagation assumption in low strain integrity testing of cylindrical structures. Under such assumption if the velocity is known accurately, NDTs can produce reasonably good results for the condition assessment of the structure. However, for guided wave propagation in timber pole-like structures, it is rather complicated as timber is an orthotropic material and wave propagation in an orthotropic medium exhibits different characteristics from that in isotropic medium. It is possible to obtain solutions for guided wave propagation in orthotropic media for cylindrical structures, even though the orthotropic material greatly complicates GW propagation. In this paper, timber has been considered as a transversely isotropic (i.e. simplified orthotropic) material and a comparative study of GW propagation in a timber pole is conducted considering isotropic and transversely isotropic modelling. Phase velocity, group velocity and attenuation are the main parameters for this comparative study. Moreover, tractionfree situation and embedded geotechnical condition are also taken into consideration to evaluate the effect of boundary. Displacement profile, wave propagation pattern and power flow at particular frequency are utilized to determine different displacement components of longitudinal and flexural waves along and across the timber pole. Effect of temperature and moisture content (in terms of modulus of elasticity) in timber pole is also compared to show the variation in phase velocity.

Determination of embedment depth of timber poles and piles using wavelet transform

This paper presents an investigation on the wave propagation in timber poles with Wavelet Transform (WT) analysis for identification of the condition and underground depth of embedded timber poles in service. Most of non-destructive testing (NDT) applications for timber poles using wave-based methods consider only single wave mode and no dispersion. However, for wave propagations in timber poles (damaged/undamaged), such simplification may not be correct, especially for broad band excitation using impulse impact. To investigate the problem, a 5m timber pole was investigated numerically and experimentally. A dispersion curve is generated from the numerical results to provide guidance on the velocity and wave mode selection. Continuous wavelet transform (CWT) is applied on the same signal to verify the presence of modes and to process data from experimental testing. The results are presented in both time domain and time-frequency domain for comparison. The results of the investigation showed that, wavelet transform analysis can be a reliable signal processing tool for NDT in terms of condition and embedment length determination.

Condition assessment of timber utility poles based on a hierarchical data fusion model

This paper proposes a novel hierarchical data fusion technique for the non-destructive testing (NDT) and condition assessment of timber utility poles. The new method analyzes stress wave data from multisensor and multiexcitation guided wave testing using a hierarchical data fusion model consisting of feature extraction, data compression, pattern recognition, and decision fusion algorithms. The researchers validate the proposed technique using guided wave tests of a sample of in situ timber poles. The actual health states of these poles are known from autopsies conducted after the testing, forming a ground-truth for supervised classification. In the proposed method, a data fusion level extracts the main features from the sampled stress wave signals using power spectrum density (PSD) estimation, wavelet packet transform (WPT), and empirical mode decomposition (EMD). These features are then compiled to a feature vector via real-number encoding and sent to the next level for further processing. Principal component analysis (PCA) is also adopted for feature compression and to minimize information redundancy and noise interference. In the feature fusion level, two classifiers based on support vector machine (SVM) are applied to sensor separated data of the two excitation types and the pole condition is identified. In the decision making fusion level, the Dempster–Shafer (D-S) evidence theory is employed to integrate the results from the individual sensors obtaining a final decision. The results of the in situ timber pole testing show that the proposed hierarchical data fusion model was able to distinguish between healthy and faulty poles, demonstrating the effectiveness of the new method.

Efeito da alteração do hábitat sobre assembleias de peixes em igarapés afogados da Amazônia oriental

Os ecossistemas aquáticos de água doce constituem sistemas complexos que estão sendo expostos a uma variedade de perturbações. Na região Amazônica, o uso dos recursos e ocupação da terra tem alterado a estrutura física do hábitat desses ambientes, especialmente os de pequeno porte (conhecidos como igarapés), influenciando a estrutura e composição de suas comunidades. Vários estudos e programas de avaliação têm sido desenvolvidos a fim de verificar como essas alterações afetam as comunidades bióticas, através de características do hábitat que se mostram mais sensíveis às perturbações. Nesse contexto, o objetivo desse estudo foi mensurar e descrever atributos do hábitat de igarapés afogados e verificar como as assembleias de peixes respondem aos diferentes níveis de integridade física apresentados por esses igarapés. Para isso, testamos a hipótese de que ambientes estruturalmente mais íntegros suportam uma ictiofauna mais diversa do que ambientes impactados, em virtude destes apresentarem uma diminuição na complexidade ambiental. O estudo foi realizado em 34 igarapés, sendo 17 situados dentro do território da Floresta Nacional de Caxiuanã, e 17 em seu entorno, localizados próximos aos centros urbanos dos municípios de Portel e Melgaço (PA). O processo de urbanização encontra-se em expansão na região, alcançando áreas de florestas e corpos hídricos que ainda permanecem preservados. Também há uma intensa atividade extrativista madeireira, pois a área está inserida no principal pólo madeireiro da zona do estuário no estado do Pará. O hábitat físico dos igarapés foi avaliado seguindo um protocolo padronizado de avaliação. Para a coleta dos peixes foram utilizadas redes de mão em um trecho de 150 metros por igarapé durante seis horas (divididas entre os segmentos e entre os coletores). Apesar de detectarmos um conjunto de métricas que responderam ao gradiente de alteração local, estas não se mostraram suficientes na redução ou aumento do número de espécies ao longo dos níveis de preservação, mantendo praticamente constante a riqueza e abundância para os três grupos (alterado, intermediário e íntegro). Porém, a diferença foi significativa para a composição, com onze espécies exclusivas de ambientes alterados e oito exclusivas de ambientes íntegros. A degradação do ambiente físico, mesmo que em escalas menores favorece a ocorrência e maior abundância de espécies tolerantes e com grande plasticidade fenotípica, além do aumento populacional de espécies oportunistas. Diferentes efeitos podem ser exercidos sobre os grupos de espécies que compõem uma comunidade, pois elas apresentam diferentes atributos biológicos e ecológicos que incluem também suas respostas para as mesmas variáveis ecológicas. Portanto, a possível desconstrução da comunidade em grupos de espécies (sejam taxonômicos, funcionais, etc) pode mostrar respostas diferenciadas frente às alterações do hábitat, sendo uma estratégia promissora para associar características ambientais aos padrões de riqueza apresentado por essas comunidades. A avaliação da integridade biótica também é uma alternativa para identificar efeitos da alteração do hábitat sobre as espécies, principalmente considerando a peculiaridade da região e a falta de informações acerca da ictiofauna local.

Determination of the embedded lengths of electricity timber poles utilizing flexural wave generated from impacts

Round timbers are extensively used as utility poles in Australia for electricity distribution and communication. Lack of information on their conditions results in great difficulties on asset management for industries. Despite the development of various non-destructive testing (NDT) techniques for evaluating the condition of piles, few NDTs are reported for applications on timber poles. This paper addresses challenges and issues on development of NDTs for condition assessment and embedded length of timber poles. For this paper, it is mainly focusing on determining the embedded length of the pole considering loss of the sufficient embedment length is a main factor compromising capacity and safety of timber poles. Since it is impractical for generating longitudinal waves by impacting from the top of poles, utilizing flexural wave from side impact on poles becomes attractive. However, the flexural wave is known by its highly dispersive nature. In this paper, one dimensional wave theory, guided wave theory and advanced signal processing techniques have been introduced in order to provide a solution for the problem. Two signal processing techniques, namely short kernel method and continuous wavelet transform, have been investigated for processing flexural wave signals to evaluate wave velocity and embedment length of timber poles in service.

Domestic and export marketing of Auracaria timber

This article examines the need for a marketing approach to support the expansion of trade in Australian forest Products. Opportunities available for trade in hoop pine ( Araucaria cunninghamii), a Queensland species of timber, are examined. Markets within China and Japan are found to have substantial potential end product uses for the plantation timber.

The role of timber plantations in UK Investment portfolios

Although timber plantations and forests are classified as forms of agricultural production, the ownership of this land classification is not limited to rural producers. Timber plantations and forests are now regarded as a long-term investment with both institutional and absentee owners. While the NCREIF property indices have been the benchmarks for the measurement of the performance of the commercial property market in the UK, for many years the IPD timberland index has recently emerged as the U.K. forest and timberland performance indicator. The IPD Forest index incorporates 126 properties over five regions in the U.K. This paper will utilise the IPD Forestry Index to examine the performance of U.K. timber plantations and forests over the period 1981-2004. In particular, issues to be critically assessed include plantation and forest performance analysis, comparative investment analysis, and the role of plantations and forests in investment portfolios, the risk reduction and portfolio benefits of plantations and forests in mixed-asset portfolios and the strategic investment significance of U.K. timberlands.

The role of timber plantations in U.K. investment portfolios

Although timber plantations and forests are classified as forms of agricultural production, the ownership of this land classification is not limited to rural producers. Timber plantations and forests are now regarded as a long-term investment with both institutional and absentee owners. While the NCREIF property indices have been the benchmarks for the measurement of the performance of the commercial property market in the UK, for many years the IPD timberland index has recently emerged as the U.K. forest and timberland performance indicator. The IPD Forest index incorporates 126 properties over five regions in the U.K. This paper will utilise the IPD Forestry Index to examine the performance of U.K. timber plantations and forests over the period 1981-2004. In particular, issues to be critically assessed include plantation and forest performance analysis, comparative investment analysis, and the role of plantations and forests in investment portfolios, the risk reduction and portfolio benefits of plantations and forests in mixed-asset portfolios and the strategic investment significance of U.K. timberlands.