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Design of long-span lightweight timber floors subject to walking excitations: a case study
Get PDFLightweight timber construction is popular in buildings with two or more storeys in Australia. The floors are made of a floorboard supported on joists or trusses. Recently, the sector is moving towards multi-storey construction of different building classes with different floor usages and shared tenancy. Thus, a need for high performing lightweight floor systems becomes urgent. The current vibration control criteriain the Australian standard recommends limitingstatic deflection, which is a coarse method and does not necessarily guarantee satisfactory performance.In the current study, vibration performance of a 6m×6m floor system with particleboard flange and trusswebs is investigated under single walker excitations and at different walking frequencies. The vibration responses are compared to the predictions and performance criteria recommended in international standards and guidelines. The results show inconsistencies in the calculated levels of acceptance from different sourcesusing simplified expressions and more rigorous methods of analysis. This highlights the significance of the need for further research to developa harmonised method of analysis that can be used by manufacturers and engineers in Australia to confidently design floors for vibrations
Influence of the moisture content on the fracture energy and tensile strength of hardwood spotted gum sawn timber and adhesive bonds (gluelines)
Get PDFThis study aims to measure the fracture properties, including crack initiation and propagation, of Australia’s native forest grown spotted gum ([SPG], Corymbia citriodora) sawn timber and associated adhesive bonds at different moisture content levels. The collected data were used as input values to develop a numerical model to understand the delamination of SPG glulam beams when exposed to a wetting and drying process. Thus, Mode I and Mode II fracture energies for crack propagation along radial and glueline directions were experimentally investigated under various moisture content levels (8%, 12% and 16%). Single-end notched beams and compact shear specimens were used to capture the Mode I and Mode II fracture energies, respectively. For crack initiation, the tensile strength perpendicular to the grain and the shear strength (taken as the maximum stress from the Mode II fracture tests) were also measured. In total, 200 experimental tests were performed. One-way analysis of variance statistical analyses showed that the fracture energies and shear strengths were independent of the range of moisture content levels investigated. In addition, the collected data were compared with the limited published fracture properties of other hardwood species
Reducing granulation in the production of Imperial mandarins
Get PDFGranulation is a physiological disorder in which juice vesicles are hardened, gelled or granular. Severely granulated fruit are an opaque white in colour, with no or minimal extractable juice. Partially granulated fruit are ‘crunchy’, with less extractable juice and with less flavour than unaffected fruit.
Granulation of Imperial mandarins is a significant problem for the Australian domestic mandarin market. Incidence varies with season and, because affected fruit cannot reliably be detected by appearance or density, a significant proportion of granulated fruit reaches the market in some years. Despite international research on this issue since the 1930s, until now little progress has been made in identifying the causes or providing solutions to this problem.
Granulation is more severe in years with high rainfall or with low crop loads. In research trials and surveys conducted as part of this project, we found granulation is associated with larger fruit size, lower acid content in juice, lighter (sandier) soils, vigorous rootstocks, and the position of fruit in the tree, with fruit inside the canopy granulating more. These factors are the basis of our hypothesis that granulation is caused by higher water potential in juice cells as the fruit develop. High water potential in juice cells is due to low soluble solid content (such as sucrose and acids) and/or higher turgor pressure. High water potential may lead to cell wall thickening and subsequent gellification or granulation of juice cells. Our hypothesis suggests that nutrition, irrigation and crop load management are key to managing this problem.
In this project, we conducted a range of on-farm trials of management techniques to give growers strategies for reducing the incidence of granulation in their crops. The most successful strategies were avoiding overwatering early in fruit development, maintaining consistently high crop loads and applying adequate nitrogen fertiliser in winter to support the spring flowering and flush.
The project included trials that attempted to answer in more detail the questions, ‘How much water should we apply?’ and ‘Which are the critical times for reducing irrigation?”. Unfortunately, frequent rainfall in several of the trial years meant these questions remain largely unanswered, although several aspects of our research suggest that the earlier stages of fruit development are more important. We tried to find management practices that might help after a wet spring, that is, strategies that can be applied later in fruit development, including foliar application of fertilisers. These were unsuccessful, emphasizing that early fruit development is the critical period. We found some influence of competition between spring flush growth and fruit quality, but our attempts to reduce this competition with the use of plant growth regulators, later pruning and branch girdling were also disappointing.
Growers are thus encouraged to focus on the three proven strategies of avoiding overwatering in early fruit development, applying sufficient nitrogen in winter and managing crop loads through thinning and timely picking of crops
Litterpedia [website]
No full textLitterpedia brings together chicken bedding and litter management information for the Australian chicken meat industry in one, easily accessible location.
Chicken litter, or bedding, is an essential part of breeding and growing meat chickens. Litter in good condition—dry and friable—optimises chicken health and welfare, improving their growth and productivity.
Here you will find litter resources and tools for meat chicken growers and breeders including fact sheets, guides, videos and webinar recordings. There are also links to research project summaries and completed project final reports.
Topics covered include:
Litter selection
Litter assessment
Drinker management
Litter tilling
Ventilatio
Building a better Mungbean: Breeding for reproductive resilience in a changing climate
Get PDFMungbean (Vigna radiata (L.) R. Wilczek var. radiata) is a significant food and cash crop grown in tropical and subtropical regions. Mungbean production and consumer demand have increased substantially over the last two decades, owing to its agronomic, nutritional and economic benefits. Despite increased breeding efforts and the expansion of mungbean production in various agro-climatic regions, further production is hindered by low yield and variability, which is partly attributed to the impacts of abiotic stress. Abiotic stress impacts on the physiology, morphology and reproductive ability of mungbean which influences yield. Exposure to abiotic stresses at the reproductive stage is considered the most critical for yield production. In this review, we evaluate how abiotic stress impacts mungbean growth and productivity when occurring during the reproductive stage and traits that may confer adaptation. We present the limitations of current research including limited number of genotypes, lack of field experiments and detailed experimental information. We highlight the opportunities to exploit new tools and technologies, such as high-throughput phenotyping platforms, gene editing, and genomic selection, to accelerate breeding efforts to develop more resilient mungbean cultivars for today and tomorrow
Understanding the complexity of the Indonesian fresh mango industry in delivering quality to markets: A systems thinking approach
No full textIn response to anticipated export demand growth and the expansion of the modern domestic market, the Indonesian mango industry faces both opportunities and challenges in elevating the production of high-quality mangoes. This industry’s complexity, characterised by various actors with wide-ranging interests, poses a key challenge. We implemented a systems thinking approach in this study to comprehend this complex Indonesian mango value chain and identify deep-rooted issues that could obstruct high-quality mango production. Our research employed participatory group model building with primary actors and stakeholders, which disclosed that conventional agricultural management practices, inadequate postharvest handling, and a lack of coordinated quality standards are key drivers of low-quality mango production. By utilising system archetypes—interpretive tools capturing complex food system behaviour—we demonstrate that adopting clear market orientation through mutual contractual arrangements and fostering collaboration among key actors can significantly influence high-quality mango production. This study provides a nuanced understanding of the underlying factors affecting system behaviour over time, a component often overlooked in traditional value chain analysis. As a result, policy formulation can better address the root causes of Indonesia’s low production of high-quality mangoes
Legume options for summer-active pastures in a temperate rainfall environment of south-eastern Australia
Get PDFContext: High-quality, summer-active pastures could improve meat production in south-eastern Australia by facilitating livestock finishing over summer, with legumes critical for enhancing the nutritive value of pasture mixes. Available legumes vary in their ability to withstand moisture stress and grazing.Aims: We aimed to identify legumes suitable for a summer–autumn finishing system.Methods: We tested pure swards of 12 cultivars across eight legume species in replicated small-plot experiments at Goulburn and Bombala, New South Wales, assessing productivity, persistence and warm-season nutritive characteristics over 2–3 years.Key results: Lucerne (Medicago sativa) was clearly the most productive species during summer and outperformed the clovers (Trifolium spp.) in terms of persistence and productivity throughout most of the experimental period at both sites, except during autumn 2021 after high rainfall in March. Caucasian clover (T. ambiguum) was also highly persistent at both sites. Talish clover (T. tumens) and strawberry clover (T. fragiferum) were more persistent than white clover (T. repens) and red clover (T. pratense). White clover recovered strongly under high rainfall after drought, whereas red clover established rapidly but showed less capacity for post-drought recovery. Hybrid Caucasian × white clover was the least productive legume. Alternative clover species sometimes had slightly lower values of nutritive characteristics than white clover; red clover sometimes had distinctly lower values.Conclusions: Lucerne performed best but several clovers were also productive, persistent and of high nutritive value over the summer–autumn period.Implications: Talish, Caucasian and strawberry clovers warrant further investigation for inclusion in summer-active pastures in south-eastern Australia
Stuck in the mud: Persistent failure of ‘the science’ to provide reliable information on the ecological roles of Australian dingoes
Get PDFApex predators are believed to play important roles in maintaining the structure and function of ecological systems, but actual evidence for mesopredator releases and trophic cascades in terrestrial systems is mixed and equivocal, largely due to the systemic and continued use of weak-inference or correlative study designs to investigate these hypothesised causal processes. Here we critically review the experimental designs of empirical studies examining relationships between dingoes and mesopredators in Australian ecosystems. We found that 83 % (30 out of 36) of recent study designs lacked one or more of the essential experimental design elements needed to assess causal relationships (such as experimental treatments and controls, treatment replication, and/or treatment randomisation), demonstrating that the inferential strength or reliability of ‘the science’ on this subject remains weak and equivocal. Only five studies published in the last decade (N = 36), and eight in total since 1993 (or 11 %, N = 76), were capable of assessing dingoes' potential causal roles in mesopredator release; and all eight studies consistently demonstrated that dingoes do not supress mesopredators or initiate trophic cascades through mesopredator release effects at a population level, independent of ecological context. Thus, there is a demonstrable absence of evidence and evidence of absence for dingo suppression of mesopredators in Australia. We encourage large carnivore conservation managers and policymakers to base their decisions on the strongest available science. In this way, researchers and managers will have the best chance of conserving these important and valuable species into the future
Vibration of Timber and Hybrid Floors: A Review of Methods of Measurement, Analysis, and Design
Get PDFFloor vibration, although not a safety concern, is a prevalent performance complaint in multi-story structures. With the increasing use of mass timber construction, various types of long-span timber floors (LSTFs), including plain cross-laminated timber (CLT), CLT with secondary beams (ribbed-deck), and hybrid systems such as timber–concrete composite (TCC) and CLT on-steel-support beams, are gaining popularity. However, due to limited knowledge regarding their vibration characteristics and acceptance criteria, these construction types are often overlooked during the design stage by architects, engineers, and builders. Existing standards and guidelines primarily calibrated for steel and concrete floors lack a validated and calibrated method for evaluating the vibration performance of LSTFs. Nonetheless, it is essential for structural engineers to address vibration concerns during the design stage and potentially investigate excessive vibration in existing buildings, providing mitigation solutions. This article provides a comprehensive overview, discussion, and analysis of the measurement, analysis, design, perception, and acceptability of vibration of timber floors as outlined in international standards and commonly used guidelines. Experimental and theoretical case studies, including vibration measurements of a CLT floor and a comparison of vibration acceptability in lightweight timber floors using different methods, are reported. The results highlight discrepancies between simplified equation calculations and modal analysis observations, underscoring the limitations of relying solely on simplified equations. Furthermore, it is observed that current modal superposition methods tend to be conservative in predicting floor acceleration and velocity responses. Recommendations are provided for future research in the field to enhance floor vibration assessment techniques, aiming for improved design optimization and occupant comfort
An investigation into potential genetic predictors of birth weight in tropically adapted beef cattle in northern Australia
Get PDFContext: Birth weight can be an important trait in beef cattle through its association with dystocia and increased likelihood of calf and cow mortality. Recording large numbers of birth weights in beef cattle to obtain a suitable genetic evaluation has often been hard to achieve.Aims: We assess if coronet circumference measurements taken at birth and weights and coronet circumference measured post-birth are suitable predictors of birth weight for use in genetic evaluation in northern Australian tropically adapted beef breeds.Methods: Animals were recorded at birth for weight (N = 5352) and coronet circumference (N = 2552), at 3 months of age for the liveweight (N = 2848) and coronet circumference (N = 2855) and liveweight at 6 months (N = 4929). Data were from three tropically adapted beef cattle breeds (viz. Brahman, Droughtmaster and Santa Gertrudis) recorded in two northern Australia herds. Genetic parameters were estimated from a pooled dataset containing all three breeds.Results: Birth weight had an estimated direct and maternal heritability of 0.51 (0.04) and 0.14 (0.02) respectively. Coronet circumference also had high heritabilities, with estimates at birth and 3 months of 0.50 (0.07) and 0.55 (0.06) respectively. The estimated genetic correlation between birth weight and coronet circumference measured at birth was 0.86 (0.03). Birth weight genetic correlations were 0.75 (0.05) with 3-month weight, 0.69 (0.05) with weaning weight and 0.62 (0.05) with coronet circumference at 3 months.Conclusions: Coronet measurements could be used in genetic evaluation as a proxy for birth weight. However, the most useful coronet measure was when it was recorded at birth. This would still require catching the calf at birth, thus greatly reducing the benefit of having an alternative measure. Coronet circumference recorded in the branding cradle at 3 months of age was also a useful predictor of birth weight but added little if post-birth weights were available. Importantly, all post-birth indirect measures of birth weight require adjustment for animal age and, therefore, would need recording of the individual calf’s date of birth.Implications: Coronet circumference recorded at birth and 3 months of age does not appear to be a suitable proxy for genetic evaluation of birth weight