A framework for predicting the residual load carrying capacity of concrete structures exposed to aggressive environments

Reinforced concrete structures are susceptible to a variety of deterioration mechanisms due to creep and shrinkage, alkali-silica reaction (ASR), carbonation, and corrosion of the reinforcement. The deterioration problems can affect the integrity and load carrying capacity of the structure. Substantial research has been dedicated to these various mechanisms aiming to identify the causes, reactions, accelerants, retardants and consequences. This has improved our understanding of the long-term behaviour of reinforced concrete structures. However, the strengthening of reinforced concrete structures for durability has to date been mainly undertaken after expert assessment of field data followed by the development of a scheme to both terminate continuing degradation, by separating the structure from the environment, and strengthening the structure. The process does not include any significant consideration of the residual load-bearing capacity of the structure and the highly variable nature of estimates of such remaining capacity. Development of performance curves for deteriorating bridge structures has not been attempted due to the difficulty in developing a model when the input parameters have an extremely large variability. This paper presents a framework developed for an asset management system which assesses residual capacity and identifies the most appropriate rehabilitation method for a given reinforced concrete structure exposed to aggressive environments. In developing the framework, several industry consultation sessions have been conducted to identify input data required, research methodology and output knowledge base. Capturing expert opinion in a useable knowledge base requires development of a rule based formulation, which can subsequently be used to model the reliability of the performance curve of a reinforced concrete structure exposed to a given environment.

Strategies for minimising the whole of life cycle cost of reinforced concrete bridge exposed to aggressive environments

n design of bridge structures, it is common to adopt a 100 year design life. However, analysis of a number of case study bridges in Australia has indicated that the actual design life can be significantly reduced due to premature deterioration resulting from exposure to aggressive environments. A closer analysis of the cost of rehabilitation of these structures has raised some interesting questions. What would be the real service life of a bridge exposed to certain aggressive environments? What is the strategy of conducting bridge rehabilitation? And what are the life cycle costs associated with rehabilitation? A research project funded by the CRC for Construction Innovation in Australia is aimed at addressing these issues. This paper presents a concept map for assisting decision makers to appropriately choose the best treatment for bridge rehabilitation affected by premature deterioration through exposure to aggressive environments in Australia. The decision analysis is referred to a whole of life cycle cost analysis by considering appropriate elements of bridge rehabilitation costs. In addition, the results of bridges inspections in Queensland are presented

Evaluation of distress mechanisms in bridges exposed to aggressive environments.

There are about 2500 bridges in Queensland, Australia. Majority of these structures require significant repairs around the halfway mark of their design life with probably 1% or less reaching a 100 year design life. (Carse, 2005). This is due to the fact that bridges constructed in aggressive environments such as the coastal regions experience accelerated deterioration. As a result, maintaining the service delivery of these assets has become one of the important issues for the Queensland Department of Main Roads (QDMR).

Implementation of an integrated, technology-based, discovery mode assessment item involving an incubation period to enhance learning outcomes for engineering maths students

In this paper we discuss our current efforts to develop and implement an exploratory, discovery mode assessment item into the total learning and assessment profile for a target group of about 100 second level engineering mathematics students. The assessment item under development is composed of 2 parts, namely, a set of "pre-lab" homework problems (which focus on relevant prior mathematical knowledge, concepts and skills), and complementary computing laboratory exercises which are undertaken within a fixed (1 hour) time frame. In particular, the computing exercises exploit the algebraic manipulation and visualisation capabilities of the symbolic algebra package MAPLE, with the aim of promoting understanding of certain mathematical concepts and skills via visual and intuitive reasoning, rather than a formal or rigorous approach. The assessment task we are developing is aimed at providing students with a significant learning experience, in addition to providing feedback on their individual knowledge and skills. To this end, a noteworthy feature of the scheme is that marks awarded for the laboratory work are primarily based on the extent to which reflective, critical thinking is demonstrated, rather than the amount of CBE-style tasks completed by the student within the allowed time. With regard to student learning outcomes, a novel and potentially critical feature of our scheme is that the assessment task is designed to be intimately linked to the overall course content, in that it aims to introduce important concepts and skills (via individual student exploration) which will be revisited somewhat later in the pedagogically more restrictive formal lecture component of the course (typically a large group plenary format). Furthermore, the time delay involved, or "incubation period", is also a deliberate design feature: it is intended to allow students the opportunity to undergo potentially important internal re-adjustments in their understanding, before being exposed to lectures on related course content which are invariably delivered in a more condensed, formal and mathematically rigorous manner. In our presentation, we will discuss in more detail our motivation and rationale for trailing such a scheme for the targeted student group. Some of the advantages and disadvantages of our approach (as we perceived them at the initial stages) will also be enumerated. In a companion paper, the theoretical framework for our approach will be more fully elaborated, and measures of student learning outcomes (as obtained from eg. student provided feedback) will be discussed.

Cryoreservation of alginate-fibrin beads involving bone marrow derived mesenchymal stromal cells by vitrification

Application of cell-–biomaterial systems in regenerative medicine can be facilitated by their successful low temperature preservation. Vitrification, which avoids ice crystal formation by amorphous solidification, is an emerging approach to cryopreservation. Developing vitrification strategy, effective cryopreservation of alginate–fibrin beads with porcine mesenchymal stromal cells has been achieved in this study. The cell–biomaterial constructs were pre-cultured for 20 days before cryopreservation, allowing for cell proliferation and construct stabilization. Ethylene glycol (EG) was employed as the basic cryoprotectant for two equilibration solutions. Successful cryopreservation of the constructs was achieved using vitrification solution composed of penetrating (EG MW 62 Da) and non-penetrating (sucrose MW 342 Da) cryoprotectants. Stepwise procedure of introduction to and removal of cryoprotectants was brief; direct plunging into liquid nitrogen was applied. Cell viability, evaluated by combining live/death staining and confocal laser microscopy, was similar for both control and vitrified cells in the beads. No detectable damage of microstructure of cryopreserved beads was found as shown by scanning electron microscopy. Both osteogenically induced control and vitrified cells in the constructs were equally capable of mineral production and deposition. There was no statistically significant difference in metabolic activity and proliferation between both groups during the entire culture period. Our study leads to the conclusion that the developed cryopreservation protocol allowed to maintain the integrity of the beads while preserving the ability of the pig bone marrow derived mesenchymal stromal cells to proliferate and subsequently differentiate; demonstrating that vitrification is a promising approach for cryopreser-vation of “ready-to-use” cell–biomaterial constructs.

Vision, functional and cognitive determinants of motor vehicle incidents in older drivers

Background: The proportion of older individuals in the driving population is predicted to increase in the next 50 years. This has important implications for driving safety as abilities which are important for safe driving, such as vision (which accounts for the majority of the sensory input required for driving), processing ability and cognition have been shown to decline with age. The current methods employed for screening older drivers upon re-licensure are also vision based. This study, which investigated social, behavioural and professional aspects involved with older drivers, aimed to determine: (i) if the current visual standards in place for testing upon re-licensure are effective in reducing the older driver fatality rate in Australia; (ii) if the recommended visual standards are actually implemented as part of the testing procedures by Australian optometrists; and (iii) if there are other non-standardised tests which may be better at predicting the on-road incident-risk (including near misses and minor incidents) in older drivers than those tests recommended in the standards. Methods: For the first phase of the study, state-based age- and gender-stratified numbers of older driver fatalities for 2000-2003 were obtained from the Australian Transportation Safety Bureau database. Poisson regression analyses of fatality rates were considered by renewal frequency and jurisdiction (as separate models), adjusting for possible confounding variables of age, gender and year. For the second phase, all practising optometrists in Australia were surveyed on the vision tests they conduct in consultations relating to driving and their knowledge of vision requirements for older drivers. Finally, for the third phase of the study to investigate determinants of on-road incident risk, a stratified random sample of 600 Brisbane residents aged 60 years and were selected and invited to participate using an introductory letter explaining the project requirements. In order to capture the number and type of road incidents which occurred for each participant over 12 months (including near misses and minor incidents), an important component of the prospective research study was the development and validation of a driving diary. The diary was a tool in which incidents that occurred could be logged at that time (or very close in time to which they occurred) and thus, in comparison with relying on participant memory over time, recall bias of incident occurrence was minimised. Association between all visual tests, cognition and scores obtained for non-standard functional tests with retrospective and prospective incident occurrence was investigated. Results: In the first phase,rivers aged 60-69 years had a 33% lower fatality risk (Rate Ratio [RR] = 0.75, 95% CI 0.32-1.77) in states with vision testing upon re-licensure compared with states with no vision testing upon re-licensure, however, because the CIs are wide, crossing 1.00, this result should be regarded with caution. However, overall fatality rates and fatality rates for those aged 70 years and older (RR=1.17, CI 0.64-2.13) did not differ between states with and without license renewal procedures, indicating no apparent benefit in vision testing legislation. For the second phase of the study, nearly all optometrists measured visual acuity (VA) as part of a vision assessment for re-licensing, however, 20% of optometrists did not perform any visual field (VF) testing and only 20% routinely performed automated VF on older drivers, despite the standards for licensing advocating automated VF as part of the vision standard. This demonstrates the need for more effective communication between the policy makers and those responsible for carrying out the standards. It may also indicate that the overall higher driver fatality rate in jurisdictions with vision testing requirements is resultant as the tests recommended by the standards are only partially being conducted by optometrists. Hence a standardised protocol for the screening of older drivers for re-licensure across the nation must be established. The opinions of Australian optometrists with regard to the responsibility of reporting older drivers who fail to meet the licensing standards highlighted the conflict between maintaining patient confidentiality or upholding public safety. Mandatory reporting requirements of those drivers who fail to reach the standards necessary for driving would minimise potential conflict between the patient and their practitioner, and help maintain patient trust and goodwill. The final phase of the PhD program investigated the efficacy of vision, functional and cognitive tests to discriminate between at-risk and safe older drivers. Nearly 80% of the participants experienced an incident of some form over the prospective 12 months, with the total incident rate being 4.65/10 000 km. Sixty-three percent reported having a near miss and 28% had a minor incident. The results from the prospective diary study indicate that the current vision screening tests (VA and VF) used for re-licensure do not accurately predict older drivers who are at increased odds of having an on-road incident. However, the variation in visual measurements of the cohort was narrow, also affecting the results seen with the visual functon questionnaires. Hence a larger cohort with greater variability should be considered for a future study. A slightly lower cognitive level (as measured with the Mini-Mental State Examination [MMSE]) did show an association with incident involvement as did slower reaction time (RT), however the Useful-Field-of-View (UFOV) provided the most compelling results of the study. Cut-off values of UFOV processing (>23.3ms), divided attention (>113ms), selective attention (>258ms) and overall score (moderate/ high/ very high risk) were effective in determining older drivers at increased odds of having any on-road incident and the occurrence of minor incidents. Discussion: The results have shown that for the 60-69 year age-group, there is a potential benefit in testing vision upon licence renewal. However, overall fatality rates and fatality rates for those aged 70 years and older indicated no benefit in vision testing legislation and suggests a need for inclusion of screening tests which better predict on-road incidents. Although VA is routinely performed by Australian optometrists on older drivers renewing their licence, VF is not. Therefore there is a need for a protocol to be developed and administered which would result in standardised methods conducted throughout the nation for the screening of older drivers upon re-licensure. Communication between the community, policy makers and those conducting the protocol should be maximised. By implementing a standardised screening protocol which incorporates a level of mandatory reporting by the practitioner, the ethical dilemma of breaching patient confidentiality would also be resolved. The tests which should be included in this screening protocol, however, cannot solely be ones which have been implemented in the past. In this investigation, RT, MMSE and UFOV were shown to be better determinants of on-road incidents in older drivers than VA and VF, however, as previously mentioned, there was a lack of variability in visual status within the cohort. Nevertheless, it is the recommendation from this investigation, that subject to appropriate sensitivity and specificity being demonstrated in the future using a cohort with wider variation in vision, functional performance and cognition, these tests of cognition and information processing should be added to the current protocol for the screening of older drivers which may be conducted at licensing centres across the nation.

Pram and stroller related injury in Queensland children under 5 years of age

An estimated 200 Queensland children under 5 years of age are injured every year in incidents involving prams or strollers. The majority of injuries are due to falls from or falls with the pram or stroller Nineteen children were identified as having been caught in the pram or stroller mechanism (13 sustained finger injuries). Stairs and escalators were a factor in nearly 10 percent of pram or stroller fall injuries, with children being tipped out of the pram or stroller, or rolling down the stairs in the device. Roll away injuries accounted for eight percent of all pram or stroller fall injuries (some also involving stairs) Roll away injuries could be prevented by a default brake system similar to airport trolleys. Pram or stroller failure was identified in 2% of injuries

A discrete-trial approach to the functional analysis of aggressive behaviour in two boys with autism

Intervention to reduce challenging behaviour may be enhanced when based on a prior functional analysis. The present study describes a discrete-trial approach for the functional analysis of aggressive behaviour in two boys with autism. Twenty brief assessment trials were conducted in the classroom by the teacher under each of three conditions (i.e., attention, task and tangible). The results showed a clear pattern to each child's aggressive behaviour and suggested logical intervention strategies, although the study is limited because it involved only two children. The discrete-trial approach would appear to represent a practical and ecologically valid technique for conducting a functional analysis of challenging behaviour in applied settings

Osteoarthritic cartilage chondrocytes alter subchondral bone osteoblast differentiation via MAPK signalling pathway involving ERK1/2

Osteoarthritic subchondral bone is characterized by abnormal bone density and enhanced production of bone turnover markers, an indication of osteoblast dysfunction. Several studies have proposed that pathological changes in articular cartilage influence the subchondral bone changes, which are typical of the progression of osteoarthritis; however, direct evidence of this has yet to be reported. The aim of the present study was to investigate what effects articular cartilage cells, isolated from normal and osteoarthritic joints, may have on the subchondral bone osteoblast phenotype, and also the potential involvement of the mitogen activated protein kinase (MAPK) signalling pathway during this process. Our results suggest that chondrocytes isolated from a normal joint inhibited osteoblast differentiation, whereas chondrocytes isolated from an osteoarthritic joint enhanced osteoblast differentiation, both via a direct and indirect cell interaction mechanisms. Furthermore, the interaction of subchondral bone osteoblasts with osteoarthritic chondrocyte conditioned media appeared to significantly activate ERK1/2 phosphorylation. On the other hand, conditioned media from normal articular chondrocytes did not affect ERK1/2 phosphorylation. Inhibition of the MAPK–ERK1/2 pathways reversed the phenotype changes of subchondral bone osteoblast, which would otherwise be induced by the conditioned media from osteoarthritic chondrocytes. In conclusion, our findings provide evidence that osteoarthritic chondrocytes affect subchondral bone osteoblast metabolism via an ERK1/2 dependent pathway.

Meniscal repair in the elite athlete : results of 45 repairs with a minimum 5-year follow-up

Background The preservation of meniscal tissue is important to protect joint surfaces. Purpose We have an aggressive approach to meniscal repair, including repairing tears other than those classically suited to repair. Here we present the medium- to long-term outcome of meniscal repair (inside-out) in elite athletes. Study Design Case series; Level of evidence, 4. Methods Forty-two elite athletes underwent 45 meniscal repairs. All repairs were performed using an arthroscopically assisted inside-out technique. Eighty-three percent of these athletes had ACL reconstruction at the same time. Patients returned a completed questionnaire (including Lysholm and International Knee Documentation Committee [IKDC] scores). Mean follow-up was 8.5 years. Failure was defined by patients developing symptoms of joint line pain and/or locking or swelling requiring repeat arthroscopy and partial meniscectomy. Results The average Lysholm and subjective IKDC scores were 89.6 and 85.4, respectively. Eighty-one percent of patients returned to their main sport and most to a similar level at a mean time of 10.4 months after repair, reflecting the high level of ACL reconstruction in this group. We identified 11 definite failures, 10 medial and 1 lateral meniscus, that required excision; this represents a 24% failure rate. We identified 1 further patient who had possible failed repairs, giving a worst-case failure rate of 26.7% at a mean of 42 months after surgery. However, 7 of these failures were associated with a further injury. Therefore, the atraumatic failure rate was 11%. Age and size and location of the tears were not associated with a higher failure rate. Medial meniscal repairs were significantly more likely to fail than lateral meniscal repairs, with a failure rate of 36.4% and 5.6%, respectively (P < .05). Conclusion Meniscal repair and healing are possible, and most elite athletes can return to their preinjury level of activity.

Investigation of inclusions trapped inside Libyan Desert glass by Raman microscopy

Several specimens of Libyan Desert Glass (LDG), an enigmatic natural glass from Egypt, were subjected to investigation by micro-Raman spectroscopy. The spectra of inclusions inside the LDG samples were successfully measured through the layers of glass and the mineral species were identified on this basis. The presence of cristobalite as typical for high-temperature melt products was confirmed, together with co-existing quartz. TiO2 was determined in two polymorphic species, rutile and anatase. Micro-Raman spectroscopy proved also the presence of minerals unusual for high-temperature glasses such as anhydrite and aragonite.

Inside alluvium

Observation bores from lower Lockyer creek are displayed with classified geology and water levels disks. The disks are interpolated to form a water surface (surface red/yellow/green). The image is taken from below the ground surface (surface cream), in the alluvium.

The role of traffic violations in police-reported bicycle crashes in Queensland

Media articles have promoted the view that cyclists are risktakers who disregard traffic regulations, but little is known about the contribution of cyclist risk-taking behaviours to crashes. This study examines the role of traffic violations in the 6774 police-reported bicycle crashes in Queensland between January 2000 and December 2008. Of the 6328 crashes involving bicycles and motor vehicles, cyclists were deemed to be at fault in 44.4% of the incidents. When motorists were determined to be at-fault, ‘failure to yield’ violations accounted for three of the four most reported contributing factors. In crashes where the cyclist was at fault, attention and inexperience were the most frequent contributing factors. There were 67 collisions between bicycles and pedestrians, with the cyclist at fault in 65.7%. During the data period, 302 single-bicycle crashes were reported. The most frequent contributing factors were avoidance actions to miss another road user and inattention or negligence.