Bamboo reinforced concrete: a critical review

The use of small diameter whole-culm (bars) and/or split bamboo (a.k.a. splints or round strips) has often been proposed as an alternative to relatively expensive reinforcing steel in reinforced concrete. The motivation for such replacement is typically cost—bamboo is readily available in many tropical and sub-tropical locations, whereas steel reinforcement is relatively more expensive—and more recently, the drive to find more sustainable alternatives in the construction industry. This review addresses such ‘bamboo-reinforced concrete’ and assesses its structural and environmental performance as an alternative to steel reinforced concrete. A prototype three bay portal frame, that would not be uncommon in regions of the world where bamboo-reinforced concrete may be considered, is used to illustrate bamboo reinforced concrete design and as a basis for a life cycle assessment of the same. The authors conclude that, although bamboo is a material with extraordinary mechanical properties, its use in bamboo-reinforced concrete is an ill-considered concept, having significant durability, strength and stiffness issues, and does not meet the environmentally friendly credentials often attributed to it.     

Extracting Hidden Context

Concept drift due to hidden changes in context complicates learning in many domains including financial prediction, medical diagnosis, and communication network performance. Existing machine learning approaches to this problem use an incremental learning, on-line paradigm. Batch, off-line learners tend to be ineffective in domains with hidden changes in context as they assume that the training set is homogeneous. An off-line, meta-learning approach for the identification of hidden context is presented. The new approach uses an existing batch learner and the process of contextual clustering to identify stable hidden contexts and the associated context specific, locally stable concepts. The approach is broadly applicable to the extraction of context reflected in time and spatial attributes. Several algorithms for the approach are presented and evaluated. A successful application of the approach to a complex flight simulator control task is also presented.     

Geothermal energy in Australia

Although Australia is not usually associated with geothermal energy, it possesses significant amounts of both conventional (wet) geothermal and hot dry rock (HDR) geothermal resources. The country's conventional geothermal resources are extensive, but are low temperature and are located in areas of low population density with the result that they are not used extensively for either electricity generation or for direct heating. Australia's HDR resources, on the other hand, represent a world-class resource but have not been used to date because the technology for converting HDR resources into electricity is not yet fully commercial. The effort being directed towards exploring economically useful HDR resources and in the development of technology to convert this energy resource into electricity could make HDR resources an important part of Australia's energy mix in the near future, but there are major barriers.     

Basic Oxygen Furnace: Assessment of Recent Physicochemical Models

Metallurgical and Materials Transactions B - Modeling of the basic oxygen furnace (BOF) process, both for online monitoring and fundamental research, has gained importance in steelmaking industry...     

Reduced specificity of autobiographical memory in Cluster C personality disorders and the role of depression, worry, and experiential avoidance.

The study objective was to investigate whether, compared with nonclinical controls, participants with an avoidant, dependent, or obsessive–compulsive Cluster C personality disorder (PD) manifested reduced levels of memory specificity and whether the association of Cluster C PDs with memory specificity is mediated by repetitive negative thoughts and experiential avoidance. The Autobiographical Memory Test (R. J. McNally, N. B. Lasko, M. L. Macklin, & R. K. Pitman, 1995) was administered along with self-report measures (translated into Dutch) for repetitive, uncontrollable, and negative thinking in the form of worry (Penn State Worry Questionnaire; T. J. Meyer, M. L. Miller, R. L. Metzger, & T. D. Borkovec, 1990) and experiential avoidance (Acceptance and Action Questionnaire; S. C. Hayes et al., 2004) to 294 clinical participants diagnosed with Axis I disorders (assessed with the Structured Clinical Interview for DSM–IV Axis I Disorders [SCID-I]; M. B. First, R. L. Spitzer, M. Gibbon, & J. B. W. Williams, 1994) and Axis II disorders (assessed with the SCID-II; M. B. First, R. L. Spitzer, M. Gibbon, & J. B. W. Williams, 1997)—202 with avoidant, 49 with dependent, and 120 with obsessive–compulsive PD—and to 108 matched nonclinical controls. Participants with a Cluster C PD showed lower levels of memory specificity than did nonclinical controls. Depression and worry mediated the effect of Cluster C PDs on memory specificity. Besides depression severity, repetitive, uncontrollable, and negative thinking may constitute a general mechanism mediating the association of various Axis I and II disorders with memory specificity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determinants of the success and sustainability of Bangladesh’s SHS program

Large numbers of households in rural areas in Bangladesh have no access to electricity. Providing these households with electricity by extending the country’s already overloaded grids is neither an economically nor a technically feasible option. Rural electrification strategies therefore, by necessity, need to rely on stand-alone generation systems. One of these is solar home systems (SHS) and the SHS program developed and implemented in Bangladesh has been highly successful, with very large numbers of rural households now participating in the program. What makes the program’s success most remarkable is the fact that it targets households with very low incomes using a purely market-based approach. Those participating in the program pay the full, unsubsidised cost of their SHS using a micro-credit loan facility and are charged high interest rates. Understanding the reasons behind the success of the Bangladeshi program therefore holds potentially valuable lessons for SHS programs being implemented in other developing countries. A comprehensive qualitative and quantitative survey was used to find those factors perceived by program stakeholders as being most critical to the program’s success to date and the factors considered most likely to impact on its future success. The two primary reasons for the program’s success were perceived to be its strong focus on meeting householders’ needs and on its ability to make the solar home systems as affordable as possible. The continued success of the program was considered likely to be determined by a variety of factors, including the ability of program implementers to control increases in the cost of SHS, to maintain the quality of SHS and components and to increase program loan recovery rates, the degree to which the program is integrated into national, energy policy, and the degree to which local banks become involved in the program.     

Hydro,tidal and wave energy in Australia

The three renewable energy technologies discussed in this paper are based on water, but differ markedly in terms of the size of the available potential resource, the maturity of the associated conversion technologies, the extent to which they have been exploited to date, and the current research effort being devoted to their future development. Hydro-electricity and tidal power are both very mature technologies. The exploitation of Australia's relatively limited potential for hydro-electric development began over a century ago and the opportunities for further hydro-electric development are now very restricted. The country's significant tidal power resources, on the other hand, have not been exploited for electricity generation to date, but continual assessment of the feasibility of tidal power projects has been undertaken over the past half century. Although Australia has large ocean wave energy resources, ocean wave energy conversion technology is not yet fully commercial and no commercial wave generation plants are operating in Australia. A small number of wave energy conversion devices, however, are at the pilot testing stage.     

Evaluation of Effective Width and Distribution Factors for GFRP Bridge Decks Supported on Steel Girders

Glass fiber-reinforced polymer (GFRP) bridge deck systems offer an attractive alternative to concrete decks, particularly for bridge rehabilitation projects. Current design practice treats GFRP deck systems in a manner similar to concrete decks, but the results of this study indicate that this approach may lead to nonconservative bridge girder designs. Results from a number of in situ load tests of three steel girder bridges having the same GFRP deck system are used to determine the degree of composite action that may be developed and the transverse distribution of wheel loads that may be assumed for such structures. Results from this work indicate that appropriately conservative design values may be found by assuming no composite action between a GFRP deck and steel girder and using the lever rule to determine transverse load distribution. Additionally, when used to replace an existing concrete deck, the lighter GFRP deck will likely result in lower total stresses in the supporting girders, although, due to the decreased effective width and increased distribution factors, the live-load-induced stress range is likely to be increased. Thus, existing fatigue-prone details may become a concern and require additional attention in design.     

Debonding- and Fatigue-Related Strain Limits for Externally Bonded FRP

Available guidance for mitigating debonding failure of externally bonded fiber reinforced polymer (FRP) composites applied to concrete is evaluated based on data obtained from large- and full-scale experimental programs. Current recommendations are inadequate to effectively mitigate intermediate crack-induced debonding in flexural members. An improved, although still simple to apply, equation for determining limiting FRP material properties to mitigate debonding is presented and evaluated. Additionally, the effect of fatigue loading on the debonding behavior of externally bonded FRP is not adequately addressed in practice. In the limited data presented, a degradation of bond behavior is observed even under fatigue loading conditions amounting to an FRP stress range of no more than 4% of the FRP capacity.