Structural evaluation of concrete expanded polystyrene sandwich panels for slab applications

Sandwich panels are being extensively and increasingly used in building construction because they are light in weight, energy efficient, aesthetically attractive and can be easily handled and erected. This paper presents a structural evaluation of Concrete-Expanded Polystyrene (CEPS) sandwich panels for slab applications using finite element modeling approach. CEPS panels are made of expanded polystyrene foam sandwiched between concrete skins. The use of foam in the middle of sandwich panel reduces the weight of the structure and also acts as insulation against thermal, acoustics and vibration. Applying reinforced concrete skin to both sides of panel takes the advantages of the sandwich concept where the reinforced concrete skins take compressive and tensile loads resulting in higher stiffness and strength and the core transfers shear loads between the faces. This research uses structural software Strand7, which is based on finite element method, to predict the load deformation behaviour of the CEPS sandwich slab panels. Non linear static analysis was used in the numerical investigations. Predicted results were compared with the existing experimental results to validate the numerical approach used

The Evaluation of a Rapid In Situ HIV Confirmation Test in a Programme with a High Failure Rate of the WHO HIV Two-Test Diagnostic Algorithm

BACKGROUND: Concerns about false-positive HIV results led to a review of testing procedures used in a Médecins Sans Frontières (MSF) HIV programme in Bukavu, eastern Democratic Republic of Congo. In addition to the WHO HIV rapid diagnostic test algorithm (RDT) (two positive RDTs alone for HIV diagnosis) used in voluntary counselling and testing (VCT) sites we evaluated in situ a practical field-based confirmation test against western blot WB. In addition, we aimed to determine the false-positive rate of the WHO two-test algorithm compared with our adapted protocol including confirmation testing, and whether weakly reactive compared with strongly reactive rapid test results were more likely to be false positives. METHODOLOGY/PRINCIPAL FINDINGS: 2864 clients presenting to MSF VCT centres in Bukavu during January to May 2006 were tested using Determine HIV-1/2 and UniGold HIV rapid tests in parallel by nurse counsellors. Plasma samples on 229 clients confirmed as double RDT positive by laboratory retesting were further tested using both WB and the Orgenics Immunocomb Combfirm HIV confirmation test (OIC-HIV). Of these, 24 samples were negative or indeterminate by WB representing a false-positive rate of the WHO two-test algorithm of 10.5% (95%CI 6.6-15.2). 17 of the 229 samples were weakly positive on rapid testing and all were negative or indeterminate by WB. The false-positive rate fell to 3.3% (95%CI 1.3-6.7) when only strong-positive rapid test results were considered. Agreement between OIC-HIV and WB was 99.1% (95%CI 96.9-99.9%) with no false OIC-HIV positives if stringent criteria for positive OIC-HIV diagnoses were used. CONCLUSIONS: The WHO HIV two-test diagnostic algorithm produced an unacceptably high level of false-positive diagnoses in our setting, especially if results were weakly positive. The most probable causes of the false-positive results were serological cross-reactivity or non-specific immune reactivity. Our findings show that the OIC-HIV confirmation test is practical and effective in field contexts. We propose that all double-positive HIV RDT samples should undergo further testing to confirm HIV seropositivity until the accuracy of the RDT testing algorithm has been established at programme level

Embedding cultural competence in faculty : a mixed-methods evaluation of an applied Indigenous proficiency workshop

One of the most pressing issues in Australian society is the gap between Indigenous and non-Indigenous health and life expectancies (Marmot, 2017). Australia agreed with the World Health Organisation’s 2008 Closing the Gap in a Generation report (WHO, 2008), spending approximately 5.6% of government expenditure towards ameliorating this gap (Gardiner-Garden & Simon-Davies, 2012), yet there have been only minimal positive outcomes (Alford, 2015; Gannon, 2018). In applied terms, this means Indigenous people are still dying younger (Anderson et al., 2016), scoring higher on psychological distress (Markwick, Ansari, Sullivan, & McNeil, 2015) and suffering poorer indices on all chronic diseases (e.g. Walsh & Kangaharan, 2016; Thompson, Talley, & Kong, 2017). The level of complexity involved in addressing these “wicked” or seemingly “impossible to solve” health problems is made worse by the lack of any pan-national strategic planning and/or intervention evaluation (Lokuge et al., 2017), even though there has been a plethora of programs and projects designed to improve Indigenous health (see for example, AGPC, 2016). Leaders in health and educational institutions must consider why there is a lack of progress in closing the gap in Indigenous health and life expectancies. Addressing the inequities in Indigenous health requires a determinant of health approach (Mitrou et al., 2014), as 39% of the gap in health outcomes can be explained by social determinates (AIHW, 2017; Markwick, Ansari, Sullivan, Parsons, & McNeil, 2014). The social determinant considered to most reliably predict Indigenous poor health is racism (Kelaher, Ferdinand, & Paradies, 2014; Paradies, 2006; Paradies & Cunningham, 2009; Paradies et al., 2015; Paradies, Truong, & Priest, 2014)

Mechanical properties of polymer concrete with different types of resin

Polymer concrete is reported to have better mechanical properties than its counterpart, Ordinary Portland Cement (OPC) concrete. It is gaining increased popularity as a new construction material due to its high compressive, tensile and flexural strengths, short curing time, impact resistance, chemical resistance and freeze-thaw durability. It can be used to repair concrete structures, build slabs and beams of small cross sections and sleepers. A research program has been initiated to improve fundamental understanding of this material and to provide the knowledge required for its broad utilization. In this experimental program, two types of resins (vinylester and epoxy resin) combined with fly ash and sand were used to make polymer concrete mortar. The weight percentages used in the mix designs were selected after analyzing volumetric properties of sand. This paper presents and discusses the results from an investigation of uniaxial compressive stress-strain relationship of polymer based concrete. The effect of resin (binder), and fly ash contents on the compressive strength, flexural strength, split tensile strength and modulus of elasticity of vinylester and epoxy resin based polymer filler is reported. It has been found that epoxy resin based polymer concrete and vinylester based polymer concrete can achieve compressive strengths of 75MPa and 113MPa respectively. Vinylester polymer concrete showed 4% ultimate strain, while that for epoxy polymer concrete was 8%. Tensile strengths were as high as 15MPa for both types of polymer concrete. The results show that the polymer based filler materials are suitable for both compression and tensile loading situations

Stress-strain model for high strength concrete confined by FRP

Ductility of High Strength Concrete (HSC) columns can be increased by lateral confinement. The conventional confinement with steel reinforcement may not always be adequate to provide the ductility levels desired by the engineer. The lateral confinement by FRP can provide significantly higher confinement stresses than the conventional steel reinforcement, and convenient for repair applications. Confining pressure applied by FRP is a function of the lateral strain of concrete. Therefore information of axial stress, axial strain and lateral strain relationships of concrete is fundamental in the design of confinement. Many existing models are based on test results with low confining pressures which are not suitable for modelling FRP confined concrete. The authors present a model in this paper which is suitable for use in designing FRP confinement of concrete. Model results are compared with experimental results of FRP confined columns. The results demonstrate the model is suitable for this use

A mathematical model for complete stress-strain curve prediction of permeable concrete

An empirical equation to represent the complete stress-strain behaviour for unconfined permeable concrete with compressive strength ranging between 10-35MPa and porosity ranging between 25-15%, made with different combinations of aggregate size and sand ratios is proposed in this paper. A series of compression tests were conducted on 100 × 200 mm cylindrical samples using a modified testing method to determine the complete stress-strain behaviour of permeable concrete. Various existing models for low strength concrete and normal strength concrete were used and compared with the experimental data. Various parameters were studied and their relationships were experimentally determined. The only parameters need to run the model is the ultimate compressive strength and the density. The proposed empirical stress-strain equations were compared with actual cylinder tests results under axial compression, and demonstrated that the present model gives a good representation of the mean behaviour of the actual stress-strain response

Stress-strain behaviour of confined high strength concrete under monotonically increasing and cyclic loadings

Abstract not availabl

Stress-strain behaviour of confined high strength concrete under monotonically increasing and cyclic loadings

Abstract not availabl

Design of high-strength concrete columns for ductility

Abstract not available