A review on cement degradation under CO2-rich environment of sequestration projects

Global warming arising from the release of greenhouse gasses into the atmosphere is one of the biggest issues attracting a lot of attention. One of the conventional problems in sequestration projects is the degradation of Portland cement due to its exposure to supercritical CO2. This paper gives a review on the laboratory work performed to understand changes in the mechanical and transport properties of cement when it is in a CO2 rich environment. The results obtained indicated that pozzolanic material could be useful in enhancing the cement resistance against CO2, although more studies are still required to confirm this conclusion

Current Status of Radioisotope Applications in Defence

Reviews the current status of radioisotope applications in Defence- R&D Establishments, Defence Inspectorates, Ordnance Factories, Public Sector Undertakings under the Defence Ministry, Army, Navy and Air Force Establishments and Military Hospitals. It also lists the users of film badge service in Defence. Training programmes in radioisotope applications in Defence conducted by DRDO organisations have also been highlighted

Structural behaviour of optimized cold-formed steel beams

Cold-formed steel (CFS) members have been used significantly in light-gauge steel buildings due to their inherent advantages. Optimizing these CFS members in order to gain enhanced loadbearing capacities will result in economical and efficient building solutions. This research presents the investigation and results of the optimization of CFS members for flexural capacity. The optimization procedure was performed using the particle swarm optimization (PSO) method, while the section moment capacity was determined based on the effective width method adopted in EN 1993-1-3 (EC3). Theoretical and manufacturing constraints were incorporated while optimizing the CFS cross-sections. In total, four CFS sections – lipped channel beam (LCB), optimized LCB, folded-flange and super-sigma – were considered in the optimization process, including new sections. The section moment capacities of these sections were also obtained through non-linear finite element (FE) analysis and compared with the EC3-based, optimized section moment capacities. The results show that, compared with a commercially available LCB with the same amount of material, the new CFS sections possess the highest section moment capacity enhancements (up to 65 %). In addition, the performance of these CFS sections when subjected to shear and web-crippling actions was also investigated using non-linear FE analysis

Optimised cold-formed steel beams in modular building applications

Modular Building Systems (MBS) has seen an accelerating growth in the construction sector owing to its potential advantages, such as quick erection, improved energy efficiency and less reliant on good weather over conventional construction methods. Therefore, it could be a viable solution to supporting the efforts of solving Britain's housing crisis within a short duration. Construction industries and researchers are working towards better understanding MBS performance at different scales and contexts. To date, research on MBS focused on investigating the structural, social and economic, and safety performances and indicated that there are challenges (Need of lightweight materials and more access space, transportation restrictions, improving structural, fire and energy performances) associated with their use, yet to be addressed. This paper highlights how the incorporation of optimised Cold-Formed Steel (CFS) members with the slotted web can address these challenges. Hence, optimisation technique was employed to enhance the structural performance and to effectively use the given amount of material of CFS members. Lipped channel, folded-flange, and super-sigma have been optimised using the Particle Swarm Optimisation (PSO) method and were analysed using FEM. Results showed that the flexural capacity of the optimised sections was improved by 30–65% compared to conventional CFS sections. A conceptual design of MBS was developed using the optimised CFS members, demonstrating the potential for lighter modules and thus more sustainable structures, reducing the carbon footprint. Therefore, optimisation techniques and slotted perforations would address the aforementioned challenges related to MBS, result in more economical and efficient MBS for inhabitants and construction industries

Finite Element Modelling to Predict the Fire Performance of Bio-Inspired 3D-Printed Concrete Wall Panels Exposed to Realistic Fire

Large-scale additive manufacturing (AM), also known as 3D concrete printing, is becoming well-recognized and, therefore, has gained intensive research attention. However, this technology requires appropriate specifications and standard guidelines. Furthermore, the performance of printable concrete in elevated temperature circumstances has not yet been explored extensively. Hence, the authors believe that there is a demand for a set of standardized findings obtained with the support of experiments and numerical modelling of the fire performance of 3D-printed concrete structural elements. In general, fire experiments and simulations focus on ISO 834 standard fire. However, this may not simulate the real fire behaviour of 3D-printed concrete walls. With the aim of bridging this knowledge disparity, this article presents an analysis of the fire performance of 3D-printed concrete walls with biomimetic hollow cross sections exposed to realistic individual fire circumstances. The fire performance of the non-load-bearing 3D-printed concrete wall was identified by developing a suitable numerical heat transfer model. The legitimacy of the developed numerical model was proved by comparing the time–temperature changes with existing results derived from fire experiments on 3D-printed concrete walls. A parametric study of 96 numerical models was consequently performed and included different 3D-printed concrete wall configurations under four fire curves (standard, prolonged, rapid, and hydrocarbon fire). Moreover, 3D-printed concrete walls and mineral wool cavity infilled wall panels showed enhanced fire performance. Moreover, the cellular structures demonstrated superior insulation fire ratings compared to the other configurations

Numerical modelling and shear design rules of stainless steel lipped channel sections

The demand for highly structurally efficient stainless steel is limited to a certain extent by its high initial cost. Therefore, the utilisation of material to the optimum possible level is important. In achieving this, further consideration should be given to enhance the design rules where beneficial effects such as pronounced strain hardening in stainless steel should be taken into account in the design process. In addition to that, a thorough understanding of the structural behaviour of stainless steel sections is also required. However, the shear behaviour and capacity of cold-formed stainless steel lipped channel beams (LCBs) have not been thoroughly investigated previously. Therefore, experimental and detailed finite element (FE) modelling were undertaken to investigate the shear behaviour and strength of stainless steel LCBs. A comprehensive parametric study was also conducted by developing 100 FE models. From the results, the available post-buckling strength in slender stainless steel LCBs was highlighted. Furthermore, the beneficial strength increment due to the strain hardening effect of stainless steel, particularly for compact LCBs in shear, was investigated. Comparisons indicated that current EN1993-1-4 and direct strength method (DSM) shear design rules are too conservative in particularly for compact sections. Thus, existing shear design rules were modified to enhance the overall prediction accuracy for stainless steel LCBs while attention was given to capture the available inelastic reserve capacity

Bending-shear interaction of cold-formed stainless steel lipped channel sections

The bending-shear interaction response of cold-formed stainless steel lipped channel sections has been given inadequate attention in the past. Therefore, this paper investigates the bending and shear interaction behaviour of cold-formed stainless steel lipped channel sections using numerical studies. Finite element (FE) models were developed and validated against the experimental results found in the literature for three-point and four-point loading tests of lipped channel sections of both cold-formed stainless steel and cold-formed steel. The elaborated FE results were used for a comprehensive parametric study that was conducted comprising 60 FE models of three-point loading simulations of stainless steel lipped channels with five different aspect ratios to study the shear response and the bending-shear interaction response. Another 12 FE models of four-point bending simulations were developed to study the bending response. The numerical results were analysed and it is found that the sections with aspect ratios of 1.5 and 2.0 are subjected to the interaction of bending and shear while there is no interaction effect observed in the sections with other aspect ratios. Eurocode 3 and American specifications interaction equations were then evaluated using the numerical results. These design provisions are found to be too conservative for a higher level of applied shear force. Therefore, revised design equations for bending and shear interaction were proposed aiming better prediction accuracy. Further, a statistical evaluation was conducted for the proposed interaction equations and results suggest improved and consistent predictions

Numerical investigation of cold-formed stainless steel lipped channels with longitudinal stiffeners subjected to shear

The shear response of the cold-formed stainless steel lipped channel sections with longitudinal stiffeners has not been investigated adequately in the past. Therefore, this paper presents the details of numerical investigations conducted to study the shear behaviour of longitudinally stiffened cold-formed stainless steel lipped channel sections. Following a validation study of the finite element models of lipped channel sections, the effect of return lips and web stiffeners on the shear response of lipped channel sections was examined through comprehensive numerical parametric studies. In addition, numerical investigations were conducted to study the elastic shear buckling response of the sections and the shear buckling coefficients were back-calculated. It was found that the longitudinal web stiffeners enhance the shear buckling resistance of lipped channel sections considerably with increased stiffener depth. However, the shear capacity increment is not significant compared to plain lipped channel sections. The presence of the web stiffeners is found to be not preventing the out-of-plane buckling of the sections. The evaluation of Eurocode 3 and the direct strength method shear provisions for stainless steel channel sections with longitudinal stiffeners illustrates inaccurate capacity predictions. Therefore, modifications were proposed and comparisons reveal that the proposed provisions enhance the shear resistance predictions with good accuracy over the codified provisions

Prevalence and predictors of falls and dizziness in people younger and older than 80 years of age-A longitudinal cohort study.

The objectives were to investigate the prevalence and predictors for falls and dizziness among people younger and older than 80 years of age. The sample was drawn from the Swedish National study on Aging and Care (SNAC) and comprised 973 and 1273 subjects with data on the occurrence of falls and dizziness respectively at baseline. Follow-ups were made after 3- and 6-years. Data included socio-demographics, physical function, health complaints, cognition, quality of life and medications. The prevalence of falls was 16.5% in those under aged 80 and 31.7% in those 80+ years while dizziness was reported by 17.8% and 31.0% respectively. Predictors for falls in those under aged 80 were neuroleptics, dependency in personal activities of daily living (PADL), a history of falling, vision impairment and higher age, and in those 80+ years a history of falling, dependency in instrumental activities of daily living (IADL), fatigue and higher age. Factors predicting dizziness in those under aged 80 were a history of dizziness, feeling nervous and reduced grip strength and in those 80+ years a history of dizziness and of falling. Predictors for falls and dizziness differed according to age. Specific factors were identified in those under aged 80. In those 80+ years more general factors were identified implying the need for a comprehensive investigation to prevent falls. This longitudinal study also showed that falling and dizziness in many older people are persistent and therefore should be treated as chronic conditions

Cerebral perfusion in sepsis

This article is one of ten reviews selected from the Yearbook of Intensive Care and Emergency Medicine 2010 (Springer Verlag) and co-published as a series in Critical Care. Other articles in the series can be found online at http://ccforum.com/series/yearbook. Further information about the Yearbook of Intensive Care and Emergency Medicine is available from http://www.springer.com/series/2855