Environmental noise control during its transmission phase to protect buildings. Design model for acoustic barriers based on arrays of isolated scatterers

A new generation of acoustic barriers is being introduced into the noise control market. These barriers, based on arrays of isolated scatterers, present interesting properties to be used in cities to reduce the transmitted transport noise affecting buildings. Among them, both aesthetic and continuity factors of the urban landscape may be mentioned. This new kind of barrier is technologically advanced and acoustically competitive with respect to the current ones formed by continuous rigid materials. To design these barriers whilst taking into account their inherent acoustic complexity, we present an overlapping numerical model here that enables us to split the real three-dimensional problem into two twodimensional ones, allowing both the reduction of the computational cost and the separate analysis of each one of the noise control mechanisms involved. We analyse different cases, checking the numerical simulations with accurate experimental results.This work is supported by MEC (Spanish Government) under grant No. MTM2012-36740-C02-02.Castiñeira Ibáñez, S.; Rubio Michavila, C.; Sánchez Pérez, JV. (2015). Environmental noise control during its transmission phase to protect buildings. Design model for acoustic barriers based on arrays of isolated scatterers. Building and Environment. 93:179-185. https://doi.org/10.1016/j.buildenv.2015.07.002S1791859

Feasibility of the quantification of respirable crystalline silica by mass on aerosol sampling filters using Raman microscopy

Airborne respirable crystalline silica (RCS) is a hazard that can affect the health of workers and more sensitive measurements are needed for the assessment of worker exposure. To investigate the use of Raman microscopy for the analysis of RCS particulate collected on filters, aliquots of quartz or cristobalite suspended in isopropanol were pipetted onto silver filters. Samples were measured by arbitrarily selecting positions along the filter and collecting spectra at 50 discrete points. The calculated limits of quantification on test samples were between ~0.066 – 0.161 µg and 0.106 – 0.218 µg for quartz and cristobalite respectively. Three respirable quartz calibration dusts (A9950, NIST 1878 and Quin B) with different mass median aerodynamic particle sizes obtained similar Raman response relationships per unit mass. The difference between NIST 1878 and Quin B was not significant (p=0.22). The intermediate measurement precision of replicate samples was 10 - 25% over the measured range for quartz (0.25 – 10 µg) and could potentially be improved. Results from mixtures of quartz and cristobalite were within 10 % of their theoretical values. Results from samples of 5 % quartz in calcite were close to the theoretical quartz mass. The upper measurement limit for a mixture of 20 % RCS in the light absorbing mineral hematite (Fe2O3) was 5 µg. These data show that Raman spectroscopy is a viable option for the quantification of the mass of respirable crystalline silica on filters with a limit of detection approaching 1/10th of that obtained with other techniques. The improvement in sensitivity may enable the measurement of particulate in samples from low concentration environments (e.g. inside a mask) or from miniature samplers operating at low flow rates

Stress-strain characteristic of SFRC using recycled fibres

This paper presents work from a comprehensive study on the development of a flexural design framework for concrete reinforced with steel fibres that are recovered from used tyres. The experimental flexural behaviour of notched concrete prisms reinforced with these fibres is initially presented. For comparison purposes, prisms reinforced with industrially produced fibres are also considered. An attempt to adopt an existing RILEM design framework to derive appropriate tensile stress-strain blocks is made, but problems are identified with key parameters of the framework. The influence of crack propagation and location of neutral axis depth on the tensile stress distribution is examined. Following an analytical study, it is concluded that the uniaxial stress-strain model, proposed by RILEM overestimates the load-carrying capacity and should be modified by utilising more advanced analytical techniques. © RILEM 2006

Effect of temperature on RC elements strengthened with CFRP

The strengthening of RC elements with CFRP is a technique that has been acquiring more and more potential. The bond between the CFRP reinforcement and the concrete support is usually made with epoxy adhesives. However, it is here that the integrity of the system can be affected, namely by exposure to high temperatures. In order to study the effect of an increase of air temperature on the behaviour of the epoxy adhesive, CFRP strengthened RC and reference RC specimens were tested. After cyclical thermal exposures, with temperatures rising between 20ºC and 80ºC, specimens were subjected either to compressive shear tests or bending tests. The results demonstrated that epoxy adhesive exhibits poor behaviour when subjected to increased temperatures, causing important bond deterioration. The improvement achieved with the CFRP reinforcement tends to disappear with an increase of the environment temperature. So, the thermal resistance of this strengthened system can not be considered very high. However, the inclusion of insulating materials can be a good solution to protect the strengthened RC elements. Among tested materials, the foamed polyurethane showed the best behaviour

Accessing hospital packaged foods and beverages : the importance of a seated posture when eating

Background: Hospitalised and community dwelling older people (65 years and over), have difficulties opening food and beverage items such as cheese portions and tetra packs served in public hospitals. Previously, the role of hand strength on successful pack opening has been explored in a seated position. However, as many people in hospital eat in bed, this laboratory study examined the differences between participants opening a selection of products both in a hospital bed and a chair. Methods: This study used a qualitative method (satisfaction) and quantitative methods (grip and pinch strength, dexterity, time and attempts) in two conditions (bed; chair) with a sample of well older community dwelling adults (n=34). Packs tested included foil sealed thickened pudding, foil sealed thickened water, tetra pack, dessert, custard, jam, cereal, honey sachet and cheese portions. Results: Honey sachets, cheese portions, foil sealed thickened pudding and tetra packs were the most difficult packs to open, with 15% of cheese portions unable to be opened in either the bed or chair posture. While grip strength was consistent for each posture, pinch grips and dexterity were adversely affected by the bed posture. Lying in a hospital bed required greater pinch strength and dexterity to open packs. Conclusions: Eating in a seated position while in hospital has been shown to improve intake. This study demonstrates that eating in a seated posture is also advantageous for opening food and beverage packs used in NSW hospital food service and supports the notion that patients should sit to eat in hospital

Interoperability optimisation for shared equity housing model development and FTB homeownership in the UK

Purpose – This paper assessed financial interoperability implications associated with First Time Buyers (FTB) in housing development and the role of the Community Land Trust Shared Equity Housing Model (CLT SEHM). Design/Methodology/Approach – The Interoperability optimisation process adopted by this study involved triangulated findings from literature, semi-structured interviews and questionnaire surveys. The text analysis of interview responses was actualised with Nvivo 9.0. This process informed the validation of themes through a questionnaire survey (purposive sampling), of which findings were subsequently analysed with statistical methods including binary logistic regression to validate interoperability rational and implications. Findings – The study identified positive financial interoperability outcomes for a successful synergy between the CLT SEHM and FTBs. From the analysis, there were sustainable results for average income multiple and property transfer/resale value for the CLT SEHM compared to conventional models. However, for the most at risk FTB groups, recommendations included increased concessions for CLT SEHM developments to incentivise bespoke rent purchase hybrid schemes. Originality/value – This research provided a good starting point for achieving improved level of efficiency necessary for the introduction of emerging/renewed alternative housing models into mainstream operational capabilities in housing and local development policies. Keywords – UK Housing Development, First Time Buyers (FTB), Interoperability, Community Land Trust, Shared Equity Housing Model, Binary Logistic Regression mode