Direct stress-strain representation for coated woven fabrics

Abstract An understanding of the complex behaviour of coated woven fabrics is vital for the design of state-of-the-art fabric structures. Fabric behaviour is typically defined using elastic constants based on plane stress assumptions. This paper considers two new methods of representing fabric response: (i) use of spline functions to define response surfaces, (ii) use of stress-strain mean and difference functions (proposed by Day [IASS symposium proceedings: shells, membranes and space frames 2 (1986) 17]. Both techniques provide direct correlation between stresses and strains, eliminating the assumption of plane stress. Extensive biaxial fabric testing is proposed to assess the validity of these approaches and extend their use

Potential of relative humidity as a proxy of air temperature in developing passive and adaptive building fa\ue7ades with bio-based responsive materials

There has been significant development in thermo-responsive materials for drug delivery and bio-medical use; some are bio-based. However, the use of thermo-responsive bio-based materials in the built environment, especially on the building fa\ue7ade, is almost non-existent due to complexities including difficulties manufacturing in bulk, cost and durability to weathering. On the other hand, humidity-responsive materials such as wood are abundant and are used in buildings globally. Furthermore, new bio-based humidity-responsive materials such as bacterial cellulose (BC) and natural fibres have the potential for building applications. In this study, we hypothesised that if there was a relationship between the relative humidity and air temperature in a location, humidity-responsive materials could be used to develop passive and adaptive building fa\ue7ades, which would indirectly respond to temperature. Here, we selected two sites (New Delhi, India and Newcastle upon Tyne, UK) with temperate climates — according to the K\uf6ppen-Geiger system— to analyse the relationship between relative humidity and air temperature from 37 years (1985-2022) of weather data and typical meteorological year (TMY) climate data for 2004-2018. This relationship assessment used the Pearson correlation (coefficient and p-value) analysis. Our results showed a strong and statistically significant negative correlation between the relative humidity and air temperature in all months in 37 years in New Delhi, with the strongest correlation in the summer and monsoon months. However, the correlation was strong only in some summer months for Newcastle upon Tyne. We concluded that humidity-responsive bio-based materials have the potential to be used to actuate passive and adaptive building fa\ue7ades in New Delhi (for all-year-round use) and Newcastle (only during summer), which respond indirectly to external temperature

Bio-jaali: Passive building skin with mycelium for climate change adaptation to extreme heat

Climate change induced global warming and frequent extreme heat events have become common recently, increasing the ownership and operation of active cooling, particularly in cities and megacities. To reduce the dependency on active cooling, in this study, we aimed to re-design ‘Jaali’— perforated screens made of bricks and sandstones to cool the incoming air inspired by historical building use— with bio-based materials such as mycelium. We hypothesised that ‘Bio-jaali’ would ventilate and reduce the indoor temperature reducing energy demand for cooling. For the climatic context, we selected the temperate climate of New Delhi. We used climatic data analysis and performance-based dynamic environmental simulations with Designbuilder and Energy Plus to evaluate the effect of Bio-jaali on the indoor operative temperature in a single-zone naturally ventilated indoor office space. The simulation results showed sandstone Jaali reduced the annual average indoor operative temperature by 5.2%, whereas Bio-jaali were able to provide a reduction of 3.0% compared to the base case. Furthermore, the seasonal analysis showed that Bio-jaali reduced the summer indoor operating temperature by decreasing heat gain from outdoor heat, particularly during daytime and increased indoor temperature during winter by reducing heat loss, demonstrating its potential for year-round usage

A new biaxial and shear protocol for architectural fabrics

p. 2167-2179Architectural fabrics are translucent, lightweight and flexible allowing impressive forms to be achieved unlike any other material. However in order to create the required double curved structural form, flat fabrics must undergo shear deformation during installation. Due to the woven nature of architectural fabrics contact between neighbouring yarns during shearing leads to an increase in shear stiffness, shear lock-up and subsequent wrinkling. A picture frame shear test accessory has been designed for the biaxial test rig which enables a known biaxial stress state to be applied to the fabric and maintained throughout the shear test. A shear testing protocol is proposed for medium term loading conditions. This enables the shear characteristics of architectural fabrics to be identified for use in analysis and design. Shear behaviour is presented from initial experiments and a range of shear modulus values are proposed for loading and unloading in the shear deformation range of zero to 15°.Jackson, AL.; Bridgens, BN.; Gosling, PD. (2010). A new biaxial and shear protocol for architectural fabrics. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/727

Ponseti casting for club foot – above- or below-knee?

We undertook a randomised clinical trial to compare treatment times and failure rates between above- and below-knee Ponseti casting groups. Eligible children with idiopathic clubfoot, treated using the Ponseti method, were randomised to either below- or above-knee plaster of Paris casting. Outcome measures were total treatment time and the occurrence of failure, defined as two slippages or a treatment time above eight weeks.A total of 26 children (33 feet) were entered into the trial. The above-knee group comprised 17 feet in 13 children (ten boys and three girls, median age 13 days (1 to 40)) and the below-knee group comprised 16 feet in 13 children (ten boys and three girls, median age 13 days (5 to 20)). Because of six failures (37.5%) in the below-knee group, the trial was stopped early for ethical reasons. The rate of failure was significantly higher in the below-knee group (p = 0.039). The median treatment times of six weeks in the below-knee and four weeks in the above-knee group differed significantly (p = 0.01).This study demonstrates that the use of a below-knee plaster of Paris cast in conjunction with the Ponseti technique leads to unacceptably high failure rates and significantly longer treatment times. Therefore, this technique is not recommended.Cite this article: Bone Joint J 2013;95-B:1570–4