Novel nanocomposite clay brick for strain sensing in structural masonry

The monitoring of civil structures is critical in ensuring users\u27 safety. Structural health monitoring (SHM) is the automation of this monitoring task. It is typically used to identify incipient damages through a spatio-temporal comparison in structural behaviors. Traditional sensors exhibit mechanical characteristics that are usually very different from those of the structures they monitor, which is a factor limiting their durability. Ideally, the material of a sensor would share the same mechanical characteristics as the material onto or into which it is installed. A solution is to fabricate multifunctional materials, capable of serving both structural and sensing functions, also known as smart materials. Recent developments in nanotechnologies have given us various engineered nanoparticles with enhanced mechanical and electrical capabilities. Among them, conductive piezoresistive nanopowders, such as carbon-based ones, show promise at developing smart materials. The nanofillers, spread into a structural material matrix, can provide the material with self-sensing capabilities. Such materials can then be used to detect variations in their external stresses or strains by detecting variations in their electrical characteristics, such as electrical resistivity and conductivity. This paper presents a new smart clay brick for strain sensing in masonry structures. The optimal fabrication process in terms of stability of the nanoparticles at high temperature and the electromechanical properties of the smart brick are investigated. Results show a clear strain sensitivity of the brick sensors subjected to external loads and show their promise for SHM applications

Design methodologies for one way spanning eccentrically loaded minimally or centrally reinforced pre-cast RC panels

AbstractThis paper examines and evaluates design methodologies applicable to pre-cast reinforced concrete (RC) panels subjected to eccentric axial load. Theoretical capacities derived from existing regulatory guidance are compared against those determined from experimental investigations, showing that slender RC walls have load capacities significantly higher than the estimates based on current design equations.A simple computational procedure incorporating lumped plasticity is presented and experimentally validated. It is shown that by utilising a non-linear hinge at the critical cross section, it is possible to effectively simulate the buckling response of the slender walls considered with a modest computational effort. The proposed design strategy emerges as a viable alternative to traditional methodologies by being able to capture the main effects of geometrical and material nonlinearities. It is therefore suggested that this approach, used in conjunction with a probabilistic, semi-empirical design procedure, will lead to design capacities more representative of actual experimental findings

Flexural strain and crack width measurement of steel-fibre-reinforced concrete by optical grid and electrical gauge methods

A research programme is discussed, which has investigated the fracture of steel-fibre-reinforced sprayed concrete under flexural loading, with the aim of developing a stress-block model to predict flexural behaviour in the form of a load–deflection response. This paper reports the work associated with establishing the strain and crack width profiles in relation to mid-span beam deflection. A strain analysis technique is described, which combines the use of electrical strain gauges with a semiautomated grid method (using digital image processing) for measuring and monitoring the strain and crack width profile over the depth of a fibre-reinforced beam during a flexural test. This novel strain analysis technique has established strain/crack width data, which forms a key part of a stress-block approach for predicting residual flexural strength, an essential requirement of a much needed design rationale for steel-fibre-reinforced concrete

Predicting the flexural load–deflection response of steel fibre reinforced concrete from strain, crack-width, fibre pull-out and distribution data

A semi-analytical model is presented, based on conventional principles of mechanics, to predict the flexure behaviour of steel fibre reinforced concrete. The model uses a stress-block approach to represent the stresses that develop at a cracked section by three discrete stress zones: (a) a compressive zone; (b) an uncracked tensile zone; and (c) a cracked tensile zone. It is further shown that the stress-block, and hence flexural behaviour, is a function of five principal parameters: compressive stress–strain relation; tensile stress–strain relation; fibre pull-out behaviour; the number and distribution of fibres across the cracked section in terms of their positions, orientations and embedment lengths; and the strain/crack-width profile in relation to the deflection of the beam. An experimental investigation was undertaken on both cast and sprayed specimens to obtain relationships for use in the model. The results of the study showed a reasonable agreement between the model predictions and experimental results. However, the accuracy of the model is probably unacceptable for it to be currently used in design. A subsequent analysis highlighted the single fibre pull-out test and the sensitivity of the strain analysis tests as being the main cause of the discrepancies

Critical success factors in collaborative multi-disciplinary design projects

Purpose – The purpose of this paper is to explore critical success factors (CSFs) in interdisciplinary building design projects from the view point of the project members themselves. While there is a plethora of research on CSFs, there is a paucity of studies that examine CSFs within this unique project context. Design/methodology/approach – Semi-structured interviews, a survey and facilitated workshops were used to identify factors and their interrelationships within the project context. Findings –Thirty one primary CSFs were distilled which were then further grouped into four interdependent group factors: management factors, design team factors, competencies and resources factors and project enablers. It would appear that there are factors that are particularly important in such project environments, which do not figure strongly in other project environments. These factors are related to the socio-political dynamics of inter-disciplinary team work such as passion and enthusiasm, shared values, creativity and innovation and represent so called ‘super soft factors’ which reflect personal success and its importance in achieving positive project outcomes. Research limitations/implications – Although there has been significant research on critical success factors (CSF) in construction projects, little attention has been paid to those which are related to the collaborative design phase of such projects. Practical implications – The results suggest that it is worthwhile for managers in construction related organisations and beyond to recognise the interdependencies which exist between the project context, processes and the project members’ experience and affinity to the project and the team itself in project work to achieve desired outcomes. Originality/value – This paper extends the CSF literature by identifying the nature of the primary factors and their interrelationships which influence project outcomes in collaborative design projects

Electrochemical behaviour of steel reinforced concrete during accelerated corrosion testing

Corrosion of reinforcing steel presents a major durability issue worldwide and is the focus of much research activity. The long time periods involved in replicating reinforcement corrosion within laboratories has resulted in a number of accelerated test methods being developed. The basis of this research presented in this paper was to examine the impressed current technique often used to induce reinforcement corrosion. The suitability of the technique to model chloride induced corrosion was investigated by examining the electrochemical nature of the test method. Corrosion was induced in prisms of differing characteristic strengths and cover thicknesses by applying a current for between 3 and 17 days. The gravimetrical and theoretical mass losses are compared and a modified expression based on Faraday’s law relating the electrical current to the mass loss is also proposed which accounts for the localised nature of chloride-induced corrosion. It was found that the technique is a suitable method to simulate reinforcement corrosion

Chloride-induced reinforcement corrosion in blended cement concretes expores to chloride-sulfate environments

This paper reports the results of a study conducted to investigate the influence of sulphate concentration and associated cation type on chloride-induced reinforcement corrosion in blended cement concretes. Reinforced concrete specimens were exposed to chloride plus sulphate solutions for a period of 1200 days. The exposure solutions contained a fixed concentration of 5% sodium chloride and the sulphate concentration was varied from 0 to 4% SO4 2 . The effect of cation type associated with sulphate ions, namely Naþ and Mgþþ, on chloride-induced reinforcement corrosion was also evaluated. Reinforcement corrosion was assessed by measuring corrosion potentials and corrosion current density at regular intervals. The results indicated that the presence of sulphate ions in the chloride solution increased the corrosion current density, but no significant effect on the time to initiation of reinforcement corrosion was noted. Further, the corrosion current density increased with increasing sulphate concentration and the period of exposure. The corrosion current density on steel in the blended cement concrete specimens was much less than that in the plain cement concrete specimens, indicating that the corrosion resistance of blended cements was much better than that of plain cements. The cation type associated with sulphate ions did not significantly influence either the initiation or rate of reinforcement corrosion

Faecal microbiota of individuals with autism spectrum disorder

Many children with autistic spectrum disorders (ASDs) suffer from gastrointestinal problems such as diarrhoea, constipation and abdominal pain. Such symptoms may be due to a disruption of the indigenous gut microbiota promoting the overgrowth of potentially pathogenic micro-organisms. These observations have stimulated investigations into possible abnormalities of intestinal microbiota in autistic patients. The purpose of the present study was to determine if a relationship exists between ASD severity (mild – severe) and GI microbial populations. The faecal microbiota of 22 male and 6 female participants with ASDs (aged 7 ± 6 years) were analyzed by standard microbial culture methods and compared within-group (based on ASD severity) and with a standard laboratory reference range. Comparisons between children with mild ASD and those with moderate to severe ASD, as well as comparisons to a neurotypical control group previously reported, revealed that no significant differences appear to exist in the composition of the gut microbiota. Nevertheless, examination of each individual’s gut microbial composition showed 10 cases of unusual findings witch means 1out of 3 cases have unusual microbiota. Our data do not support consistent GI microbial abnormalities in ASD children, but the findings do suggest that aberrations may be found in a minority subset of ASD children. Further studies are required to determine the possible association between the microbiota and gastrointestinal dysfunctions in a subset of children with both ASD and gastro-intestinal problems

Conceptualizing stakeholder engagement in the context of sustainability and its assessment

Stakeholder engagement in construction projects can be conceptualized in different ways. It can be seen from a strategic management perspective aimed at capturing knowledge, increasing ownership of the project by users, reducing conflict, encouraging innovation and facilitating spin-off partnerships. From an ethical perspective, meaningful stakeholder engagement can be seen to enhance inclusive decision making, promote equity, enhance local decision making and build social capital. The benefits from both of these perspectives are vital for sustainability; however, stakeholder engagement can also be seen from the perspective of an opportunity for social learning—a social process where diverse stakeholders share a common forum, learn about each other's values, reflect upon their own values and create a shared vision and shared objectives. Dialogue is also useful in increasing awareness, changing attitudes and affecting behaviours. Existing practices view stakeholder engagement: mostly from a management perspective; sometimes from an ethical perspective; less often as a combination of the two; and rarely have any element of the social learning perspective. There is a need for an approach that combines all the three perspectives if sustainability is to be pursued. A dialogue-oriented approach to integrated sustainability assessment could provide an ideal means to do so

In-situ instrumentation and early-age monitoring of concrete structures

This paper reports the instrumentation and monitoring techniques developed to improve understanding of the early life behaviour of concrete industrial ground floor slabs. Concrete strains, temperatures and joint movements were measured using vibrating-wire embedment strain gauges and thermistors, whilst ambient conditions were monitored to assess their effects. A reliable, accurate and easy to implement methodology, developed by instrumenting 4 types of floor slab (mesh reinforced long strip, mesh reinforced jointed large area pour, steel fibre reinforced jointed large area pour, and steel fibre reinforced joint-less large area pour) is described in detail, along with the further developments and modifications to the instrumentation. The methodology developed would be equally applicable to the early-life monitoring of other concrete structural elements. Some sample results of data gathered using the instrumentation methodology developed are included