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Conchie S.M.,University of Liverpool | Moon S.,University of Liverpool | Duncan M.,Laing ORourke
Safety Science | Year: 2013

A growing body of research supports the importance of supervisors' safety leadership in promoting employees' engagement in safety. However, the factors that give rise to these safety leadership behaviors are under-explored. The current study addressed this void by adopting a Job Demands-Resources framework to identify contextual influences on supervisors' safety leadership behaviors. Focus group data from sixty-nine supervisors recruited from the UK construction industry showed that role overload, production demands, formal procedures, and workforce characteristics hindered supervisors' engagement in safety leadership. In contrast, social support (especially from the organization and co-workers) and perceived autonomy promoted supervisors' engagement in safety leadership. Exploration around these issues highlighted a need for more training for supervisors in this role and the development of a supportive environment between supervisors affiliated with different parent companies. © 2012 Elsevier Ltd. Source

Jackson A.M.,Laing ORourke | Middleton C.R.,University of Cambridge
Structural Engineer | Year: 2013

An engineer assessing the load-carrying capacity of an existing reinforced concrete slab is likely to use elastic analysis to check the load at which the structure might be expected to fail in flexure or in shear. In practice, many reinforced concrete slabs are highly ductile in flexure, so an elastic analysis greatly underestimates the loads at which they fail in this mode. The use of conservative elastic analysis has led engineers to incorrectly condemn many slabs and therefore to specify unnecessary and wasteful flexural strengthening or replacement. The lower bound theorem is based on the same principles as the upper bound theorem used in yield line analysis, but any solution that rigorously satisfies the lower bound theorem is guaranteed to be a safe underestimate of the collapse load. Jackson presented a rigorous lower bound method that obtains very accurate results for complex real slabs. Source

Farrell R.,Laing ORourke | Terry D.,London Bridge Associates
Proceedings of the Institution of Civil Engineers: Geotechnical Engineering | Year: 2015

As part of the Bond Street underground railway station upgrade works in London, UK over 500 m of tunnels are being built in a dense urban environment. Tunnelling-induced settlements presented a significant risk to the functionality of a sensitive set of escalators within the existing station. As a means of reducing the risk to their operation, a pipe canopy, consisting of 12 steel tubes 325 mm in diameter, was installed directly above the tunnel crown. Measurements of the forces required to drive the pipe canopy tubes are discussed in relation to pipe-jacking theory, with guidance being provided for the future use of this method in London Clay. Instrumentation installed within the pipe canopy is then used to describe its response to tunnelling. Tunnelling-induced settlements of the escalator are also presented and used to describe the complex soil–structure interaction mechanism. Comparisons of the pipe response with predictions made using a semi-empirical elastic continuum method demonstrate that relatively simple calculations can be used to quantify conservatively the likely reduction in settlements caused by a pipe canopy. Based on the observations, key design parameters are identified and a method for selecting values for these parameters is proposed. © ICE Publishing: All rights reserved. Source

Farrell R.,Laing ORourke | Mair R.,University of Cambridge | Sciotti A.,Italferr | Pigorini A.,Italferr
Soils and Foundations | Year: 2014

Understanding how buildings respond to tunnelling-induced ground movements is an area of great importance for urban tunnelling projects, particularly for risk management. In this paper, observations of building response to tunnelling, from both centrifuge modelling and a field study in Bologna, are used to identify mechanisms governing the soil-structure interaction. Centrifuge modelling was carried out on an 8-m-diameter beam centrifuge at Cambridge University, with buildings being modelled as highly simplified elastic and inelastic beams of varying stiffness and geometry. The Bologna case study presents the response of two different buildings to the construction of a sprayed concrete lining (SCL) tunnel, 12 m in diameter, with jet grouting and face reinforcement. In both studies, a comparison of the building settlement and horizontal displacement profiles, with the greenfield ground movements, enables the soil structure interaction to be quantified. Encouraging agreement between the modification to the greenfield settlement profile, displayed by the buildings, and estimates made from existing predictive tools is observed. Similarly, both studies indicate that the horizontal strains, induced in the buildings, are typically at least an order of magnitude smaller than the greenfield values. This is consistent with observations in the literature. The potential modification to the settlement distortions is shown to have significant implications on the estimated level of damage. Potential issues for infrastructures connected to buildings, arising from the embedment of rigid buildings into the soil, are also highlighted. © 2014 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved. Source

Brueckner R.,Mott MacDonald Ltd. | Williamson S.J.,Laing ORourke | Clark L.A.,University of Birmingham
Proceedings of the Institution of Civil Engineers: Geotechnical Engineering | Year: 2013

The stability of structures is determined by physical interactions between the foundations and the surrounding soil. Concrete foundations are also subject to chemical interactions at the concrete/clay interface, which can result in changes in the properties of the adjacent soil. The occurrence of the thaumasite form of sulfate attack particularly affects the skin friction between the concrete and the ground. In this investigation of the chemical interactions at the concrete/clay interface it was found that although an increase in moisture content and pH was confirmed, and this moisture and pH gradient was also observed within the thaumasite layer, no further effects on the adjacent clay due to thaumasite form of sulfate attack were found. Source

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