146,352 research outputs found
Sustainable earth walls to meet the building regulations
No full textThe thermal conductivity and diffusivity of un-fired clay bricks, a straw clay mixture and straw bales have been measured using a thermal probe technique, with an iterative method for data analysis. The steady-state air-to-air thermal transmittance, or U-value, and the time-dependent thermal properties of some proposed sustainable earth wall constructions are presented. Sustainable cavity walls of un-fired clay bricks with paper, straw or wool cavity insulation have thermal transmittances less than 0.35 W/m2 K, and therefore meet the current United Kingdom Building Regulations. A review of possible methods for thermally up-grading existing earth walls, by adding an internal insulated timber frame construction, again demonstrates possible compliance with the current UK thermal regulations
Centrifuge and numerical modelling of twin-propped retaining walls.
No full textPhDA series of tests on flexible model diaphragm walls embedded in an
overconsolidated clay was carried out at the London Geotechnical Centrifuge
Centre. The walls were propped at the crest and, following the simulation of
excavation, were propped at formation level. Although a retained height of 10m
was modelled in all tests, the depth of embedment below dredge level varied
between Sm, 10m and 15m. A 'softer' propping sequence was also investigated
with excavation to 5m below the retained surface prior to the installation of the
crest level prop then, following further excavation to dredge level, the bottom
prop was installed. The pre-excavation lateral earth pressure was also
investigated.
The background and use of twin-propped retaining walls is discussed together
'with the design of the centrifuge model and modelling procedure. The results of
the tests are presented and the effects of embedment depth, construction sequence
and pre-excavation lateral earth pressure coefficient is discussed.
A series of finite element analyses using the critical state soils program CRISP
was undertaken in which it was attempted to model the centrifuge models.
Generally, results were in reasonable agreement, although it was discovered that
the calculated wall movements and prop loads were sensitive to the slope of the
Hvorslev surface required for the Schofield soil model used in the analyses.
The prop loads from the centrifuge tests and finite element analyses were
compared with prop loads calculated using popular empirical methods and with
prop loads observed on site. Generally, prop loads were underpredicted using the
empirical methods which are unable to account for construction sequence effects
and probably overestimate the degree of lateral stress reduction that takes place
during excavation.TR
Out-of-plane in situ cyclic testing of unreinforced stone masonry walls with distributed loads
No full textThe present paper reports an in situ experimental test campaign carried out on existing
buildings, in order to investigate the seismic behaviour of traditional masonry walls subject to
out-of-plane loads. For the testing proposes, an experimental test setup based on a selfequilibrated
scheme was developed and optimized to be applied in situ in two specimens on
original and strengthened conditions. The obtained results are presented and carefully
discussed namely from the reinforcement solutions’ efficiency point-of-view, as well as
compared to previous experimental data obtained for the same type of masonry walls.
Additionally, a simplified linearized displacement-based procedure was adapted in order to
characterize the nonlinear force-displacement relationship for unreinforced traditional
masonry walls and to analytically predict the experimental test results. The confrontation
between the experimental and the analytical results are presented and discussed
Performance-Based approach in seismic design of embedded retaining walls
No full textThe increasing use of the underground spaces and the last seismic events in the urban areas have driven many researchers of different countries to deepen the knowledge on the dynamic behaviour of the structure embedded in the subsoil.
This thesis attempts to give some contributes on the application of the performance based approach for the seismic design of the embedded retaining walls.
After an overview on the earth pressure theories proposed by different authors, the static and seismic design methods commonly adopted in the current practice and based on pseudostatic approaches are recalled.
Several limitations on these procedures can be recognized: the difficulties on the definition of the seismic coefficient; the calculation of the expected earthquake-induced displacements around the construction. Moreover, in the framework of the Performance-Based Design, these methods do not able to describe the response of the retaining systems to a given earthquake. The seismic displacements of the flexible walls are evaluated by means of Newmark sliding block procedures, that were developed for rigid structures, and the yield sequence of the different structural components can not be predicted. Then, the application of the hierarchical resistance criteria in the dimensioning of the various parts can not be applied.
In this thesis, different level of analysis are highlighted in relation to the importance of the structure and to the design phase.
An innovative procedure that can be included in the framework of the "pushover analyses" is also proposed for the seismic design of the embedded retaining walls.
Finally, the results obtained by the application of the different methods for the ideal case study of cantilever diaphragms embedded in dry loose and dense sand are presented. The material properties used in the analyses are referred to the Fraction E (BS 100/170) of the Leighton Buzzard sand, for which a series of triaxial and torsional tests on reconstituted samples was conducted
Risk analysis of supply : comparative performance and short-term prediction
No full textManaging risk in the supply of inbound parts for the assembly of complex engineering systems is a key activity for manufacturing companies to avoid production delays and disruption. We present novel analysis of empirical data typically available in enterprise resource planning systems. The information generated through such analysis can provide useful information to support decisions to better manage supply risk. For example, identifying suppliers at risk of poor performance under different loadings or relative to peers, and assessing the financial value of investing in learning and developing suppliers. Our analysis is based on new methods developed for robust ranking, valuation of due diligence as well as more established regression modelling principles. We focus upon the ways our methods can be used to support supply risk decisions by showing how they have been applied in an industry case and the implications of our findings to date
What is the value of a standard?
No full textStandards play a critical role in the procurement of defence, and other, systems. Choosing the most appropriate standard is important but has become more topical given the UK Ministry of Defence policy of “as civilian as possible, as military as necessary”. Whereas historically managers might have selected from classes of defence standards, this choice set is now increased to include civil standards. We develop a model that has been commissioned by the UK Defence Standardisation whose responsibilities include supporting project teams on the selection of standards. Our model is based on an extension of Bayesian Belief Networks, called an Influence Diagram, which allows decisions and consequences to be represented as well as uncertain-ties. We have developed an initial model for a real case to assess the feasibility and use. We outline the con-text of the defence procurement project in our case study and describe the reasoning underpinning the model structure. We have found that it is possible to develop a simple model that captures the views of multiple stakeholders and informs a reasoned choice about the value of alternative standards
Out-of-plane seismic response of stone masonry walls: experimental and analytical study of real piers
No full textThis paper presents the application of an existing simplified displacement-based procedure to the
characterization of the nonlinear force-displacement relationship for the out-of-plane behaviour of
unreinforced traditional masonry walls. According to this procedure, tri-linear models based on three
different energy based criteria were constructed and confronted with three experimental tests on
existing stone masonry constructions. Moreover, a brief introduction is presented regarding the main
characteristics of the in situ cyclic testing recently carried out using distributed loads, as well as results
obtained during the experimental campaigns performed. The comparison between the experimental and the analytical results are presented and discussed
Extended Producer Responsibility and Product Design: Economic Theory and Selected Case Studies
No full textA core characteristic of extended producer responsibility (EPR) policies is that they place some responsibility for a product’s end-of-life environmental impacts on the original producer and seller of that product. The intent is to provide incentives for producers to make design changes that reduce waste, such as improving product recyclability and reusability, reducing material usage, and downsizing products. This paper assesses whether the range of policies that fall under the EPR umbrella can spur this “design for environment” (DfE). It summarizes the economics literature on the issue and describes conceptually how policies should affect design. It then analyzes three case studies in detail and two more case studies more briefly. The conclusion reached is that some DfE—especially reductions in material use and product downsizing—can be achieved with most EPR policies, including producer take-back mandates and combined fee/subsidy approaches. However, none of these alternative policies as they are currently implemented are likely to have a large impact on other aspects of DfE.design for environment, recycling, waste management, incentive-based policy instruments
Effect of ballast retaining walls on the lateral resistance of railway tracks
No full textIn this study, the application of a retaining wall was proposed as a solution for reducing the lateral displacement of the ballast layer, particularly in sharp curves and bridges. In this regard, a series of single tie push tests were performed on panels with shoulder ballast widths of 300 mm, 400 mm, 500 mm with and without the presence of L-shaped and T-shaped retaining walls. Overall, it was proven that the application of an L-shaped wall led to a 15.8% increase in the lateral resistance, and that T-shaped walls have a higher impact on the stability of the track. A shoulder width of 400 mm was proposed as the optimum width for ballasted tracks with retaining walls.Accepted Author ManuscriptRailway Engineerin
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