Arching or Compressive Membrane Action in Reinforced Concrete Slabs

Arching or compressive membrane action (CMA) in reinforced concrete slabs occurs as a result of the great difference between the tensile and compressive strength of concrete. Cracking of the concrete causes a migration of the neutral axis which is accompanied by in-plane expansion of the slab at its boundaries. If this natural tendency to expand is restrained, the development of arching action enhances the strength of the slab. The term arching action is normally used to describe the arching phenomenon in one-way spanning slabs and compressive membrane action is normally used to describe the arching phenomenon in two-
way spanning slabs. This encyclopedic article presents the background to the discovery of the phenomenon of arching action and presents a factual history of the approaches to the treatment of arching action in the United Kingdom and North American bridge deck design codes. The article summarises the theoretical methodology used in the United Kingdom Design Manual for Roads and Bridges, BD81/02, which was based on the work by Kirkpatrick, Rankin & Long at Queen's University Belfast.

Parker Morris and the Fordist House

6.00 pm. If people like watching T.V. while they are eating their evening meal, space for a low table is needed (Ministry of Housing and Local Government, Space in the Home, 1963, p. 4).

This paper re-examines the 1961 Parker Morris report on housing standards in Britain. It explores the origins, scope, text and iconography of the report and suggests that these not only express a particularly modernist conception of space but one which presupposed very specific economic conditions and geographies.

Also known as Homes for Today and Tomorrow Parker Morris attempted, through the application of scientific principles, to define the minimum living space standards needed to accommodate household activities. But while early modernist research into notions of existenzminimum were the work of avant-garde architects and thinkers, Homes for Today and Tomorrow and its sister design manual Space in the Home were commissioned by the British State. This normalization of scientific enquiry into space can be considered not only as a response to new conditions in the mass production of housing – economies of scale, prefabrication, system-building and modular coordination – but also to the post-war boom in consumer goods. In this, it is suggested that the domestic interior was assigned a key role as a privileged site of mass consumption as the production and micro-management of space in Britain became integral to the development of a planned national economy underpinned by Fordist principles. Parker Morris, therefore, sought to accommodate activities which were pre-determined not so much by traditional social or familial ties but rather by recently introduced commodities such as the television set, white goods, table tennis tables and train sets. This relationship between the domestic interior and the national economy are emblematized by the series of placeless and scale-less diagrams executed by Gordon Cullen in Space in the Home. Here, walls dissolve as space flows from inside to outside in a homogenized and ephemeral landscape whose limits are perhaps only the boundaries of the nation state and the circuits of capital.

In Britain, Parker Morris was the last explicit State-sponsored attempt to prescribe a normative spatial programme for national living. The calm neutral efficiency of family-life expressed in its diagrams was almost immediately problematised by the rise of 1960s counter-culture, the feminist movement and the oil crisis of 1972 which altered perhaps forever the spatial, temporal and economic conditions it had taken for granted. The debate on space-standards, however, continues.

Rapid design of application specific FFT cores

Methods are presented for developing synthesizable FFT cores. These are based on a modular approach in which parameterized commutator and processor blocks are cascaded to implement the computations required in many important FFT signal flow graphs. In addition, it is shown how the use of a digital serial data organization can be used to produce systems that offer 100% processor utilization along with reductions in storage requirements. The approach has been used to create generators for the automated synthesis of FFT cores that are portable across a broad range of silicon technologies. Resulting chip designs are competitive with ones created using manual methods but with significant reductions in design times.

Impact of composite ply continuity constraints on aerospace stiffened panel design

Considering the development of aerospace composite components, designing for reduced manufacturing layup cost and structural complexity is increasingly important. While the advantage of composite materials is the ability to tailor designs to various structural loads for minimum mass, the challenge is obtaining a design that is manufacturable and minimizes local ply incompatibility. The focus of the presented research is understanding how the relationships between mass, manufacturability and design complexity, under realistic loads and design requirements, can be affected by enforcing ply continuity in the design process. Presented are a series of sizing case studies on an upper wing cover, designed using conventional analyses and the tabular laminate design process. Introducing skin ply continuity constraints can generate skin designs with minimal ply discontinuities, fewer ply drops and larger ply areas than designs not constrained for continuity. However, the reduced design freedom associated with the addition of these constraints results in a weight penalty over the total wing cover. Perhaps more interestingly, when considering manual hand layup the reduced design complexity is not translated into a reduced recurring manufacturing cost. In contrast, heavier wing cover designs appear to take more time to layup regardless of the laminate design complexity. © 2012 AIAA.

Time Efficient Assessment and Feedback Methods for Large Computer-Aided-Design Cohorts

Timely and individualized feedback on coursework is desirable from a student perspective as it facilitates formative development and encourages reflective learning practice. Faculty however are faced with a significant and potentially time consuming challenge when teaching larger cohorts if they are to provide feedback which is timely, individualized and detailed. Additionally, for subjects which assess non-traditional submissions, such as Computer-Aided-Design (CAD), the methods for assessment and feedback tend not to be so well developed or optimized. Issues can also arise over the consistency of the feedback provided. Evaluations of Computer-Assisted feedback in other disciplines (Denton et al, 2008), (Croft et al, 2001) have shown students prefer this method of feedback to traditional “red pen” marking and also that such methods can be more time efficient for faculty.
Herein, approaches are described which make use of technology and additional software tools to speed up, simplify and automate assessment and the provision of feedback for large cohorts of first and second year engineering students studying modules where CAD files are submitted electronically. A range of automated methods are described and compared with more “manual” approaches. Specifically one method uses an application programming interface (API) to interrogate SolidWorks models and extract information into an Excel spreadsheet, which is then used to automatically send feedback emails. Another method describes the use of audio recordings made during model interrogation which reduces the amount of time while increasing the level of detail provided as feedback.
Limitations found with these methods and problems encountered are discussed along with a quantified assessment of time saving efficiencies made.

Perceived difficulty of various steps of manual small incision cataract surgery among trainees in rural China

Background: The perceived difficulty of steps of manual small incision cataract surgery among trainees in rural China was assessed. Design: Cohort study. Participants: Fifty-two trainees at the end of a manual small incision cataract surgery training programme. Methods: Participants rated the difficulty of 14 surgical steps using a 5-point scale, 1 (very easy) to 5 (very difficult). Demographic and professional information was recorded for trainees. Main Outcome Measure: Mean ratings for surgical steps. Results: Questionnaires were completed by 49 trainees (94.2%, median age 38 years, 8 [16.3%] women). Twenty six (53.1%) had performed ≤50 independent cataract surgeries prior to training. Trainees rated cortical aspiration (mean score±standard deviation=3.10±1.14) the most difficult step, followed by wound construction (2.76±1.08), nuclear prolapse into the anterior chamber (2.74±1.23) and lens delivery (2.51±1.08). Draping the surgical field (1.06±0.242), anaesthetic block administration (1.14±0.354) and thermal coagulation (1.18±0.441) were rated easiest. In regression models, the score for cortical aspiration was significantly inversely associated with performing >50 independent manual small incision cataract surgery surgeries during training (P=0.01), but not with age, gender, years of experience in an eye department or total number of cataract surgeries performed prior to training. Conclusions: Cortical aspiration, wound construction and nuclear prolapse pose the greatest challenge for trainees learning manual small incision cataract surgery, and should receive emphasis during training. Number of cases performed is the strongest predictor of perceived difficulty of key steps. © 2013 Royal Australian and New Zealand College of Ophthalmologists.

A Design & Feasibility Study of the Spaced Learning Programme

Objectives There is evidence from neuroscience, cognitive psychology and educational research that the delivery of a stimulus in a spaced format (over time) rather than a massed format (all at once) leads to more effective learning. This project aimed to pilot spaced learning materials using various spacing lengths for GCSE science by exploring the feasibility of introducing spaced leaning into regular classrooms and by evaluating teacher fidelity to the materials. The spaced learning methods will then be compared with traditional science revision techniques and a programme manual will be produced. Design A feasibility study. Methods A pilot study (4 schools) was carried out to examine the feasibility and teacher fidelity to the materials, using pupil workshops and teacher interviews. A subsequent random assignment experimental study (12 schools) will involve pre and post testing of students on a science attainment measure and a post-test implementation questionnaire. Results The literature review found that longer spacing intervals between repetitions of material (>24 hours) may be optimal for long term memory formation than shorter intervals. A logic model was developed to inform the design of various programme variants for the pilot and experimental study. This paper will report qualitative data from the initial pilot study. Conclusions The paper uses this research project as an example to explain the importance of conducting pilot work and small scale experimental studies to explore the feasibility and inform the design of educational interventions, rather than prematurely moving to RCT type studies.