33,576 research outputs found
Analytical studies of the behaviour of semi-rigid non-sway frames with tubular columns.
No full textThis thesis reports the research investigation on
the behaviour of non-sway frames with SHS columns taking into consideration the influence of semi-rigid flowdrill
connections. The aim of the studies was to investigate the behaviour of the non-sway frames in the elastic and inelastic ranges, the acceptability of the flowdrill connections for low-rise non-sway frames and to develop a simplified semi-rigid design that is suitable for daily design routine. The analytical studies were conducted using an existing finite element program which was modified to work with frames employing tubular columns. The program is able to simulate the response in the elastic and inelastic ranges taking into account the semi-rigid connections, the geometrical and material nonlinearities and the development of spread yield. The program has been validated against the experimental results and can reasonably predict the true frame behaviour. The results of
the parametric studies show several important observations;one of which is the phenomenon of moment shedding. This phenomenon causes the relaxation of
the detrimental moment at the column top end which in turn causes the moment redistribution to the neighbouring members. Eventually, the detrimental column moment diminishes and sometimes acts as restraining moments. As a consequence, at ultimate load, the columns behave in the general form of axially loaded compression members and the beams as simply supported with a certain degree of end restraint. Knowing that restrained beam-columns can be
treated as axially loaded, extensive parametric studies on
different frame configurations were conducted to determine
the ultimate strength of beam-columns. The studies were conducted on low rise multi-storey non-sway frames. The principal parameters varied are the column slenderness, connection types and the magnitude of beam loads. The values of ultimate strength of restrained beam-columns
are compared directly against the strength of pin ended columns as specified by the BS 5950 and EC3 codes. The results show that in many cases, the ultimate strength of restrained beam-columns are in excess to the strength of axially loaded pin ended column as specified by BS 5950 and
EC3. Based on the results of the parametric studies, a simplified design for simple, semi-rigid and rigid frames is developed. The columns are designed as axially loaded
compression members without any consideration of eccentricity or partial fixity moments. The beams for simple construction are designed as simply supported with
pin ends; whereas, the beams for semi-rigid and rigid construction are designed as simply supported with a certain amount of end restraint moment to take into account
the effect of semi-rigid and rigid connections. The design of strength for beams and columns can be
carried out individually and is not dependent on the stiffnesses of the M-0 of the connections, beams and columns. Finally, general conclusions and recommendations
for further work are also included
Behaviour of reinforced concrete frames with lightweight blockwork infill panels.
No full textThe current investigation concerns the behaviour of lightweight
blockork infill panels bounded by reinforced concrete frames. A
detailed and comprehensive review of the literature on different
frame-inf ill combinations is presented. Details are given of tests
on sixteen third-scale infilled frames and four open frames. These
were tested under two types of loading: horizontal racking loading
only and combined vertical loads on columns and racking loading.
The complete load-deflection response is considered in detail including.
initial elastic behaviour, influence of cracking and the formation of
collapse mechanisms after the attainment of peak load. The variables
investigated include the overall effects of the infill, the infill
thickness, the vertical loads, the amount of reinforcement, the change
in stiffness and strength of beams and of columns and the effect of
reinforcement detailing. Those found to have a major influence are
the vertical loads, the infill thickness, the reinforcement detailing
particularly in the opening corners of the frame, and the workmanship.
The principal parameters obtained from the tests are the initial
racking stiffness, the infill cracking strength, the ultimate load and
the plastic collapse load. Their values are compared to the available
empirical and theoretical methods. None of these methods is found to
safely predict the initial racking stiffness and the ultimate carrying
capacity of this type of structure. A plastic analysis is presented
to predict the two plastic collapse mechanisms identified in the tests.
The penalty factor to allow for idealization of plasticity of the
infill is found as part of the solution. A second penalty factor is
introduced to allow for the limited ductility of the frame. The
proposed method is found to yield satisfactory and safe predictions for the plastic resistance of these infilled frames. In conclusion
some design recommendations are proposed for the initial racking
stiffness and the cracking infill strength
Semi-Active Control of Post-tensioned Steel Frames
No full textAfter the Northridge 1994 earthquake it was found that failures in steel frame buildings were mainly concentrated in beam-column connections. This prompted researchers to work on improvements, mainly focussed on increasing the rotational ductility capacity in connections. Most of these improvements however did not eliminate the residual deformations in the connections. To overcome this weakness, researchers introduced post-tensioned steel connections, composed of post-tensioned steel strands and energy dissipating devices.
In this research, a single-element model of post-tensioned connection was developed and incorporated in a new computer program for non-linear dynamic frame analysis, which was then used to investigate the effects of the level of post-tensioning forces on seismic behaviour of frame buildings. When used in moment resisting frames, post-tensioned connections reduce residual displacements and prevent development of plastic hinges in the beams. The initial stiffness of post-tensioned frames is also similar to conventional moment resisting frames but their energy dissipation capacity is lower. The performance of the structure is sensitive to the level of post-tensioning forces, and in some cases the use of post-tensioned connections leads to increased displacements. The aim of this research was to investigate semi-active control of the post-tensioning forces as an approach for improving the seismic behaviour of multi-storey steel frame buildings.
Three control approaches were proposed to improve the dynamic behaviour of post-tensioned frames: (i) energy dissipation approach which aims to increase the energy dissipation capacity of the frame, (ii) stiffness control approach which aims to change the frequency of the frame by softening or stiffening to avoid excitation by major frequency components of the earthquake and (iii) deformation regulation approach which aims to improve the distribution of deformations along the height of the frame.
The three control approaches showed different results. Increasing energy dissipation in the connections is not an efficient approach for reducing the frame response, especially when large displacements occur in the early stages of loading. The stiffness control approach showed good performance, reducing both floor displacements and force demand on the elements. The deformation regulation approach also improved the response, providing more uniform inter-storey drift distribution. In general, the research presented here shows that semi-active control can be used to improve the seismic performance of post-tensioned steel frames
Figures Don't Lie: Spatial Humanities and Technology as Critical Thinking Tools
No full textThis presentation demonstrates the potential use of spatial humanities as both a critical thinking exercise and a computational tool in digital humanities pedagogy. “Figures Don’t Lie” presents a map of the United States that labels each state as a foreign nation according to the correlation between the GDPs of each state and their assigned countries. The map may spark classroom discussions about a range of humanities topics. Revealing the map’s underlying data shows how facts can be spun and helps students understand how the “facts” presented in the media may not be what they appear.Presented at Rutgers University's "Digital Humanities Showcase: New Methods and New Media" on January 29, 2014 (New Brunswick, N.J.)
Calculating All That Jazz: Linking Technical Specifications to the Management of Digitization Projects
No full textThe purpose of this session is to educate librarians and archivists about the technical aspects of the digitization process and demonstrate how deeper understanding of those aspects can be used to evaluate the appropriateness of digitization standards, project scope, quality of digitization equipment and storage needs for digitization projects involving photographs and documents. Most scholarship on archival-quality digitization has focused on either elements of digital library project management or on technical specifications and how to digitize materials. "Calculating All That Jazz" focuses on presenting a formula for calculating digital storage space based on analog still images and documents, demonstrating how deeper understanding of the technical elements of digitization in the formula applies directly to crucial project management considerations
The workshop as the work: white anti-racism organising in 1960s, 70s, and 80s US social movements
No full textThis thesis explores the rise of anti-racism workshops developed by white activists in various United States social movements from the late 1960s through the mid-1980s. The shifting ideology of the black freedom movement in the late 1960s, from integration to Black Power, transformed white activists‘ place within racial justice struggles. While recent scholarship has begun to turn its attention towards whites‘ ongoing racial justice activities, one of the most radical and widespread of these efforts is consistently overlooked: anti-racism workshops. Increasingly prevalent from the late 1960s through to the diversity-trainings explosion of the 1990s, this thesis demonstrates that these workshops had their roots in the black freedom, women‘s liberation and gay liberation movements. White activists from these movements led these workshops in order to examine white racial domination and privilege within both leftist social movements and larger US society.
Analysing case studies from the black freedom, women‘s liberation and gay liberation/rights movements, this thesis explores the foundational assumptions of anti-racism workshops. It seeks to explain how and why these efforts sought to frame race and racism as issues of knowledge and consciousness and why such efforts constituted radical praxis. It is argued that early anti-racism workshops were pedagogical projects that sought to confront the racial ignorance that structured the lives of whites in the US, including progressives and their liberation movements. This thesis draws attention to the efficacy and power of these workshops in terms of their epistemological effects, in the transformations they brought about in whites‘ understanding, or awareness, of racial realities
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Design optimisation of steel portal frames using modified distributed genetic algorithms
No full textDistributed genetic algorithms have been modified in this study to improve their quality, performance, and convergence to the optimum solution for structural steel frames. This was achieved by introducing some novelties of the main algorithm of distributed genetic algorithms and applying them in structural optimisation. Among these are the creation of new mutation schemes, adding a crossover scheme, definition of a penalty function, properties of twins, and definition of the reproduction scheme. Many optimisation problems have been designed to minimise the weight of a steel structure and are well documented in the literature. However, having a frame controlled by displacement will necessitate choosing a different approach for the objective function. In addition to weight minimisation, attempts have been made to investigate displacement maximisation and this also forms part of the novelty of this study. Various steel frames in terms of geometry and loading conditions are considered during the optimisation process and they are assumed to have rigid and/or semi-rigid connections. The design optimisations are conducted according to therequirements of both BS 5950 and EC3 codes of practice. A stiffness matrix is developed for a non-prismatic member that is involved in the analysis process
Finding frames: new ways to engage the UK public in global poverty
No full textThe aim of the study was to explore the potential for frames theory to be used as a practical tool to re-engage the UK public in global poverty.
In exploring the uses of frames theory, we have built on work by Tom Crompton at WWF-UK, who began the task of linking values to frames and thereby suggesting new ways forward for engaging the public in environmental issues and actions. An important finding from his Common Cause paper is that there is a common set of values that can motivate people to tackle a range of ‘bigger than self’ problems, including the environment and global poverty.
The implication is that large coalitions can – and must – be built across third- sector organisations to bring about a values change in society. This report responds to that call.
The basic argument of this paper is that there is a problem in terms of the UK public’s levels of engagement with global poverty. Simply put, people in the UK understand and relate to global poverty no differently now than they did in the 1980s. This is the case despite massive campaigns such as the Jubilee 2000 debt initiative and Make Poverty History; the widespread adoption and mainstreaming of digital communication techniques and social networks; steady growth in NGO fundraising revenues; the entire Millennium Development Goal story; and the establishment of a Westminster consensus on core elements of development policy.
By many measures we have made amazing strides forward in recent years, but the public have largely been left behind. The result is that we operate within social and, by extension, political conditions that are precarious in the immediate term and incommensurate to the challenges of poverty and climate change in the medium and long term.
This study looks at what can be learned from values (the guiding principles that individuals use to judge situations and determine their courses of action) and frames (the chunks of factual and procedural knowledge in the mind with which we understand situations, ideas and discourses in everyday life). Values and frames offer ways to look at the problem of public engagement with global poverty and to identify possible solutions. If we apply values and frames theory to the question of how to re-engage the public, we come up with some compelling insights into the impact of our existing practices and some striking solutions to the problems that these reveal. They may not be perfect solutions, and they bring with them significant challenges. But we believe they offer something valuable and timely: a fresh perspective.
The persistent problem of public engagement suggests it is time for the development sector to transform its practices radically. Values and frames offer pathways to potential solutions that should be debated across the sector, and no
Old frames and new lenses : frames of reference revisited
No full textThe ‘frames of reference’ concept has been a significant and enduring feature of industrial/employment relations since being developed by Alan Fox; and yet there has been only limited scholarly research seeking to develop the frames. We introduce this special issue by reviewing the extant literature on frames which provides a backdrop to the five article contributions that explore the frames in both new and historical light. The special issues ask the following questions: Do the traditional frames continue to provide insights into the perceptions and behaviour of employers and employees? If not, how might existing frames be broadened by new (or indeed historical) developments and insights? A re-examination of frames of reference is both important and timely given the many changes currently impacting work and employment. Our hope is that by reflecting on and celebrating the influence of Alan Fox on our thinking, we can also chart a forward-looking research agenda that continues to use his insights and apply them to the field as well as developing and continuing to engage with them
Frame behaviour with semi-rigid connections.
No full textIn this thesis both analytical and design studies have been conducted on the behaviour of fully and semi-rigidly connected multistorey steel frames. Many topics have been
addressed, current design approaches examined and new design
methods proposed to allow for such effects based upon a
first order linear elastic analysis, which is the most commonly used in normal design. These topics are as follows: 1) The well known
amplified sway method (see BS 5950: 1985: Part 1) which can
be used to incorporate the effect of the presence of axial loads on the behaviour of sway frames was studied. A modification to this method has been proposed and the validity of the proposed method was checked using an existing computer program [1] to verify the proposed method against a second order analysis. 2) The influence of the action of semi-rigid connections on
frame behaviour was examined and the need to conduct a systematic investigation into the problem verified. A
simple hand calculation method to incorporate this influence to any of the conventional design methods
has been proposed. A second computer program [2] was slightly modified to suit the university of Sheffield IBM3083 mainframe machine and this program was later
used in this study. 3) The stiffening effect due to partial sway bracing resulting from the presence of block
or brickwork walls in a practical multistorey
frame accompanied by the weakening effect due to the finite
stiffness of semi-rigid joints on frame serviceability was
investigated and a suitable design method is recommended.
4) The behaviour of columns in sway frames with and without partial sway bracing, resulting from the presence of
infill panels in practical frames, has been examined. Design charts which can be used to predict a reasonably conservative estimation of the inelastic ultimate load of a framed column in a sway structure are given. These
charts are particularly helpful in assisting a designer to make a reasonably good initial selection for the column section sizes in a flexibly connected frame. In
addition an empirical formula has been proposed to incorporate the beneficial effect on the column behaviour resulting from the presence of infill panels
in real steel frames. In order to conduct this study a computer program developed by Rifai [3] has been modified to simulate the behaviour of a flexibly connected sway subassemblages. 5) Finally general conclusions and recommendations for future work are given
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