TRANSFER LENGTH, DEVELOPMENT LENGTH, FLEXURAL STRENGTH, AND PRESTRESS LOSS EVALUATION IN PRETENSIONED SELF-CONSOLIDATING CONCRETE MEMBERS
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ABSTRACT
The first objective of this thesis was to determine the effect of using self-consolidating
concrete versus normal concrete on transfer and development lengths, and flexural strengths of
prestressed members. Three small rectangular members were made, two cast with SCC mixes
and one cast with a conventional mix, to determine the transfer length of each mix. Transfer
lengths of both ends of each member were determined by measuring the concrete surface strains.
The change in the transfer length was monitored by determining the transfer length of each
member at prestress release, 7 days after release, and 28 days after release. All concrete mixes
had lower than code determined transfer lengths at prestress release. Each concrete mix showed between a 12 to 56 percent increase in transfer length after 28 days. One SCC mix exceeded the ACI code stipulated 50 strand diameters 7 days after prestress transfer. The other SCC mix was consistently below the transfer length of the conventional concrete.
Separate development length members were cast in a stay-in-place steel form used for
creating structural double tees. Each development length member was a stub tee. Iterative load
testing was performed to determine the development length of each SCC and conventional mix.
Development lengths for both SCC mixes were approximately 20 percent shorter than ACI and
AASHTO code predictions. A development length for the conventional concrete was not
determined due to non-repeating test data. The flexural strength of each member was determined during load testing. All concrete mixes achieved higher than the ACI predicted strengths.
The second objective of this thesis was to experimentally measure prestress losses and
compare these experimental values to theoretical models. Crack initiation and crack reopening
tests were performed to experimentally determine the prestress losses in each member. Three
theoretical models were evaluated, the sixth edition PCI Design Handbook suggested model, a
1975 PCI Committee on Prestress Losses model, and the AASHTO LRFD prestress loss model.
The crack initiation experimental values tended to be between 10 and 15 percent lower than
theoretical models. In general, the crack reopening prediction of the effective prestress had a good correlation with theoretical models.
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Highways Department (HyD) of Hong Kong SAR is turning their idea for a world class bridge across Rambler Channel at the entrance to Kwai Chung Container Port into reality. Due to the spectacular location, HyD selected the concept for the bridge through an international design Competition. The competition took place in the first half of 2000 and the winning concept was a cable-stayed structure with freestanding towers located between twin box girder decks. The 1018m main span is in steel,
while the four back spans each side are in concrete. The two towers stand on shore, providing unobstructed access to the busy container port with a minimum navigation headroom of 73.5m.
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Author: James E. Piper
Publisher: Fairmont Press (February 2004) | ISBN: 0881733210 | Pages: 452 | PDF | 1.9 MB
This practical guide is designed for facility and maintenance managers who are facing "repair or replace" decisions for their buildings. Filled with useful information and resources to aid in the decision process, this hands-on reference will show you how to accurately rate the condition of existing equipment and components, effectively assess your options, and avoid making costly mistakes. Detailed step-by-step instructions are provided, along with forms listing specific criteria identified for rating each building component.
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A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.
- Douglas Adams
Aeroplanes are not designed by science, but by art in spite of some pretence and humbug to the contrary. I do not mean to suggest that engineering can do without science, on the contrary, it stands on scientific foundations, but there is a big gap between scientific research and the engineering product which has to be bridged by the art of the engineer.
- British Engineer to the Royal Aeronautical Society, 1922.
A good scientist is a person with original ideas. A good engineer is a person who makes a design that works with as few original ideas as possible
- Freeman Dyson
A great bridge is a great monument which should serve to make known the splendour and genius of a nation; one should not occupy oneself with efforts to perfect it architecturally, for taste is always susceptible to change, but to conserve always in its form and decoration the character of solidity which is proper.
- Jean Peronnet
Architects and engineers are among the most fortunate of men since they build their own monuments with public consent, public approval and often public money.
- John Prebble
Engineering is the art of modelling materials we do not wholly understand, into shapes we cannot precisely analyse so as to withstand forces we cannot properly assess, in such a way that the public has no reason to suspect the extent of our ignorance.
- Dr AR Dykes
Engineering problems are under-defined, there are many solutions, good, bad and indifferent. The art is to arrive at a good solution. This is a creative activity, involving imagination, intuition and deliberate choice.
- Ove Arup
Engineering refers to the practice of organizing the design and construction [and, I would add operation] of any artifice which transforms the physical world around us to meet some recognized need.
- GFC Rogers
Engineers … are not mere technicians and should not approve or lend their name to any project that does not promise to be beneficent to man and the advancement of civilization
- John Fowler
Engineers … are not superhuman. They make mistakes in their assumptions, in their calculations, in their conclusions. That they make mistakes is forgivable; that they catch them is imperative. Thus it is the essence of modern engineering not only to be able to check one’s own work but also to have one’s work checked and to be able to check the work of others.
- Henry Petroski
Experience serves not only to confirm theory, but differs from it without disturbing it, it leads to new truths which theory only has not been able to reach.
- Dalembert
From the laying out of a line of a tunnel to its final completion, the work may be either a series of experiments made at the expense of the proprietors of the project, or a series of judicious applications of the results of previous experience.
- HS Drinker
Go for civil engineering, because civil engineering is the branch of engineering which teaches you the most about managing people. Managing people is a skill which is very, very useful and applies almost regardless of what you do.
- Sir John Harvey Jones
He … insists that no mathematical formula, however exact it may appear to be, can be of greater accuracy than the assumptions on which it is based, and he draws the conclusion that experience still remains the great teacher and final judge.
- James Kip Finch
His father loved him dearly, but his work, that of a civil engineer, had left him with but little time for his family. Energetic, active, and always taken up with some responsible work, he did not spoil his children with excessive tenderness.
- Mme Estafavia
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I am an old man now, and when I die and go to Heaven there are two matters on which I hope for enlightement. One is quantum electrodynamics and the other is the turbulent motion of fluids. And about the former I am rather more optimistic.
- Sir Horace Lamb
In practical work he can be ingenious with regard to modifying apparatus; he uses engineering rather than imagination.
- Head Teacher’s reference for a student applying to University
It takes an engineer to undertake the training of an engineer and not, as often happens, a theoretical engineer who is clever on a blackboard with mathematical formulae but useless as far as production is concerned.
- The Rev EB Evans
Let him not be grasping nor have his mind preoccupied with … receiving perquisites, but let him with dignity keep up his position by establishing a good reputation. No work can be rightly done without honesty and incorruptibility.
- Vitruvius
Men build bridges and throw railroads across deserts, and yet they contend successfully that the job of sewing on a button is beyond them. Accordingly, they don’t have to sew buttons.
- Heywood Broun
No greater care is required upon any works than upon such as are to withstand the action of water; for this reason, all parts of the work need to be done exactly according to the rules of the art which all workmen know, but few observe.
- Sextus Julius Frontinus
Nor aught availed him now
To have built in heaven high towers; nor did he scape
By all his engines, but was headlong sent
With his industrious crew to build in hell.
- John Milton
The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong, it usually turns out to be impossible to get at and repair.
- Douglas Adams
There can be little doubt that in many ways the story of bridge building is the story of civilisation. By it we can readily measure an important part of a people’s progress.
- Franklin D Roosevelt
Therefore O students study mathematics and do not build without foundations.
- Leonardo Da Vinci
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…as for earthquakes, though they were still formidable, they were so interesting that men of science could hardly regret them.
- Bertrand Russell
This is not the age of pamphleteers. It is the age of engineers. The spark-gap is mightier than the pen. Democracy will not be salvaged by men who talk fluently, debate forcefully and quote aptly.
- Lancelot Hogben
You have been found guilty of indulging in unnatural practices under one of London’s most beautiful bridges.
- Judge reprimanding prisoner before sentence
Urban myth at the Bar
Shallow slip failures on embankment and cutting slopes are more likely in certain geologies, particularly over-consolidated clays. The reinstatement of these shallow failures can be costly and the potential for slips may be reduced not only by the use of vegetation planted to provide reinforcement, through the plant root system, but also by a reduction in moisture content and pore water pressure. Report reviewing the potential for vegetation as a preventative measure in high-risk areas as well as investigating associated aspects such as the use of vegetation on reinforced steepened slopes in road widening and the use of live willow poles in reducing the risk of shallow failures.
Subject(s)
Civil engineering and public utilities
Earthworks/foundations/piling/retaining walls
Embankments
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Posted by: debpriya1984 - 01-26-2010, 11:27 AM - Forum: Archive
- No Replies
Dear friends,
I´m looking for this book:
International Conference Tunnelling Asia '2000, 26-29 September, New Delhi ... By S. P. Kaushish, T. Ramamurthy, International Tunnelling Association (India)
Paper on ‘tsunami resistant’ houses wins the Institution of Civil Engineers Bill Curtin prize
A paper by Dr Indrasenan Thusyanthan, former Lecturer in the University of Cambridge Geotechnical Research Group and Dr Gopal Madabhushi, Reader in Geotechnical Engineering, has won the Bill Curtin prize awarded by the Institution of Civil Engineers (ICE) for the Best Paper in the 'ICE Civil Engineering' magazine.
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