Author: C W BROWN, D C ILES | Size: 0.2 MB | Format:PDF | Publisher: SCI | Year: 1995 | pages: 21 | ISBN: 1859420281
The design of a new bridge can directly affect the durability and the maintenance costs, and hence the whole-life cost. Careful consideration should be given to whether an increase of initial capital cost may be warranted in order to reduce the subsequent maintenance costs. Such consideration would be particularly important in the case of a bridge where the notional costs of traffic delay and disruption during maintenance were disproportionately high - in such cases large increases in initial
capital cost can be justified to reduce the duration of maintenance. Steel bridges have an unjustified reputation for high cost maintenance. For instance, to some designers, the one word “rust” is a serious disincentive to the use of a steel bridge; this is a shortsighted and unreasonable attitude, for several reasons. To a large extent this view has been based upon experience of older structures where the choice of steelwork details and protective coating had been based on lower relative labour costs than currently prevail. Furthermore, it cannot be emphasised too strongly that corrosion of structural steel is a surface phenomenon; it is readily detectable in its early stages and, provided remedial action is taken, will not affect the overall
integrity of the structure in any significant way. Another perceived “problem” with steel bridges is that of fatigue. The resistance to fatigue of some early bridges in high strength structural steel was not adequate: some of these bridges are showing evidence of premature fatigue failure, although in most cases this can be repaired relatively easily. In the last twenty years a vast amount of research into fatigue has been carried out and this, together with extensive test programmes, has ensured that the subject of fatigue is much better understood now than it was in, say, 1950. Designers can now design bridges that have a high probability of lasting without serious fatigue problems for more than 100 years, using well-proven details. It is important not to become complacent, since there are unfortunately occasional examples of steel bridges where unexpected and unwelcome problems have occurred. However, it is pertinent to point out that repair or strengthening of deficient steel bridges can be a comparatively straightforward process, usually involving in-situ welding or bolting on additional steelwork without restricting
traffic. To summarise, a steel bridge is durable, when properly designed and maintained, and its whole-life cost is competitive with that of a bridge in any other material. In particular, it should be noted that:
C Design for durability is a well known and proven technology
C Steel bridges have more than 100 years proven record of durability
C Corrosion of structural steel is a surface phenomenon; it is readily detectable in its early stages and, provided remedial action is taken, will not affect the overall integrity of the structure in any significant way
C When deterioration is noted, it can readily be rectified
C Reliable coating systems, both for initial painting and maintenance painting, are available
C Modern steel bridges are designed to be easily inspectable and maintainable
C Maintenance should be regular; it is a known technology with quantifiable costs, and is thus easy to discount to present values that can be included in the whole life cost of the bridge
C Satisfactory design against fatigue has now become routine for steel bridge designers.
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SCI P057: Design of Members Subject to Combined Bending and Torsion
Author: D. A. NETHERCOT, P. R. SALTER, A. S. Malik | Size: 4.6 MB | Format:PDF | Publisher: SCI | Year: 1997 | pages: 128 | ISBN: 1870004442
The causes of torsional loading on structural members are discussed and those situations in which the explicit consideration of torsion needs to form part of the design calculations are identified. The basic theory of the torsion of both open and closed steel sections is presented. Solutions of the resulting equations in terms of both design charts and formulae for a selection of applied torsional loadings and support conditions are provided. A simple method for combining the effects of torsion and bending, consistent with the approach of BS 5950: Part I is presented. The complete design approach for combined bending and torsion is illustrated by means of a number of worked examples. These show that design will frequently be governed by the need to restrict twisting at working load to acceptable levels, rather than by considerations of ultimate strength.
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This Standard describes the procedure for determining the creep of standard concrete test cylinders subjected to a sustained longitudinal compressive load. This method does not provide means for calculating time-dependent deflection of reinforced or prestressed concrete members.
NOTE: The conditions for curing and storage (see Clause 6) can be varied to suit different requirements, e.g. early pre-stress. The time of loading (see Clause 7) can also be varied to give an indication of other properties. These variations, however, will not comply with the requirements for a creep test as specified in this Standard.
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This Standard sets out a method for the securing and testing of cylindrical cores from hardened concrete for the determination of compressive strength for an estimate of the inservice strength of a structure or part thereof.
NOTE: Because of the increased variability associated with core strengths, it is not recommended that concrete cores be used for direct quality control purposes.
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This Standard sets out a method for preparing and curing of concrete shrinkage specimens, and for determining the length changes of these specimens due to drying in air. It provides for testing of specimens prepared in the laboratory or in the field, in which the nominal size of aggregate in the concrete, in accordance with AS 2758.1, does not exceed 40 mm. The precision statement in Clause 9 does not apply to specimens which have had non-standard initial curing (normally field-prepared specimens). In addition this Standard requires that field-prepared specimens are marked, recorded and reported as such.
NOTES:
This test method is not always suitable for very low slump concrete (less than 20 mm), primarily due to the difficulties in obtaining adequate compaction. Provided adequate compaction is obtained, the method is applicable. The method is specifically designed for measurement of drying shrinkage of concrete, but it is capable of adaptation for measurement of length changes of specimens subjected to a variety of environmental conditions.
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It makes the color of your computer's display adapt to the time of day, warm at night and like sunlight during the day.
It's even possible that you're staying up too late because of your computer. You could use f.lux because it makes you sleep better, or you could just use it just because it makes your computer look better.
f.lux makes your computer screen look like the room you're in, all the time. When the sun sets, it makes your computer look like your indoor lights. In the morning, it makes things look like sunlight again.
Tell f.lux what kind of lighting you have, and where you live. Then forget about it. F.lux will do the rest, automatically.
for XP/Vista/7
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Dear Admin, Dear Protectors and Moderators,I think there is a problem with text formating in postgen since this morning.
I also saw that the medals are gone. Is this had happened by chance or they will no longer exist?
If medals continue to exist, I believe that the Forum team must establish clear criteria for their receipt - the number of posts,
number of threads or number of points .
This guide contains information on the design, specification, manufacture and maintenance of stainless steel architectural components. It is structured into two sections: Design and Technology and Case Studies. The first section includes structural and performance information on stainless steel and reviews production and finishing processes. It focuses on those grades of stainless steel and techniques that are commonly used in relation to architectural components. The second section provides an overview of the contemporary use of stainless steel in architecture. It comprises a broad and representative selection of building projects by leading architects and engineers.
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SCI P247: Over-cladding of Existing Buildings using Light Steel
Author: R M Lawson, R Pedreschi, I Falkenfleth, S O Popo-Ola | Size: 2.4 MB | Format:PDF | Publisher: SCI | Year: 1993 | pages: 60 | ISBN: 1859420842
Buildings are commonly over-clad to improve their appearance, to increase thermal insulation, and to reduce maintenance costs. This publication reviews the use of light steel construction in the over-cladding of existing concrete and masonry buildings as part of a renovation process. The over-cladding systems use sub-frame members that are connected to the existing structure or cladding. The new facade is attached directly to the subframe members. The sub-frame members are assembled from galvanized cold formed steel components, and a variety of different cladding materials may be used. The design aspects for over-cladding systems are reviewed, and the use of steel in over-cladding is discussed. A series of Case Studies from Belgium, Canada, Denmark, Finland, Germany and the United Kingdom are presented to show the range of applications of light steel in over-cladding. A prototype steel intensive over-cladding system is described, and interim results from the testing of this system are reported. It is demonstrated that in most cases the cost of the over-cladding will be re-couped within a 20 year period, if all the potential savings are considered.
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