Training programe

In April 2004 Building Design began publishing working details from contemporary
building projects that illustrate innovative construction techniques,
forty of which are collated in this book. The projects have deliberately not
been classifi ed and appear in the order in which they were originally published.
They exemplify the forefront of thinking in building technology yet also
address timeless problems of architectural detailing.
The purpose of the details is not to provide ready-made solutions but to
add to the resource base and stimulate thought. There are aspects of them
all that can be criticised. Although the principles applied in solving different
problems may be similar the fi nal details are always specifi c to the conditions
of the particular situation. The projects are presented here in the belief that
by offering a tentative analogous solution that can then be criticised, we gain
insight into our own problem and fi nd fresh strands of thought to follow.
I would like to thank all the architects, engineers and photographers who
have allowed their work to be reproduced in this book. (A full list of credits
for each project is given before the index at the back of the book.) Thank you
also to Robert Prewett for many stimulating conversations and to Emily Pitt
for her inspiration, advice and support.
..................

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Steels for application in bridges are covered by A709, which includes steel in several of the categories mentioned above. Under this specification, grades 36, 50, 70, and 100 are steels with yield strengths of 36, 50, 70, and 100 ksi, respectively. (See also Table 11.28.) The grade designation is followed by the letter W, indicating whether ordinary or high atmospheric corrosion resistance is required. An additional letter, T or F, indicates that Charpy V-notch impact tests must be conducted on the steel. The T designation indicates that the material is to be used in a non-fracture-critical application as defined by AASHTO; the F indicates use in a fracture-critical application.

A trailing numeral, 1, 2, or 3, indicates the testing zone, which relates to the lowest ambient temperature expected at the bridge site. (See Table 1.2.) As indicated by the first footnote in the table, the service temperature for each zone is considerably less than the Charpy V-notch impact-test temperature. This accounts for the fact that the dynamic loading rate in the impact test is more severe than that to which the structure is subjected. The toughness requirements depend on fracture criticality, grade, thickness, and method of connection.

A709-HPS70W, designated as a High Performance Steel (HPS), is also now available for highway bridge construction. This is a weathering plate steel, designated HPS because it possesses superior weldability and toughness as compared to conventional steels of similar strength. For example, for welded construction with plates over 21⁄2 in thick, A709-70W must have a minimum average Charpy V-notch toughness of 35 ft _ lb at _10_F in Zone III, the most severe climate. Toughness values reported for some heats of A709-HPS70W have been much higher, in the range of 120 to 240 ft _ lb at _10_F. Such extra toughness provides a very high resistance to brittle fracture. (R. L. Brockenbrough, Sec. 9 in Standard Handbook for Civil Engineers, 4th ed., F. S.

McGraw-Hill, Inc., New York.)