Archive for August, 2012

15th WCEE in Lisbon, Portugal

Posted by cdj On August - 29 - 2012

A reminder that the 15th World Conference in Earthquake Engineering, is held in Lisbon, Portugal from September 24 to 28, 2012. Registrations using the conference Online registrations website feature are still possible until September 17th, 2012. Registration at the conference is also available. Conference cost is about E 600 (Euros).

Lisbon, 1755

Lisbon before & after earthquake of 1755 (from: Kozak Coll.)

Lisbon, 1755

Lisbon, Nov. 1, 1755 (from: Kozak Coll.)

The inaugural World Conference in Earthquake Engineering was held in Berkeley, California in June, 1956, to coincide with the 50th anniversary of the Great 1906 San Francisco Earthquake and Fire. The event was co-sponsored by the (then) fledgling Earthquake Engineering Research Institute (EERI) and by the Department of Engineering, University of California through the offices of University Extension. The National Science Foundation helped to support the conference financially. The 1956 organizing committee included R.W. Binder, J.A. Blume, W.K. Cloud, R.W. Clough, H.J. Degenkolb, C.M. Duke, A.L. Miller, H.C. Powers, and was chaired by J.E. Rinne. George W. Housner was EERI President and unofficial conference chairman. The printed Proceedings of the World Conference on Earthquake Engineering were made available by Karl V. Steinbrugge, EERI Secretary ($8.50 – to cover printing costs). These individuals represent a ‘who’s who’ of earthquake engineering in the USA at that time. Like today, although at a much smaller scale, the 1956 conference was international in scope with representations from USA, Japan, New Zealand, Chile, Mexico, Colombia, Turkey, Pakistan, Greece, Italy, Germany, and India. Participants provided 38 technical papers, two formal panel discussions, and conference organizers allowed for wide consultation among the conference registrants. To understand the style of the conference, a small portion of the final panel discussion (John A. Blume on Structural Design and Practice) from the 1956 conference is reproduced below. Some of the themes remain remarkably resilient today:

Question: Is building design to resist earthquakes often done with the aid of dynamic methods including dynamic model experiments?
Minami (Japan): Only in exceptional cases.
Pinzon (Colombia): In Colombia we do not as yet design by dynamic methods, although I understand Venezuela is conducting some research along those lines.
Barnes (U.S.): Until dynamic methods are available which can be done in the time for which engineers can get compensated, I think the nearest approach which static methods can provide will be generally used.
Blume (U.S.): In the United States the codes are being modified to simulate dynamic conditions for average structures by static methods. Special structures require special treatment for satisfactory and economic results.

Question: In Japan, do you ever set out to design beyond the elastic limit or is compliance with the building code the usual limit of design?
Minami: The use of basic seismic coefficients of 20% of gravity or more and allowable steel stresses of 34,000 psi bring us to the yield point. However, if some earthquakes are more severe than we anticipate, the steel would go into
the plastic range.
Rinne (U.S.): Many of us feel that a better balanced design will be obtained with higher coefficients and higher allowable stresses. This, of course, approaches a kind of limit design.
Blume: It can be shown by simple arithmetic that members carrying only lateral forces have less residual strength, not to mention energy absorbtion value, compared to other basic members under the low stress increases in codes.
Rosenblueth (Mexico): The Mexican code generally follows American codes, but some engineers raise stresses up to 100% or to the yield point, often with greater seismic coefficients. There are various practices.

Question (Binder from audience): Mr. Blume, in the December 23, 1948, Engineering News Record you listed some unsolved or controversial problems. Have these matters been resolved in the meantime?
Blume: A copy of that article is here. I shall first read and then comment briefly on each problem listed.
(1) “Design of all structures on the basis of a percentage of weight as an assumed lateral force.” This has been discussed a great deal at this conference. Modern codes vary the percentages for various conditions to better simulate dynamic phenomena. Great progress has been made.
(2) “The percentages required by various codes for such forces.” This has also been discussed, especially in the last panel question. Damping, energy absorbtion, allowable damage, etc., are all involved.
(3)“The way such percentages are reduced according to the number of stories for high buildings, regardless of width or other dynamic characteristics.” Same reply as for (1) above.
(4)“The amount of live load required by various codes to be included m the weight used in seismic computations.” Progress is being made on this also. The trend in recent codes is to approach actual average live loading.
(5)“The variation of coefficients for soft ground conditions.” This item is still controversial no doubt because many generally unrecognized factors enter the problem. American codes have in recent years tended to eliminate or reduce former variations in coefficients with ground conditions.
(6)“The amount of stress increase permitted under earthquake motion.” This has been widely discussed at this conference, particularly on this panel.
(7)“The handling of the overturning (cantilever) moment problem for high buildings or units thereof which act structurally for many stories.” This item, which is still controversial, has also been discussed on this panel. More research is indicated.
(8)“Design practice does not adequately differentiate between flexible and rigid structures.” This is still a problem although recent codes, particularly the new San Francisco code, approach the matter more realistically.
(9)“The definition of a diaphragm as a horizontal distributing element.” This problem has been worked on perhaps more than the others. I’ll ask Mr. Barnes to discuss this.
Barnes: A diaphragm is essentially a horizontal girder to distribute horizontal forces to the various vertical resisting elements. In addition to strength, there should be certain limitations on deflections of these diaphragms in order
that the vertical elements not be subjected to movement which would cause distress or failure.

Blume: In summary, may I say that progress has been made on these problems as-well as others. This conference has also contributed in no small degree toward the ultimate solution of many important matters in seismological engineering. There is, however, a great deal more to be done.

Lisbon, 1755

Lisbon earthquake, fire and tsunami, 1755 (Kozak Coll.)

Please note : EERI has announced a bid to host the next WCEE in 2016 in San Francisco. The bid was formally presented to the IAEE directors in Lisbon in September.

The Board of the International Association for Earthquake Engineering awarded the 16th WCEE to the Chilean Association of Seismology and Earthquake Engineering and the 2016 WCEE will be held in Santiago, Chile.

More on Fukushima Daiichi and ‘Morning Dew’

Posted by cdj On August - 21 - 2012

In a Wall Street Journal short essay of Saturday, August 18, 2012 examining the case for nuclear power generation, a professor of physics at the University of California, Berkeley, and the Lawrence Berkeley National Laboratory, Dr. Rich Muller reviews the”panic over Fukushima” following the great 2011 Tohoku earthquake and tsunami. This essay finds it “remarkable that so much attention has been given to the radioactive release from Fukushima, considering that the direct death and destruction from the tsunami was enormously greater…” and concludes that several post-earthquake actions surrounding the Fukushima reactors in Japan may have been predicated by panic rather than by a reliable (probabilistic) scientific reasoning. This essay, adapted from a new book, “Energy for Future Presidents: The Science Behind the Headlines” was written about one year after the events of March, 2011 unfolded in Japan.

Irrelevant Extra Credit : The Morning Dew reference in the title and then any Jeff Beck Group version of the 1962 song including this live version.

Risk models, uncertainty, and insured losses

Posted by cdj On August - 17 - 2012

A short paper, “Modelling vulnerability in earthquake risk models: an insurance perspective” presented at the 8th Pacific Conference on Earthquake Engineering (Singapore : Nanyang Technological University, December 5-7, 2007) written by M. Spranger, D. Hollnack, A. Allmann, and A. Smolka of the Munich Reinsurance Company succinctly recounts some problems with seismic risk assessment from the re-insurance perspective. Observing that “the correlation between damage and PGA seems to be rather poor” the authors point out that “reviewing the loss experience from big earthquakes during the last two decades indicates that the influence of hazard-related uncertainties is highly variable and depends on seismicity.” So, in regions with a small historical record and/or weak to moderate earthquake activity, “the hazard uncertainties are quite large”… and… “in most regions of the world, the historical record is too short for sound statistical tests.”

Even when the earthquake record is more plentiful, fragility curves, generally derived for the structural components of a building, account only for a “minor portion” of the overall insured loss of an earthquake in most cases. Secondary effects like soil liquefaction and soil amplification account for a small part of this discrepancy. But within increasing globalization of production and distribution, the authors point out that “economic and social components like demand surge or repair cost inflation as well as business interruption or loss of production are increasingly driving factors for monetary earthquake losses.” The Chi-Chi 1999 (Taiwan) is provided as a prominent example of an earthquake resulting in surprisingly high business interruption losses as opposed to building damage. (See for example: RMS Chi Chi earthquake report) Nor are the issues of greater levels of data resolution, as far as spatial distribution and building details are concerned, necessarily likely to prove more reliable or even helpful for modeling purposes in the authors’ opinion. They suggest “it is possible that an increasing number of parameters and information leads to higher uncertainties and more inaccurate results.”

The division between engineering sciences and actuarial sciences blurs within an environment of financial catastrophe modeling, site specific seismic risk assessment, and structural damage prediction. This division was first investigated in the U.S.A. in John R. Freeman’s now classic Earthquake Damage and Earthquake Insurance (New York : McGraw Hill, 1932). Today, at least two books may provide a clear introduction to this field for earthquake engineering:
Catastrophe Modeling: A New Approach to Managing Risk [New York : Springer Science, 2005 - available as hardback, paperback, and e-book] edited by Patricia Grossi and Howard Kunreuther. And “Seismic Hazard and Risk Analysis,” by Robin K. McGuire, [Oakland, Calif : EERI Publications, 2004] No. MNO-10, Oakland, CA.

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