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Bay Bridge bolt pulled for testing

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Bay Bridge bolt pulled for testing

Here is an interesting news story by Andrew McGall of Contra Costa
Times regarding
anchor rods of the new Bay Bridge.

<http://cirrus.mail-list.com/seaint-seaosc/84583842.html>

I like to bring up two items on this and appreciate your comments:

1. In the story, Professor Bea , a colleague and a friend , correctly
points out the importance of the "independence" of the experts who will
examine the test results. The conflict of interest in this bridge has been
so profound that it has resulted in passage of two bills by California
state legislature to force Caltrans to avoid such conflicts in its
projects.

2. According to the story Caltrans  has released a news letter yesterday
stating that it has done "pull test" on hot dip galvanized A354 BD anchor
rods of the tower of the new Self Anchored Suspension Bay Bridge and 99% of
the rods have passed the test.  No details of "pull tests" are provided.

Here are the facts: three of the 424 Three inch diameter anchor rods have
been pulled out so far and two had cracks related to hydrogen embrittlement
and one actually had fractured due to hydrogen embrittlement.

 It appears that the claim that since the anchor rods have passed the "pull
test" without giving information on the amount of pull force and the test
procedures , therefore they are good to resist earthquake may be premature
at best and probably incorrect.  The reason is that according to
metallurgists and material scientists, hydrogen embrittled   high strength
steel develops cracks over time and the rate of crack initiation and
propagation depends on several parameters  including corrosion and stress
corrosion. Even if the proof pull tests were done near the Ultimate
Strength Fu of the rods and the rods survived without fracture, there is no
reason to believe that they will not have hydrogen embrittlement cracks
tomorrow, next months or next year or at any time during the 150 years
design life of the bridge.

It seems that the only way Caltrans can claim that these rods will be able
to resist the tension due to seismic events in the future is to tighten the
bolts to near ultimate and leave them at that level of tightness. Then
inspect them continuously to make sure they are not fractured and popped-up
. Otherwise, the pull tests done today ( even if they are done correctly
which we don't know yet ) will not be valid even tomorrow yet alone decades
from now when most of the rods will develop hydrogen embrittlement cracks
being submerged in salt water.

Regards

--

 Abolhassan ASTANEH-ASL, Ph.D., P.E., Professor
2013 Minner Faculty Fellow in Engineering Ethics and Social/Professional
 Responsibility and
2013-14 U.S. Fulbright Senior Research Scholar
Department of Civil and Environmental Engineering
781 Davis Hall,  MC 1710
University of California,
Berkeley,  CA 94720-1710, USA
Web: www.ce.berkeley.edu/~astaneh
Web: www.astaneh.net
Phone; (510) 642-4528

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