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08:08 Aug-08-2007

Rolf Diederichs

Director, Editor, Publisher, Internet, PHP MySQL
NDT.net,
Germany,
Joined Nov 1998
598
NDT and the Minneapolis Bridge Collapse

In our August issue we have some early information on the matter.
We added also the term "Bridge Testing" in the NDT Encyclopedia here: www.ndt.net/ndtaz/content.php?id=635
Forum members can sign-in at the bottom of the Encyclopedia page and add comments.

Bridge inspection comes into sharp focus after Minneapolis bridge collapse, which is one of the worst bridge collapses in US history.
Why frequent inspections of the bridge failed to prevent the worst collapse?
Aging bridges and infrastructure in general is a widespread problem all over the world and the risk of new tragedies rises. Is NDT sufficiently applied?
One study by the Federal Highway Administration (FHWA) found that over 90% of fatigue cracks were missed with visual inspection. Are many other NDT techniques not applied because authorities want to save costs?

I believe that almost nobody of the field of bridge inspection reading this forum. Or someone is here? Is traditional NDT fare away of this market?



 
02:17 Aug-08-2007
Allen Green
Re: NDT and the Minneapolis Bridge Collapse ----------- Start Original Message -----------
: In our August issue we have some early information on the matter.
: We added also the term "Bridge Testing" in the NDT Encyclopedia here: www.ndt.net/ndtaz/content.php?id=635
: Forum members can sign-in at the bottom of the Encyclopedia page and add comments.
: Bridge inspection comes into sharp focus after Minneapolis bridge collapse, which is one of the worst bridge collapses in US history.
: Why frequent inspections of the bridge failed to prevent the worst collapse?
: Aging bridges and infrastructure in general is a widespread problem all over the world and the risk of new tragedies rises. Is NDT sufficiently applied?
: One study by the Federal Highway Administration (FHWA) found that over 90% of fatigue cracks were missed with visual inspection. Are many other NDT techniques not applied because authorities want to save costs?
: I believe that almost nobody of the field of bridge inspection reading this forum. Or someone is here? Is traditional NDT fare away of this market?
------------ End Original Message ------------

Acoustic Emission has been used in the inspection of bridges since the mid 1960's here in Sacramento, CA. Today a number of our clients use their Vallen AMSY AE systems in this work. It surely will continue to expand as more inspection groups become familiar with its success.


 
09:43 Aug-09-2007

Toni Hakkarainen

Director, Technical manager of industrial services
Bureau Veritas Branch Office Finland,
Finland,
Joined Jun 2006
4
Re: NDT and the Minneapolis Bridge Collapse I have experience in bridge inspection with NDT-techniques. With common techniques the steel constructions and concrete construction may be assessed in some level for fit for service. These services are not commonly used but they are effective and reliable.

Main issue is to tranfer this information about possibilities of inspections to authorities and personnel responsible for maintenance. The lack of use of NDT is I suppose due lack of knowledge of possibilities.

Further on how many of common NDT companies are willing to take the step to unknown?


 
04:53 Aug-10-2007

Rolf Diederichs

Director, Editor, Publisher, Internet, PHP MySQL
NDT.net,
Germany,
Joined Nov 1998
598
Re: NDT and the Minneapolis Bridge Collapse ----------- Start Original Message -----------
: : In our August issue we have some early information on the matter.
: : We added also the term "Bridge Testing" in the NDT Encyclopedia here: www.ndt.net/ndtaz/content.php?id=635
: : Forum members can sign-in at the bottom of the Encyclopedia page and add comments.
: : Bridge inspection comes into sharp focus after Minneapolis bridge collapse, which is one of the worst bridge collapses in US history.
: : Why frequent inspections of the bridge failed to prevent the worst collapse?
: : Aging bridges and infrastructure in general is a widespread problem all over the world and the risk of new tragedies rises. Is NDT sufficiently applied?
: : One study by the Federal Highway Administration (FHWA) found that over 90% of fatigue cracks were missed with visual inspection. Are many other NDT techniques not applied because authorities want to save costs?
: : I believe that almost nobody of the field of bridge inspection reading this forum.Or someone is here? Is traditional NDT fare away of this market?
: Acoustic Emission has been used in the inspection of bridges since the mid 1960's here in Sacramento, CA. Today a number of our clients use their Vallen AMSY AE systems in this work. It surely will continue to expand as more inspection groups become familiar with its success.
------------ End Original Message ------------

Here in Germany the BAM seems to play an important role what kind of technique to use. When I spoke with BAM people after the Bad Reichenhall roof collapse in Germany last year I was told that AE is not accepted in infrastructure testing, but many other NDT methods would be used after visual testing shows the needs for further tests. So why Germany is still behind US 1960's?

Rolf



 
04:58 Aug-10-2007

Rolf Diederichs

Director, Editor, Publisher, Internet, PHP MySQL
NDT.net,
Germany,
Joined Nov 1998
598
Re: NDT and the Minneapolis Bridge Collapse ----------- Start Original Message -----------
: I have experience in bridge inspection with NDT-techniques. With common techniques the steel constructions and concrete construction may be assessed in some level for fit for service. These services are not commonly used but they are effective and reliable.
: Main issue is to tranfer this information about possibilities of inspections to authorities and personnel responsible for maintenance. The lack of use of NDT is I suppose due lack of knowledge of possibilities.
: Further on how many of common NDT companies are willing to take the step to unknown?
------------ End Original Message ------------

The mentioned lack of knowledge of possibilities is of course correct, however, I believe there is much more to improve, like: reliability, usability, validation, standards.

Rolf



 
05:21 Aug-10-2007

Ernst

R & D, -
BAM (Fed. inst. for material research and testing,
Germany,
Joined Jun 2001
7
Re: NDT and the Minneapolis Bridge Collapse In addition to Rolfs comment:
Yes, we at BAM are doing a lot of research (and more and more practical NDT work at bridges). You will find a lot of articles on ndt.net. Our work is supported by german authorities.
For example, we are part of a European project an railway bridges with a lot of inspection/testing (www.sustainablebridges.net).
We put no effort on AE so far, but other institutions in Germany do.
Ernst

----------- Start Original Message -----------
: : : In our August issue we have some early information on the matter.
: : : We added also the term "Bridge Testing" in the NDT Encyclopedia here: www.ndt.net/ndtaz/content.php?id=635
: : : Forum members can sign-in at the bottom of the Encyclopedia page and add comments.
: : : Bridge inspection comes into sharp focus after Minneapolis bridge collapse, which is one of the worst bridge collapses in US history.
: : : Why frequent inspections of the bridge failed to prevent the worst collapse?
: : : Aging bridges and infrastructure in general is a widespread problem all over the world and the risk of new tragedies rises. Is NDT sufficiently applied?
: : : One study by the Federal Highway Administration (FHWA) found that over 90% of fatigue cracks were missed with visual inspection. Are many other NDT techniques not applied because authorities want to save costs?
: : : I believe that almost nobody of the field of bridge inspection reading this forum. Or someone is here? Is traditional NDT fare away of this market?
: : Acoustic Emission has been used in the inspection of bridges since the mid 1960's here in Sacramento, CA. Today a number of our clients use their Vallen AMSY AE systems in this work. It surely will continue to expand as more inspection groups become familiar with its success.
: Here in Germany the BAM seems to play an important role what kind of technique to use. When I spoke with BAM people after the Bad Reichenhall roof collapse in Germany last year I was told that AE is not accepted in infrastructure testing, but many other NDT methods would be used after visual testing shows the needs for further tests. So why Germany is still behind US 1960's?
: Rolf
------------ End Original Message ------------




 
07:57 Aug-10-2007
chris s
Re: NDT and the Minneapolis Bridge Collapse ----------- Start Original Message -----------
: I have experience in bridge inspection with NDT-techniques. With common techniques the steel constructions and concrete construction may be assessed in some level for fit for service. These services are not commonly used but they are effective and reliable.
: Main issue is to tranfer this information about possibilities of inspections to authorities and personnel responsible for maintenance. The lack of use of NDT is I suppose due lack of knowledge of possibilities.
: Further on how many of common NDT companies are willing to take the step to unknown?
------------ End Original Message ------------

In my opinion, the inspections of the bridge were adiquite. the issue is what was done with the resulting information. A state DOT rep decided that the bridge would be ok. From what i've read thay were monitoring cracks for a couple years. the testing appears to have worked, It looks more like a budget issue to me.


 
09:44 Aug-14-2007

Rolf Diederichs

Director, Editor, Publisher, Internet, PHP MySQL
NDT.net,
Germany,
Joined Nov 1998
598
Re: NDT and the Minneapolis Bridge Collapse There are obviously different options on AE feasibility for bridge testing.
Who can say for what acoustic emission in bridge testing is useful or for what not?

Rolf


 
02:15 Aug-14-2007

Christian Grosse

Teacher,
Technische Universität München,
Germany,
Joined Nov 2000
11
Re: NDT and the Minneapolis Bridge Collapse Dear Rolf: I am aware of two German groups using AE for bridge monitoring. Gerd Kapphahn in Leipzig is using AE in combination with a test load to record AE activity under controlled load conditions applied to bridges. We in Stuttgart develop AE techniques in combination with innovative sensong techniques e.g. based on wireless sensor nodes (motes). Both techniques doesnt seem to be applicable to a very large amount of structures. While the first technique is more or less a short-term monitoring (typically hours or a few days) the latter focus on a continuous monitoring in terms of months up to 1-2 years. AE is able to detect an unusual AE activity e.g. in a certain region of interest. We favourize a combination of different sensing techniques, combining for example strain, temperature, humidity and AE data.
However, the applicablity of AE techniques is of cause mainly driven by the structure, the material (composition) and the boundary conditions (geometry) of the object. Most successfull seems to be the detection of wire breaks in prestressed cable bridges - there are even some companies offeringa regular service in this field.
More information about applications, limits and benefits can be found in the book by Grosse and Ohtsu that will be published at the end of this year by Springer publishers. Here is the link: http://www.springer.com/dal/home/generic/search/results?SGWID=1-40109-22-173738721-0

----------- Start Original Message -----------
: There are obviously different options on AE feasibility for bridge testing.
: Who can say for what acoustic emission in bridge testing is useful or for what not?
: Rolf
------------ End Original Message ------------




 
02:34 Aug-15-2007

shashi valiyani

Consultant, consulting civil & structural engineer
Futurestress Laboratories,
India,
Joined Jul 2000
1
Re: NDT and the Minneapolis Bridge Collapse Dear Rolf & Christian ,

so far we know there is only one method and only one organization "CORDEC INTERNATIONAL INC." offering / doing detection for break of pre stress wire of bridge girder by way of Ndt method called RIMT - RELECTOMETRIC IMPULSE MEASUREMENT TECHNIQUE.

Anybody know other method , organization and manufacturer / supplier of instrument and offering training ?

valiyani



 
04:23 Aug-15-2007

John O'Brien

Consultant, -
Chevron ETC ,
USA,
Joined Jan 2000
278
Re: NDT and the Minneapolis Bridge Collapse These highly newsworthy events drive excellent discussions but also often reveal the lack of understanding of many of the root causes of the incident. I am sure it will be some time before a full report is available so that we can understand the underlying causes of what drove the final catastrophic failure.

Many of the issues discussed here are extremely valid and demonstrates that the examination of bridge structures is more extensive than many may realize.

No one should really be surprised that a bridge collapse occurred as several years ago the FHWA published data showing that much of the US infrastructure was ageing and the task of maintaining or replacing that infrastructure was immense. The US is not alone in facing this situation.

I winced when I saw the first TV reports as the regulatory spokesmen struggled to convey the real message behind the term 'structurally deficient' which was a ranking that had been applied to this bridge. It is a classic example of engineers needing to think through terminology that we apply and how it may be perceived by the general public when 'misinterpreted' for dramatic effect by the media.

This bridge did have an examination regime and how effective that was remains to be seen. The actual performance in sizing and monitoring existing structural flaws will be interesting.

The discussion about the use of AE is enjoyable. I believe that AE is used throughout the bridge community for a number of monitoring applications including crack growth and activity in box girders through cable breaks in prestressed concrete tendons. There are a number of companies actively undertaking this work so to suggest there is a single source is slightly misleading. The most significant issue is do the technicians have experience in the installation, noise rejection and signal analysis programs to make your monitoring successful.

The larger question is whether any technique even if permenently installed can predict any collapse of this type.

One of the critical questions I would pose is whether the in-servcie examination regime was designed to look at non construction flaws. One of the lessons we have learnt in the hydrocarbon industry is that NDE for construction flaws is not the same as for in-service degradation. We also understand that to provide accurate data for Fitness For Service assessments often requires a higher degree of skill, procedures and techniques. I wonder if the same is being applied to degrading flaws in bridges.

You can design an examination regime based on expected operational loadings, but what if those loadings are exceeded and in the case of this incident I am sure that operational procedures may come into play considering that traffic flows had been amended whilst maintenance activities were undertaken.



 


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