Generational Dynamics Forum - New Site

Juggalows over thar also http://www.rferl.org/content/ukraine-le ... 90324.html
Waka Flaka Flame in July

John wrote:

Higgenbotham wrote: > A structural engineer should be able to tell approximately when a
> bridge will fail based on design principles and looking at the
> structure.

I'm not so sure about this, Higgie.

Recall the paper that I referenced a few weeks ago:

** How Complex Systems Fail, Richard I. Cook, MD
** Cognitive technologies Laboratory, University of Chicago
** http://GenerationalDynamics.com/gdgraph ... msFail.pdf

Note the following paragraph:

> 3) Catastrophe requires multiple failures – single point failures
> are not enough. The array of defenses works. System operations
> are generally successful. Overt catastrophic failure occurs when
> small, apparently innocuous failures join to create opportunity
> for a systemic accident. Each of these small failures is necessary
> to cause catastrophe but only the combination is sufficient to
> permit failure. Put another way, there are many more failure
> opportunities than overt system accidents. Most initial failure
> trajectories are blocked by designed system safety
> components. Trajectories that reach the operational level are
> mostly blocked, usually by practitioners.

Applying this to the bridge situation, a structural engineer might
evaluate a bridge and decide that there are no significant risks of
catastrophe. But he cannot predict when a "perfect storm" of minor
failures combine in an unexpected way to produce a major catastrophic
failure. I know that's what happens in large software systems.

Structures made out of metals and other materials have defined failure points. A material fails when subjected to a stress equal to its tensile strength (or tensile strength adjusted by the geometry of the structure). A material also fails with regularity after a defined number of stress cycles. These failure points can be demonstrated repeatedly and the test methods defined so that it can be predicted where the material will fail with a high degree of certainty. A software system doesn't have a defined failure point or any material properties that can be demonstrated.

However, a structure such as a bridge can fail before a defined failure point is reached by a mechanism we talked about a few years back where the vibration doesn't damp as normal but builds to the point where the structure collapses due to loads that it would not normally encounter. This would be a failure mechanism that is comparable to a complex software system. It would also seem to me that when the structure nears the end of its useful life, that any propagation of a stress crack that causes the ultimate failure cannot be predicted.

As an ideal example of how a boiler or a bridge can fail in a manner where the failure point can be predicted, let's say the boiler or the bridge experiences ideal uniform corrosion such that no defects like stress cracks occur in the structure. When the thickness of the metal is eroded to the point where the load on it is equal to its tensile strength (or tensile strength adjusted by the geometry of the structure) it will fail precisely at this point.

Since the real world isn't ideal, the structural analysis will be subject to a certain amount of error in any estimate of the life of the structure.

Overall, I think the fact that materials properties can be defined lends a degree of predictability to the design and failure of a structure that overcomes the effects of small undefined weaknesses in the material until the material reaches a point where it is subject to failure by the small undefined weaknesses.

No Veneer anywhere with people who will do anything to maintain the quid quo pro.

http://www.ibtimes.co.in/isis-bans-yazi ... ide-633084

http://finance.yahoo.com/news/businesse ... 19420.html

Same as it ever was. Without intrapreneurs who can identify and exploit new opportunities, organizations will naturally die.

Higgenbotham wrote: Structures made out of metals and other materials have defined failure points. A material fails when subjected to a stress equal to its tensile strength (or tensile strength adjusted by the geometry of the structure).

After I posted this, I recalled the fundamental reason why this is true. It's because metals are arranged atomically into lattice structures that are uniform. The lattice structures have uniform distances between the atoms, uniform forces of attraction, etc., that don't vary.

Higgenbotham wrote:

Higgenbotham wrote: Structures made out of metals and other materials have defined failure points. A material fails when subjected to a stress equal to its tensile strength (or tensile strength adjusted by the geometry of the structure).

After I posted this, I recalled the fundamental reason why this is true. It's because metals are arranged atomically into lattice structures that are uniform. The lattice structures have uniform distances between the atoms, uniform forces of attraction, etc., that don't vary.

In an old bridge this is not so easy because you need to know how much metal is left in each of the parts. Once there is rust you need to know how much rust. It costs to do the inspections and it seems they are often not done.

http://www.nbcnews.com/id/20998261/ns/u ... WWLb9RdXC8

vincecate wrote:

Higgenbotham wrote:

Higgenbotham wrote: Structures made out of metals and other materials have defined failure points. A material fails when subjected to a stress equal to its tensile strength (or tensile strength adjusted by the geometry of the structure).

After I posted this, I recalled the fundamental reason why this is true. It's because metals are arranged atomically into lattice structures that are uniform. The lattice structures have uniform distances between the atoms, uniform forces of attraction, etc., that don't vary.

In an old bridge this is not so easy because you need to know how much metal is left in each of the parts. Once there is rust you need to know how much rust. It costs to do the inspections and it seems they are often not done.

http://www.nbcnews.com/id/20998261/ns/u ... WWLb9RdXC8

from the above link --

"Several state transportation officials said in interviews that, although they want to do the right thing, there’s not enough money to inspect all the bridges on time. They don't lack for staff — in response to msnbc.com's questions, every state said it has sufficient inspectors, when counting outside contractors. But some said they lack for money to pay those contractors and supervise all the counties and communities that own bridges.
"It is a function of funding, ultimately," said David Severns, the assistant chief structures engineer for Nevada"

Where have we heard this before?

http://people.virginia.edu/~gk/publicat ... trauss.pdf

They do not care since plan b was plan a. Our prop 1 was voted down. We knew that over two years ago.
I can recheck how much it was. The core focus was qualified steps.
More than 30 percent of the money from the so-called road package would go to other purposes.


https://www.youtube.com/watch?v=1DsH3NKGbu4
http://justfixtheroads.com/legislative- ... alculator/

vincecate wrote:

Higgenbotham wrote:

Higgenbotham wrote: Structures made out of metals and other materials have defined failure points. A material fails when subjected to a stress equal to its tensile strength (or tensile strength adjusted by the geometry of the structure).

After I posted this, I recalled the fundamental reason why this is true. It's because metals are arranged atomically into lattice structures that are uniform. The lattice structures have uniform distances between the atoms, uniform forces of attraction, etc., that don't vary.

In an old bridge this is not so easy because you need to know how much metal is left in each of the parts. Once there is rust you need to know how much rust. It costs to do the inspections and it seems they are often not done.

http://www.nbcnews.com/id/20998261/ns/u ... WWLb9RdXC8

I find that the media often dwells on whether inspections got done without ever commenting on whether the inspection were done correctly. They talk as if doing an inspection is a cure-all. I can attest to the fact that in my experience the act of inspecting something is not always meaningful.

A case in point I can think of is (I don't what to identify this) but a large system was inspected every 3 years. There was a clear violation going way back in time. It would have been visible to any inspector with an IQ of 100 who would have done their job. The violation had to do with the fact that a pumping station was located in a place such that it was in violation of state regulations. The nature of the violation was that it was a potential public health hazard. The violation was found during an inspection that occurred every 3 years as scheduled and the officials came in to meet with the state agency whose inspector found the violation to propose corrective action. I sat in the meeting. The question was asked of the officials as to how long the violation had existed. They said it was discoved by the state inspector after it had existed for 48 years. It was now year 50. The state officials then began to backtrack. First they would have difficulty justifying how they had failed to discover a violation that could be a public health hazard for 48 years. So they began to look at how to give a variance so it could be buried.

vincecate wrote:

Higgenbotham wrote:

Higgenbotham wrote: Structures made out of metals and other materials have defined failure points. A material fails when subjected to a stress equal to its tensile strength (or tensile strength adjusted by the geometry of the structure).

After I posted this, I recalled the fundamental reason why this is true. It's because metals are arranged atomically into lattice structures that are uniform. The lattice structures have uniform distances between the atoms, uniform forces of attraction, etc., that don't vary.

In an old bridge this is not so easy because you need to know how much metal is left in each of the parts. Once there is rust you need to know how much rust. It costs to do the inspections and it seems they are often not done.

http://www.nbcnews.com/id/20998261/ns/u ... WWLb9RdXC8

As in this article, I find that the media often dwells on whether inspections got done without ever commenting on whether the inspections were done correctly. They talk as if doing an inspection is a cure-all. I can attest to the fact that in my experience the act of inspecting something is not always meaningful.

A case in point I can think of is (I don't what to identify this) but a large system was inspected every 3 years. There was a clear violation going way back in time. It would have been visible to any inspector with an IQ of 100 who would have done their job. The violation had to do with the fact that a ****ing station was located in a place such that it was in violation of state regulations. The nature of the violation was that it was a potential public health hazard. The violation was found during an inspection that occurred every 3 years as scheduled and the officials came in to meet with the state agency whose inspector found the violation to propose corrective action. I sat in the meeting. The question was asked of the officials as to how long the violation had existed. They said it was discovered by the state inspector after it had existed for 48 years. It was now year 50. The state officials then began to backtrack. First they would have difficulty justifying how they had failed to discover a violation that could be a public health hazard for 48 years. So they began to look at how to give a variance so it could be buried.

As to whether a bridge can be properly inspected, I think it can. There are radiographic machines that can detect the thickness of sound metal and also defects. There are even machines that can be put on concrete surfaces that can measure the thickness of sound rebar in the concrete below. But whether bridges are being properly inspected when they are inspected, I doubt it based on what I've seen of other types of inspections.

A random article I found on rebar detection in concrete which has applicability to bridge deck inspection. I just skimmed it but I think what they are trying to say is they can detect the thickness of sound rebar through concrete with an accuracy of plus or minus 10 percent.

http://geopick.uncc.edu/geologyWeb/Cour ... ection.pdf

Detection of reinforcing bars in concrete is one of the most widespread applications of GPR in
Civil Engineering [20, 22, 23], but the results is very difficult to interpret and may require the skills of
an experienced operator and the use of lengthy manual post-processing and subjective expertise to
produce a reliable end result [10, 15].

The fitting technique is applied on a variety of real hyperbolic signatures that are collected from
a controlled test site, the results indicate this technique is fully capable of successfully estimating
the depth and radius to within 10%, which validates the method and justify the assumptions used.