Miami pedestrian bridge collapse

[swines]

Is it not possible to tension such a structure that the whole thing is ridged, like a steel truss, and can carry at least it's own weight, regardless of support, or would this be considered wasteful for the end requirement?

How rigid? If you mean zero deflection - that's nearly impossible to achieve. Every bridge structure has some deflection.

Generally, structures are designed using a computer aided design program and loads are simulated and stresses analyzed through finite element analysis. Programs like AutoCAD have many add on modules like Nastran, the FEA module, and several others. Depending upon the work done by the engineering firm they may also use specialized analysis programs like Dlubal that provides analysis and design of beam structures, concrete structural members, steel and aluminum structures, timber structures, glass structures, connection analysis, dynamic stress analysis, and tensile membrane structures.

The point being - you can design the entire structure and the stress analyze every member and the entire structure. This includes static loads, dynamic loads, wind loading, lifting points, support points, etc.

I'm sure the NTSB will be going over the engineering documents and CAD analysis to determine whether the design, construction, or movement procedure were at fault. But, it is hard to believe that the engineering firm did not design the bridge with a safety factor as engineers are, by nature, conservative and philosophically use a "belt and suspenders" approach. Engineers are well aware of their responsibility in providing safe designs and their liability if something goes wrong.

 

[swines]

And I am telling you what the Managers at the customer end sees. Maybe things are different in Canada.

Then Canadians don't know how to negotiate and write contracts. You can have the engineering firm do whatever you want - you simply put it in the contract. If you want a dedicated project manager - that's what you put in the contract. You'll pay for a full time person - but, that's the cost for that level of service. What you're asserting, as to your experience, only points to bad contract negotiating, undefined / unclear client requirements, or a total lack of understanding of how to run a project from the client's side.

As an example of a maximum service level, the last project I worked on was for one of the U.S. national laboratories for the Department of Energy (DoE) and National Nuclear Security Agency (NNSA). The level of service required by the client was to have personnel dedicated to the project and on-call as required. They had the project budget to pay for that level of service, so we provided a dedicated project manager plus a number of key personnel that had no other project. That professional service level cost the project about $4.5M a year for the seven years it took to complete the project.

If you're not getting the support services you want, you need to figure out if you can pay the cost for the level of support you desire - if you can afford the cost to the project - then put the requirements in the client / engineer contract. If you can't afford the cost, then you need to learn how to better manage the project from the client side of the project.

In the U.S. you figure 2080 hours per year per person. If you work for an engineering firm, you're responsible for being reimbursable for the 2080 hours - as a client, you can't expect the engineer to do free work for you, as they're accountable for the 2080 hours. So, as the client you either pay for the time or find a way to manage certain aspects of the project yourself.

And, I'm telling you, as a person who's worked in the field for 32 years - that's how it works.

 

[/pine]

...as a client, you can't expect the engineer to do free work for you...

At your firm and others there...What is the main source of clients?...do you not bid on jobs from services like 'Dodge Reports' etc??

 

[swines]

At your firm and others there...What is the main source of clients?...do you not bid on jobs from services like 'Dodge Reports' etc??

A variety of sources. There are bid/project aggregation sources like the Commerce Business Daily, for airports there is the AAAE (American Association of Airport Executives), National Business Aviation Association, Airport Council International, keeping current with past clients, etc. Today, most government-based entities (federal, state, local) have project websites that allow you to sign up for automatic notification of upcoming projects. There are also "on-call services" contracts where you negotiate a contract to be the resident engineer for a fixed period of time and perform projects as called on by the client.

In a large engineering firm (the one I worked for grossed $12B the last year I worked for them), you get work from other offices. Large engineering firms have "centers of expertise" within the company. As an example, if you wanted an airport baggage system designed as part of an airport project you'd call a specific office that had personnel that did that type of work. If you needed a specific type of architect (airport terminal building, school, high rise, etc.) - you'd call the office that had the personnel that specialized in that area of work.

For the work I did, most of the projects were done for other offices in other states or even other countries.

 

[Industrial Toys]

I saw a very interesting video of the bridge prior to installation on youtube via apple TV so I can't paste the link.

Personally, that thing inspired zero confidence in me. Like a house of cards if you ask me. Of course that's easy to say after the fact. But I guess, the puters know best.

 

[swines]

=Industrial Toys;5055661. But I guess, the puters know best.

"Puters" don't "know' anything. Computers are simply tools and provide engineers the means to design without using slide rules and pads of paper...if you know what those are...

 

[California]

slide rules and pads of paper...if you know what those are...

Used to do my homework on the Marchant calculator at the survey firm where I worked part time. It wasn't very good for long division though, the gears whirled endlessly. All mechanical.

Pads of paper? (10 years later) They were for coding your data for keypunch to make cards from! You were lucky if the cards came back overnight. Verify visually then submit for the next night's run.

I was fortunate to have a progressive teacher for freshman 'intro to math'. He said learn all this computer stuff, presently it's convoluted, awkward, expensive but the future will run on computers which will be infinitely cheaper and easier to operate. He instinctively understood Moore's law before Moore postulated it. That perspective has served me well.

 

[Industrial Toys]

I saw more material on the bridge o YouTube last night. One guy thinks the tensioning was not built according to design. HOWEVER, there was a clear picture of the wreckage, with a duct, plus strand that had not been grouted! Considering, there were not many tensioning strands in this structure, having at least one ungrouted one, surprises me.

 

[California]

Another update - cracks were photographed after stripping the concrete forms and before the transport vehicles lifted the structure off its construction location.

Collapsed FIU bridge cracked days before deadly accident | Miami Herald

"A key concrete support truss developed worrisome cracks 10 days before the structure was lifted into place

"The cracks were found in late February at the base of a diagonal support member. Independent engineers have identified that as the point where the structure shattered on March 15

"Linwood Howell, a senior engineer at a Texas firm that specializes in bridge design and inspection, said the cracks were signs of the structure's imminent failure. "There's nothing they could have done short of starting over and redesigning the structure."

 

[MossRoad]

Jesus.... that's just bad.