Miami pedestrian bridge collapse

[crashz]

Preface - Below is my arm-chair QB opinion of the failure. It is only my opinion and worth pretty much nothing other than the time during work hours that I'm wasting to write it!

Some new info to me anyway, in this post. I only read the first few news articles( Miami Herald, Times, etc) , so I had heard of the "testing" right before the collapse and the prolific use of the term "Accelerated Bridge Program", which has absolutely nothing to do with the failure

Now knowing of the bridge being post tension, the story makes more sense now. It also rings alarm bells. An engineer from the design firm called DOT stating that there were cracks forming in the structure. That's bad. A post-tension bridge act as a monolith, ie the deck is the "beam" section. So the post tension cables or rods provide enough tension to keep the concrete in the deck in compression. Cracks perpendicular to the post tension cables indicate a failure of either the cable to keep the concrete in compression or the concrete itself. There are temp related cracking and other inconsequential cracking that can occur, but not related to my rant.

From the story being told, it sounds like the engineer assumed that the cables/rods were slack causing cracking. Bad mistake. Those cables should have been tension-ed to the proper spec before it was moved. These are extensively recorded prior to tying off with the lock nut. They should have never re-tightened those cables, especially to "lift" the structure! The cables could have failed elastically, that that could have been the warning.

They should have stopped traffic and inserted cribbing before anything else. Of course, that is a big change order...

 

[Industrial Toys]

To me, it's just a sign of the times. More and more dysfunction, and choosing fanciness over integrity. When I heard that it was to be a cable stay bridge, but that had not been built yet, I couldn't believe how they could leave it unsupported. When I learned that the cable portion of it was to be just cosmetic, I thought, how retarded!

I have witnessed projects recently where nothing can be done without the Engineers approval. At the end of the day, nothing works right and the Engineers are not ever available it seems. And then, they don't seem accountable for their screw ups. In fact, they charge EXTRA! I don't understand this system. In many cases, we would be better off without them.

 

[MossRoad]

The bridge is a truss bridge, so you heard wrong info.

 

[crashz]

True - I should have stated member, but my experience has been monolith slabs. And as demonstrated, I'm not familiar withvthe design. Either way, the point remains: They should not have re-tensioned that chord.

 

[cqaigy2]

As far as college kids paying attention, I have been working on a college campus for the last year, and have watched the kids walk into the side of trucks pulling into the job site, and even fences surrounding the site. Not all of them were on their phones.

I might have been one of those, back in the days, as i would have been checking out the co-eds.

 

[swines]

At the end of the day, nothing works right and the Engineers are not ever available it seems. And then, they don't seem accountable for their screw ups.

I worked in engineering for 32 years. I worked for two of the largest engineering firms in the world. I can tell you that engineers, through their companies, are responsible for EVERYTHING THEY DESIGN, which is why engineering firms are required to carry both liability and errors and omissions insurance.

If you want an engineer to answer a question that involves liability, you have to put the question in writing. I would not respond to any question over the phone. There are specific methods of asking for information in a project, its called a "request for information." or RFI. The contractor submits the RFI using the RFI process. It's officially logged into the project records, and the engineer responds. There is usually a specified maximum response time which is generally either 7 or 10 working days. This gives the engineer time to research the question if required and formulate the answer. Most engineers will answer an RFI as quickly as possible, as they realize that the project may be waiting for the answer and that costs money.

I have gotten RFI's in the morning and had the answer back to the contractor either later that morning or early afternoon. Conversely, when the RFI included a change in field conditions that required a modified design, that one may have taken the full 10 days as a modified or new design had to be created. That may have involved creating new drawings and even modifying specifications in order to cover the change.

Your simplistic view of what engineers do as part of a project is not consistent with my experiences on ANY of the projects that I've worked on.

 

[KennyG]

swines has it right. On the large projects I have worked on, we often had an engineer on site during construction to address construction issues. If we don't, the constructor has home and cell numbers and we were available 24 hours. Most RFIs are simply requests for clarification or a need to confirm something. Engineers do make mistakes but I can tell you from experience that design errors are far outnumbered by change requests to accept or fix construction errors.

 

[swines]

I have witnessed projects recently where nothing can be done without the Engineers approval. At the end of the day, nothing works right and the Engineers are not ever available it seems. And then, they don't seem accountable for their screw ups. In fact, they charge EXTRA!

Now I'm going to tell you how engineering firms work.

Engineering firms want employees to be at least 85% reimbursable. This means you have to charge a minimum of 85% of your time to projects. If you fall below 85% for any length of time (3-4 weeks), the firm lays you off and transfers the work to a different engineer.

To meet the 85% requirement, design personnel work on multiple projects simultaneously. By doing that, most design personnel reach nearly 100% chargeable project time. The only time design personnel are fully chargeable to a project is during design. During construction there is not enough project work to keep them dedicated to a specific project. That's why engineers and architects may not be immediately reachable during project construction. They're working on other projects and may be out of the office at a project site or meeting with another client. They can't respond to the RFI until they're back in the office, so it may take up to the maximum allowable time to answer a question, even one as simple as "what color do you want this painted?"

Another aspect is that the personnel working on a project may be in different offices. I've worked from my office in Albuquerque, NM on projects that had engineering personnel from offices in: Tampa, FL, Denver, CO, Seattle, WA, San Francisco, CA, and Cleveland, OH. This means that an RFI coming in to the project manager may have to be forwarded to the correct person who's in a different office. So, it's not like everyone is sitting in the same office simply waiting for the contractor to ask questions - they're not. Everybody is busy working on other projects from their respective office.

Your claim "In fact they charge extra!" Totally false. You have a contract and most of the time the fee is a negotiated fixed fee. Here's how fees work. There are a number of different types of fee structures. The ones I've worked with are: time and materials, cost plus, cost plus not to exceed, and fixed fee.

The only cost plus work I've ever done has been for the federal government (US Army Night Vision Laboratory - a technology development project) and it was always cost plus not to exceed. Construction work is generally done as a negotiated fee between the engineering firm and client. The ONLY time you get to charge an additional fee is if the client changes their requirements or adds additional work to the project. If you have to do additional design work caused by the client OR CONTRACTOR - you get paid for that because it's work that is outside of the original negotiated fee.

Now, lets talk about how fees are generated. For a lot of projects you're in competition with other engineering firms and the client will narrow the final selection down to two or three finalists. The firms are asked to provide a proposed project fee based on the services required and a schedule. The client then selects the firm that is either the lowest cost or provides "best value."

To top it off - the Congressional Budget Office published an architectural and engineering fee schedule a number of years ago. It's a sliding scale based on the constructed value of the project. The maximum allowable fee is about 13% of the constructed value. By the time you get to a $50M project - the allowable fee is 5%. Local and state governments use the CBO fee structure when negotiating fees because projects often have a federal money component. Even if no federal money is involved, they will use the CBO fee structure because it gives them a guideline and negotiating point for the project.

Federal government projects. The federal government, by law, always gets the lowest price. That means your markup (overhead + profit) has to be lower than any other client. If you're audited by the government and you've charged a lower price on another project - you get to refund money to the federal government on ALL of your federal projects going back seven years so that all of the projects were done at the lowest price.

I could go on and on and on about contractors and the fishing expeditions they go on for change orders...but that's another discussion about how people purposely misinterpret and misread things hoping to benefit monetarily instead of simply doing the project that they've bid.

 

[Industrial Toys]

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

 

[KennyG]

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

There are different kinds of engineering firms. swines and I seem to have worked for large full service engineering firms. We hire only the best people and charge accordingly. New engineers quickly make 6 figures but we expect them to work whatever it takes to make the job successful. A lot of engineering is done by small firms with 5 or 10 engineers. They have some very good people but there is only so much capability in a small firm.

At least in the US, many local and federal government projects can only be awarded to small firms that are minority or women owned. That's fine but they are often smaller and less capable than large firms.

I don't know anything about the firms involved with the Florida bridge but while I was working full time we made a lot of money salvaging projects awarded to low priced small firms.