Thoughts on the Engineering Industry

A blog covering engineering, technology and business topics

Archive for the month “June, 2013”

Can the World’s Tallest Building Be Built in 90 Days?

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Hello everyone, I hope y’all are doing well.  Today, I want to talk about an article I found a while back.  In the article, the construction company building the next building slated to be the tallest building world claims that they will do it by the end of 2013.

At first, I thought this was not possible at all.  However, the company, Broad Sustainable Building, has previously built a 30 story apartment building in 15 days.  Apparently, the plan will be to prefabricate as much as they can off site in the 4 months before on site construction starts.  Since they just got their permit this June that means they should be done with that by the end of September.  This leaves them 3 months to do the on site construction if they want to finish in 2013.  According the article, the plan is to build five stories of the building each day.  Along with the quick construction time, the skyscraper will only cost $628 million; half the cost of Burj Khalifa.

However, as cool as this sounds, I have some skepticism about how this can be done and so does the author.  A 30 story apartment building has far fewer critical design issues than 220 story skyscraper.  In the article, Head of Structures for WSP Middle East, Bart Leclercq, believes that they will run into issues with the required use of on site concrete work which provides the extra stiffness needed.   In order to safely construct the building, adequate curing times are needed which would be hard to manage with the fast pace of construction.  The other concern that crossed my mind even though it wasn’t stated in the article is this – what will be done about inspections and oversight?  If a building is being erected this quickly, a lot of oversight and coordination will be required and I could see a lot of mistakes being made as rushed as the process would be.  What is your opinion on this project?  Do you think that this building schedule is attainable?  What about safety and risk in regards to the building schedule?  Thanks for reading and have a good weekend.

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The Philadelphia Building Collapse in Regards to Responsibility in Building Design and Construction

Hello everyone.  Sorry I have been away for so long.  I haven’t felt particularly inspired to write blog posts lately, which is not a good excuse, but I am finally getting back around to writing some now.  Nothing has really changed in my professional career or school activities.  I am still looking for work and planning on taking the comprehensive exam to graduate.  On a fun side note, I have discovered that I lost some important notes over the years so I need to figure out what to do about that.  Other than that, everything is going smoothly.  Today, I would like to discuss an incident in which a building collapsed and causes several deaths and injuries in Philadelphia.

First of all, let’s start with a recap of what happened.  The construction worker, Sean Benschop, was demolishing a four story building and part of the structure collapsed onto the Salvation Army next door.  He will be charged with one count of risking a catastrophe, six counts of involuntary manslaughter, along with counts of recklessly endangering another person.  Benschop turned himself and this his attorney made this statement, “He and his family are extremely sympathetic and remorseful with respect to what happened. This was an accident. Mr. Benschop is not responsible and we believe that in time the facts will show that he is not responsible and the responsible party will be held accountable.”  Philly.com reports that there was marijuana and pain killers in Benschop’s blood two hours after the accident.  His attorney claims that Benschop was fully able to operate the backhoe in a safe manner.  In response to this incident, the city of Philadelphia has inspected hundreds of demolition sites and is planning to implement changes in building demolition regulations.

This incident illustrates an interesting topic that any engineer with a PE License should understand, the designer is held responsible when his or her structure fails.  And apparently, based on this specific incident, a construction worker can be held accountable if there are deaths involved.  However, I think there are important questions that need to be asked.  The first one is this: What is the building designers role in this?  Was there an on-site structural engineer that should have noticed the danger that structure next to it could be damaged?  The second is this: What is the construction managers role?  Should he be held responsible for allowing an operator to work in an unsafe manner considering the pain killers and marijuana is his system?  Would the construction manager be liable for the safety zone and structural concerns on site as well?  And finally: Was the construction worker ordered to do the work?  Is the work environment such that he can voice concerns for the safety conditions if needed?  It is my opinion that not enough investigation has been done into the operation of the construction project at the time of the accident.  I don’t think there will be an accurate picture of who is responsible and what actually happened in regards to the decision process if that isn’t done.  What is your opinion?  Who do you think is more responsible for the pedestrians deaths and why?  Thank you for reading and have a good week.

Source:  “Construction Worker In Custody For Phila. Building Collapse”, National Public Radio, June 8, 2013, http://tinyurl.com/mn6vrqp

“Fracture Critical” Bridges and Other US Infrastructure Issues

Removal of the fallen Interstate 5 bridge over the Skagit River begins Monday, after barges carrying heavy cutting and lifting equipment from Atkinson Construction arrived in Mount Vernon. After removing the fallen span from the river, final inspections can begin before WSDOT can begin designing a preferred option for repairing the bridge and reopening the interstate.

Hello everyone.  I hope y’all are doing well.  Nothing new has really happened with me; just enjoying summer and my family visiting – all the summer type things.  Today I want to discuss “fracture critical” bridges and the issues in regards to US infrastructure in regard to the bridge collapse of the I-5 bridge in Seattle, Washington.  A recent article I read from the Associated Press, “Thousands of Bridges at Risk of Freak Collapse”, has discussed some of the statistics related to the issue.

The article opens with this quote to describe the bridge category of “fracture critical”: “Thousands of bridges around the United States may be one freak accident or mistake away from collapse, even if the spans are deemed structurally sound.”  In essence, this means that these bridges have no extra level of strength or redundancy incorporated into their design.  Further more these bridges carry millions of drivers every day.  This is the stated reason for the I-5 bridge collapse a couple weeks ago.  Recently, the government has focused on repairing bridges in the “structurally deficient” category – this means that portions of these bridges are poor condition or worse.  The most recent bridge failure in the “fracture critical” category was the I-35W bridge failure in Minneapolis which had a much higher passenger injury rate and even some deaths.  A study performed in the wake of that bridge failure revealed that only a few “fracture critical” bridges fail overall.  However, the government still builds these type of bridges in the belief that they won’t fail – the reason this design is still being used instead of the more conservative redundant design methods is monetary issues.  18,000 “fracture critical” bridges have been built from 1950 to 1980.  On a similar note, 30% of the bridges in the US fall into the “structural deficient” and “functionally obsolete” category; the “functionally obsolete” means that the design of the bridge is not suitable for it’s current usage.  The current spending on these repairs is $28.5 billion and this spending is double that of the budget in 1998.  However, this increase has barely kept up with the demand for repairs and while public officials agree something has to be done, they have not agreed on any solutions to effectively increase the bridge repair budget.  Currently, progress is being made by states in that they are trying to increase state budget investment using toll roads, gas taxes and sales tax.  Along with that, $3 billion of the $27 billion stimulus went to bridge repair budget as well.  Washington state Rep. Judy Clibborn states that “We can’t possibly do it all in the next 10 years, but we’re going to do the first bite of the apple.”

There are several things that can be learned from this bridge collapse.  The main one is that the analyzation of a bridge structure is more complicated than being structurally safe or unsafe.  While some of the bridges that get the most concern are the ones that aren’t structurally safe, there are a lot more that fall into that gray zone.  The secondary thing in relation to that is that in order to understand the complexity politicians need to have a better understanding of bridge design philosophy – especially the importance of redundancy and increased strength.  There also needs to be understanding by the population and politicians alike that there needs to be an increase in budgeted time and money to implement these concepts in order to construct the best quality bridges for our infrastructure.  What are your opinions on how to implement this?  What do you think are the best ways to increase the budget in regards to time/money and improve design/construction methods?  Thanks for your time and have a good week.

Source:
“Thousands of bridges at risk of freak collapse”, Associated Press, May 26th, 2013, http://tinyurl.com/myor9uf

Internally Cured Concrete as a Solution to Cracking and Lifecycle Issues in Bridge Decks

Hello everyone, I hope y’all are doing well.  I had a pretty good week.  The school year for the school district is winding down so I should only have a few days of substitute teaching left and then a long summer break.  I also know for sure now that I can register for my comprehensive exam and I already know the test date – once that is done I can apply for graduation on my Masters of Engineering program.  I also just got back from floating the river in Gruene, TX which I haven’t done in ages.  All in all, things are looking up.  Today I want to talk about an innovation in curing concrete being researched at Purdue University which could significantly reduce cracks in concrete bridge decks.

The concept being researched is a high strength concrete being cured using an internal curing process and the research shows that it could double the life of the bridge deck.  The concept was first discovered in high strength concrete by Dr. Jason Weiss in 2004.  Further research by Dr. Weiss also showed that there could be a lot of potential uses for moderate grade concrete as well.  The normal curing process works by adding the aggregate, cement mix and water separately.  The way internal curing works is that highly porous aggregate with moisture and cement mix are combined and the curing process occurs from the inside out as the water is pulled out of the aggregate by the cement mix.

Once the appropriate proportions were determined, samples were tested for salt ingress, corrosion and cracking.  The material has now passed the test on samples 15 ft. long and 3 ft. wide.  Along with that, a few bridges built by INDOT have used internally cured concrete as well and they seem to be holding up.  INDOT believes this curing process has potential and plans on moving into full scale field trials while also trying to gain more accurate information on life cycle data.

However, there are a couple challenges with this new process as well.  One challenge is that moisture content of aggregate is much more critical.  It may seem like an easy issue to account for; but if the crew doesn’t have the training to account for this, it could make it more difficult to construct.  The other is that there is a slightly increased up front cost as compared to the traditional process; however, Dr. Weiss believes that the large decrease in maintenance cost in the future should make up for that.

Overall, I believe that this is a promising improvement in the bridge deck curing process.  Not only does it reduce cracking and maintenance cost; it also increases the lifetime of a bridge deck.  Along with that, there is a lack of resources in regards to construction crews and budgets – implementing this process could do a lot to ease the load in both of these areas.  What is your opinion on internally cured concrete?  Do you think the benefits projected by Dr. Weiss are too optimistic, not optimistic enough or mostly accurate?  Thank you for your time and have a good weekend!

 

Source:

“Internally Cured Concrete May Lead to Crack-Resistant Bridge Decks”, Civil Engineering Magazine, May 2013, pg 36-37

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