The Earthquake-Proof Building That Is Built to Collapse

The Brilliant Idea: A replaceable, building-wide system to help hospitals, apartment buildings and office towers survive severe seismic shaking.

 Innovators: Gregory Deierlein, Stanford University; Jerome F. Hajjar, Northeastern University


"Elastic high-strength steel cables run down the center of the system’s frame. The cables control the rocking of the building and, when the earthquake is over, pull it back into proper alignment."

"A steel frame situated around a building’s core or along exterior walls offers structural support. The frame’s columns, however, are free to rock up and down within steel shoes secured at the base."

World’s longest tunnel “Gotthard Base Tunnel” : Hot Topic

After two decades’ construction, the Gotthard Base Tunnel in southern Switzerland broke through the final 1.8 meters Friday to create the world’s longest tunnel at 57 kilometers.

Civil Engineering Award for Delhi Metro

The Delhi Metro Rail Corporation(DMRC) has won the Outstanding Civil Engineering Project Award for the year 2010 specially for completing various infrastructural projects in record time, an official said today. The award will be given by the international Asian Civil Engineering Coordinating
Council(ACECC). The council works for the promotion and advancement of the science and practice of civil engineering and related professions for sustainable development in the Asian region.

The award is given to agencies involved in infrastructural projects that have made exemplary contribution to the progress of civil engineering works.

The project taken up by the agency should contribute to the nation where the project is located and they should have impacted on or spread through other Asian nations or ACECC member economies.

Work on a 125-km stretch of the Delhi Metro is in progress in Phase II and will be completed before the Oct 3-14 Commonwealth Games. Large sections of this have already been opened for the public.

What is Underwater Antiwash Concrete?

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Although underwater concreting has been in use for a long time, development of the technique has mainly proceeded in the areas of concrete placing method and improvements to the construction machinery. The prepacked concrete method, tremie method, concrete pump method, and others are now the representative underwater concreting methods. With all these concreting methods, the essential aim of technological development has been to improve how the concrete is placed and to minimize contact between the water and mortar so as to prevent the concrete from segregating under water.

On the other hand, antiwashout underwater concrete is quite different in concept from the methods mentioned above; the developmenta1aim in this case was improved performance of the fresh concrete. That is, the viscosity of the concrete was increased and its resistance to segregation under the washing action of water was enhanced by mixing an antiwashout admixture with the concrete. The effect of this is not only to greatly improve the reliability of Concrete placed underwater, but it also has remarkable effects on environmental preservation in the construction area. In addition, the earlier tremie and concrete pump placing methods can be adopted for construction.

The specific advantages of antiwashout underwater concrete include the following:

• Compared with ordinary concrete, antiwashout underwater concrete is highly resistant to the washing action of water, and rarely separates even when dropped under water

• Its yield value is small and viscosity high, so the concrete components never segregate and it displays high fluidity.

• As a result of the high fluidity, filling property and self-leveling ability are improved.

• Almost no bleeding occurs.

These qualities are taken full advantage of in work which would be difficult to handle using conventional underwater concrete. This includes work where high reliability is required, work in flowing water, work where water turbidity is restricted due to environmental considerations, and work where construction stretches over a considerable area and good flatness is necessary. On the other hand, however, handling is more difficult than with ordinary concrete, and in order to produce concrete of the required quality and a structure of the required performance, careful consideration of mix proportion, mixing, transport, and placing, etc. is necessary when antiwashout underwater concrete is used.

In particular, when producing the underwater antiwash concrete it is necessary to mix it for longer than ordinary concrete in a mixer large enough to uniformly disperse the antiwashout admixture. Also, when using concrete pumps for placement, it is necessary to design a pumping plan with care as regards pumping equipment, pumping distance, etc., because the pumping resistance is increased by the higher viscosity.

The Era of Flexible Concrete?

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 Looks like the brittle concrete has been tamed at last!
A team of researchers at the University of Michigan has developed a concrete material that bends like rubber, cracks very little, heals itself with no manual intervention, and is almost as good as new concrete upon recovery, with its stiffness and strength intact.
The research team led by Professor Victor C. Li more here , Professor of Civil and Environmental Engineering
at the University of Michigan, has achieved this by designing the new material with tiny crack widths. This ensures that any damage caused due to overloading and subsequent tensile strain manifests itself as small cracks that are autogenously healed.
Here’s how the self-healing mechanism works. The extra dry cement that is exposed on the surface of the crack reacts with water and carbon dioxide to form calcium carbonate, a strong and resilient compound that brings back the material to its original state. But this works only if the crack width is tiny, a factor that is taken care of by the nature of the material itself. The new material is an improvement over the bendable engineering cement composite (ECC) that Li and his team have been developing for the past decade and a half. The research team discovered that the brittleness of concrete could be altered by limiting the crack width to 150 microns, preferably 50 microns to enable full healing. The average crack width in the ECC was found to be 60 microns, half the width of human hair.
While traditional concrete is brittle and rigid, prone to failure and breakage under strain, the flexible ECC is held together with reinforcing fibers. So while traditional concrete fractures under a tensile strain of 0.1%, experiments revealed that the ECC is able to withstand a tensile strain of up to 5%. That makes it an astounding 500 times more durable than concrete.
The flexible ECC has several obvious advantages over traditional concrete as a construction material.

Stronger Structures
Presently, concrete structures are reinforced with steel reinforcement (aka “rebar”) to minimize concrete cracking, as well as provide tensile strength for bending moments for structural beams and columns. While ECC cannot replace rebar for structural tensile strength, it can reduce the need for rebar to limit concrete cracking. In addition, ECC has the added benefit of self-healing these cracks, thereby reducing the risk of water and de-icing salts penetrating into the structure, causing corrosion of reinforcement steel that might be present.

Decreased Costs
While ECC is three times as expensive as traditional concrete, these costs are outweighed in the long run since the structure would not require extensive repair and maintenance. Li claims that ECC could help do away with repair and rebuilding processes for about an additional five to ten years. It could also eliminate the need to monitor seismic stresses on structures.

Reduced Environmental Impacts
Use of the ECC is also expected to reduce the energy and carbon footprints of infrastructure, thereby reducing the detrimental effects of construction on the natural environment.

Quieter Structures
In 2006, a bridge over Interstate 94 in Michigan was built with a similar self-healing concrete, which was reinforced with toothed metal slats that allowed concrete to expand and contract without bending. However, this structure turned out to be a noisy affair as vehicles rattled over the metal slats. In contrast, ECC is a silent material.

The research certainly bodes well for the construction industry. In addition to the obvious applications in buildings and infrastructure, self-healing concrete could also very well be the solution to potholes and cracks on roads and bridges, and leaky walls. Flexible ECC is also being considered for use in irrigation channels in Montana.
However, the one crucial factor that could put a wrench in the works is that the self-healing process is almost entirely dependent on the availability of water. Under laboratory conditions, ECC was found to require about one to five cycles of wetting and drying in order to self-heal. Extrapolating this finding to large structures such as bridges, it can be concluded that the ability for the material to self-heal is likely to be seasonal in nature. This leads one to question whether the new material would be suitable for commercial use in dry arid lands, and under all climatic conditions. And, would the alternate freeze-thaw cycles during our cold winters, complicated by use of de-icing salts, affect ECC’s material properties? These are some of the questions that should be addressed.
All said and done, should ECC prove to be a success in terms of industrial and commercial use, we are likely to see safer, smarter and more durable structures being erected.

The Need of Low Cost Software for Structural Engineering Design

       Tedious hand calculations and slide rules for structural engineering design and analysis has given way to a plethora of low cost or even free structural engineering design software. A few example links are listed for convenience.

The Evolution of Structural Engineering Design Software

It wasn’t too long ago that structural engineering design calculations were performed on paper, with support from that ancient device called the slide rule. Static models ruled, and dynamic response models were limited at best. When mainframe computers were commercially available, software programming advances were developed primarily to speed up the computational processes. Electronic calculators arrived and also began to make significant contributions, and the writing was on the wall for the venerable slide rule. Then, in the early 1960’s, a newer modeling process called finite element analysis became encoded into NASTRAN software, and in the mid 1970’s started to become widely available on mainframe computers. This analysis complemented the more traditional static and dynamic models also being incorporated at the time into structural engineering software. Structural engineering students began to obtain access to unprecedented engineering design software, but only at the price of school tuition. Structural engineers could utilize these engineering programs if their employers had the resources to obtain the expensive computers, software, and technical expertise to install and maintain them.
The development of the personal computer drove another round of developmental structural engineering software, and as the pc became more and more capable the software evolved as well. Today, incredibly powerful (compared to the last century) engineering analysis software is available at little or no cost to the user. While not as capable as commercial versions, free structural engineering design software modules can take on formerly unprecedented analysis and design tasks using personal computers no larger than the “ancient” desk top electronic calculators of the 1960’s.

Sources of Low Cost or Free Structural Engineering Design Software

Following are a few of the many freely available programs that can be utilized for structural engineering design and analysis. By no means a comprehensive list, and no claims, representations, warranties, or guarantees for fitness of use are made here; the usual admonitions re viruses, personal information disclosure, etc. when downloading programs from the internet do apply. “Free” may apply for a limited time, or to trial and evaluation versions only:

• http://yakpol.net/ Combination shareware and freeware spreadsheets.
• http://www.seaoc.org/software.html Various freeware download listing maintained by The Structural Engineers Association Of California.
• http://www.grapesoftware.mb.ca/index.html Evaluation copy is free, continued use requires payment.
• http://www.elpla.com/elpla_en/download.htm Trial versions only, geotechnical analysis and design.
• http://www.fabsec.co.uk/free_fbeam.asp Beam analysis, trial versions.
• http://frame3dd.sourceforge.net/ Open source structural analysis software for static and dynamic analysis of 2D and 3D frames and trusses.
• http://www.ecf.utoronto.ca/~bentz/mhome.shtml Reinforced concrete panel analysis.
• http://opensees.berkeley.edu/index.php Software framework for developing applications to simulate the performance of structural and geotechnical systems subjected to earthquakes. Requires registration.
• http://www.lisa-fet.com/index.htm Free trial version, low cost full version finite analysis software.

What we learn from the history in the design's mistake!

What we learn from the history in the design's mistake!

I’m going to make a couple of points today. First of all, when you are new to civil engineering and first learning to calculate things like concrete columns and roadway curves, it can seem like everything that is in the real world is over designed. There are many rules and regulations that must be followed in your designs. My second point is about engineering ethics. All of the rules can’t cover everything.
Tacoma Narrows Bridge

Every civil engineering student gets to see the one of the videos of the Tacoma Narrows bridge collapse. I was shown this video in three or four different classes in school. If you haven’t seen the video here’s one I found on YouTube. This one is in color and has some additional information.
As far as I’ve been able to find out, the engineers followed the standard rules of the day. By their calculations the bridge should have been fine. But it wasn’t. It collapsed four months after being finished. The engineers fail to account for wind. In a lot of ways, because of this bridge, we have to take into account aerodynamics when designing virtually any structure. Not just aerodynamics, though, we as engineers need to take into account every potential source of forces that may affect our structures.
I 35W Bridge

Here’s a video of the I 35W bridge collapse in Minnesota. This bridge had held well for many years. The initial design could handle the current expected loads. However, later engineers didn’t fully account for additional loads from improvements to the bridge. Specifically, it appears that the gusset plates didn’t have a large enough safety factor. More information on the cause can be found in this article about the University of Minnesota’s Independent Study. According to the study, in addition to the gussets and later improvements, temperature changes played a large role in the collapse. These kinds of things should be considered in an original design. They also need to be double checked when making improvements.
Cypress Street Viaduct
This third video has two parts. One is about the Cypress Street Viaduct and the other about a dam at a coal mine. The Cypress Street Viaduct is another bridge that collapsed due to greater than expected forces. In this case an earthquake. The bridge was designed to easily handle the vertical loads, however they didn’t account for the lateral loads caused by an earthquake. They really only considered enough lateral load to handle wind.
All three of these videos show reasons that we have some of the design standards that we do. We have to include all of the forces that will act on the structure. Not only the everyday forces, but also expected maximum forces. Then we add a safety factor on top of that to take into account anything we didn’t think of.
The second half of that last video adds something else to this. The dam collapsed even though engineers at the time knew how to construct a safe dam. At the time, however, there were no regulations on this type of dam. To save money no engineering was actually done, and no standard maintenance or construction standards were followed. This resulted in the dam collapsing. What this means to us as engineers is that even if there isn’t a law saying that we have to do something a certain way, we should still do it the right way.
Engineering ethics is extremely important to civil engineers. This is one of the few industries where people can get seriously hurt or killed if we don’t do things the right way. Because of that, follow the law and approved standards. If they don’t provide enough guidance then use your engineering judgment and the experience of experts to do the right thing.
Have you had any experience where the standards didn’t meet the needs of you project? What kinds of things have you seen?

Dangers of Using Online Tools to Design

Dangers of Using Online Tools to Design

As civil engineers, there is no way that we can have a perfect set of plans.  Our plans can’t include every possible thing.  We are limited to the information that we have.  Survey crews can only shoot a limited number of points, field conditions may have changed without as-built plans being updated, mathematical models are based on assumptions, or any thing else can cause errors in design.
Because of that I encourage civil engineers to use all available resources to limit as many errors as possible.  Some of the great new resources that have come out in the past few years are online resources like satellite maps, Google Street View and Microsoft Bird’s Eye View.  They work well as aerial overlays on plan maps.  They can also be used to get a quick look at where a river runs or where certain features are in relation to everything else.
However, be careful, they are not updated in real time.  In many cases they aren’t updated more than every few years.  Many things can change in that time.  Be sure to verify important features with a field visit before changing your plans.
I learned this early on.  During my internship days I was working on traffic model.  I compared my traffic model to Google’s Street View.  Google’s Street View and aerial map had a traffic signal that my model didn’t.  Well, I updated my model to include that signal and redid the calculations to include that signal.  Fortunately the engineer that I worked for was more skeptical and sent me on a field visit.  Sure enough, the traffic signal had been removed.  I had wasted some time rebuilding the model, but I learned that there is no substitute for a field visit.
Since then I’ve seen many other examples of the same thing: walls put up since the survey was done, driveways added and removed, intersection geometry changed, gas lines installed, just to list a few.
The bottom line, these tools are great and can help in your designs, but there is no substitution for a field visit.  You should visit your site during both the design and construction phases of your projects whenever practical.