Thoughts on the Engineering Industry

A blog covering engineering, technology and business topics

Archive for the month “January, 2014”

Potential Applications of Cellulose Nanocrystals in Structural Engineering

Hello everyone! Today, I am going to take a break on my Karuna House series and write a post about cellulose nanocrystals.  Cellulouse nanocrystals are the material that gives plants and trees their stiffness. Their dimensions are 3 nanometers wide by 500 nanometers long – about .1% the width of a grain of sand.  They can be easily harvested with a sustainable process and can be produced from paper waste as well.  A recent study by Purdue University has found that these nanocrystals are light weight, have high strength, are highly resistant and have the stiffness of steel.  “It (the research) is also the first step towards a multiscale modeling approach to understand and predict the behavior of individual crystals, the interaction between them, and their interaction with other materials,” Zavattieri said. “This is important for the design of novel cellulose-based materials as other research groups are considering them for a huge variety of applications, ranging from electronics and medical devices to structural components for the automotive, civil and aerospace industries.”  The article shown in the link here, http://goo.gl/8Pl8LB, provides a quick overview of characteristics with extremely basic explanations in regards to applications and I am going to expand on possible applications as they pertain to structural engineering.

Organic Polymer for Concrete:

     Fiber reinforced concrete can be designed to reduce the amount of steel required.  In this way, cost and heavy material requirements can be reduced in the construction process.  I believe that cellulose nanocrystals can be used in the same way.  They can be placed in concrete and improve the tension strength where needed.  These also have the added benefit of being more sustainable and less expensive in regards to material accessibility as compared to fiber reinforcement.  That being said, it is not clear if the cost of the production once the material is obtained would be out-weigh the cost savings in accessibility.  More research and practical application of the production process is needed to determine that.

Reinforcement Against Cracking:

A very common issue with concrete infrastructure is cracking.  Currently, when cracking starts occurring at the base of a beam, a method where steel reinforcement is bolted into the concrete is used to prevent further expansion of the cracks.  While it is an efficient solution in regards to time and money, steel is not as environmentally friendly a material.  Along with that, once research into production and application is completed, the amount of time and money can be reduced to that of the steel reinforcement method.  This means that an approach where an organic polymer sheet covered by a layer shotcrete could be a better solution at that point.

Additional Reinforcement for Timber Structures:

Engineered lumber is a recent development in timber design.  These are basic timber building elements that are created from pieces of timber.  Some good examples of this are cross laminated timber/particle board panels and glulam beams /columns.  Along with that, other applications such timber restoration apply this same concept of combining pieces of timber to create a stronger building element.  The same type of organic polymer sheet used for reinforcement against cracking could also be used to provide some extra tension strength in these situations.  This would be very beneficial in timber elements that are designed to resist high levels of flexure.  Another added benefit would be that the nanocrystals are extremely thin and can be applied in design with very tight tolerances.

Cellulose nanocrystals could have a lot promising a applications for structural engineering designs and I look forward to seeing what improvement can be made using this material.  What is your opinion on the possible applications mentioned above?  Are there any other structural engineering applications that you can see this material for?  Thanks for your time and have a good week!

Sources:

Zavattieri, Pablo. “Cellulose Crystals Are a Possible ‘Green’ Wonder Material.” Red Orbit Online.  December 17, 2013. http://goo.gl/8Pl8LB

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High Performance Energy Saving Design for the Karuna House – Wall System

Passive House Green Home Building Tips: Karuna House Wall Assembly

Hello everyone.  I hope your weekend went well.  Everything is picking up for me again – my day job and school included.  Not in a stressful way though; it feels good to be doing some productive stuff again.  Today, I want share the second part of my series of post describing the design of the Karuna House and the topic this time around will be the wall system.

As stated in the article, the main issues in designing the wall were moisture, heat and air control.  Along with that, this design added the other standard of being able to release moisture once it entered the system as well.  With that in mind, the main goal of the wall design was to create a building envelope that was air tight, water tight, vapor permeable and super insulated.  On the inside of the wall, standard natural lime coating and dry wall were used for interior design purposes.  Beneath that, a stud frame of engineered wood members was built to support the wall structure and was insulated with high density cellulose.   The high density cellulose consisted of recycled newspaper and naturally buffered against moisture which improved the walls durability.  After that, there was the air barrier which prevented air from flowing through the wall and allowed the insulation to perform at a much higher level.  The air barrier was created using plywood coated with vapor permeable liquid applied membrane.  After that level, a frame of Z Joists with foil faced Polyiso Foam was placed over that.  This element was the critical part of the design in regards to performance and durability.  The final element was the rain screen system made out of cedar siding placed 1 inch off of the Polyiso Foam.  Window frames were sealed using Joint Seam Filler and Fast Flash around the window structure.  Details aren’t provided about door frames but it would be a reasonable assumption that they did the same thing there as well.

In my opinion, the design of the wall framing system isn’t as unique as the foundation system.  It has been standard practice for a while to use foam insulation and air barriers.  The same goes for the window sealant process.  However, the attention to detail in what to use and how to apply it is still a good take away for building design in the future.

What is your opinion on the wall frame system?  Is there any improvement they could have made that would have increased energy efficiency?  Thanks for your time and have a good week! 🙂

Source:

Hammer and Hand, “The Karuna House: Wall Assembly”, http://goo.gl/sHU7kv

High Performance Energy Saving Design for the Karuna House Part 1 – Foundation Design

     Hello everyone! I hope your holiday break went well.  I had a fun time with my family and definitely felt like I recharged my batteries as well. Hopefully you guys could do the same.  Today I want to start a series of blog posts on a detailed overview of the high performance systems used in the Karuna House created by Holst Architecture and Hammer & Hand.

The Karuna House is a house designed to meet Passive House standards, Minergie-P-ECO, and Platinum LEED Home Standards.  The client is a leading proponent of high performance design technology for climate control.  This house is intended to be a case study in the usage of the current technology on the market today.  In the first part of this blog post series, I am going to discuss the design of the foundation and the energy saving technology applied in that part of the design.

The main concern for the foundation involved insulating the basement and foundation.  With that in mind, most of the technology focuses on maintaining a good quality building envelope that insulates well.  The first step was the cut and fill for the excavation.  In this step, the cut was balanced with the fill to ensure that there wasn’t a need to haul around aggregate to complete the fill process.  For the next step, an Expanded Polystyrene (EPS) geofoam foundation insulation was placed around the cut and fill earthwork before the concrete foundation was constructed.  Next, the footings beneath the structure were placed and a moisture blocking capillery break material was placed on top of that.  Once the footings were in place, gravel fill was placed for the foundation base and the basement foundation wall was constructed with a vapor barrier extending to both sides of the wall.  The concrete mix used in the basement foundation wall consisted of 30% fly ash and used locally sourced aggregate.  In order to obtain better energy efficiency, EPS was placed in critical thermal bridge sections.  Along the foundation walls, a product called a drain board was applied to it’s surface as well to allow water to flow down the foundation walls and past the footings.  Once all that was completed, they applied the vapor barrier over the gravel base and laid some more EPS foam before they constructed the slab portion of the foundation.

My take away from reading the article and watching the videos is that there are two critical issues that affect house foundations – moisture control and thermal bridging.  The designers used the EPS and vapor barriers to address these issues.  Along with that, methods of construction were used that reduce the use of energy/material in construction as well.  Overall, I think this was a good application of some practical design ideas.  A lot of designs like this get caught up in following the latest complex and cool looking trend instead of finding a solid and fundamental solution to the problem – this design avoids that fairly well.

What are your thoughts on the design?  Does it seem like a practical application to use for increased energy efficiency?  Any issues you worry about over it’s life cycle?  Thanks for your time and have a good week! 🙂

Source:

Hammer and Hand, “The Karuna House: Foundation System”, http://goo.gl/C9Hccu

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