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Greetings!
In the 24+ years I have lived in Las Vegas, the transition from the long hot summer months to the cooler fall season has always been a welcome relief and one of my favorite times of the year. It is a wonderful time to go out and enjoy the pleasant weather and the natural beauty of our Mojave Desert area. We have an abundance of incredible recreation sites located a short distance from Vegas to explore. The Red Rock Canyon National Conservation Area, Mount Charleston, and the Lake Mead National Recreation Area, which includes Hoover Dam, are all within less than an hour drive from Vegas.
Recently, I revisited Red Rock and hiked an intermediate level trail with my wife and a couple of friends. On the way driving to the park, I noticed an unfinished building project on the side of the freeway. The multi-story steel structure has been left unprotected and exposed to the elements for the past few years. I had seen it before, but this time I could not help but wonder how the naked structure is coping with the drastic temperature changes and exposure to weather over the years. Just as the change in seasons has an impact on our life, it also affects our built environment and the structural systems within.
 This month's Structural Moments looks at how structures respond to temperature variations and some approaches in designing for thermal loads. We also spotlight a couple of projects where temperature effects were a major design consideration.
Best regards,
Mohammed Thomad, PE, SE
Principal
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Focus On: Design For Temperature
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Expansion joint
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As temperatures begin to dip, and we prepare for the colder winter months ahead, it is timely to look at how structures respond to temperature changes. Building materials expand and contract as the temperature changes from season to season, and even night to day.
For example, a 60 foot long piece of mild steel experiencing a change in temperature from 60 to 100 Degrees Fahrenheit will have a change in length of about 3/16 inch. If the ends of that member are fixed, meaning the member is not allowed to expand or contract freely, the change in its unit stress will be about 7,540 pounds per square inch (PSI).
Structural engineers understand and know how to account for thermal changes and their impact on the design of structures. One of the most effective measures to account for thermal effects on structures is to provide the structural members with the ability to expand and contract freely. This can be done in many ways. The use of slotted, bolted member to member connections, sliding non-friction bearing connections and expansion joints filled with flexible materials are some of the more common methods. In some cases, an expansion joint dividing the entire structure into two separate parts from top to bottom becomes necessary to prevent damage due to thermal changes. This method is commonly used in very large open parking garages.
Structural Engineers can also design structural members and their connections to withstand applied thermal forces. Depending on the area and the level of temperature change, thermal forces can be substantial and can play a significant role in the life long performance of a structure. Have a look below at a few examples of structures that are exposed to the elements and were designed to account for temperature changes.
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Featured Projects: Weather Exposed Structures
Space Frames
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A new space frame structure being installed to adorn and shade the interior courtyard of a corporate office building in Las Vegas, completed in August 2012 |
Space frames are a great example of exposed structures that demand special attention to temperature loads. These structures are typically used for ornamental purposes and as solar shading devices. The constant exposure to changes in temperature causes expansion and contraction in the frame members. Therefore, space frames must be designed to resist these thermal loads and deformation forces when the choice for sliding connections is not available.
Parking Structures
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Whittlesea-Bell Transporation's mixed use office, storage, service garage and 1000+ company vehicle parking garage in Las Vegas. The design-build project was completed in 2009 (click photo for more information) |
A parking garage is another primary example of a structure that is entirely exposed to the elements and has unique characteristics that distinguish it from other buildings. Garage structural systems commonly consist of cast in place reinforced concrete or precast concrete. The whole structure will respond to changes in temperature. A garage that has a large plan area will experience volume change resulting in cracks which in turn provide access to moisture, chlorides and other aggressive chemicals. The design engineer must be able to predict where cracking is most likely to occur and specify expansion joints for proper durability and serviceability. |
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Who We Are:
THOMAD Engineering is a client focused structural engineering design and consulting firm established in 2003 and based in Las Vegas, Nevada. We are committed to providing creative solutions and excellent services to loyal clients on a wide range of projects.
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'Structural Moments' Archive:
September 2012
August 2012
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'Structural Moments' is a monthly e-newsletter published by the staff of THOMAD Engineering. It is intended to inform our valued clients, associates, and colleagues in the A/E/C industry and stimulate thoughtful dialogue with them. |
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THOMAD Engineering has been a proud member and supporter of the AIA Las Vegas chapter since 2003.
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Upcoming Projects
The following projects are currently under design or construction and will be featured in future issues of Structural Moments
- Bagatelle at Tropicana Las Vegas
- Custom Residence designed by noted architect Richard Meier
- Red Garter Casino Expansion & Facade Renovation in Northern Nevada
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