Calvin Curtis

Snicker-Snack! Post-Tension Tendon Finishing Options

by Calvin Curtis July 23, 2018
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Long ago, when I started my career, a contractor asked me if he could use a concrete saw to “cut all of the tendon tails at once” on his new post-tension slab on grade.  That is to say — he was hoping to cut all […]

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Reinforcing Concrete Slabs-on-Grade

by Calvin Curtis May 11, 2018

A few weeks ago, I got a great question regarding the reinforcement of concrete slabs-on-grade, so I thought I’d take a quick minute to share how rebar works structurally when the slab is continuously supported by earth. First, it’s important to understand that, structurally, no […]

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Balancing Post-Tension

by Calvin Curtis March 27, 2018

Last month, I wrote a quick post about understanding the sources of long-term losses with post-tension tendons.  One of the key points to take away from that is that the more post-tension material you use, the less effective each individual tendon becomes.  However, this is […]

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Understanding Long-Term Losses in Post-Tension Tendons

by Calvin Curtis December 7, 2017

As a structural designer, I started my career working on post-tension structures.  Those of you who have been with us for some time know that those can include things as small as a single tennis or basketball court as well as some of the tallest […]

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Denver Dad Saves $$$ on Post-Tension Tendon Supports Using One Simple Trick

by Calvin Curtis November 29, 2017

Last month, I discussed the need for precompression in a post-tensioned slab.  In that post, I mentioned that the code minimum amount of precompression is 125 psi for elevated slabs. I’ve also mentioned some of the various types of elevated decks in the past.  One […]

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Restrained versus Unrestrained Members

by Calvin Curtis November 14, 2017
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In the last several months, I’ve had many questions about what constitutes a “restrained” concrete member, and what constitutes an “unrestrained” concrete member.  The volume has been such that I’ve decided to take a break from my usual post-tensioned discussions and lay this out. This […]

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Sequential Stressing and Elastic Losses

by Calvin Curtis October 19, 2017
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In a previous post, I discussed the sources of short- and long-term losses in unbonded post-tension tendons.  Recently, a question came up on one of my LinkedIn groups regarding elastic shortening and sequential stressing. To refresh your minds, concrete — which is generally regarded by […]

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Reviewing Elongation Reports

by Calvin Curtis August 25, 2017
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At this point, I think it’s fair to say that I’m a proponent of post-tensioned structures.  I’ve found that they can be very economical, and there are many things you can only do with post-tensioned concrete.  However, there’s one point that I think all structural engineers […]

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Precompression vs. Balanced Load in Post-Tension Concrete

by Calvin Curtis January 6, 2017

My Post–Tension elevator speech is pretty well rehearsed at this point: “We drape steel cables — tendons — in the concrete forms, and then place the concrete.  Once it cures, we pull the ends of the tendons, which try to straighten out.  That does three […]

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What is Punching Shear?

by Calvin Curtis November 30, 2016
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There are several factors that come into play when designing an elevated concrete slab.  Obviously, the ability to support the design loads comes first, followed by the allowable deflections and long-term serviceability of the slab.  However, the factor that most frequently comes up when I’m […]

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Denver Engineers Not Surprised by New Post-Tension Rule

by Calvin Curtis November 30, 2016
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Good day!  Your usual post–tension maniac here, with more exciting information on post-tensioning! A few months ago, I mentioned that finishing post-tension tendons was an area of special concern, since corrosion is very much the arch-enemy of post-tension tendons.  There are actually a lot of […]

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Damaged Post-Tension Tendons

by Calvin Curtis February 25, 2016
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I’ve written a great deal in the last couple of years regarding design considerations for post-tension slabs, as well as the “right” way to install and finish post-tension tendons.  And while I’ve touched briefly on some of the potential pitfalls of post-tensioning, I haven’t discussed […]

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