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Re: Minimum (or zero?) Temperature Reinforcement

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Dear Nels,

You've brought to us very interesting points that we sure will consider.
There really is no problem in getting nonmetallic reinforcement, the
problem is cost, as usual. We really didn't consider not using
reinforcement at all, that's why we now are wondering how to determine this
minimum amount of steel.
About research done by Dr. Bariola we do know, but we also are trying to
preserve soils. As you know adobe is a non cooked brick which is made out
of clay. There's an ecological way to focus research now. Quincha is an
excellent earthquake resistant system, but as it was originally, now with
the storey heights used it has evolutioned to make it cheaper but not
necesarily safer.
Thanks a lot for your advice.



At 09:20 PM 03/09/1999 EDT, you wrote:
>Walter,  
>
>Research to provide low cost durable housing for low income folks is 
>important and laudable.  I hope you find the effective means of
accomplishing 
>this in your country.  It's challenging if you are working in reinforced 
>concrete.  I have some thoughts on the nature of the challenge.
>
>A number of innovative architects designed and built reinforced concrete and 
>reinforced masonry homes in California in about the 1920's.  Frank Lloyd 
>Wright and Rudolph Shindler are two of the more well known of those 
>innovators.  About 50 to 60 years later, serious problems developed in many 
>of their projects due to corrosion of reinforcing steel.  These and a number 
>of other observations have led to my maxim that reinforced concrete has a 
>serviceability period of 100 years plus or minus a few decades.  On the
other 
>hand, unreinforced masonry structures can last millennia without suffering 
>similar effects -- but, on the other-other hand, they may not survive in 
>earthquake zones.  Nevertheless, the use of steel reinforcing has inherent 
>limitations when long-term serviceability is important among your goals.  
>
>Inadequate concrete cover over reinforcing steel is a major reason for early 
>corrosion damage due to carbonization (a change in the pH of the concrete 
>brought about by the reaction of atmospheric CO2 with the constituents of
the 
>concrete -- CO2 penetrates slowly into the concrete lowering the pH as it 
>advances).  In 4" thick sections, a means of keeping the reinforcing in the 
>center of the section will be vital to the long-term serviceability of the 
>structures you are developing.  
>
>Portland cement protects embedded reinforcing steel against carbonization
for 
>many years, but the slow process of carbonation eventually reduces the pH to 
>a level at which the protection is lost.  I'm concerned about the low 
>strength (= low cement content) that you are proposing  -- it may result
in a 
>shortened serviceability period.
>
>Education to provide an understanding of the importance of moisture control 
>as a defensive strategy should be another component of the system you
develop 
>for the folks you are hoping to help.  Roof leaks, plumbing leaks, poor site 
>drainage, irrigation near the house -- these all can let moisture into the 
>structure that may leach away protective cementitous components of the 
>concrete and accelerate the corrosion process.
>
>Coatings that exclude CO2 and moisture may be something that you should look 
>into.  However, if moisture cannot be completely excluded, its better not to 
>use a sealant at all -- moisture trapped inside a coating quickly leads to 
>deterioration of the concrete.  I believe that Sika makes a product that is 
>supposed to block CO2 while allowing water vapor to pass, but that may be
too 
>exotic for your low-cost program.
>
>Many of the California houses suffering corrosion problems have well-to-do 
>owners, but, even for them, the problems that they face in restoring their 
>corrosion-damaged homes are overwhelming.  The heirs of the builders of the 
>system you are developing may have to face similar overwhelming
difficulties. 
> If you could find a way to not only minimize, but eliminate the temperature 
>steel, while maintaining seismic resistance, you would have a most
satisfying 
>system.  Have you tested structural components that have no reinforcing?  On 
>the other hand, I know that I'd be reluctant to live in a house that has 
>unreinforced concrete overhead.  Are any of the nonmetallic fiber 
>crack-control products available to you?  What other materials with tension 
>strength are at hand in Peru that you could test or for which you might seek 
>out test results from other researchers?
>
>Are you familiar with the research by Julio Vargas Neumann and Juan Bariola 
>at the Pontifical Universidad Catolica del Peru into earthquake resistant 
>house construction methods using locally available materials (adobe and 
>quincha)?  I suppose that you certainly are, but if not, they may be onto 
>something that could be helpful to your project.
>
>I hope your small-house development project is a success.
>
>Nels Roselund
>Structural Engineer
>
>


Walter E. Sheen
Civil Engineer
Paseo de la Republica 6403. Lima 04
(511) 446-6237 (511) 446-9407
Lima, Peru
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