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Wednesday, December 16, 2009

High Strength Steel Reinforcing

High strength steel reinforcing, i.e., 90ksi and 100ksi, is gaining use in contrast to previous years when this reinforcing was cost prohibitive.

It appears that competition between the very few manufacturers of this kind of reinforcing lowered the price, making it more usable from an economical stance.

The professionals at Construction Advisory Group note that it is important to realize that while this rebar is more expensive than the conventional one, it drastically reduces the reinforcing congestion by reducing the amount of horizontal bars in columns and shearwalls -- thus generating substantial labor savings.

The reduction of horizontal reinforcing when 100ksi is used is 40% and 30% compared to when using 90ksi.

This certainly translates into less field labor, less material that is lighter in weight, less hoisting, fewer problems threading mechanical and electrical conduits and sleeves through rebar and easier concrete casting.

The use of 90ksi and 100ksi steel will be eased by the American Concrete Institute’s Design Guide for the Use of ASTM A1035 Grade 100 Steel Bars for Structural Concrete, on course for publication early next year.

This is considerable progress that deserves undivided attention.

Construction Advisory Group strongly recommends that all preconstruction efforts and cost evaluations, prior to job bid, should take into consideration this factor. Owners, general contractors, concrete contractors will all benefit, should the structural engineer of record be in agreement.

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  1. Reginald Fequiere, M. Sc., P.E.December 28, 2009 at 6:36 PM

    The cost of 100 Ksi steel has been competitive over the past 5 years. When you factor in the reduction in the amount of material and labor you actually obtain significant cost savings. That is why many engineering firms have proposed the use of high strength steel when value engineering projects.

    I personally was involved in two projects where the use of 93 Ksi steel was proposed. In one case it was accepted by ownership due to significant savings that were obtained by using this high strength steel in the reduction of steel congestion. In the other case it was rejected even though it offer significant cost savings, because the steel had to come from Germany and ownership was concerned about delivery and customs delays that may affect the project schedule.

    However the biggest hurdle for high strength steel is code provisions. At this time the ACI only allows the use of up to 80 Ksi steel for flexure and no more than 60 Ksi for shear. Currently to implement the r use of this steel you have to get approval from the building official whit jurisdiction on the project, and some they will not take a step into what is outside their comfort zone. If the codes raise the maximum yield strength of steel to 100 Ksi then bureaucratic hurdle would be behind us and now it would come down to availability and cost, and at this point the market would, in my opinion, tilt in favor of the higher strength steel. Note also that of these product have amazing corrosion resistance (MMFX steel) and also provide a longer life span for the structures being used.

    I agree it that high strength steel is the future and if the building codes would allow their use, then I believe more daring structures will see the light of day.

    I am not sure if there are any mills that produce this steel in the US, if not we need to make sure that it happens, because if the product is more readily available locally, the construction industry will definitely have more interest.

    Reginald Fequiere, M. Sc., P.E.

  2. Thanks Reggie and nice to hear from you.

    As far as I know/read, this high strength steel is currently produced by Harris Rebar Seattle Inc., MMFX Technologies Corp., Irvine Calif. and Nucor Steel Seattle Inc.

    Indeed, this info must be verified.

    Best Regards, Val T.

  3. The MMFX is certainly worth reading about, however, what is the bars' track record among the projects that have used it? I'm looking for information to that dampens the fact that the bars have a relatively short service record.

    Any information you have would be appreciated! Thank you,