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  1. TXStructural

    Material Testing - Rebar

    Test full samples. Do not mill or neck them. The nature of rebar leads to differential characteristics across the cross section so milling it gives you incorrect values. If the sample fails outside the measured length (i.e., in the grip), try another sample. This is how every mill tests bar...
  2. TXStructural

    Aggregate placement under foundations

    IBC 2012 (the year closest to my desk) 1809.2 "Supporting soils" requires that footings be placed on undisturbed soil, compacted fill, or CLSM. This would seem to require that any fill materials be both capable of being compacted and have been compacted after placement. 3/8" pea gravel cannot be...
  3. TXStructural

    Is it permissible to splice 7-wire strands without prestress by lapping?

    The limits on bend diameter are not just about the bending of the bar. One primary mode of failure in tight bends is crushing of the concrete inside the bend when force is applied. I also doubt that 7-wire can be bent tighter than a 10 mm or 12 mm rebar without compromise.
  4. TXStructural

    Concrete Cylinders Initial Curing

    This is a hot topic in ACI 301 (as far as who provides what for initial curing). ASTM C31 is the spec you need to use to guide how you cure. There is a difference between field-cured and standard condition-cured cylinders. As far as vibration goes, people walking around in the trailer should not...
  5. TXStructural

    Minimum Temperature to Bend Rebar

    CRSI has looked at this in the past but since I am no longer there I cannot comment on their current recommendations. Check the tech notes available on crsi.org That said, some bar may be brittle at temps below about 32F while some may be ductile below that temp. I would expect A706 and...
  6. TXStructural

    Splice length reduction using hooked bars

    A couple of thoughts: First, hooks only work in tension (so no lateral or reversal of forces). Other Code limits notwithstanding, the orientation of the hooks would be important to avoid doubling the splitting force in the concrete created by the hooks. Two hooks occupying the same concrete...
  7. TXStructural

    Reinforcement Spacing

    Don't aggregate "slabs" and "footings". Slab reinforcement usually has more things to consider, like crack control and the degree to which the reinforcement will be supported and walked on/over. Hokie covered the important parts for footings. In slabs, two of the biggest problems are 1) widely...
  8. TXStructural

    bend rebars - tension + shear reinforcement?

    These bar serve as negative moment reinforcement over supports, shear reinforcement, and as midspan moment reinforcement. If you have discrete shear reinforcement, the bent bars are probably designed only to resist positive and negative beam moments. They are commonly called trussed bars but the...
  9. TXStructural

    Zap Screwlok Bar-Splice

    There are two specs of splices, one that will take full specified tensile (Type 2) and one that will go to 125% of yield (Type 1). The Barsplice products are generally very good products, along with Erico, Dayton Superior, and a number of others. You should be ok as long as they comply with the...
  10. TXStructural

    ACI 332.1 R-06, ACI 332-14, aversus ACI 318-11

    All ACI codes use 318 as the basis for design requirements. Design standards like 332 are based on 318 but usually place limits/constraints in order to simply the standard. If you know 318, use it. If you want shortcuts in order to get an adequate design out the door quicker, use the specialty...
  11. TXStructural

    High strength bars

    The reinforcing industry is currently working to develop materials up to fy=100 ksi for flexure. There is now an ASTM that includes grade 100 for non-seismic use, BUT a designer who uses this material current does so of their own accord. ACI 318 does not incorporate grade 100 for...
  12. TXStructural

    Concrete Repair

    Has the concrete stopped developing strength? If there is any chance that it will reach sufficient strength with more time, I would probably wait. Does the design have some latitude? Many times, especially in thick walls, the design may not be governed by concrete strength. I do not know how...
  13. TXStructural

    Lap Splice vs. Bundled Bars

    I should have read more carefully. And that makes clear Koot's remark - yes, that would be troublesome.
  14. TXStructural

    Remote Jobsites

    Short answer is because the rocks aren't dry and you will end up with a mess. Even relatively dry rock (the phrase is SSD - saturated, surface dry) will have enough water to cause cement to stick to the surface and start the hydration process. The ASTM rules for transit time are being changed as...
  15. TXStructural

    Flat Slab

    A slab supported (more or less) continuously on soil is not a flat slab, rather it is a slab on ground (aka, slab on grade.) The rules are entirely different and the design strategy is completely different. Also, depending upon soils and foundation type, designing a soil-supported slab as an...
  16. TXStructural

    Lap Splice vs. Bundled Bars

    There is no restriction about maximum reinforcement ratio due to laps. The limits are practical, for construction purposes. In the section shown, it seems that you are lapping top and bottom bars in the same section. While I do advocate for laps at 1/4 or 1/3 points, the practice is not widely...
  17. TXStructural

    One Way Slab

    Your OP doesn't specify what kind of girders. You do mention extending bars four feet beyond the supports, which wouldn't work if the slab stops as the support, but you mention "edge girders." If you provide more details, we can provide a more complete answer.
  18. TXStructural

    footing foundation concrete covering exposed to earth 75 mm min

    The cracks at the surface may be wider in thinner members (not always the case), but the crack width at the reinforcement will be the same, under the same forces. More cover is ALWAYS acceptable as long as it is added concrete rather than reduction of structural depth or compromise of member...
  19. TXStructural

    Can Crest Toppling factor of safety be below 1.5 for retaining walls?

    This discussion should move to the Earth Retention Forum since it is not really concrete engineering. You will have a different audience over there.
  20. TXStructural

    One Way Slab

    As a general rule, reinforcement is required to extend a full development length beyond the point at which is it required. For flexure, this may be reduced if there is more steel than required for flexure. Since this application does not have vertical stirrups, the steel will have a role is...

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