The development of the reinforcing bars relies on mechanical interlock of the bar deformations, hook, and/or anchor along with sufficient masonry cover to prevent splitting of the masonry. Reinforcement can be developed by embedment length, hook, or mechanical anchoring device. Splicing of reinforcement serves a similar purpose: to adequately transfer stresses from one reinforcing bar to another. Minimum development lengths are necessary to adequately transfer stresses between reinforcement and the grout or mortar in which it is embedded. 7), covers these requirements based on the 20 editions of the IBC. TEK 12-6, Splices, Development and Standard Hooks for Concrete Masonry (ref. In addition, prestressing steel is discussed in Post-Tensioned Concrete Masonry Wall Construction, TEK 3-14 (ref. 5) includes basic material requirements, corrosion protection and placement tolerances for reinforcement used in concrete masonry construction. the 2011 MSJC includes new lap splice length provisions for when confinement reinforcement is used at lap splices.under 2011 MSJC allowable stress design, the allowable tensile stress, F s, of Grade 60 steel was increased from 24,000 psi (166 MPa) to 32,000 psi (221 MPa), and.There are two main differences between the 20 editions of the MSJC that impact reinforcement development and splice lengths in the corresponding 20 editions of the IBC: Differences between the MSJC and IBC are noted in the text when they occur. Masonry design in these codes is primarily based on Building Code Requirements for Masonry Structures (MSJC) (refs. This TEK presents these requirements, based on the provisions of both the 20 editions of the International Building Code (IBC) (refs. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.Building codes include requirements for minimum reinforcement development lengths and splice lengths, as well as requirements for standard hooks, to ensure the adequate transfer of stresses between the reinforcement and the masonry. I like to debate structural engineering theory - a lot. If it was a zillion #4 bars at 12" o/c, I'd be willing to let it go. In my opinion, this kind of thing largely defies rational analysis and testing must be held as the gold standard. Rationally, bars developed via hooking would have less of that problem and therefore, all other things being equal, I'd expect them to perform better. My understanding is that the 1.3 factor on splicing is mostly about the possibility of reduced bond development where the bars might be in physical contact with one another. 180 hooks with transverse bars in the bends. I've seen a number of delay strip details where this strategy was employed to minimize the width of the delay strip. I've seen it done which is not to say that it should have been done. RE: Splice length reduction using hooked bars dik (Structural) 8 Jul 17 18:41 Obviously the length of the lap is not much of an issue if you are lapping bars. The savings in physical bar length would be no more than about 4.9 lbs per lap for #8 (trivial when compared to the added labor to bend, bundle, transport, handle, and precisely place bent bars). 14 inches of additional bar would be required for the bend and the required extension on a 180 bend, on each side. The overlap in a typical case lap length vs typical case ldh would be reduced from 42 inches to 17 inches. Confinement and congestion will be a issues. Two hooks occupying the same concrete will increase the crushing and splitting forces in the concrete. 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. First, hooks only work in tension (so no lateral or reversal of forces).
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