Question about designing and detailing bundled reinforcing steel in a shear wall
Question about designing and detailing bundled reinforcing steel in a shear wall
(OP)
I have a question regarding how to lap splice bundled reinforcing bars. We always try to avoid using bundled bars, but we were asked to investigate whether using #11 bars in 4-bar bundles will be less expensive than mechanically spliced #14 and #18 bars. (The bars are the chord steel in a shear wall. The large area is required for tension - so increasing the concrete strength won't reduce the required area of steel.)
Here's what ACI 318-08 says about bundled bars,
Bundles are limited to 4 bars (Section 7.6.6)
Development length has to be increased by 33% for 4-bar bundles (12.4.1)
Lap splice lengths are determined based on the individual bar size and no more than one bar in the bundle may be lap spliced at any one location. (12.14.2.2). This means that I have to stagger the splices.
If I have a 4-bar bundle and I stagger the splices one bar at a time, I will essentially have a 5-bar bundle (with four bars being effective in tension). Am I interpreting this correctly? Or am I limited to a 4-bar bundle with three of the bars being effective (due to the staggered splices)?
Here's what ACI 318-08 says about bundled bars,
Bundles are limited to 4 bars (Section 7.6.6)
Development length has to be increased by 33% for 4-bar bundles (12.4.1)
Lap splice lengths are determined based on the individual bar size and no more than one bar in the bundle may be lap spliced at any one location. (12.14.2.2). This means that I have to stagger the splices.
If I have a 4-bar bundle and I stagger the splices one bar at a time, I will essentially have a 5-bar bundle (with four bars being effective in tension). Am I interpreting this correctly? Or am I limited to a 4-bar bundle with three of the bars being effective (due to the staggered splices)?






RE: Question about designing and detailing bundled reinforcing steel in a shear wall
As an aside, I really think we need to reexamine lap lengths and design strategies, since the difference between a 113 and 118 inch lap is really unsupportable, given the variability in all of the factors involved.
RE: Question about designing and detailing bundled reinforcing steel in a shear wall
RE: Question about designing and detailing bundled reinforcing steel in a shear wall
Yakpol