2/28/2024 0 Comments Lts versus lap splice notationThis length is similar to the lap length. For example-Main bar of the beam in column at beam column junction. is about 50 times the dia of bar is consider to safe.Īnchorage length- this is the additional length of bar required it insert in another at the junction. So when you see a chart on one project, it can differ from another for these reasons.ĭevelopment length is the length overlap of bars tied to extend the reinforcement length. These include but are not limited to concrete strength, rebar size, rebar coating and concrete cover or clearance. They are dependent upon different factors. The lengths of both splice and development do vary. So simply put, development is rebar to concrete, splice is rebar to rebar. The lap splice length is the length two rebar pieces must overlap and be tied together to create a bond as if there was no break and the run is “continuous”. A development length is the amount of rebar length that is needed to be embedded or projected into concrete to create a desired bond strength between the two materials. If we can't rely on strut & tie type mechanisms to reliably achieve this, we're in trouble.The difference between the two is in the application. In practice, we frequently count on tension getting transferred between offset rebar segments. Typically we extend the trim reinforcement beyond the opening so that it can be consider "lapped" with the reinforcement interrupted by the opening. This situation concerns me as the standard design methodology doesn't seem to consider the need for "tie" elements.ģ) The design of trim reinforcement around openings in reinforced concrete slabs. In these situations, we typically "lap" the offset bars by an entire storey.Ģ) The design of footing extensions where the new rebar is drilled and epoxied into place and assumed to lap with the existing (offset) rebar. I know of three similar situations that we encounter routinely:ġ) The design of shear walls where concentrated vertical reinforcing is interrupted by door openings etc. I certainly wouldn't be shy about exaggerating the lap splice length in this situation. In reality, you were probably going to do this anyhow as a matter of good judgment.Ģ) Worked out on a strut & tie basis, your "lap splice" length will likely be substantially longer than a code lap splice. In your case, this probably means:ġ) A group of stirrups and/or ties at the top and bottom of the pseudo-lap splice. Based on testing, judgment, or both, it seems that ACI has decided that 6" is the appropriate limit.I think that it's perfectly acceptable to "splice" bars that are offset more than 6" so long as you provide the ties required to justify the strut & tie model. I believe that a code defined "lap splice" is simply a version of this strut & tie model where we have deemed that the offset between bars is small enough that it is not necessary to provide the "ties" in the strut and tie system. Since we're dealing with two tension forces connected by a concrete strut of some sort, I believe that strut & tie methodology is a reasonable way to approach this problem. The most common failure found in lap splice locations is debonding, which occurs at the splice region and insufficient lapped length is considered as the primary cause because of design or construction mistakes, design by outmoded code, and natural catastrophes. This is true even when the bars are in direct contact with one another since there is no inherent shear connection between the bars. Here's my opinion:ġ) The situation that you've described does not constitute an ACI lap splice.Ģ) With the appropriate detailing, you can do what you've proposed in your sketch.Īny time that you are transferring stress from one rebar segment to another via a "lap", there is concrete compression involved. The more basic question about this, however, is does this constitute a lap splice per ACI? RE: What EXACTLY is a lap splice? Lion06 (Structural) Point is well taken about overlapping the bars by ld of the #11 plus the #18. If, however, there are #18 bars developed above and below that plane then all was good in my mind. The remaining length of bar would just pull out of the parent member because the remaining embedded length is just so small. a tension failure would look something like a tensile failure of the concrete section but above the bottom of the #11 bars. First, if you have this column that is anchored at the bottom and the # 11 bars stop short of the bottom by 20'. I had a two step thought process in my head. Is there a reason you picked halfway? I was thinking (even though I didn't draw it that way), and said in an earlier post, that the #18 should be developed above the line defined as follows: the line that marks where the tensile capacity of the concrete is exceeded as the tensile force sheds from the steel to the concrete.
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