![]() The average bar stresses resulting from this test were compared with the predictions by the ACI 318 provisions. Most of the specimens were designed to satisfy the Class B splice length specified by ACI 318. Concrete strengths ranged from 24.7 to 55.3 MPa (3582 to 8021 psi). The test parameters were the reinforcing bar diameter, concrete cover thickness, concrete strength, and stirrup spacing. Twelve simply supported beams and slabs with reinforcing bar splices were tested under monotonic loading. Abstract: An experimental study was performed to evaluate the applicability of ACI 318 to the Class B splice of 600 MPa (87 ksi) reinforcing bars.If you enjoyed reading it, consider subscribing to be one of the first to get new emails on Thursdays (plus other goodies – e.g., dad jokes!). ![]() Perhaps Class A could be helpful in highly congested areas? I am not sure.īy the way, this is a rehash of an article I wrote in my weekly email newsletter, “Back of the Envelope" - where I teach you SE-related things in 5 minutes (or less), once every other week. Makes sense… but I believe the common practice is to use Class B and splice at a location of minimum stress anyway.Ĭlass A is generally avoided (as far as I know) since staggering requires extra labor and may be prone to errors. “The tension lap splice requirements encourage the location of splices away from regions of high tensile stress to locations where the area of steel provided is at least twice that required by analysis.” ![]() “The two-level lap splice requirements encourage splicing bars at points of minimum stress and staggering splices to improve behavior of critical details.” So why would anyone ever consider using that? Here is a fancy graphic that depicts the difference:Īs you can see, even though Class A requires less length, it needs to meet the As provided/required ratio, and it needs to be staggered. This is actually just a fancy way of saying that if you stagger your splice, the percent would be 50, and you’d be using Class A. What is the “maximum percent of As spliced within required lap length”? And if you provided at least double the amount needed, you are at the “>= 2.0” row. You run the analysis and see how much steel is required. Maximum percent of As spliced within required lap lengthįor the first one, “As,provided/As,required over length of splice,” it’s fairly straightforward: In this case, the two bars are “lapped” in the concrete by lap splice length.įor bars in tension, the lap splices can be classified as either Class A or Class B, and that’s where it gets slightly confusing.ĪCI 318 Table 25.5.2.1 (screenshot below) defines the two based on two parameters:Īs,provided/As,required over length of splice Lap splice, on the other hand, represents the connection required to consider two separate bars as a single continuous bar. I'm not going to go into details here, so some snippets below just FYI to refresh your memory. In other words, it’s the required embedment length such that when the bar is under tension, it will yield before it slips or breaks away from the concrete.ĪCI 318 Table 25.4.2.3 and Equation 25.4.2.4a shows how this is calculated. "Length of embedded reinforcement required to develop the design strength of reinforcement at a critical section." This is one most of us are familiar with. “CLASS B LAP LENGTH SHALL BE 1.3 TIMES THE DEVELOPMENT LENGTH”ĭevelopment length = Class A splice lengthĭevelopment length x 1.3 (or Class A splice length x 1.3) = Class B splice length. “UNLESS INDICATED OTHERWISE, USE THE CLASS “B” LAP SPLICE LENGTHS” “ALL SPLICES SHALL BE CLASS B TENSION LAP SPLICE U.N.O” “BAR SPLICE SCHEDULE IS BASED ON LAP CLASS B” You’ve probably seen this in various versions every time you see a lap splice length table or development length table of some sort: (Estimated read time: 3 minutes and 4 seconds)ĭevelopment Length vs. It’s one of those things that you say to yourself, “I feel like I should know this, and I kind of do, but not really…” I am talking about “development length” vs. Kind of know it but never really looked into it. Today, I am going to talk about something related to concrete reinforcing that you either: This is Back of the Envelope – the newsletter where I share things I learned (or relearned) recently, in 5 minutes or less.
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