However, both codes do allow distances larger than this limit so long as the splice length is increased accordingly. In this case, there's the question of which $\phi$ to use, and I honestly don't know. The Brazilian code NBR-6118 and EC2 both put that limit at $4\phi$ or 50 mm. The codes usually define a maximum distance between lapping rebars. The arrows roughly represent the furthest distance that tension needs to travel from each bar. In the figure below, for instance, assume this is a splice section, with the tension from the large red bars being transferred to the small blue ones. However, if you are splicing multiple rebars in the same position, going from a few large diameter bars to many smaller ones, an incremement to the splice length may be required. So there's no reason to design your splice to withstand a force larger than the yield strength of the smaller bar. If the tensile force is larger (say, equal to the yield strength of the larger rebar), then the smaller rebar will rupture immediately after the splice. Therefore, if you are splicing two rebars of different diameters, the maximum tensile force that can be transferred via the splice is equal to the yield strength of the smaller rebar. However, once the splice is over, all the tension from the first rebar has been transferred to the other one, which must also be capable of withstanding that same tension. Since concrete is very weak against tension, large lap lengths are required such that the stress at any point in the concrete is not excessive. What is a splice? It is when tension force in a rebar is transferred to the concrete via adhesion and then to another rebar. Where normal weight concrete is used, λ = 1.0.The use of the smaller diameter is theoretically correct. (d) Where lightweight concrete is used, λ shall not exceed 0.75 unless fct is specified (see 8.6.1). 6 and smaller bars and deformed wires, ψs = 0.8. However, the product ψtψe need not be greater than 1.7. For uncoated and zinc-coated (galvanized) reinforcement, ψe = 1.0. For all other epoxy-coated bars or wires, ψe = 1.2. (b) For epoxy-coated bars or wires with cover less than 3db, or clear spacing less than 6db, ψe = 1.5. of fresh concrete is cast below the development length or splice, ψt = 1.3. (a) Where horizontal reinforcement is placed such that more than 12 in. Please let me know my "gap" in my knowledge on the code.ġ2.2.4 - The factors used in the expressions for development of deformed bars and deformed wires in tension in 12.2 are as follows: I've no access to, nor knowledge on, ACI318-19 though. RE: Rebar lap splice transverse reinforcement additional to shear links Agent666 (Structural) 10 Jan 21 20:06īelow is copied from ACI318-08. To the OP, did you get your answer in amongst that? No need to double count the requirement, all transverse reinforcement contributes. R13, probably best to start your own thread in future if you have gaps in your knowledge of codes and principles involved rather than get into sideline conversations in others threads. There are also specific reductions to column splices allowed if you have sufficient confinement (CL 10.7.5.2.1). Other international codes all have similar reduction factors to the development lengths and hence splice lengths where there is sufficient confinement of splices. development length clauses, in particular the Ktr factor.Įarlier versions of ACI318 had similar reductions. For example in ACI318-19 look into 25.4.2. For example in ACI take a look at how this is calculated and you'll find the answer. The splice length is a function of the development length.
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