The anchorage and lap lengths presented in the tables assume full utilization of the reinforcement bar yield stress, i.e.The favorable effect of these factors is described in EN §8.4.4. The required anchorage and lap length may be further reduced when one or more of the following conditions are present: a) adequate concrete cover, b) adequate confinement by transverse reinforcement, c) welded transverse bars along the anchorage length, and d) compressive pressure transverse to the plane of splitting. The anchorage and lap lengths presented in the tables are conservative values for ribbed bars with diameter Φ ≤ 32 mm.The different bond regions are shown in the figure above that is reproduced from EN Figure 8.2. 'Poor' bond conditions are applicable for all other cases and also for bars in structural elements built with slip-forms, unless it can be shown that 'good' bond conditions exist. 'Good' bond conditions are applicable when any of the following conditions is fulfilled: a) Vertical bars or almost vertical bars inclined at an angle 45° ≤ α ≤ 90° from the horizontal, b) bars that are located up to 250 mm from the bottom of the formwork for elements with height h ≤ 600 mm, or c) bars that are located at least 300 mm from the free surface during concreting for elements with height h > 600 mm.When adequate cover is not present the anchorage and lap lengths for other-than-straight bars in compression should be used instead. The condition of adequate cover c d > 3 Φ for other-than-straight bars in tension is defined in EN Figure 8.3.The detailing rules and the equivalent anchorage length for each of these standard shapes are defined in EN Figure 8.1. Other-than-straight bar shapes include a) standard bend, b) standard hook, and c) standard loop.The lapping length provided must not be less than 75 mm.The rebars are staggered and lapped correctly so that they maintain the clear cover of the column.The lapping must be provided alternatively so that the lapping of adjacent rebars does not come in a sequence.The lapping must not be performed at the column-beam junction because the area experiences maximum stress.When bars of two different diameters are to be lapped, the lap length is calculated for the bar with the smaller diameter.As per the ductile reinforcement concept, closely spaced special confined reinforcement is also provided at a distance l o from the top and bottom of the column, as shown in Figure-3. The lateral reinforcement or the links are provided closely in the lap length region.This value is considered if the structural designer does not provide a lap length value. The general lap length for column reinforcement is the greater of development length L d and 30d, where ‘d’ is the diameter of the reinforcement bar.Lapping is not provided on the tension zones (Zone-A).For larger bars, connections can be made either using welding, couplers, or welding with helical reinforcement. ![]()
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