Reinforce Column Splices correctly in Construction
A space between two bars is referred to as the overlapped or spliced column, as indicated by the terms overlapping length and lap length.
Lap splicing is a technique used to overlap two reinforcement bars. Loads are transferred securely from one member to another through the overlapping of reinforcement bars.
Reinforcement bars can be bought on the market in lengths up to 12 m. Reinforcement bars are joined together to obtain the required length for a structure larger than 12 m. Splicing or lapping uses this connection.
Depending on the method of laying the surface is staggered, welded, or provided via a couple. Column capping is equipped with lap splices, whose length will be determined by the concrete grade and steel reinforcement.
Lapping Column Zone
Three zones are formed based on the moment diagram for a column under lateral load. A maximum moment is applied to the center of a column by load, while no moment is applied to its ends.
Zones A and B of a column are categorized according to the maximum moment experienced by the upper and lower portions, respectively.
Zone-B of the column, therefore, becomes the lapping zone of it since it is less critical. For ductile detailing of RCC columns, ductile zones are designated to provide confining reinforcement.
Zone-A has a length like hc/4, if the clear distance is hc. Consequently, the height of Zone-B is calculated by (hc- (h/4 + hc/4)) = hc/2.
Lap Splices for Column
1. If the bar is greater than 36 mm, lapping is not used. Welded connections or welding with reinforcing helices can use for larger bars.
2. There is no lapping provided on tension zones such as Zone-A.
3. For column reinforcement, the general lap length is greater than the development length Ld and the reinforcement bar diameter?d?. In the absence of lap length values by the structural designer, this value is taken into consideration.
4. As the lap length increases, the lateral reinforcement and links get closer in proximity. With the ductile reinforcement concept, the top and bottom of the column are also reinforced with a close-spaced special confining reinforcement.
5. Lap lengths are calculated for bars of different diameters separately when they are to lap. The bar of smaller diameter will have a longer lap length.
6. In this area, there is the greatest amount of stress, so column-beam lapping must be avoided.
7. To prevent adjacent rebar from being lapped in succession, tops of adjacent rebar must be provided alternately.
8. The rebar are staggered and lapped correctly to preserve the clear cover of the column.
9. You must provide a lapping length of at least 75 mm.
10. Lapping two bars of different diameters is accomplished by measuring the lap length that corresponds to the smaller diameter bar.
Crank Length for Reinforcement
That is the length of the reinforcement that is bent to maintain the cover's clarity. Most crank slopes are set at one to ten, and the crank consists of 300mm at the minimum.
The crank length is equal to (D1+D2+5)*10 mm, where Diameter D1 is for the smaller bar and diameter D2 is for the longest bar.
To learn more, watch the following video tutorial.
Video Source: IBU Learning
Purpose
Reinforcement bars can be bought on the market in lengths up to 12 m. The length of reinforcement required for structures larger than 12 m is reached by connecting two or more vertical bars. The connection is made by lapping. Reinforcement bars are layered from one on top of the other to transfer loads securely.
