The correct position for column rebar laps, or the location where two pieces of reinforcing bars are joined together, depends on the design requirements and structural considerations. Generally, column rebar laps should be placed at specific locations to ensure proper load transfer and structural integrity. Here's an explanation with an example:
Vertical Rebar Laps: In columns, the vertical reinforcing bars (commonly referred to as longitudinal bars) are extended vertically to the full height of the column. The laps for these bars are typically positioned at specific points to provide continuity and transfer load effectively. The exact positioning of the laps may vary based on design specifications, but common locations include: a. At column intersections: When multiple vertical bars intersect at a column, it is common to place the laps at these intersections. This helps distribute the load across the various bars and maintains the required strength. b. Above beam intersections: If the column is supporting beams, the laps are often positioned above the points where the beams intersect the column. This ensures that the load from the beams is adequately transferred to the column. c. At mid-height or critical sections: In some cases, the laps may be located at mid-height or specific critical sections of the column. This can be determined based on the structural design requirements, such as where higher stress concentrations are expected.
Horizontal Rebar Laps: Horizontal rebar laps, also known as tie bars or lateral reinforcement, are typically placed at specific intervals around the circumference of the column. These laps help enhance the column's resistance to lateral forces, such as seismic or wind loads. The following examples illustrate common locations for horizontal rebar laps: a. Regular spacing along the height: The laps are often evenly spaced along the column's height, adhering to the design requirements and specified lap lengths. This ensures uniform lateral reinforcement and effective load transfer. b. Above and below beam intersections: Horizontal rebar laps are commonly positioned above and below the points where beams intersect the column. This helps reinforce the critical regions where bending moments are concentrated. c. At critical sections or joints: Depending on the structural analysis, specific critical sections or joint locations might require additional horizontal reinforcement. Laps can be placed at these locations to enhance the column's performance under various loading conditions.
It's important to note that the exact positioning of rebar laps should be determined by the project's structural engineer, following the applicable design codes and standards. The laps should be adequately detailed and clearly indicated in the bar bending schedule (BBS) to guide the construction team during reinforcement placement. Regular inspections and quality control measures should be implemented to ensure proper lap lengths, splice techniques, and adequate concrete cover for the reinforcement laps.