Category: Structure & materials
Prepared by Eng. Ahmed Fathy, Projects Manager ·
Definition
A lap splice is the length over which two bars overlap to transfer force from one to the other where a single bar is not long enough. The structural designer sets it by bar size, stress type and concrete grade, and it is commonly 40 to 50 times the bar diameter.
Why it matters on a project
A short lap is a serious weak point, and laps grouped at one section weaken the member. Staggering them correctly is part of steel inspection before the pour.
Measurement and pricing
Included in the steel weight in the bar bending schedule and affects waste. Each lap adds its length to the bar length.
Worked example
A 16 mm bar with a lap of 50 diameters: 50 × 16 = 800 mm, so 0.8 m is added for each lap in the bar bending schedule.
Common mistake
Placing all laps at the same section of a beam or column instead of staggering them, or shortening laps to save steel.
Frequently asked questions
Can welding replace a lap?
Welded or mechanical splices are possible under specific conditions and specifications with the designer's approval, and not with non-weldable steel.
Where should laps not go?
Away from zones of maximum moment and beam column joints, with the designer setting the allowed zones.
Related terms
- Reinforcement (rebar)Steel bars placed inside concrete per bar-bending schedules to strengthen structural elements.
- Bar bending schedule (BBS)A schedule listing the diameter, length, shape and number of reinforcement bars per element.
- ColumnA vertical element that carries slab and beam loads down to the footings.
- BeamA horizontal element that carries the slab and transfers its loads to the columns.
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