Rebar Grid Weight with Lapping Factors

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Equation / Last modified by KurtHeckman on 2017/06/15 17:00
`"Length"_"Rebar" = `
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The Rebar Grid Weight with Lapping Factors calculator computes theslab 1.png total weight of rebar in one or more mats of rebar in a concrete slab including lapping.

INSTRUCTIONS: Choose your preferred units and enter the following:

  • (L) The length of the slab
  • (W) The width of the slab 
  • (oC) The on-center spacing of the rebar spacing (defaults 18")  
  • (i) The inset distance from the side of the slab to the rebar grid (default of 3").
  • (m) The number of mats.  (default is one).
  • (rS) The size of rebar  which is used to compute the diameter for lapping considerations.
  • (rL) The length of the pre-cut reinforcement bars being used to determine if lapping is required.
  • (LF)  The lapping factor is the multiple of the diameter of the rebar to specify the lapping distance.  40 (default) and 60 are common.

Weight of Rebar: The calculator returns the weight of rebar in pounds.   However, this can be automatically converted into other weight units (e.g. kilograms or tons) via the pull-down menu.  Tocompute the length of reinforcement bars, use the Rebar LENGTH Calculator.

General Information

The user inputs are as follows:slabtotalgridrebarlength-illustration.png                   Rebar Grid (one mat) with no lapping  

  • The slab is defined by a length (l) and a width (w). 
  • The user enters an on-center (oC) for the rebar spacing, which defaults to 18".  
  • The user can also input an inset (i) for the distance from the side of the slab to the first row of the rebar grid,  The inset has a default of 3".
  • The user can specify the number of mats (m).  The default is one.
  • The user can specify the length of the pre-cut reinforcement bars being used (rL) which is used to determine if lapping is required.
  • The user can specify the size of rebar (rS).  This is the size of rebar which is used to compute the diameter for lapping considerations.
  • The user can specify the lapping factor(lF).  This is the multiple of the diameter of the rebar to specify the lapping distance.  40 (default) and 60 are common.

Description

This calculator computes the length of a simple rectangular grid of rebar.RebarSpec.jpg Rebar Specifications   It employs lapping for dimensions (length or width) in excess of the user specified rebar lengths (rL: see Lapping below).  A tolerance for determining the need for an extra rebar is set to less than one inch  for a spacing fraction above the tolerance.

Lapping

When the dimensions of your slab or wall exceed the length of a single piece of rebar, it is required to lap bars and tie them to create the added length.  There are a few considerations.  First, the length of the lap is often specified as 40 times the diameter of the rebar.  In this case, 40 is lapping factor.  60 is also a common factor, but the engineering specifications should always be applied.  See these YouTube videos to better understand rebar lap:

Second, the typical length of rebar is 40' and 60' in the United States.

See how much the rebar will weigh - Rebar Weight