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[GEN/Design]How to Select and Design RC Members as Single or Double Beams in Automatic Design

Question

Is it possible to design beams with double reinforcing bars?

In the GEN program, for beam members, it is indeed possible to design them as double reinforcing beams. This means that by default, the design is done for single reinforcing beams, but under specific user-defined conditions, the design can be adjusted to accommodate double reinforcing beams.

This function is available when the Doubly Rebar option is checked on in Design > Concrete Design Parameter > Design Criteria for Rebars (by Member).

When this option is unchecked, the program will perform the design for single reinforcing beams. However, when the option is checked, if the required amount of rebars for the beam is greater than k * ρmax, the design will be adjusted for a double reinforcing beam. In this case, the value of k is a coefficient that determines the amount of rebars needed for the double reinforcing beam design and can be set between 0.5 to 1.

This value is not prescribed by the standard and is a coefficient that determines how much rebar the user wishes to design for a beam that will not be designed as a single beam, or a double beam that will not be designed as a single beam.

ρmax represents the maximum rebar ratio for single reinforcing beam design and varies based on different design codes:

KCI-USD 03                  : 0.75 * ρb(balanced rebar ratio)

KCI-USD07, KCI-USD12 : εt=0.004 (Strain at ultimate state of the outermost tension rebar)

KDS 41 30 : 2018         : εt=0.004 (Strain at ultimate state of the outermost tension rebar)

KDS 14 20 20 :2018 Concrete Structure Beam and Compression Design Standard

The minimum allowable deformation (ε_a,min) for beam members is 0.004 for rebar with a yield strength of 400MPa or lower. For rebar with a yield strength exceeding 400MPa, the minimum allowable deformation is set to twice the yield strain of the rebar.

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