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The flexural design of steel composite castellated beams according to AISC 360-16 is explained in detail under this title. Composite castellated beam design is done in two steps: Construction stage design and composite design.
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Symbols
Cb : The lateral-torsional buckling modification factor
Zx = Plastic section modulus about the x-axis, in.3 (mm3)
E: Modulus of elasticity of steel = 29,000 ksi (200 000 MPa)
Fy : Specified minimum yield stress of the type of steel being used, ksi
Fcr : Critical stress
K : Effective length factor
L: Laterally unbraced length of the member
Pr: Required axial force resistance for LRFD or ASD load combinations
Pc: Strength of axial compressive force available according to Section E
Mr: Required bending moment strength for LRFD or ASD load combinations
Mc: current bending moment strength according to Section F
r: Radius of gyration
λ: Width-to-thickness ratio for the element as defined in Section B4.1
λr : Limiting width-to-thickness ratio as defined in Table B4.1a
Lb : Length between points that are either braced against lateral displacement of the compression flange or braced against twist of the cross-section, in. (mm)
Lp : The limiting laterally unbraced length for the limit state of yielding, in. (mm)
Lr: The limiting unbraced length for the limit state of inelastic lateral-torsional buckling, in. (mm),
Mn : The nominal flexural strength
Mp : Plastic bending moment
Sx : Elastic section modulus taken about the x-axis, in.3 (mm3)
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Castellated Beam Sections
Castellated hexagonal, castellated circular, castellated octagonal, and angelina sections can be defined. Castellated hexagonal and castellated circular sections are designed.
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mm3)
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Composite castellated beam design is done in two steps: Construction stage design and composite design. The following conditions are checked in each design step.
Construction Stage Design
Construction stage design is done with the lowest design ratio value obtained according to the limit states given below.
Biaxial Bending
Gross and Net Area Shear Check
Horizontal Shear Check
Web Post Buckling Check
Vierendeel Bending Check
The construction stage design cross-section sample is given below.
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Composite Design
Composite castellated design is done with the lowest design ratio value obtained according to the limit states given below.
Gross and Net Area Shear Check
Horizontal Shear Check
Web Post Buckling Check
Vierendeel Bending Check
Deflection Check
The composite design cross-section sample is given below.
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Biaxial Bending and Axial Force
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Shear control with the gross area is the full whole web part of the castellated beam, while the shear control with the net area is calculated by considering the castellated beam's hollow section.
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Vierendeel Bending Control
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