ASD Design Procedure (9th Edition)

Using ASD requirements for the calculation of allowable stresses, with some modification to account for the different nature of Castellated beams, the following design checks are performed.

Shear on Gross Section

This is done by calculating the maximum shear along the span (this is usually one end or the other) from which the actual shear stress fv is calculated and compared with the allowable shear stress Fv per Eq (F4-1) or (F4-2) based on the h/tw of the gross section.

Shear on Net Section

This is done by calculating the maximum shear at any hole and splitting the shear between the top and the bottom tees, from which the actual shear stress fv is calculated and compared with the allowable shear stress Fv per Eq (F4-1) or (F4-2) based on the h/tw of each tee individually.

Horizontal Shear (through web post)

This is done by calculating the worst horizontal shear stress fv through any web post and comparing it with the allowable shear stress Fv which is given as 0.4Fy. The noncomposite beams and for the precomposite condition of composite beams the methodology is based on the third method given in Design of Welded Structures by Omer W. Blodgett, pp4.7-8 and 4.7-9. The composite condition is also checked. When the top piece is made from a different beam size than the bottom piece, the stress is based on the thinner of the web thicknesses of the top and bottom pieces.

Web Post Buckling

This is done by calculating the capacity of the web post against a buckling failure, and comparing it to the actual forces on the most critical web post.

Lateral Torsional Buckling / Unbraced Length

This check is done for Noncomposite C-Beam™ only. It is not done for Composite C-Beam since they are continuously braced by the deck, nor is it done for the precomposite condition. The actual bending stress fb and the allowable bending stress Fb are based on the gross cross section of the Castellated beam. When the unbraced length is greater than Lc, Fb calculated per (F1-6) or (F1-7), and it is reduced by Qs to account for slenderness. The section is not allowed if $h / t_{w} > 760 / \sqrt{F_{b}}$ .

Vierendeel Bending

This check examines the combined effects of the bending and axial forces on the top and bottom tees resulting from the shear and moments on the beam. The Vierendeel Bending check is performed on every tee, and is performed for both the precomposite section and the composite section for composite C-Beam. The axial force and bending moment on the tee is calculated, from which the actual axial stress fa and the actual bending stress fb are calculated. The allowable axial stress Fa and the allowable bending stress Fb are based on the properties of the tee. The interaction of the actual and allowable stresses is then calculated. The stresses on both the flange and the tip of the web are considered.