Beam Design & Plate Girders | Design of Steel Structures - Civil Engineering (CE) PDF Download

Beams

Design for Bending

Effective Length of Compression Flange

Check for Shear

• Max permissible, shear stress t_vm = 0.45 f_y
• For design purpose, the above condition is deemed to be satisfied if the average shear stress in an unstiffened member calculated on the cross-section of the web does not exceed the value T_va = 0.4 f_y

Built‐up Beams

• Symmetrical built-up beams
  each cover plate
  
  where z₁ = Section modulus of rolled I section available.
  d = depth of the beam
• Unsymmetrical built-up beams
  The area of cover plates
  

Gantry Girders

Where L = span of crane runway girder

Axial Compression + Bending

• Members subjected to axis! compression and bending are proportional to satisfy the Eq. (1)
  
  However, if the ratio σ_ac.cal/σ_ac is less than 0.15, Eq (ii) may be used in lieu of Eq. (i)
  

Plate Girders

• Economic depth of the girder D = 1.1

Design of Web

• Average shear stress in the web  permissible average shear stress, t_vα

Web stiffeners

•  and 85. No stiffener is required. 
•  and 200. Vertical stiffeners are provided.
•  and 250. Vertical
•  or 400. 

Permissible Bending Stress

• The maximum tensile stress is calculated on the net flange area i.e.,
  permissible bending stress in tension, σ_bt

Curtailment of Flange Plates

• Length of the plate to be curtailed
  
  Where, I = span, n = no. of plates to be curtailed counting 1, 2, 3,.... from outer plate. A_we = effective web area

Web Stiffeners

• Bending moments on stiffener due to eccentricity of vertical loading with respect to  vertical axis of the web.
  
• Lateral loading on stiffener
  
  c = actual distance between vertical stiffeners
• For second horizontal stiiener at the neutral axis.
  I ≥ d₂ x t³
• Stiffeners are connected to web to withstand a shearing force not less than kN/m, where h = outstand of stiffener in mm.

Load Bearing Stiffeners

• Bearing Stiffeners are provided at the points of concentrated loads and at supports.
• Where these stiffeners are to provide restraints against torsion of the plate girder at the ends,