Shear Lug Design Calculator - Indian Standards

Shear Lug Design Calculator

Indian Standards (IS 456, IS 800, IS 1893-Part 4) – 2025 Practice

Input Parameters

Normal Compression Force (N)	kN
Shear Force X-direction (Vux)	kN
Shear Force Y-direction (Vuy)	kN
Concrete Grade (fck)	MPa
Steel Yield Strength (Shear Lug) fy	MPa
Base Plate Size (A × B)	× mm
Grout Thickness (g)	mm
Shear Lug Height (hsl)	mm
Shear Lug Width (bf)	mm
Shear Lug Web Thickness (tw)	mm
Shear Lug Flange Thickness (tf)	mm
Section Modulus Sx	mm³
Section Modulus Sy	mm³
Anchor Bolt Diameter	mm
No. of Anchor Bolts

Theoretical Background & Design Methodology

This calculator evaluates the adequacy of a shear lug for transferring horizontal shear forces from a steel column base plate to the concrete foundation as per Indian Standards.

Key Design Steps (as implemented in the tool)

1. Friction Resistance:
\( V_{\text{friction}} = \mu \times N \) where \(\mu = 0.40\)

2. Net Shear on Lug:
\( V_{\text{net-x}} = \max(0, V_{ux} - V_{\text{friction}}) \)
\( V_{\text{net-y}} = \max(0, V_{uy} - V_{\text{friction}}) \)

3. Concrete Bearing Capacity:
Permissible bearing stress = \( 0.6 f_{ck} \)
Effective area = \( b_f \times h_{sl} \)
\( V_{\text{bearing}} = 0.6 f_{ck} \times A_{ef} / 1000 \)

4. Shear Capacity of Lug Web (IS 800 WSM):
\( \tau_v = 0.4 f_y \)
\( V_{\text{shear,web}} = 0.4 f_y \times (h_{sl} \times t_w) / 1000 \)

5. Bending Check:
Eccentricity \( e = 0.5 h_{sl} + g \)
\( M_u = V_u \times e \times 10^{-6} \) kN·m
Allowable bending stress = \( 0.66 f_y \)

Important Notes from Indian Practice

• Friction coefficient 0.40 is commonly used for grouted base plates.
• Bearing area is taken conservatively without dispersion.
• Working Stress Method (WSM) is used for steel lug design.
• Provide full penetration welds between lug and base plate.
• Confinement reinforcement (ties) around the lug pocket is recommended.

Disclaimer: This tool is for preliminary design and learning purposes. Final design must be reviewed and certified by a qualified structural engineer as per latest Indian Standards.