1. The Component Method (EN 1993-1-8)
Eurocode 3 Part 1-8 (EN 1993-1-8) evaluates joint behavior using the Component Method. Every structural connection is modeled as an assembly of basic springs representing elemental components: column web in tension, beam flange in compression, end-plate in bending, and bolts in tension or shear.
This approach allows engineers to calculate joint resistance (Mj,Rd), rotational stiffness (Sj,ini), and rotation capacity (φcd) in a unified framework.
2. Bolted Connection Verification
Bolts are categorized by grade (e.g., 8.8 or 10.9) and preloading status (Category A, B, C for shear; Category D, E for tension). For non-preloaded Category A bolts in shear, the design shear resistance per shear plane Fv,Rd is:
Where αv = 0.6 for Grade 8.8 (when shear plane passes through threaded portion) and γM2 = 1.25. The bearing resistance Fb,Rd of the connected plate is verified by:
When bolts experience simultaneous shear (Fv,Ed) and tension (Ft,Ed), the interaction criterion must be satisfied:
3. Fillet Weld Design (Directional Method)
EN 1993-1-8 provides two methods for weld design: the Directional Method and the Simplified Method. Under the Directional Method, stresses on the throat area (a · l) are resolved into normal stress perpendicular to the throat (σ⊥), normal stress parallel to throat (σ||), shear stress perpendicular to throat (τ⊥), and shear stress parallel to throat (τ||).
The weld is adequate if both criteria are satisfied:
Where correlation factor βw depends on steel grade (0.8 for S275, 0.85 for S355, 1.0 for S460).
4. Bolted End-Plate Moment Connections & T-Stubs
T-stub model idealization is used to evaluate equivalent tension resistance of end-plates and column flanges. Three failure modes are evaluated:
| Mode | Description | Governing Factor |
|---|---|---|
| Mode 1 | Complete yielding of the flange / end-plate | Plastic bending resistance of plate (prying action present) |
| Mode 2 | Bolt failure with yielding of the flange / end-plate | Combined bolt tension + reduced prying action |
| Mode 3 | Bolt failure alone | Tension resistance of bolt group (no prying) |
Key Design Rules
- 1
Edge Distances
Ensure e1 ≥ 1.2 d0 and e2 ≥ 1.2 d0 to avoid premature tear-out.
- 2
Stiffness Classification
Classify joints as Rigid, Semi-Rigid, or Nominally Pinned relative to beam stiffness EI/L.
- 3
Ductility & Detailing
In plastic analysis, ensure connection resistance exceeds member capacity to guarantee hinge formation in member.