Steel lateral systems: moment frame, braced frame, EBF, shear wall

One-line orientation

Steel buildings resist wind and earthquake forces with moment frames, braced frames, shear walls or cores, and sometimes staggered trusses. Compare them by stiffness, ductility, cost, and how much they obstruct the plan.

Key points

• Moment-resisting frame: uses designated beams, columns, and moment connections in the lateral-force-resisting frame. Other joints in the building may be simple connections.
  • Pros: architecturally open bays (no diagonals), flexible planning.
  • Cons: uses more steel; costly and labor-intensive (many moment connections).
• (Concentrically) braced frame: diagonal bracing in selected bays.
  • Pros: stiff and efficient; removes the need for moment connections across the whole frame.
  • Cons: braces obstruct openings in the braced bays; limited to those bays.
• Eccentrically braced frame (EBF): brace deliberately offset from the joint creates a short link beam that yields ductilely.
  • Pros: resists lateral seismic force without buckling the braces; good energy absorption / ductility for earthquake zones.
  • Cons: more complex than a standard braced frame.
• Shear wall / braced core: solid wall (often concrete) or braced core acting as a deep vertical cantilever.
  • Pros: very effective for high-rise rigidity; typically one per axis to brace both directions.
• Staggered truss system: story-deep trusses on alternating floors, each carrying the floor above.
  • Pros: maximizes usable floor area and distributes loads efficiently.

Steel lateral systems — two-story bay elevations

Same frame and side load; only the stabilizing element changes

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Key

• rigid joint
• pinned joint

A fifth system, the staggered truss, uses story-deep trusses on alternating floors — it maximizes clear floor space and is not drawn here.

Confusions / comparison

System	How it resists lateral load	Stiffness / ductility	Architectural impact
Moment frame	Rigid moment joints	Ductile; less stiff; most steel	Open bays, no diagonals
Concentrically braced frame	Diagonal braces at joints	Stiff, efficient; less ductile	Braces obstruct openings
Eccentrically braced frame (EBF)	Braces + yielding link beam	Stiff + ductile (seismic)	Braces present; some openness via link bay
Shear wall / core	Solid wall / braced core	Very stiff/rigid	Wall occupies the plane; great for high-rise
Staggered truss	Story-deep trusses, alternating floors	Efficient load distribution	Maximizes clear floor space

Related

→ Steel connections (this module): moment connections enable moment frames; bolted braces build braced frames · Steel shapes and members (this module): the W-shapes, HSS braces, and trusses used · Steel types and production (this module): ductility (low-carbon steel) underpins seismic performance.