Concrete Deflection

Background information on deflection calculations for concrete structures.

Calculation Method

Concrete deflection is calculated according to Eurocode 2: EN 1992-1-1.

Factors Affecting Deflection

• Cracking - Reduced stiffness due to cracking in tension zones
• Creep - Long-term deformation under sustained load
• Shrinkage - Deformation due to concrete shrinkage

Effective Moment of Inertia

The effective moment of inertia accounts for:

• Uncracked section stiffness
• Cracked section stiffness
• Degree of cracking

Deflection Limits

Standard deflection limits according to Eurocode 2:

• Active deflection: L/500
• Total deflection: L/250

Where L is the span length.

Long-term Effects

Long-term deflection multiplier accounts for:

• Creep coefficient (φ)
• Shrinkage effects
• Reinforcement ratio