The development length of reinforcement is a critical parameter in structural concrete design, ensuring that reinforcing bars can adequately transfer stresses between the concrete and steel. Sectie 8.4 of EN 1992-1-1 provides the method for calculating development length to achieve proper anchorage of reinforcement. This ensures structural integrity, veiligheid, and serviceability under various loading conditions. The development length is influenced by bar size, beton sterkte, bond conditions, omslag, spatiëring, and whether the bar is in tension or compression.
The latest SkyCiv Foundation Design update supports standard hooked reinforcements, enabling precise development length checks. Users can now customize footing bar ends as straight bars, 90° hooks, or 180° hooks, ensuring flexibility for various design needs. This guide outlines the step-by-step process for determining the required anchorage length for pad footings following EN 1992-1-1 Sectie 8.4, considering relevant influencing factors to comply with code requirements.
Column Anchorage Length Check
Dowel bars in pad footings ensure a strong connection between the footing and columns, effectively transferring loads and maintaining structural integrity. Typisch, column pedestals are subjected to compression loads, and the required development length is calculated using the provisions under Section 8.4.
Sectie 8.4.3: Basic anchorage length (lb,rqd)
Sectie 8.4.4: Design anchorage length (lbd)
fbd = Ultimate bond stress (MPa)
σsd = Design stress of the bar at the position from where the anchorage is measured from (MPa)
db = Dowel bar diameter (mm)
Available depth (l)
The available depth should be greater than or equal to the calculated required embedment of the dowel bars. This depth is checked using Equations 2, then compared to the computed development length for the utility ratio.
\(l = t – (omslag + d_{b,X} + d_{b,z}) \) (Eq. 3)
Waarbij:
t = Footing Thickness (mm)
cover = Bottom concrete cover (mm)
db,X, db,z = Footing bar size in the x and z directions (mm)
Anchorage Length Check For Footing Reinforcements
The SkyCiv Foundation Design module allows users to specify bar end configurations as straight or hooked bars (90° or 180°).
Calculating the required development length for footing reinforcements directly influences the footing’s dimensions, ensuring they are adequate to anchor the reinforcement against tensile forces. Sectie 9.8.2.2 provides a guide on determining this tensile force which is then used in the calculation of anchorage length.
Similar to what was presented in Equations 1 en 2, the tension anchorage length check uses the same formula but with varying influencing factors.
Available Anchorage Length
\(l_{b} = x – omslag \) (Eq. 4)
\(l_{b} \geq l_{bd}\) (Eq. 5)
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BSc, MEng (Civiel)
