Calculation of Time-Dependent Deflections

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Notation

A_s' = area of the compression reinforcement, in²
b = width of compression face of member, in.
d = distance from extreme compression fiber to centroid of logitudinal tension reinforcement, in.
ρ' = ratio of A_s' to bd
ξ = time-dependent favtor for sustained load
λ_Δ = multiplier used for additional deflection due to long-term effects

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According to ACI 24.2.4.1.1. additional time-dependent deflection resulting from creep and shrinkage of flexural members can be calculated as the product of immediate deflection caused by sustained load and the factor λ_Δ.

ρ' is the ratio of the A_s' ,area of the compression reinforcement, to bd

Time-dependent factor ξ is calculated in accordance with ACI Table 24.2.4.1.3

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