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How does ideCAD calculate time-dependent deflections according to ACI 318-19?


Tip
  • Time-Dependent Deflection is calculated automatically.


Notation

As'= 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 As' to bd
ξ = time-dependent favtor for sustained load
λΔ = multiplier used for additional deflection due to long-term effects


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 λΔ.

Mathinline
hostConfluence:2933017122
body--uriencoded--$$ \lambda_%7B\Delta%7D = \frac%7B\xi%7D%7B1+50\rho'%7D\; \; \; \; \; \; \; \; \; \; \; \;(24.2.4.1.1) $$

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

Time-dependent factor ξ is 2.0 in accordance with ACI Table 24.2.4.1.3