Calculation of Immediate Deflections per ACI 318-19 with ideCAD

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

• Immediate Deflection is calculated automatically

Notation

E_c = modulus of elasticity of concrete, psi
f_r = modulus of rupture of concrete, psi
f_c^' = specified compressive strength of concrete, psi
I_cr = moment of inertia of cracked section transformed to concrete, in⁴
I_e = effective moment of inertia for calculation of deflection, in⁴
I_g = moment of inertia of gross concrete section about controidal axis, neglecting reinforcement, in⁴
M_a = maximum moment in member due to service loads at stage deflection is calculated, in.-lb
M_cr = cracking moment, in.-lb
y_t = distance from centroidal axis of gross section, neglecting reinforcement, to tension surface, in.
w_c = density, unit weight, of normalweight concrete, lb/ft³

According to ACI 24.2.3.1, Immediate deflection is calculated using elastic deflection formulas, considering the effects of cracking and reinforcement on member stiffness.

According to ACI 24.2.3.4 Modulüs of elasticity, E_c is calculated in accordance with the following equation.

According to ACI 24.2.3.5, the effective moment of inertia I_e is calculated in accordance with the following equation and ACI Table 24.2.3.5.

According to ACI 24.2.3.6, continuous one-way slabs and beams, I_e can be taken as the average of values obtained from ACI Table 24.2.3.5. For the critical positive and negative moment sections.

According to ACI 24.2.3.7 for prismatic one-way slabs and beams, I_e can be taken as the average of values obtained from ACI Table 24.2.3.5. At midspan for simple and continuous spans and at support for cantilevers.

Next Topic

Calculation of Time-Dependent Deflections per ACI 318-19 with ideCAD

Related Topics

• Maximum Permissible Calculated Deflections per ACI 318-19 with ideCAD