# Instantaneous Deflections (TS500)

For beams, Instantaneous Deflection is calculated automatically according to

**TS500 13.2.2**

For slabs, Immediate Deflection is calculated automatically according to

**TS500 13.2.2**

The deflection limit is determined by the user.

**Notation**

**E _{c}**

**Modulus of elasticity of concrete,**

_{ }=

**f**_{ctd}**Design tensile strength of concrete**

_{ }=

**I**_{cr}**Moment of inertia of cracked section transformed to concrete**

_{ }=

**I**_{ef}**Effective moment of inertia for calculation of deflection**

_{ }=

**I**_{c}**Moment of inertia of gross concrete section about controidal axis**

_{ }=

**l**_{n}**span length of beam or one-way slab;**

_{ }=

**M**_{cr}**cracking moment**

_{ }=

**M**_{max}**maximum moment in member due to service loads at stage deflection is calculated**

_{ }=**y**distance from centroidal axis of gross section, neglecting reinforcement, to tension surface

_{ }=*= Total deflection*

**δ**_{t}*= Instantaneous deflection*

**δ**_{i}*= Instantaneous deflection due to permanent loads*

**δ**_{ig}*= time-dependent favtor for sustained load*

**γ**_{t}*= multiplier used for additional deflection due to long-term effects*

**λ***= compression reinforcement ratio*

**ρ'**According to **TS500 13.2.2** Immediate deflections of reinforced concrete bending members under dead and live loads is calculated in accordance with the conditions given below.

If

moment of inertia of gross concrete section**M**_{max}≤ M_{cr}is used for deflection.**I**_{c}If

Effective moment of inertia**M**_{max}> M_{cr}is used for deflection.**I**_{ef }

It is calculated using and taking into account the support conditions. * M_{max} ≤ M_{cr}* corresponds to no cracking in the element and therefore the entire moment of inertia of gross concrete section

*, is used. In the case of*

**I**_{c}*, it corresponds to the cracking of the element and the deflection is calculated using Effective moment of inertia*

**M**_{max}> M_{cr}

**I**_{ef.}Effective moment of inertia * I_{ef}* is calculated in accordance with

**TS500 13.1.**

Allowable maximum deflections for flexural members are given in **TS500 Table 13.3**.

Deflection limits can be adjusted in the **Cracking / Deflection** tab of the **Beam Settings** window .

The deflection limits conditions can be adjusted in the **Deflection** tab of the **Tiling Settings** window .

Deflection results can be examined in the **Deflection & Crackings** tab of the **Beam Reinforcements **window .

**The** results of Instantaneous deflection and time-dependent deflection of beams can be examined from the **Beam Deflection and Crack Control** report.

The results of Instantaneous deflection and time-dependent deflection of the slabs can be examined from the **Slab Deflection Control** report.

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