- #1

LDC1972

- 65

- 0

**Second moment of area "I" and deflecton relationship**

## Homework Statement

What I value will halve the beam deflection

## Homework Equations

I = bd^3 / 12

and

y max = - 5wL^4 / 384EI

## The Attempt at a Solution

Transpose y max = - 5wL^4 / 384EI to:

I = - 5wL^4 / 384Ey max

This makes the value of I (2nd moment of area) double to achieve a halved deflection. Is this just a commonly known relationship?

Obviously I'm not inferring that the beam CSA be doubled, only 'I', and I'm also aware that when thinking of CSA, it takes approximately 26% of a rectangular beam depth increase to halve deflection.