Question

For an i- beam shape factor is 1.12. The factor of safety in bending is 1.5. If the allowable stress is increased by 20% wind and earthquake loads then the load factor is

Answer 1

Answer:

Answer is 1.40

Explanation:

The factor of safety is given as F1 =

Yield stress/Allowable stress=1.5

When the allowable stress is increased by 20%, then factor of safety will be

F2=Yield stress/ 1.2×Allowable stress

⇒ F2=1/1.2×Yield stress/ Allowable stress

⇒ F2=1/1.2×1.5 1.25

Load factor = Shape factor × Factor of safety

= 1.12 × F2 = 1.12 × 1.25

= 1.40

Answer 2

• According to the question:

       Factor of safety in bending is 1.5 = $F_{x}$

       I- beam shape factor is = 1.12

       Allowable stress is increased by a percentage of = 20%

• Therfore, load factor is the product of I - beam shape determining factor and the factor of safety in bending.

• Since stress is increased we have to also multiply the load factor with the percentage value = 0.83 x 1/20 x 1.5

• Thus, the load factor = 1.55 (approx)