Small Foundation Design calculation (Simple Design)

In this article we are going to learn how to calculate the simple foundation design.

 

 

  • Loads
  1. Weight of Panel             :           25 Ton (OR) 2.5 KN
  2. Size of Foundation`             :           900 (L) x 750 (W) x 750 (D) mm.
  3. Volume of Foundation             :           90x.075×0.75 = 0.5063 M3
  4. Unit Weight of Concrete             :           5 Ton/M3
  5. Self weight of Foundation :           5063 Cum @ 2.50 Ton/ M3 =1.266 Tons

(OR) 12.66 KN

  • Soil Data
  1. Assuming existing soil Allowable (permissible) bearing capacity : 100 KN/ M2

(considered in the obscene of Geo technical Investigation Recommendation)

  • Check for Soil Stress
  1. Total weight including Panel : 12.66+02.5 = 15.16 KN
  2. Multiplying factor             :           30
  1. Total factored weight (W) :           16 KN x 1.30 = 19.71 KN
  2. Area of Panel foundation (A) :           90 x 0.75 = 0.675 M2
  3. Soil stress (W/A)                           :           71/0.675 = 29.20 KN/ M2

Allowable bearing pressure          :           100 KN/ M2

Since, Applied bearing pressure < Allowable bearing pressure.

Panel foundation is safe.

 

  • Check for Sliding
  1. Design service load (Total vertical force of foundation) :           66 KN
  2. Total horizontal Force (Htotol) :           20% of Vertical force

:           = 12.66 x 20%=2.532     KN

  1. Foundation depth :           75 m
  2. Design service moment :           532 x 0.75 =  1.899 KN.m
  3. Restoring force :           4 x Total vertical force

:           0.4 x 12.66 = 5.064 KN

  1. Factor of safety against sliding :           Restoring Force/Total Horizontal force

:           5.064/2.532 = 2

:           >1.5

Hence, foundation is safe against sliding.

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