Expert: Dr. Abdulaziz Jarkas - 4/27/2007

Question
how would you calculate the area of a strip foundation with the allowing bearing pressure of the sub soil being 150 KN/m2 and the internal column load is 500KN and the external column load 230KN. The foundations are 2.5 m below groun level and the water rabel is 2m below ground level.

Answer
Dear Said,

First, you need to find the resultant load and location by summing moment at, say, one of the edges of the foundation. To do this, assume a length.

Having located the resultant load, based on the soil capacity, you can determine the required area of the footing. Once the final length and width are known, use the soil reaction to model the footing to safely resist the bending moment and shear forces. You may also want to check punching shear to determine the adequacy of the thickness.

For more information, please consult any reinforced concrete design textbook.

Hope this helps!

Dr. Jarkas