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Robot Structural Analysis

Active Contributor
Posts: 47
Registered: ‎05-14-2012
Accepted Solution

mat foundation

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11-28-2012 05:33 AM


for a mat foundation (plan) found the soil bearing capacity by setting the  soil parameters at slab thickess at Kz=1kn/m^3.

Calculated the avarage soil reaction for strips of the mat, but not succiding finding the shear forces and bending moments in the strips.

The bending moments manually are calculated as resting on soil, no supports, so actions from the columns and reactions from the soil, is the a way to do this in RSA? I am attaching the model also.


Thank you in advance

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Posts: 5,115
Registered: ‎12-17-2010

Re: mat foundation

11-28-2012 06:21 AM in reply to: alb2
  • The comparison of the results in not obvious as the book uses the beam model disregarding any bi-directional behavior of the raft foundation and assumes that the load distribution from point forces is 'uniform' across the beam.


I defined one more cut at the end of the 4.25 m wide strap and assumed that the change of values of bending moments is linear (which obviously is not true).


The moment over the middle column could be roughly approximated as:

0.5*(1259.98+213.31)*4.25 = 3130.74 kNm (compared to 2660.5)


The moment in the first span:

0.5*(244.39+98.57)*4.15 = 728.79 kNm (compared to 503)


As you can see looking at the 1/2 cut defined in the middle of the strap the values are different than the average between its ends so the 'total' value of bending for the strap is not exactly the 'average' value I calculated making the linear approximation.


e,g. 0.5*(1259+400)*0.5*4.25 + 0.5*(400+213)*0.5*4.25 = 2414 (2660.5)


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Artur Kosakowski
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