Hello,
I recently verified the foundation design for a Combined Foundation by using COMBINED type in the General Foundation Mode of STAAD Foundation Advanced and found the results matching with manual calculations except for punching check. Now I am doing the verification of the same foundation by creating it in MAT. Though I have analysed the same, the results were not matching with the results obtained when designed as COMBINED type.
Input data for both are the same except that instead of 30.4 T/m2 Gross pressure in COMBINED, the subgrade modulus in MAT has been taken as 7450kN/m2/m for 40mm all. settlement (25t/m2 net + 3m soil wt @1.8t/m3).
In order to compare the results and jump to a conclusion, I need help in understanding the results available for MAT Foundation. I require clarifications on the following:
1.) The governing moments for the concrete design should be relative to the values shown in Plate Stress Summary. Say Governing moment for Top Mat Long Dir should be a derivative from Max MX plate stress value. How is this calculation done?? (I understand that the governing moments are derived for various design points defined after analysis but even these values should be calculated based on plate stresses).
2.) The Node Displacement summary table shows nodal displacements for ultimate load cases. Shouldnt this be shown for service load cases??
I have attached the file for reference. I am working in SI units and in IS Code.
Awaiting assistance from the forum members
The answer to your first question is posted at
http://communities.bentley.com/products/structural/structural_analysis___design/w/structural_analysis_and_design__wiki/17844.the-moments-reported-in-the-calculation-sheet-for-design-of-mat-foundation-do-not-match-the-moments-reported-in-the-plate-stress-table
The answer to the question 2 is, the nodal displacements are reported for all cases irrespective of whether the cases are service or ultimate. However you may only consider the ones corresponding to the service cases, if you want to check whether displacements are within allowable limits.