I was designing a Mat foundation ,the thickness of my raft which i wanted was 350mm thickness and the depth of the beam to be 900mm or 800 mm depth with width of 1000m, but when i run the design, the mat and the beam fail under punching shear even if i try to increase the depth of the beam to 1500mm.But when i increase the depth of my raft to be 900mm with or without beam inside it, the punching shear check will pass.
Iam using Staad Pro Update 5.I have attached my model i need a help what is the reason behind
55375.Structure1_foundation.sfa
04548.Structure1.STD
You currently have 4 separate mats in the job named "MAT". Change it so that you have only 1 mat per job. Thus, create 4 different jobs, with each job having only one mat.
Also, in the past few months, a few defects have been corrected in punching shear checks for mats. So, install the latest version - 9.6.1.74
A similar question from you was answered at the discussion titled TRUSS DESIGN IN STAAD PRO CONNECT EDITION
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How does Staad Advanced Foundation compute shear on beam,i thought axial load on column goes directly on beam in the raft?may i get a detail manual example on how the software transmit column axial load to get shear on beam in raft foundation
Answer to the question posted on November 30 on shear in a beam
The program generates a STAAD FE model consisting of line members (by segmenting the beams) and finite elements (generated during meshing). Hence, loads are transferred to members using the stiffness method. The load acting from a column doesn't go entirely on the beam. Instead, the load is shared by all the elements and members meeting at the node.
A beam develops shear if its 2 ends undergo unequal displacements, or if a load is applied within the member span.
Thank you for the explanation but may you help me to elaborate with supporting calculation like the way you did on punching shear check and area of reinforcement ,with any specific values of axial load and moment from column to compute beam shear force.
When finite elements are involved, I do not know of any hand calculations that one can perform to show the manner in which loads are distributed to the various entities.
Ok what about the issue of a beam on expansion joint,to carry the two columns on the joint,as the shown on the picture attached above?how can i model that in staad advanced foundation for mat foundation
SFA works best when you have one mat per job. Without significant testing, it would be hard to recommend the program for designing physically separate mats connected by beams. I assume that due to the expansion joint, the 2 mats are physically separate.