Design model: Emir Engineering co.LTD (Turkey)
The technical support of our company received the task with the information about geometrical variability and errors of solution control from the structural engineers of the company Emir Engineering co.LTD (Turkey).
The fragment of the «decision protocol» is shown on the picture 1.
As you can see from the protocol, the task is quite impressive: 307634 nodes, 322352 elements, and the stiffness matrix amounted to 1,621,783 equations. 13 different load cases are specified in the calculation.
This calculation scheme was compiled using the "Assemble schemes" function from several calculation problems, that were solved successfully separately.
A detailed analysis of the design model showed that the geometric variability and control errors of the solution are associated with a large spread in the rigidity of the elements of the design model.
The method of spacing the median surfaces of the FE shells using bar elements of very high final rigidity is used to model the capitals in the floor slabs. These elements, having small dimensions and very high rigidity, led to the "bad conditionality" of the stiffness matrix of the whole scheme. This problem can be solved in two ways.
1. Reduce stiffness spread. For this problem, it is sufficient to reduce the value of bending stiffnesses for elements modeling the eccentricity of capitals by two orders of magnitude.
2. Apply another method for modeling capitals using absolutely rigid bodies.
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