I am doing the analysis and design of a twenty story reinforced concrete building with a core shear wall at the center. During linear analysis the modal periods were worked out using shell elements to model the shear wall. During the nonlinear phase, the shell elements were replaced with nonlinear shell-fibre elements. However the modal ;periods in this case were found to be altogether different (very much larger)from the one obtained using shell elements,
Can anyone help to resolve the crisis..???
Periods in the nonlinear phase is larger due to smaller stiffness of shell-fiber elements than linear shell elements.
ACI318 recommends using stiffness modifiers for inertia to take into account cracks and material non linearity for concrete elements in linear analysis. I remember it uses 70% of shear walls inertia. Try this modifier.
Shell element to fiber element how is the connection. In between type of contact also plays very vital role
There is nothing like a shell element to fibre element connection..!!!
Fibres represent only discretization of shell elements in transverse and long.dirn for the definition of healthy integration points.
Furthet this is not a contact problem of course...!!!!!
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