Fibre section macroelement definition - eesd-epfl/OpenSees GitHub Wiki
The sectional response of the macroelement can also be assigned through a generic fibre section model, which needs to be defined before the element declaration. If a standard Gambarotta-Lagomarsino model is used for shear, the input string is as follows:
-fiberSection $secI $secE $secJ $h $L $t $E $G $fc $mu $c $Gc $beta
Where:
| secI | tag of the section model for the base interface |
| secE | tag of the section model for the element interface |
| secJ | tag of the section model for the end interface |
If, otherwise, the user wants to apply a generic phenomenological law for shear, in combination with a fiber section model for the flexural interfaces, a different input structure can be used. The generic shear model specified here can be any uniaxial material model, whose response will be uncoupled from the axial forces applied to the element.
-fiberSectionShearModel1d $secI $secE $secJ $shearIP $shearOOP $h
Where:
| secI | tag of the section model for the base interface |
| secE | tag of the section model for the element interface |
| secJ | tag of the section model for the end interface |
| shearIP | tag of the uniaxial material defining the in-plane shear response |
| shearOOP | tag of the uniaxial material defining the out-of-plane shear response |
As an example of uniaxial material model for the shear response, the Ibarra-Medina-Krawinkler model describes a complex hysteretic response of elements showing limited displacement capacity and strength and stiffness degradation in the post-peak branch and after repeated cycles.
All remaining parameters have the same meaning explained in the Tremuri-equivalent initialisation.
The automatically assigned weights are the ones of the “–tremuri” initialisation (i.e., 0.495h to the end sections and 0.01h to the central section). In order to obtain a correct elastic response they can be imposed manually equal to 1/6h and 2/3h, respectively.
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