Standard element definition - eesd-epfl/OpenSees GitHub Wiki
The standard use of the element is obtained through the flags “-pier”, “-spandrel”, or “-gable”. The sectional and shear models are created automatically and do not need to be defined before. For all three, the input structure is:
-pier $h $L $t $E $G $fc $mu $c $Gc $dropDrift $muR
-spandrel $h $L $t $E $G $fc $mu $c $Gc $dropDrift $muR
-gable $h $L $t $E $G $fc $mu $c $Gc $dropDrift $muR
Where:
| h | height of the macroelement (dimension in the axis direction, x) |
| L | length of the section (dimension in local direction y) |
| t | thickness of the section (dimension in local direction z) |
| E | Young’s modulus of masonry |
| G | Shear modulus of masonry |
| fc | compressive strength |
| mu | friction coefficient defining the peak strength |
| c | cohesion (Mohr-Coulomb force criterion) |
| Gc | parameter defining the pre-peak deformability in shear (see Penna et al. (2014)) |
| dropDrift | drift at 20% force capacity loss |
| muR | residual friction coefficient, defining residual capacity and hysteretic behaviour |
For spandrels, as in Tremuri, the height dimension is the horizontal, corresponding always to the dimension in the axis direction. All of these element types can have any orientation; the difference between the three types of elements implemented lays in the type of sectional behaviour that is defined:
-
pier: all three sections are equal, with a nonlinear behaviour; the nonlinear correction term accounting for crushing is applied. Zero tensile strength is applied to all sections, therefore if the element is subjected to traction it can indifferently open in any section (possible convergence/uniqueness of solution issues)
-
spandrel: the central section of the element is linear elastic, and the two end sections do not include the nonlinear correction term for crushing. An additional elastic contribution, equal to 1e−5 times the initial elastic stiffness, is always added to their response: this correction is meant to always provide a non-zero stiffness to the element, improving convergence and avoiding local collapse of elements for large deformations. If this approach is considered not adequate, or not necessary, spandrels can be modelled also with “pier” type elements without further modifications.
-
gable: equivalent to the “pier” type element in terms of section models. The in-plane dimension of the sections decreases with the height, being equal to L at the base section, 0.5L at the middle section and to 0.05L at the end section. The axis direction must point in the direction from the base to the top of the element. If a distributed mass is applied, a suitable mass distribution representing a triangular element is considered and the correct self weight can still be applied through an elemental load.
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