the HingeLength of BeamWithHinges Element

[wunico]

i found the hingelength decide the result of analysis in BeamWithHinges Element.how to choose the length of hinge normally? the hingelength is length of hinge or the ratio of hinge's length to element's length?

[wunico]

when i use the beamwithhinges element to define a cantilever.the hinges length is 0.6m,the cantilever length is 6m.according to the manual"HingeLength:ratio of hinge length to total element length at node",so the HingeLength should be 0.6/6=0.1.and we know the beamwithhinges element only have two integrator section.each section is at middle part of hinge.
when add gravity load -1KN at node 2,we can speculate that the moment of section1(left section of cantilever)should be 1*(6-0.3)=5.7KN*M;
but the result of section1 is 5.95.it happen equal to the moment when the hinges length is 0.1m.
so i think HingeLength is not ratio of hinge length to total element length at node,it should be the real length of hinge.

[berktaftali]

It used to be the ratio in the earlier versions. As far as the latest version goes, it is the actual hinge length, not the ratio...

[Rocky]

I think the length is to a certain extent related to the material. If the material is a elasto-perfect plastic one, the length is sometimes like a magnitude of the height of the crosssection. However, if the material is a hardening one, the length should be the full length of the element.

[Rocky]

Mr. Berk Taftali:
I found in the version of 1.6.2, in the definition of beamwithhinges,
the ratio is still used......

[berktaftali]

I'm looking at the source code and it reads

Changing BWH input to actual hinge length

for the latest change...

[silvia]

Berk is right, it is the actual hinge length. this was changed in released 1.6.2 or slightly before.
please refer to the manual:
http://opensees.berkeley.edu/OpenSees/m ... sermanual/
under nonlinear beam-columnelements

Beam With Hinges Element

This command is used to construct a beamWithHinges element object, which is based on the non-iterative (or iterative) flexibility formulation, and considers plasticity to be concentrated over specified hinge lengths at the element ends.

The arguments for the construction of the element depend on the dimension of the problem, ndm.

For a two-dimensional problem:

element beamWithHinges $eleTag $iNode $jNode $secTagI $HingeLengthI $secTagJ $HingeLengthJ $E $A $Iz $transfTag <-mass $massDens> <-iter $maxIters $tol>

For a three-dimensional problem:

element beamWithHinges $eleTag $iNode $jNode $secTagI $HingeLengthI $secTagJ $HingeLengthJ $E $A $Iz $Iy $G $J $transfTag <-mass $massDens> <-iter $maxIters $tol>



$eleTag


unique element object tag

$iNode


$jNode


end nodes

$secTagI


identifier for previously-defined section object corresponding to node I

$HingeLengthI


hinge length at node I

$secTagJ


identifier for previously-defined section object corresponding to node J

$HingeLengthJ


hinge length at node J

$E


Young's Modulus

$A


area of element cross-section

$Iz


section moment of inertia about the section local z-axis

$Iy


section moment of inertia about the section local y-axis

$G


Shear Modulus

$J


torsional moment of inertia of cross section

$transfTag


identifier for previously-defined coordinate-transformation (CrdTransf) object

$massDens


element mass density (per unit length), from which a lumped-mass matrix is formed (optional, default=0.0)

$maxIters


maximum number of iterations to undertake to satisfy element compatibility (optional, default=1)

$tol


tolerance for satisfaction of element compatibility (optional, default=10-16)

The -iter switch enables the iterative form of the flexibility formulation. Note that the iterative form can improve the rate of global convergence at the expense of more local element computation.

NOTE: The elastic properties are integrated only over the beam interior, which is considered to be linear-elastic. Forces and deformations of the inelastic regions are sampled at the hinge midpoints, using mid-point integration.

The valid queries to a beamWithHinges element when creating an ElementRecorder object are 'force,' 'stiffness,' 'rotation' (hinge rotation), or 'section $secNum secArg1 secArg2...' Where $secNum refers to the integration point whose data is to be output.

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