ElasticPP Gap

[danusaht]

Hello,

I'm having problems with a Zero-Length element. When I tested it isolated, with only two points and a mass of 22000kg in a transient analysis, it works just fine. But, when I applied to a 3D bridge model I get convergence problems. The bridge model works fine if I don't apply the gap to this element.

The materials definition is as follows, the units are in meters and Newton

# EXPANSION BEARING
# Elastomeric pad
set Fy 35569.25
set E 3350000.0
set b 0.0
# matTag Fy E b
uniaxialMaterial Steel01 5 $Fy $E $b

# Gap
set E 9.9E8
set Fy 9.9E6
set gap1 0.0254
# matTag E Fy gap
uniaxialMaterial ElasticPPGap 13 $E $Fy $gap1
uniaxialMaterial ElasticPPGap 14 $E -$Fy -$gap1
# matTag tags
uniaxialMaterial Parallel 15 13 14

# Dowel
set e1 0.0012
set s1 110400.0
set e2 0.0053
set s2 114500.0
set e3 0.005301
set s3 0.0
# matTag s1p e1p s2p e2p s3p e3p s1n e1n s2n e2n s3n e3n pinchX pinchY D1 D2 beta
uniaxialMaterial Hysteretic 9 $s1 $e1 $s2 $e2 $s3 $e3 -$s1 -$e1 -$s2 -$e2 -$s3 -$e3 1.0 0.0 0.0 0.0 0.0
# matTag tags
uniaxialMaterial Series 16 15 9

# Expansion Elastomeric Bearing
# matTag tags
uniaxialMaterial Parallel 17 16 5

Is there any problems with this element besides the fact that it is unstable with the gap?[/url]

[fmk]

there is no problem with the element, it behaves as specified .. the problem is typically with how it is used in the models and convergence criteria .. if for example stiffness of this ele is much larger than any other ele sharing node it can cause conditioning problems of matrix, iff stiffness is large and big changes between loading & unloading it again causes problems. you might want to put a one at end of convergence test routine to have a look at what are norms on disp and force to see what is going on.