Hi Engineers,
I would like to model a gap inside a truss. When the truss is horizontal, OpenSEES gives correct results. But it fails when the truss is diagonal or has an angle.
Consider a cantilever column and a truss, with two configurations: in Configuration 1 (Fig. 1), the truss is horizontal and in configuration 2, the truss is diagonal with an angle of 45 degree(Fig. 2).
In both configurations, there is a gap inside the truss with a gap distance of "D".
I modelled the gap with the ZEROLength element and defined a PPgap metrail. For the diagonal configuration (Fig. 2), I also defined the gap orientation as below:
Orient 1 1 0 1 1 0
Both trusses are subjected to a Horizontal force "F". Thus, for the horizontal configuration (Fig. 1), the gap is closed when the lateral displacement at the top of the column reaches "D". The model confirmed this.
However, for the diagonal configuration (Fig 2), the gap is expected to be closed earlier, say " D1 ". But I was not able to capture this in OenSEES. The gap works well in other software such as SAP, SeismoStruct, ANSYS, etc.
When the gap is horizontal, OpenSEES gives correct results. But it fails when the gap has an angle.
Any thought is appreciated. Did I miss something? or is there anyone else who had similar issues?
F > _ _ _ _ _ _ _ gap _ _ _ <











Fig. 1 (horizontal gap)
F >
 \
 \
 \
 \
 \
 \
 /
 gap /
 \
 \
 ^
Fig. 2 (diagonal gap)
Model a diagonal gap
Moderators: silvia, selimgunay, Moderators

 Posts: 879
 Joined: Mon Sep 09, 2013 8:50 pm
 Location: University of California, Berkeley
Re: Model a diagonal gap
Your model with the gap could be unstable when the truss is at an angle

 Posts: 2
 Joined: Thu Mar 11, 2021 10:24 am
Re: Model a diagonal gap
Dear Selimgunay:
Thank you for your response.
actually, i got better results by changing the shear and the rotational stiffness of the link and using pdelta for geomTransf
Thank you for your response.
actually, i got better results by changing the shear and the rotational stiffness of the link and using pdelta for geomTransf