Can someone please provide the formulation details of singleFPbearing element in OpenSees,
In the Opensees site there are no references to the formulation.
Accord to the website :
Image with the circle of FY/Fx and FZ/FX is given, Limit is given as the coefficient of friction. Along with the same image there is FY/FX or FZ/FX versus dy or dz graph is given, In the graph, the ratio crosses the value of the coefficient of friction but circle with radius coefficient of friction is given in former image.
How can I give the input displacement capacity of bearing?
What are the criteria for bearings to fail in this formulation?
Single friction bearing element
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NALLAGATLABHAGYASREE
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- Location: Indian Institute of Technology Hyderabad
Re: Single friction bearing element
Hello,
In its basic form, horizontal displacement-force relationship of single concave Friction Pendulum bearing can be formulated as follows:
F(u)= (N/R)*u + (Mu*N)*sign(udot) where F: horizontal force, u: horizontal displacement, udot: velocity, N: axial load on the bearing, R: effective radius, Mu: coefficient of friction of the sliding interface. As the parameter N depends on load, independent from geometry of the bearing, the parameters that governs behavior of the bearing are R and Mu(and they should be provided by user).
However, due to some problems associated with this representation, different models have been proposed and implemented in programs(e.g. Bouc-Wen model in Sap2000, and bidirectional plasticity model in singleFPBearing element of OpenSees). These models require additional parameter Kinit(meaning initial or elastic, or loading/unloading stiffness) which is why it should be also provided by user.
So, displacement capacity of the bearing is not required(or asked) because there is no mention as to the capacity of bearing in element models.
You can see [1] and [2] for details on element models:
[1] Mosqueda G., Whittaker A.S., Fenves G.L., Mahin S.A., 2004, Experimental and Analytical Studies of the Friction Pendulum System for the Seismic Protection of Simple Bridges
[2] Huang W.H., 2002, Bi-directional Testing, Modeling, and System Response of Seismically Isolated Bridges
Hope this helps.
In its basic form, horizontal displacement-force relationship of single concave Friction Pendulum bearing can be formulated as follows:
F(u)= (N/R)*u + (Mu*N)*sign(udot) where F: horizontal force, u: horizontal displacement, udot: velocity, N: axial load on the bearing, R: effective radius, Mu: coefficient of friction of the sliding interface. As the parameter N depends on load, independent from geometry of the bearing, the parameters that governs behavior of the bearing are R and Mu(and they should be provided by user).
However, due to some problems associated with this representation, different models have been proposed and implemented in programs(e.g. Bouc-Wen model in Sap2000, and bidirectional plasticity model in singleFPBearing element of OpenSees). These models require additional parameter Kinit(meaning initial or elastic, or loading/unloading stiffness) which is why it should be also provided by user.
So, displacement capacity of the bearing is not required(or asked) because there is no mention as to the capacity of bearing in element models.
You can see [1] and [2] for details on element models:
[1] Mosqueda G., Whittaker A.S., Fenves G.L., Mahin S.A., 2004, Experimental and Analytical Studies of the Friction Pendulum System for the Seismic Protection of Simple Bridges
[2] Huang W.H., 2002, Bi-directional Testing, Modeling, and System Response of Seismically Isolated Bridges
Hope this helps.