# 4.2.6.6. Triple Friction Pendulum Element¶

element('TripleFrictionPendulum', eleTag, *eleNodes, frnTag1, frnTag2, frnTag3, vertMatTag, rotZMatTag, rotXMatTag, rotYMatTag, L1, L2, L3, d1, d2, d3, W, uy, kvt, minFv, tol)
 eleTag (int) unique element object tag eleNodes (list (int)) a list of two element nodes frnTag1, frnTag2 frnTag3 (int) = tags associated with previously-defined FrictionModels at the three sliding interfaces vertMatTag (int) = Pre-defined material tag for COMPRESSION behavior of the bearing rotZMatTag rotXMatTag rotYMatTag (int) = Pre-defined material tags for rotational behavior about 3-axis, 1-axis and 2-axis, respectively. L1 L2 L3 (float) = effective radii. Li = R_i - h_i (see Figure 1) d1 d2 d3 (float) = displacement limits of pendulums (Figure 1). Displacement limit of the bearing is 2 d1 + d2 + d3 + L1. d3/ L3 - L1. d2/ L2 W (float) = axial force used for the first trial of the first analysis step. uy (float) = lateral displacement where sliding of the bearing starts. Recommended value = 0.25 to 1 mm. A smaller value may cause convergence problem. kvt (float) = Tension stiffness k_vt of the bearing. minFv (>=0) (float) = minimum vertical compression force in the bearing used for computing the horizontal tangent stiffness matrix from the normalized tangent stiffness matrix of the element. minFv is substituted for the actual compressive force when it is less than minFv, and prevents the element from using a negative stiffness matrix in the horizontal direction when uplift occurs. The vertical nodal force returned to nodes is always computed from kvc (or kvt) and vertical deformation, and thus is not affected by minFv. tol (float) = relative tolerance for checking the convergence of the element. Recommended value = 1.e-10 to 1.e-3.