Problem Description

This example uses a single degree of freedom structure to test the behavior of a plastic kinematic link element. Multi-linear force-deformation characteristics are defined for the link element for both tension and compression behavior. The force-deformation characteristics modeled for tension are different from those modeled for compression. A nonlinear static analysis is used to push the link element to a positive 12 inch displacement. Then, a second nonlinear load case is started from the final conditions of the first load case and used to push the link element to a negative 12 inch displacement, a 24 inch push. The resulting link force at various deformations is compared with the defined link forcedeformation characteristics.
The SAP2000 model consists of a single joint, labeled joint 1, and one link element. The model is created in the XZ plane. Only the Uz degree of freedom is active for the analysis. The plastic kinematic link element is modeled as a singlejoint link element at joint 1. This means that one end of the link element is connected to the ground and the other end is connected to joint 1. The link element is oriented such that its positive local 1 axis is parallel to the positive global Z axis. This is the default orientation of single joint link elements. Only U1 degree of freedom properties are defined for the link element.
Only the nonlinear properties of the link element are relevant for this example because the only load cases used are nonlinear load cases. The nonlinear forcedeformation characteristics of the link are defined in the table and chart on the following page.
The weight of the link is 1 kip. This is the only load acting on the link, and it is applied as a gravity load acting in the Z direction.
Two displacement-controlled nonlinear static load cases are used in this example. They are named NLSTAT1 and NLSTAT2. NLSTAT1 starts from zero initial conditions and pushes the link to a positive 12 inch deformation. NLSTAT2 starts from the conditions at the end of NLSTAT1 and pushes the link from a positive 12 inch deformation to a negative 12 inch deformation.

Tested Features

Plastic kinematic links
Displacement-controlled nonlinear static analysis
Link gravity load

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