Abstract

This article presents application examples of nonlinear advanced supports. The purpose is to highlight how these supports work and the different mechanisms they have.

Keywords: Advance Design, Advanced Supports, Nonlinear Analysis.

1.Introduction

Some structures require special type of supports such as:

• Supports that work only in tension or compression (tension or compression only supports).
• Supports that allow displacements/rotations within specified limits. Once these limits are reached, the supports are activated and no further displacements/rotations are allowed (gap supports).
• Supports that block displacements/rotations until specified reaction forces/moments limits are reached. Once these limits are reached, displacements/rotations are allowed while maintaining the limit forces/moments reactions (hardening supports).

Advance Design has all these special supports available in the advanced supports feature. They can be assigned to each DOF separately and are available for point, line and surface supports (refer to Figures 1 and 2)

In addition to these supports, a user defined nonlinear support mechanism is also possible (“NL-Diagram” option in Figure 2).

2.     Application examples

1.1.            Gap supports

Two identical 2D frame structures are considered. A pin support is used on the left side and an advanced support on the right side for each frame (refer to Figure 3). Frame 2 carries double the load of frame 1.

The advanced support for both frames is fixed in the vertical translation and presents a 2 cm displacement gap in the horizontal translation (refer to Figure 4).

Since nonlinear supports are used, a nonlinear analysis is conducted and the results are presented in Figures 5 and 6:

In Figures 5 and 6, it is clear that for frame 1 the gap support did not reach its limit (1.67 cm < 2 cm) therefore no horizontal support force was applied to block the displacement. For frame 2, theoretically we should get twice the displacement since it carries double the load. However, the gap limit of 2 cm is reached and a horizontal support force is applied to block any further displacement.

2.2.            Hardening supports

Considering similar frame structures to paragraph 2.1. A pin support is used on the left side and an advanced support on the right side for each frame (refer to Figure 7). Frame 2 carries double the load of frame 1.

The advanced support for both frames is fixed in the vertical translation and presents a 10 kN limit hardening support in the horizontal direction (refer to Figure 8).

Since nonlinear supports are used, a nonlinear analysis is conducted and the results are presented in Figures 9 and 10:

In Figures 9 and 10, it is clear that for frame 1 the hardening support limit is not reached (8.27 kN < 10 kN) therefore the support was able to block the displacement. For frame 2, theoretically we should get twice the support force since it carries double the load. However, the hardening support limit of 10 kN is reached and it can no longer block any further displacement requiring more than 10 kN of force.

3.     Conclusion

The advanced supports are a powerful tool in Advance Design for modeling structures with particular support conditions. The user can choose between predefined support mechanisms such as gap and hardening supports or define his own mechanisms.

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