# Simcenter 3D Solutions Topology optimization of a Bridge Structure - Part 4: Apply Loads and constraints

2023-04-07T05:33:59.000-0400
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## Summary

In this example the process of performing a topology optimization for a simple bridge structure will be illustrated. The objective is to minimize the mass of the bridge while keeping the deflection less than 1mm. This is a 7 parts tutorial that includes the following: 1. Geometry creation - simple bridge shape 2. Mesh the bridge geometry 3. Apply material properties 4. Apply Loads and constraints 5. Setup and Run the analysis 6. Postprocessing results 7. Animate the Topology optimization iterations

## Details

Part 4: Apply Loads and constraints

Step 10: Constrain the Sides of the Bridge Volume

•Double click the Bridge_Optimisation_sim part in the Simulation File View pane using the left mouse button
•Select User Defined Constraint from the Constraint Type drop-down menu in the Loads and Conditions group of the Home tab tool ribbon
•Set DOF2 to Fixed
•Select the faces of volume that point in the positive and negative y direction (large faces)
•Click Apply

Step 11: Constrain the Bottom Left Corner of the Bridge Volume

•Set DOF1 and DOF3 to Fixed
•Select the edge at the bottom left corner of volume
•Click Apply

Step 12: Constrain the Bottom Right Corner of the Bridge Volume

•Set DOF3 to Fixed
•Select the edge at the bottom right corner of volume
•Click OK

Step 13: Create the Gravity Load

•Select Gravity from the Load Type drop-down menu in the Loads and Conditions group of the Home tab tool ribbon
•Set Acceleration to 9810mm/s2
•Set Specify Vector to -ZC
•Click OK

Step 14: Create the Load at the Centre of the Bridge

•Select Force from the Load Type drop-down menu in the Loads and Conditions group of the Home tab tool ribbon
•Set Type to Magnitude and Direction
•Select the edge in the middle of the bottom face of the volume (face pointing in -Z direction)
•Set Force to 1250000N
•Set Specify Vector to -ZC
•In the Distribution section of the menu, set Method to Geometric distribution
•Click OK

Step 15: Setup the Design Objective

•Right click on the Design Objective and select New or Replace Design Objective…
•Set Name to Minimise_Mass
•Set Response Type to Total Model Weight (WEIGHT)
•Set Method to MIN

Step 16: Setup the Frozen Area

•Right click on the Design Area and select New Design Area…
•Set Name to Frozen
•Set Area Type to Frozen Area
•Enter Label to 2
•Select the bottom row of elements of the bridge volume
•Click OK

Step 17: Create the Symmetrical Manufacturing Constraint

•Right click on the Manufacturing Constraint and select New Manufacturing Constraint…
•Set Name to Symmetry
•Set Constraint Type to Planar Symmetry (SYMP)
•Select a point in the middle of the bottom edge (as indicated)
•Set Specify Vector to +X
•Click OK

Step 18: Create the Minimum Member Size Constraint

•Right click on the Manufacturing Constraint and select New Manufacturing Constraint…
•Set Name to Min_Size
•Set Constraint Type to Minimum Member Size (MINS)
•Set Minimum Member Size to 200mm
•Click OK

Step 19: Setup the Design Constraint

•Right click on the Design Constraint under the Nastopt – Statics 1 subcase and select New Advanced Design Constraint…
•Set Name to Disp_Constraint
•Click on the Create Modeling Object… icon
•Set Name to Disp_Response
•Set Label to DR
•Set Response Type to Displacement (DISP)
•Set DOF3 to On
•Select New Group
•Select the nodes at the bottom of the design volume

Step 20: Setup the Design Constraint

•Click OK and OK again
•Set Lower Bound to -1
•Set Upper Bound to 0
•Click OK

This completes Topology optimization of a Bridge Structure - Part 4: Apply Loads and constraints
Please continue with Topology optimization of a Bridge Structure - Part 5: Setup and Run the analysis

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