# How to Analyze Truss Problems in SOLIDWORKS Simulation

Article by Mehdi Rezaei, CSWE updated May 7, 2018

###### Article

This article will show you how to model and analyze truss problems in SOLIDWORKS Simulation. This article might be more useful for mechanical or civil engineering studies. However, any engineer dealing with structural member analysis can use this functionality to save time on design or evaluation of their structures.

Truss elements are special beam elements that can resist axial deformation only. So, no moment, torsion, or bending stress results can be expected from a simulation with truss elements. The joints in this class of structures are designed so that no moments develop in them. Only axial forces are developed in each member. The axial force which causes an axial stress on the member is constant along the member length and uniform across the cross-section area of the member. A truss element has only two nodes, one at either end of a member. Each node has three degrees of freedom. A node can only have displacements in 3 orthogonal directions.

Note: Trusses are commonly used in architectural and structural applications such as bridges, roofs, power towers, and others.

The axial stress Sx = Force / Area, and the axial displacement of its node Ux = (Force x Length) / (Area x Modulus of Elasticity). A truss element’s axial spring stiffness is define as k = (Area x Modulus of Elasticity) / Length. For analysis, the modulus of elasticity has to be defined under the member material specification. However, density is required only when gravity load is considered. More information on truss elements can be found in the SOLIDWORKS help.

## Simulate a Bridge Structure with Truss Elements

The steps of modeling a simple bridge structure is demonstrated in this section. First of all, a 2D or 3D sketch is needed. To model the structural members, the sketch must have small lines starting from one joint and ending on the other joint of the member.

A 2D or 3D Sketch is needed for Truss Models. Small segments of lines represent Truss Member lengths and locations

Then, these lines are used to assign 3D weldment components. Then, in simulation properties tree, the components will be selected and defined as truss elements.

Weldment Components Are Assigned to the Sketch. Various Cross Section Sizes Could Be Assigned for Specific Sketch Segment as it is required.

The corner treatment option must be unchecked to ensure joints will computed properly.

Corner Treatment Must not Be Checked off. This Setting Prevents from Cut off or Corner Breaks

Right-click on members on the Simulation properties tree and select Edit definition. As shown in the following image, select Truss as element type and then click on green checkmark to update the element type.

Switching the Element Type from Default Beam to Truss under Edit Definition of Members

The joint on the left side is going to be pinned fixture meaning that it will not translate in X or Y directions but rotation is allowed. Immovable fixture will do it. For the joint on the right side roller fixture must be defined. That is done using “Use Reference Geometry” option and fixed translation normal to top plane at the right joint. Also, all the joints must be eliminated from translation or rotation normal to Front plane. Reference Geometry is used to add that fixture to all joints.

Immovable Fixture Fixes the joint from Translation but Allow Rotation

Last step in settings is adding a vertical load to a joint.

Truss Deformed Shape

Probing Stress Results for each Element