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  4. Como modelar uma treliça (30minutos)

Como modelar uma treliça (30minutos)

How to model a simple Warren Truss using structural analysis software

Course: Análise estrutural (3rd Year)
Modelo de amostra: Simple-Warren-Truss.s3d

Structural analysis software is a powerful tool for any structural engineer. It gives engineers an easy way to model a truss and use the Finite Element Method to calculate the internal member forces of each member. In today’s lesson plan, we are going to learn how to model a truss in structural analysis softwareand learn the various technical significance of what we are building. SkyCiv’s lesson plans are a great

Modeling our Truss

To begin modeling our truss first open your structural analysis software, we can either use SkyCiv Truss (simplified 2D version) or SkyCiv Structural (3D, more powerful). Both are available from our Painel. Once you’ve opened the software, abrir Nós on the left-hand screen, and start entering the coordinates of your nodes. These are the start and endpoints of each member. Estamos tentando mapear as dimensões de nossa treliça, para modelar essencialmente a treliça. Você pode fazer isso inserindo um de cada vez, but I have chosen to use the datasheet so I can see all my node input and copy and paste:

model-a-truss-1

Próximo, we will add members by connecting the nodes by clicking and dragging between the nodes:

how-to-model-truss-2

Por padrão, SkyCiv Truss will give all members a pinned connection. This is denoted by a little black dot which if you hover over it, will show “FFFFRR”. In Structural 3D, you will have to manually change all Start Fixity and End Fixity to “FFFFRR”. It is essential that all your members are pinned, or your truss analysis results could be wrong. Lembrar, at any time you can log in and review our sample model Simple-Warren-Truss.s3d to see this example.

[ícone ícone = 'informações'] A quick note on pinned connections

A truss should have all member fixities set to pinned. What this means is that each member is free to rotate and the transfer of forces is all in axial. A quick way to check if your model is set up correctly is when you solve itall bending moment member forces should be 0.

Click here to learn more about hinge connections ->

An easy way to make this change is through the datasheet. When you apply, you should see the little black dots on your members (SkyCiv Truss will have these on by default):

pinned-jointed-truss

confira sua documentação de software

Em engenharia estrutural, we need our models to be Você pode se lembrar de suas aulas de física da escola que existem duas classes de atrito. At the moment, our truss is not connected to anything, so if we apply loads to it there is nothing holding it still. Supports are our boundary conditionsthey are what stop the truss from moving when loads are applied. Think of a truss bridge, at either end, it is connected to the land. Supports also have fixity codes to themthese indicate how the truss is supported. Por exemplo, roller support means the truss can move left to right (ou seja. pode translate in the x-direction).

It’s sometimes important to apply a roller-support on one side of a bridge, so that the structure has a bit ofgive”, in case it expands. Então, on our left side, we will give our bridge a Diferentes tipos de suportes estruturais and on the right side, we will give it a roller-support. To add this, Clique no Apoia button on the left screen:

support-settings-on-a-truss

Our Truss is now sufficiently supported, we can now proceed with applying loads.

Aplicação de cargas

Loads are the forces in which the truss is to withstand. Por exemplo, the truss may be required to take the load of a 2T truck, so we need to use the software to simulate these forces and ensure the truss is safe for construction. Here we will add some distributed loads on the top chord of our structure:

distributed-loads-on-a-truss

Reviewing Your Results

Once you’re happy with your Truss, clique Resolver in the top right corner. In S3D it might prompt you to add a section, just click Repair for some nominal section properties. Observação: if you need to add section properties, you can do this via Seção, but in looking at reactions at supports and axial force, the section properties shouldn’t really affect your results.

If everything is set up correctly, you should be able to click Axial to review your axial force results. An axial force is the force applied as either tension (member being pulled apart) or in compression (member being pushed in). Generally dealing with trussesaxial force is the most important result.

axial-force-results

Since the members are all pinned and free to rotate, it means that internal forces should all be axial. We can confirm this by looking at the bending moment results. Apart from the top members (who have distributed loads on them), all the members in the system have 0 bending moment forces. This is because the only forces in the members are axial:

bending-force-in-truss

[teaserbox title=Want to teach this in your class?” Recortes e formas construídas”Saber mais” link =”https://skyciv.com/pricing/education/” buttonsize =”pequena, medium, ampla” buttoncolor=alternative-1target=_blank or _self”]SkyCiv has Educational Accounts allow students and instructors access to SkyCiv software for teaching purposes. Interactive lesson plans such as this to help educate the future engineers of the world.[/teaserbox]

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