Adding hinges to the frame

[SerGlushko]

Greetings. I don't think it's a bug, but rather myself misunderstanding the situation. I have a simple 2d frame and I want to add a hinge near one of the nodes. The only tool I found for that is Partial End Release Condition. My code:

var model = new Model();

model.Nodes.Add(new Node(0, 0, 0) { Label = "n1" }); model.Nodes.Add(new Node(0, 0, 6) { Label = "n2" }); model.Nodes.Add(new Node(6, 0, 6) { Label = "n3" }); model.Nodes.Add(new Node(6, 0, 0) { Label = "n4" });

model.Nodes["n1"].Constraints = Constraints.Fixed; model.Nodes["n4"].Constraints = Constraints.Fixed;

model.Nodes["n2"].Loads.Add(new NodalLoad(new Force(10000, 0, 0, 0, 0, 0)));

model.Elements.Add(new BarElement(model.Nodes["n1"], model.Nodes["n2"]) { Label = "r1" }); model.Elements.Add(new BarElement(model.Nodes["n2"], model.Nodes["n3"]) { Label = "r2" }); model.Elements.Add(new BarElement(model.Nodes["n3"], model.Nodes["n4"]) { Label = "r3" });

(model.Elements["r1"] as BarElement).Section = new BriefFiniteElementNet.Sections.UniformGeometric1DSection(SectionGenerator.GetRectangularSection(0.01, 0.01)); (model.Elements["r2"] as BarElement).Section = new BriefFiniteElementNet.Sections.UniformGeometric1DSection(SectionGenerator.GetRectangularSection(0.01, 0.01)); (model.Elements["r3"] as BarElement).Section = new BriefFiniteElementNet.Sections.UniformGeometric1DSection(SectionGenerator.GetRectangularSection(0.01, 0.01));

(model.Elements["r1"] as BarElement).Material = BriefFiniteElementNet.Materials.UniformIsotropicMaterial.CreateFromYoungPoisson(210 Math.Pow(10, 9), 0.3); (model.Elements["r2"] as BarElement).Material = BriefFiniteElementNet.Materials.UniformIsotropicMaterial.CreateFromYoungPoisson(210 Math.Pow(10, 9), 0.3); (model.Elements["r3"] as BarElement).Material = BriefFiniteElementNet.Materials.UniformIsotropicMaterial.CreateFromYoungPoisson(210 * Math.Pow(10, 9), 0.3);

(model.Elements["r3"] as BarElement).StartReleaseCondition = new Constraint(dx: DofConstraint.Fixed, dy: DofConstraint.Fixed, dz: DofConstraint.Fixed, rx: DofConstraint.Fixed, ry: DofConstraint.Released, rz: DofConstraint.Fixed);

model.Solve_MPC();

Console.WriteLine((model.Elements["r2"] as BarElement).GetInternalForceAt(1, LoadCase.DefaultLoadCase).My.ToString()); Console.WriteLine((model.Elements["r3"] as BarElement).GetInternalForceAt(-1, LoadCase.DefaultLoadCase).My.ToString()); Console.ReadKey();

My result: I think, that even with the hinge there, the internal moments in two rods near the same node should be close to zero.

[epsi1on]

Yes, End release feature on BarElement is not working right, I'm going to remove it. But in FrameElement2Node it works good.

[epsi1on]

Hello again, Instead of removing, I've made some changes to code, It should work fine now. can you please have a check?

This is result of your code with updated source code of library:

Thanks

[SerGlushko]

As far as I can see, the hinges work fine now, although isolating node with hinges causes symmetric positive definite exception.

I think I found a problem related to my previous issue, which is closed now. Using GetExactInternalForceAt gives results, mirrored along the rod. And I have noticed that internal moments are inverted now to the compression side, rather than tension side as it was previously. I can give you some more context here or create new issue for this.