plotting problem?

[mskz1]

@SaMohamed
Hi,
Thank you for releasing such a nice library.
It matches my needs very well, so I'm trying it now.

But I think there is some problem in plotting diagram.

For example, fixed end beam with distributed load,
flat(no slope) beam and inclined slope beam plot seems correct,
but declined slope beam plot seems wrong (upside down ?)

shear force, bending moment and deformed shape plot sample

inclined slope beam (correct)

declined slope beam (upside down?)

[SaMohamed]

Thank you for raising this issue, I will investigate to see the source of the problem.
It may be the plotting algorithm or may be the methods for getting internal forces which may inverse the sign of internal forces.

[SaMohamed]

Can you share the code to get similar results as you posted?

[mskz1]

Hi, SaMohamed.
Here is some part of my test code.
My environment is macOS 10.13 and .NET SDK Version: 5.0.302

        public void TestFixedEndBeam()
        {
            // units are N, mm
            FEALiTE2D.Structure.Structure structure = new FEALiTE2D.Structure.Structure();

            Node2D n1 = new Node2D(    0,    0, "n1");
            Node2D n2 = new Node2D( 5000,    0, "n2");

            Node2D n11 = new Node2D(    0,    2000, "n11");
            Node2D n12 = new Node2D( 4000,    5000, "n12");

            Node2D n21 = new Node2D(    0, 5000, "n21");
            Node2D n22 = new Node2D( 4000, 8000, "n22");

            Node2D n31 = new Node2D( 0, 14000, "n31");
            Node2D n32 = new Node2D( 4000, 11000, "n32");

            n1.Support = new NodalSupport(true, true, true);
            n2.Support = new NodalSupport(false, true, true);

            n11.Support = new NodalSupport(true, true, true);
            n12.Support = new NodalSupport(true, true, true);

            n21.Support = new NodalSupport(true, true, true);
            n22.Support = new NodalSupport(true, true, true);

            n31.Support = new NodalSupport(true, true, true);
            n32.Support = new NodalSupport(true, true, true);

            structure.AddNode(n1);
            structure.AddNode(n2);
            structure.AddNode(n11);
            structure.AddNode(n12);
            structure.AddNode(n21);
            structure.AddNode(n22);
            structure.AddNode(n31);
            structure.AddNode(n32);

            IMaterial material = new GenericIsotropicMaterial() { E = 205000, U = 0.3, MaterialType = MaterialType.Steel };
            IFrame2DSection section1 = new Generic2DSection(2667, 1600, 1100*100, 18100000, 1, 1, 200, 100, material);  // H-200x100

            FrameElement2D e1 = new FrameElement2D(n1, n2, "e1") { CrossSection = section1 };
            FrameElement2D e2 = new FrameElement2D(n11, n12, "e2") { CrossSection = section1 };
            FrameElement2D e3 = new FrameElement2D(n21, n22, "e3") { CrossSection = section1 };
            FrameElement2D e4 = new FrameElement2D(n31, n32, "e4") { CrossSection = section1 };

            structure.AddElement(e1);
            structure.AddElement(e2);
            structure.AddElement(e3);
            structure.AddElement(e4);

            LoadCase loadCase = new LoadCase("G", LoadCaseType.Dead);
            structure.LoadCasesToRun.Add(loadCase);
            e1.Loads.Add(new FrameUniformLoad(0.0 ,-0.8, LoadDirection.Global, loadCase));
            e2.Loads.Add(new FrameUniformLoad(0.0 ,-0.8, LoadDirection.Global, loadCase));
            e3.Loads.Add(new FrameUniformLoad(0.0 ,-0.8, LoadDirection.Local, loadCase));
            e4.Loads.Add(new FrameUniformLoad(0.0 ,-0.8, LoadDirection.Global, loadCase));
            structure.LinearMesher.NumberSegements = 20;

            structure.Solve();
  
            // checking some result
            // ....

            var op = new Plotting.Dxf.PlottingOption
            {
                NFDScaleFactor = 0.2,
                SFDScaleFactor = 0.2,
                BMDScaleFactor = 0.001,
                DisplacmentScaleFactor = 1000,
                DiagramsHorizontalOffsets = 2000
            };
        
            FEALiTE2D.Plotting.Dxf.Plotter plotter = new Plotting.Dxf.Plotter(structure, op);
            plotter.Plot("somefolder/fixedEndBeam.dxf", loadCase);

         }

[isukces]

I had the same problem. I discovered that the error may be due to miscalculation of the perpendicular vector to the finite element. Using Math.Atan gives results in the range -π/2 ≤ θ ≤ π/2. From this, it follows that cos never gives negative values. The calculated perpendicular vector will never point to the left.

https://github.com/FEALiTE/FEALiTE2D/blob/main/FEALiTE2D.Plotting/Dxf/ExtensionMethods.cs#L41-L46

I used the Atan2 function in my code, , which seems to work better.

var theta = Math.Atan2(x1 - x2, y2 - y1);

[SaMohamed]

Thank you Piotr, I have adjusted this line and i think it works fine now.
please recheck and let me know if this issue still exists.