SBMD and Reactions calculator

BeamAnalysis.vb

Imports System.Drawing
Imports System.Linq
Imports System.Collections.Generic
Imports System.Drawing.Printing

Public Structure BeamLoads
    Public PointLoad As (Magnitude As Double, Position As Double)
    Public RectLoad As (Magnitude As Double, StartPos As Double, EndPos As Double)
    Public TriLoad As (Magnitude As Double, StartPos As Double, EndPos As Double, IsLeftHigh As Boolean)
    Public MomentLoad As (Magnitude As Double, Position As Double, Direction As Integer) ' 0=CCW, 1=CW
End Structure

Public Structure BeamResult
    Public Position As Double
    Public Shear As Double
    Public Moment As Double
End Structure

Public Class Form2

    Public Const BeamLength As Double = 10.0

    ' Calculate support reactions for simply supported beam
    Public Shared Function CalculateReactions(loads As BeamLoads) As (RA As Double, RB As Double)
        Try
            If loads.RectLoad.EndPos < loads.RectLoad.StartPos Then
                MessageBox.Show("Please enter a value greater than " & loads.RectLoad.StartPos, "Invalid Input", MessageBoxButtons.OK, MessageBoxIcon.Warning)
            End If

            If loads.TriLoad.EndPos < loads.TriLoad.StartPos Then
                MessageBox.Show("Please enter a value greater than " & loads.TriLoad.StartPos, "Invalid Input", MessageBoxButtons.OK, MessageBoxIcon.Warning)
            End If

            Dim totalLoad As Double = 0
            Dim momentAboutA As Double = 0

            ' Point load
            totalLoad += loads.PointLoad.Magnitude
            momentAboutA += loads.PointLoad.Magnitude * loads.PointLoad.Position

            ' Rectangular uniform load
            Dim w = loads.RectLoad.Magnitude
            Dim a = loads.RectLoad.StartPos
            Dim b = loads.RectLoad.EndPos
            Dim lengthR = b - a
            If lengthR > 0 Then
                Dim Frect = w * lengthR
                totalLoad += Frect
                momentAboutA += Frect * (a + lengthR / 2)
            End If

            ' Triangular load (linear)
            With loads.TriLoad
                Dim baseT = .EndPos - .StartPos
                If baseT > 0 Then
                    Dim Ftri = 0.5 * .Magnitude * baseT
                    Dim centroidX = If(.IsLeftHigh,
                                  .StartPos + baseT / 3,
                                  .StartPos + baseT * 2 / 3)
                    totalLoad += Ftri
                    momentAboutA += Ftri * centroidX
                End If
            End With

            ' Moment load (external)
            Dim momentLoadVal = loads.MomentLoad.Magnitude
            If loads.MomentLoad.Direction = 0 Then
                momentAboutA -= momentLoadVal ' CCW positive
            Else
                momentAboutA += momentLoadVal ' CW negative
            End If

            ' Reactions by equilibrium
            Dim RB = momentAboutA / BeamLength
            Dim RA = totalLoad - RB

            Return (RA, RB)
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End Function

    ' Calculate shear at position x
    Public Shared Function CalculateShearAt(x As Double, loads As BeamLoads, RA As Double) As Double
        Try
            Dim V = RA

            ' Point load effect
            If x >= loads.PointLoad.Position Then
                V -= loads.PointLoad.Magnitude
            End If

            ' Rectangular load effect
            If x >= loads.RectLoad.StartPos Then
                Dim endX = Math.Min(x, loads.RectLoad.EndPos)
                Dim length = endX - loads.RectLoad.StartPos
                If length > 0 Then
                    V -= loads.RectLoad.Magnitude * length
                End If
            End If

            ' Triangular load effect
            If x >= loads.TriLoad.StartPos Then
                Dim endX = Math.Min(x, loads.TriLoad.EndPos)
                Dim baseT = endX - loads.TriLoad.StartPos
                If baseT > 0 Then
                    Dim h = loads.TriLoad.Magnitude
                    If loads.TriLoad.IsLeftHigh Then
                        ' load linearly decreasing from h to 0 over baseT
                        Dim loadAtX = h * (1 - baseT / (loads.TriLoad.EndPos - loads.TriLoad.StartPos))
                        V -= 0.5 * baseT * (h + loadAtX)
                    Else
                        ' load linearly increasing from 0 to h over baseT
                        Dim loadAtX = h * (baseT / (loads.TriLoad.EndPos - loads.TriLoad.StartPos))
                        V -= 0.5 * baseT * loadAtX
                    End If
                End If
            End If

            Return V
        Catch ex As Exception
            MsgBox(ex.Message)
            Return 0
        End Try
    End Function

    ' Calculate bending moment at position x
    Public Shared Function CalculateMomentAt(x As Double, loads As BeamLoads, RA As Double) As Double
        Try
            Dim M = RA * x

            ' Point load
            If x >= loads.PointLoad.Position Then
                M -= loads.PointLoad.Magnitude * (x - loads.PointLoad.Position)
            End If

            ' Rectangular load moment
            If x >= loads.RectLoad.StartPos Then
                Dim endX = Math.Min(x, loads.RectLoad.EndPos)
                Dim lengthR = endX - loads.RectLoad.StartPos
                If lengthR > 0 Then
                    Dim w = loads.RectLoad.Magnitude
                    M -= w * lengthR * (x - (loads.RectLoad.StartPos + lengthR / 2))
                End If
            End If

            ' Triangular load moment
            If x >= loads.TriLoad.StartPos Then
                Dim endX = Math.Min(x, loads.TriLoad.EndPos)
                Dim baseT = endX - loads.TriLoad.StartPos
                If baseT > 0 Then
                    Dim h = loads.TriLoad.Magnitude
                    Dim area = 0.5 * h * baseT
                    Dim centroidX = If(loads.TriLoad.IsLeftHigh,
                                  loads.TriLoad.StartPos + baseT / 3,
                                  loads.TriLoad.StartPos + baseT * 2 / 3)
                    M -= area * (x - centroidX)
                End If
            End If

            ' Moment load (external)
            If x >= loads.MomentLoad.Position Then
                Dim mVal = loads.MomentLoad.Magnitude
                If loads.MomentLoad.Direction = 0 Then
                    M -= mVal
                Else
                    M += mVal
                End If
            End If

            Return M
        Catch ex As Exception
            MsgBox(ex.Message)
            Return 0
        End Try
    End Function

    ' Generate shear and moment data for plotting
    Public Shared Function GetShearMomentData(loads As BeamLoads, RA As Double, Optional stepSize As Double = 0.1) As List(Of BeamResult)
        Try
            Dim results As New List(Of BeamResult)
            Dim x As Double = 0
            While x <= BeamLength
                Dim shear = CalculateShearAt(x, loads, RA)
                Dim moment = CalculateMomentAt(x, loads, RA)
                results.Add(New BeamResult With {.Position = x, .Shear = shear, .Moment = moment})
                x += stepSize
            End While
            Return results
        Catch ex As Exception
            MsgBox(ex.Message)
            Return New List(Of BeamResult)()
        End Try
    End Function

    Private Sub btnCompute_Click(sender As Object, e As EventArgs) Handles btnReactions.Click
        Dim loads As New BeamLoads With {
        .PointLoad = (txtMagP.Text, txtLocP.Text),
        .RectLoad = (txtMagR.Text, txtLocSR.Text, txtLocER.Text),
        .TriLoad = (txtMagT.Text, txtLocST.Text, txtLocET.Text, cmbT.SelectedIndex),
        .MomentLoad = (txtMagM.Text, txtLocM.Text, cmbM.SelectedIndex)
    }

        ' Calculate reactions
        Dim reactions = Form2.CalculateReactions(loads)

        ' Display reactions in textboxes
        txtRA.Text = reactions.RA.ToString("F2") ' 2 decimal places
        txtRB.Text = reactions.RB.ToString("F2")
    End Sub

    Private Sub btnReset_Click(sender As Object, e As EventArgs) Handles btnReset.Click
        ' Clear all input TextBoxes
        txtMagP.Clear()
        txtLocP.Clear()
        txtMagR.Clear()
        txtLocSR.Clear()
        txtLocER.Clear()
        txtMagT.Clear()
        txtLocST.Clear()
        txtLocET.Clear()
        txtMagM.Clear()
        txtLocM.Clear()
        txtMagP.Focus()

        ' Reset ComboBoxes to default index (e.g., 0 or -1 if none)
        cmbT.SelectedIndex = -1
        cmbM.SelectedIndex = -1

        ' Clear reaction output TextBoxes
        txtRA.Clear()
        txtRB.Clear()

        ' Clear the drawing area (PictureBox)
        picDiagram.Refresh()
    End Sub

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        txtRA.ReadOnly = True
        txtRB.ReadOnly = True
        txtMagP.Focus()
    End Sub

    Private Sub TextBoxes_OnlyDigitsAndPeriod_KeyPress(sender As Object, e As KeyPressEventArgs) _
    Handles txtMagP.KeyPress, txtLocP.KeyPress, txtMagR.KeyPress, txtLocSR.KeyPress, txtLocER.KeyPress, txtMagT.KeyPress, txtLocST.KeyPress, txtLocET.KeyPress, txtMagM.KeyPress, txtLocM.KeyPress
        ' Allow digits, control keys (Backspace), and one period (.)
        If Not Char.IsDigit(e.KeyChar) AndAlso
       Not Char.IsControl(e.KeyChar) AndAlso
       Not (e.KeyChar = "."c) Then
            e.Handled = True
        End If

        Dim txt As TextBox = CType(sender, TextBox)
        ' Prevent entering more than one period
        If e.KeyChar = "."c AndAlso txt.Text.Contains(".") Then
            e.Handled = True
        End If
    End Sub

    Private Sub LocationTextBoxes_ValidateRange(sender As Object, e As System.ComponentModel.CancelEventArgs) _
    Handles txtLocP.Validating, txtLocSR.Validating, txtLocER.Validating,
            txtLocST.Validating, txtLocET.Validating, txtLocM.Validating

        Dim txt As TextBox = CType(sender, TextBox)
        Dim value As Double

        ' Check if input is a valid number
        If Double.TryParse(txt.Text, value) Then
            If value < 0 OrElse value > 10 Then
                MessageBox.Show("Value must be between 0 and 10.", "Invalid Input", MessageBoxButtons.OK, MessageBoxIcon.Warning)
                e.Cancel = True ' Keep focus on textbox
            End If
        Else
            MessageBox.Show("Please enter a valid numeric value.", "Invalid Input", MessageBoxButtons.OK, MessageBoxIcon.Warning)
            e.Cancel = True ' Keep focus on textbox
        End If
    End Sub

    Private Sub DrawShearMomentDiagrams(results As List(Of BeamResult), loads As BeamLoads)
        Dim g As Graphics = picDiagram.CreateGraphics()
        g.SmoothingMode = Drawing2D.SmoothingMode.AntiAlias
        g.Clear(Color.White)

        Dim pic = picDiagram
        Dim width = pic.Width
        Dim height = pic.Height
        Dim margin As Integer = 40

        ' Find max shear and moment values for scaling
        Dim maxShear = results.Max(Function(r) Math.Abs(r.Shear))
        Dim maxMoment = results.Max(Function(r) Math.Abs(r.Moment))

        ' Reserve vertical space for each diagram
        Dim midY = height \ 2
        Dim shearYBase = midY \ 2               ' Top half center (shear axis)
        Dim momentYBase = midY + midY \ 2       ' Bottom half center (moment axis)

        ' Define scaling functions
        Dim xScale = Function(x As Double) margin + x / BeamLength * (width - 2 * margin)
        Dim shearScale = Function(V As Double) shearYBase - V / maxShear * (midY \ 2 - margin)
        Dim momentScale = Function(M As Double) momentYBase - M / maxMoment * (midY \ 2 - margin)

        ' Draw separate horizontal axes
        Dim axisPen As New Pen(Color.Black, 1)
        g.DrawLine(axisPen, margin, shearYBase, width - margin, shearYBase)     ' Shear axis
        g.DrawLine(axisPen, margin, momentYBase, width - margin, momentYBase)   ' Moment axis

        ' Collect important x-locations
        Dim importantX As New List(Of Double) From {0, BeamLength}
        If loads.PointLoad.Magnitude <> 0 Then importantX.Add(loads.PointLoad.Position)
        If loads.RectLoad.Magnitude <> 0 Then
            importantX.Add(loads.RectLoad.StartPos)
            importantX.Add(loads.RectLoad.EndPos)
        End If
        If loads.TriLoad.Magnitude <> 0 Then
            importantX.Add(loads.TriLoad.StartPos)
            importantX.Add(loads.TriLoad.EndPos)
        End If
        If loads.MomentLoad.Magnitude <> 0 Then importantX.Add(loads.MomentLoad.Position)

        Dim distinctX = importantX.Distinct().OrderBy(Function(x) x).ToList()
        Dim dashedPen As New Pen(Color.Gray) With {.DashStyle = Drawing2D.DashStyle.Dash}
        Dim font = New Font("Arial", 8)

        ' Draw vertical lines and labels at key x-positions
        For Each xPos In distinctX
            Dim xPixel = CSng(xScale(xPos))
            g.DrawLine(dashedPen, xPixel, margin, xPixel, height - margin)

            ' Find closest result
            Dim pt = results.OrderBy(Function(r) Math.Abs(r.Position - xPos)).FirstOrDefault()

            ' Draw shear and moment values
            g.DrawString($"V={pt.Shear:F2}", font, Brushes.Red, xPixel + 2, shearScale(pt.Shear) - 15)
            g.DrawString($"M={pt.Moment:F2}", font, Brushes.Blue, xPixel + 2, momentScale(pt.Moment) + 2)
        Next

        ' Draw Shear Diagram
        Dim shearPen As New Pen(Color.Red, 2)
        For i = 1 To results.Count - 1
            Dim x1 = CSng(xScale(results(i - 1).Position))
            Dim y1 = CSng(shearScale(results(i - 1).Shear))
            Dim x2 = CSng(xScale(results(i).Position))
            Dim y2 = CSng(shearScale(results(i).Shear))
            g.DrawLine(shearPen, x1, y1, x2, y2)
        Next

        ' Draw Moment Diagram
        Dim momentPen As New Pen(Color.Blue, 2)
        For i = 1 To results.Count - 1
            Dim x1 = CSng(xScale(results(i - 1).Position))
            Dim y1 = CSng(momentScale(results(i - 1).Moment))
            Dim x2 = CSng(xScale(results(i).Position))
            Dim y2 = CSng(momentScale(results(i).Moment))
            g.DrawLine(momentPen, x1, y1, x2, y2)
        Next

        ' Draw diagram labels
        g.DrawString("Shear Diagram", font, Brushes.Red, margin, shearYBase - margin \ 2)
        g.DrawString("Moment Diagram", font, Brushes.Blue, margin, momentYBase - margin \ 2)

        ' Clean up
        font.Dispose()
        axisPen.Dispose()
        shearPen.Dispose()
        momentPen.Dispose()
        dashedPen.Dispose()
        g.Dispose()
    End Sub


    Private Sub btnDraw_Click(sender As Object, e As EventArgs) Handles btnDraw.Click
        ' Prepare loads from user input
        Dim loads As New BeamLoads With {
            .PointLoad = (Double.Parse(txtMagP.Text), Double.Parse(txtLocP.Text)),
            .RectLoad = (Double.Parse(txtMagR.Text), Double.Parse(txtLocSR.Text), Double.Parse(txtLocER.Text)),
            .TriLoad = (Double.Parse(txtMagT.Text), Double.Parse(txtLocST.Text), Double.Parse(txtLocET.Text), cmbT.SelectedIndex = 0),
            .MomentLoad = (Double.Parse(txtMagM.Text), Double.Parse(txtLocM.Text), cmbM.SelectedIndex)
        }

        ' Calculate reactions
        Dim reactions = CalculateReactions(loads)

        ' Get results
        Dim results = GetShearMomentData(loads, reactions.RA)

        ' Draw diagrams
        DrawShearMomentDiagrams(results, loads)
    End Sub



    'VISUALIZING BEAM BUTTON
    Private Sub btnBeam_Click(sender As Object, e As EventArgs) Handles btnBeam.Click
        ' Create Bitmap and Graphics
        Dim bmp As New Bitmap(picDiagram.Width, picDiagram.Height)
        Dim g As Graphics = Graphics.FromImage(bmp)
        g.Clear(Color.White)

        ' Beam settings
        Dim beamLength As Integer = 400 ' fixed beam length in pixels
        Dim beamStartX As Integer = (picDiagram.Width - beamLength) \ 2 ' center horizontally
        Dim beamY As Integer = 200 ' center vertically

        Dim beamEndX As Integer = beamStartX + beamLength

        ' Draw the beam
        g.FillRectangle(Brushes.White, beamStartX, beamY - 5, beamLength, 10)
        g.DrawRectangle(Pens.Black, beamStartX, beamY - 5, beamLength, 10)

        ' Draw supports
        DrawPinSupport(g, beamStartX, beamY)
        DrawRollerSupport(g, beamEndX, beamY)

        ' Distance line (closer to beam)
        Dim lineY As Integer = beamY + 25
        g.DrawLine(Pens.Red, beamStartX, lineY, beamEndX, lineY)
        g.DrawLine(Pens.Red, beamStartX, lineY - 5, beamStartX, lineY + 5)
        g.DrawLine(Pens.Red, beamEndX, lineY - 5, beamEndX, lineY + 5)

        ' Distance label in red
        Dim labelFont As New Font("Arial", 10)
        Dim labelText As String = "10 m"
        Dim labelSize As SizeF = g.MeasureString(labelText, labelFont)
        Dim labelX As Integer = beamStartX + (beamLength - labelSize.Width) \ 2
        Dim labelY As Integer = lineY + 5
        g.DrawString(labelText, labelFont, Brushes.Red, labelX, labelY)

        ' ========== Point Load ==========
        Dim magnitudeP As Double
        Dim positionMetersP As Double
        Dim drawPointLoadFlag As Boolean = False

        If Not String.IsNullOrWhiteSpace(txtMagP.Text) OrElse Not String.IsNullOrWhiteSpace(txtLocP.Text) Then
            If Not Double.TryParse(txtMagP.Text, magnitudeP) Then
                MessageBox.Show("Please enter a valid number for point load magnitude.")
            ElseIf Not Double.TryParse(txtLocP.Text, positionMetersP) Then
                MessageBox.Show("Please enter a valid number for point load position.")
            ElseIf positionMetersP < 0 OrElse positionMetersP > 10 Then
                MessageBox.Show("Point load position must be between 0 and 10 meters.")
            Else
                drawPointLoadFlag = True
            End If
        End If

        If drawPointLoadFlag Then
            Dim loadXP As Integer = beamStartX + CInt(positionMetersP / 10 * beamLength)
            DrawPointLoad(g, loadXP, beamY, magnitudeP, Math.Abs(magnitudeP).ToString("0.##") & " kN")
        End If

        ' ========== Rectangular Load ==========
        Dim magnitudeR As Double
        Dim startPosR As Double
        Dim endPosR As Double
        Dim drawRectLoadFlag As Boolean = False

        If Not String.IsNullOrWhiteSpace(txtMagR.Text) OrElse Not String.IsNullOrWhiteSpace(txtLocSR.Text) OrElse Not String.IsNullOrWhiteSpace(txtLocER.Text) Then
            If Not Double.TryParse(txtMagR.Text, magnitudeR) Then
                MessageBox.Show("Enter a valid number for rectangular load magnitude.")
            ElseIf Not Double.TryParse(txtLocSR.Text, startPosR) Then
                MessageBox.Show("Enter a valid number for rectangular load start position.")
            ElseIf Not Double.TryParse(txtLocER.Text, endPosR) Then
                MessageBox.Show("Enter a valid number for rectangular load end position.")
            ElseIf startPosR < 0 OrElse startPosR > 10 OrElse endPosR < 0 OrElse endPosR > 10 Then
                MessageBox.Show("Rectangular load positions must be between 0 and 10 meters.")
            ElseIf startPosR >= endPosR Then
                MessageBox.Show("Rectangular load end position must be greater than start position.")
            Else
                drawRectLoadFlag = True
            End If
        End If

        If drawRectLoadFlag Then
            Dim loadStartXR As Integer = beamStartX + CInt((startPosR / 10) * beamLength)
            Dim loadEndXR As Integer = beamStartX + CInt((endPosR / 10) * beamLength)
            DrawRectangularLoad(g, loadStartXR, loadEndXR, beamY, magnitudeR)
        End If

        ' ========== Triangular Load ==========
        Dim magnitudeT As Double
        Dim startPosT As Double
        Dim endPosT As Double
        Dim drawTriLoadFlag As Boolean = False

        ' Check if user started input for triangular load
        If Not String.IsNullOrWhiteSpace(txtMagT.Text) OrElse Not String.IsNullOrWhiteSpace(txtLocST.Text) OrElse Not String.IsNullOrWhiteSpace(txtLocET.Text) OrElse cmbT.SelectedIndex <> -1 Then
            ' Validate combo box
            If cmbT.SelectedIndex = -1 Then
                MessageBox.Show("Please select a triangular load direction (Left High or Right High).")
            ElseIf Not Double.TryParse(txtMagT.Text, magnitudeT) Then
                MessageBox.Show("Enter a valid number for triangular load magnitude.")
            ElseIf Not Double.TryParse(txtLocST.Text, startPosT) Then
                MessageBox.Show("Enter a valid number for triangular load start position.")
            ElseIf Not Double.TryParse(txtLocET.Text, endPosT) Then
                MessageBox.Show("Enter a valid number for triangular load end position.")
            ElseIf startPosT < 0 OrElse startPosT > 10 OrElse endPosT < 0 OrElse endPosT > 10 Then
                MessageBox.Show("Triangular load positions must be between 0 and 10 meters.")
            ElseIf startPosT >= endPosT Then
                MessageBox.Show("Triangular load end position must be greater than start position.")
            Else
                drawTriLoadFlag = True
            End If
        End If

        If drawTriLoadFlag Then
            Dim isLeftHigh As Boolean = (cmbT.SelectedIndex = 0)
            Dim loadStartXT As Integer = beamStartX + CInt(startPosT / 10 * beamLength)
            Dim loadEndXT As Integer = beamStartX + CInt(endPosT / 10 * beamLength)
            DrawTriangularLoad(g, loadStartXT, loadEndXT, beamY, magnitudeT, isLeftHigh)
        End If

        ' ========== Moment Load ==========
        Dim magnitudeM As Double
        Dim positionMetersM As Double
        Dim drawMomentLoadFlag As Boolean = False

        If Not String.IsNullOrWhiteSpace(txtMagM.Text) OrElse Not String.IsNullOrWhiteSpace(txtLocM.Text) OrElse cmbM.SelectedIndex <> -1 Then
            ' Validate combo box
            If cmbM.SelectedIndex = -1 Then
                MessageBox.Show("Select moment direction: Clockwise or Counterclockwise.")
            ElseIf Not Double.TryParse(txtMagM.Text, magnitudeM) Then
                MessageBox.Show("Enter a valid number for moment magnitude.")
            ElseIf Not Double.TryParse(txtLocM.Text, positionMetersM) Then
                MessageBox.Show("Enter a valid number for moment position.")
            ElseIf positionMetersM < 0 OrElse positionMetersM > 10 Then
                MessageBox.Show("Moment position must be between 0 and 10 meters.")
            Else
                drawMomentLoadFlag = True
            End If
        End If

        If drawMomentLoadFlag Then
            Dim direction As String = cmbM.SelectedItem?.ToString()
            Dim isClockwise As Boolean = (direction = "Clockwise")
            Dim loadXM As Integer = beamStartX + CInt(positionMetersM / 10 * beamLength)
            DrawMomentLoad(g, loadXM, beamY, magnitudeM, Math.Abs(magnitudeM).ToString("0.##") & " kNm", isClockwise)
        End If

        ' Set the image to the PictureBox
        picDiagram.Image = bmp

        ' Dispose graphics
        g.Dispose()
    End Sub
    ' Draws a Pin Support symbol at (x, y)
    Private Sub DrawPinSupport(g As Graphics, x As Integer, y As Integer)
        Dim pinPoints() As Point = {
            New Point(x, y),
            New Point(x - 8, y + 15),
            New Point(x + 8, y + 15)
        }
        g.FillPolygon(Brushes.White, pinPoints)
        g.DrawPolygon(Pens.Black, pinPoints)
    End Sub

    ' Draws a Roller Support symbol at (x, y)
    Private Sub DrawRollerSupport(g As Graphics, x As Integer, y As Integer)
        Dim rollerPoints() As Point = {
            New Point(x, y),
            New Point(x - 8, y + 15),
            New Point(x + 8, y + 15)
        }
        g.FillPolygon(Brushes.White, rollerPoints)
        g.DrawPolygon(Pens.Black, rollerPoints)

        g.FillEllipse(Brushes.White, x - 6, y + 15, 3, 3)
        g.DrawEllipse(Pens.Black, x - 6, y + 15, 3, 3)
        g.FillEllipse(Brushes.White, x - 1, y + 15, 3, 3)
        g.DrawEllipse(Pens.Black, x - 1, y + 15, 3, 3)
        g.FillEllipse(Brushes.White, x + 4, y + 15, 3, 3)
        g.DrawEllipse(Pens.Black, x + 4, y + 15, 3, 3)
    End Sub

    ' Draws a Point Load arrow at (x, beamY), magnitude positive = upward below beam, negative = downward above beam
    Private Sub DrawPointLoad(g As Graphics, x As Integer, beamY As Integer, magnitude As Double, label As String)
        Dim arrowLength As Integer = 50
        Dim headSize As Integer = 6
        Dim offset As Integer = 5
        Dim arrowPen As Pen = Pens.Green
        Dim labelFont As New Font("Arial", 9)
        Dim labelBrush As Brush = Brushes.Green

        If magnitude > 0 Then
            ' Arrow below beam pointing up
            Dim arrowTipY As Integer = beamY + offset
            Dim arrowStartY As Integer = arrowTipY + arrowLength

            g.DrawLine(arrowPen, x, arrowStartY, x, arrowTipY)
            g.DrawLine(arrowPen, x, arrowTipY, x - headSize, arrowTipY + headSize)
            g.DrawLine(arrowPen, x, arrowTipY, x + headSize, arrowTipY + headSize)

            Dim labelSize As SizeF = g.MeasureString(label, labelFont)
            g.DrawString(label, labelFont, labelBrush, x - labelSize.Width \ 2, arrowStartY + 2)
        ElseIf magnitude < 0 Then
            ' Arrow above beam pointing down
            Dim arrowTipY As Integer = beamY - offset
            Dim arrowStartY As Integer = arrowTipY - arrowLength

            g.DrawLine(arrowPen, x, arrowStartY, x, arrowTipY)
            g.DrawLine(arrowPen, x, arrowTipY, x - headSize, arrowTipY - headSize)
            g.DrawLine(arrowPen, x, arrowTipY, x + headSize, arrowTipY - headSize)

            Dim labelSize As SizeF = g.MeasureString(label, labelFont)
            g.DrawString(label, labelFont, labelBrush, x - labelSize.Width \ 2, arrowStartY - labelSize.Height - 2)
        Else
            ' zero load - no arrow drawn
        End If
    End Sub

    ' Draws a Rectangular Load distributed between startX and endX at beamY, positive magnitude below beam, negative above
    Private Sub DrawRectangularLoad(g As Graphics, startX As Integer, endX As Integer, beamY As Integer, magnitude As Double)
        Dim arrowLength As Integer = 50
        Dim headSize As Integer = 6
        Dim offset As Integer = 5
        Dim arrowPen As Pen = Pens.Green
        Dim labelFont As New Font("Arial", 9)
        Dim labelBrush As Brush = Brushes.Green

        Dim arrowSpacing As Integer = 20
        Dim arrowCount As Integer = CInt((endX - startX) / arrowSpacing)
        If arrowCount < 1 Then arrowCount = 1

        Dim arrowBaseYs As New List(Of Integer)

        For i As Integer = 0 To arrowCount
            Dim x As Integer = startX + CInt(i * (endX - startX) / arrowCount)

            If magnitude > 0 Then
                Dim arrowTipY As Integer = beamY + offset
                Dim arrowStartY As Integer = arrowTipY + arrowLength

                g.DrawLine(arrowPen, x, arrowStartY, x, arrowTipY)
                g.DrawLine(arrowPen, x, arrowTipY, x - headSize, arrowTipY + headSize)
                g.DrawLine(arrowPen, x, arrowTipY, x + headSize, arrowTipY + headSize)

                arrowBaseYs.Add(arrowStartY)

            ElseIf magnitude < 0 Then
                Dim arrowTipY As Integer = beamY - offset
                Dim arrowStartY As Integer = arrowTipY - arrowLength

                g.DrawLine(arrowPen, x, arrowStartY, x, arrowTipY)
                g.DrawLine(arrowPen, x, arrowTipY, x - headSize, arrowTipY - headSize)
                g.DrawLine(arrowPen, x, arrowTipY, x + headSize, arrowTipY - headSize)

                arrowBaseYs.Add(arrowStartY)
            End If
        Next

        If arrowBaseYs.Count >= 2 Then
            g.DrawLine(arrowPen, startX, arrowBaseYs(0), endX, arrowBaseYs(0))
        End If

        Dim textY As Integer
        If magnitude > 0 Then
            textY = arrowBaseYs(0) + 10
        Else
            textY = arrowBaseYs(0) - 25
        End If

        Dim magnitudeText As String = Math.Abs(magnitude).ToString("0.##") & " kN"
        Dim textSize As SizeF = g.MeasureString(magnitudeText, labelFont)
        Dim textX As Integer = startX + (endX - startX) \ 2 - CInt(textSize.Width / 2)
        g.DrawString(magnitudeText, labelFont, labelBrush, textX, textY)
    End Sub

    ' Draws a Triangular Load between startX and endX at beamY, magnitude positive below beam, negative above, isLeftHigh defines slope direction
    Private Sub DrawTriangularLoad(g As Graphics, startX As Integer, endX As Integer, beamY As Integer, magnitude As Double, isLeftHigh As Boolean)
        Dim maxArrowLength As Integer = 50
        Dim headSize As Integer = 6
        Dim offset As Integer = 5
        Dim arrowPen As Pen = Pens.Blue
        Dim labelFont As New Font("Arial", 9)
        Dim labelBrush As Brush = Brushes.Blue

        Dim arrowSpacing As Integer = 20
        Dim arrowCount As Integer = CInt((endX - startX) / arrowSpacing)
        If arrowCount < 1 Then arrowCount = 1

        Dim arrowPositions As New List(Of Integer)
        Dim arrowBaseYs As New List(Of Integer)

        For i As Integer = 0 To arrowCount
            Dim x As Integer = startX + CInt(i * (endX - startX) / arrowCount)
            arrowPositions.Add(x)
        Next

        For i As Integer = 0 To arrowCount
            Dim x As Integer = arrowPositions(i)
            Dim t As Double

            If isLeftHigh Then
                t = CDbl(i) / arrowCount
            Else
                t = 1.0 - CDbl(i) / arrowCount
            End If

            Dim arrowLength As Integer = CInt(maxArrowLength * t)
            Dim isLastArrow As Boolean = If(isLeftHigh, i = arrowCount, i = 0)

            If magnitude > 0 Then
                Dim arrowTipY As Integer = beamY + offset
                Dim arrowStartY As Integer = arrowTipY + arrowLength

                g.DrawLine(arrowPen, x, arrowStartY, x, arrowTipY)
                arrowBaseYs.Add(arrowStartY)

                If Not (isLastArrow And arrowLength = 0) Then
                    g.DrawLine(arrowPen, x, arrowTipY, x - headSize, arrowTipY + headSize)
                    g.DrawLine(arrowPen, x, arrowTipY, x + headSize, arrowTipY + headSize)
                End If

            ElseIf magnitude < 0 Then
                Dim arrowTipY As Integer = beamY - offset
                Dim arrowStartY As Integer = arrowTipY - arrowLength

                g.DrawLine(arrowPen, x, arrowStartY, x, arrowTipY)
                arrowBaseYs.Add(arrowStartY)

                If Not (isLastArrow And arrowLength = 0) Then
                    g.DrawLine(arrowPen, x, arrowTipY, x - headSize, arrowTipY - headSize)
                    g.DrawLine(arrowPen, x, arrowTipY, x + headSize, arrowTipY - headSize)
                End If
            End If
        Next

        If arrowBaseYs.Count >= 2 Then
            g.DrawLine(arrowPen, startX, arrowBaseYs(0), endX, arrowBaseYs(arrowBaseYs.Count - 1))
        End If

        Dim textY As Integer
        If magnitude > 0 Then
            textY = arrowBaseYs(0) + 10
        Else
            textY = arrowBaseYs(0) - 25
        End If

        Dim magnitudeText As String = Math.Abs(magnitude).ToString("0.##") & " kN"
        Dim textSize As SizeF = g.MeasureString(magnitudeText, labelFont)
        Dim textX As Integer = startX + (endX - startX) \ 2 - CInt(textSize.Width / 2)
        g.DrawString(magnitudeText, labelFont, labelBrush, textX, textY)
    End Sub

    ' Draws a Moment Load at (x, y), magnitude positive for clockwise, negative for counterclockwise
    Sub DrawMomentLoad(g As Graphics, x As Integer, y As Integer, magnitude As Double, label As String, isClockwise As Boolean)
        Dim pen As New Pen(Color.Blue, 1)
        Dim radius As Integer = 20
        Dim startAngle As Single
        Dim sweepAngle As Single

        If isClockwise Then
            startAngle = 210.0F
            sweepAngle = -300.0F
        Else
            startAngle = 30.0F
            sweepAngle = 300.0F
        End If

        ' Draw arc
        Dim rect As New Rectangle(x - radius, y - radius, radius * 2, radius * 2)
        g.DrawArc(pen, rect, startAngle, sweepAngle)

        ' Arrowhead at end of arc
        Dim endAngleRad As Double = (startAngle + sweepAngle) * Math.PI / 180

        ' TIP of the arrow is ON the arc
        Dim tipX As Integer = CInt(x + radius * Math.Cos(endAngleRad))
        Dim tipY As Integer = CInt(y + radius * Math.Sin(endAngleRad))

        ' Tangent direction (arrow points along tangent) — FLIPPED by 180°
        Dim tangentAngle As Double
        If isClockwise Then
            tangentAngle = endAngleRad + Math.PI / 2 + Math.PI  ' flipped direction
        Else
            tangentAngle = endAngleRad - Math.PI / 2 + Math.PI  ' flipped direction
        End If

        ' Wing angle offset (how "bent" the V is)
        Dim wingAngleOffset As Double = Math.PI / 6  ' 30 degrees

        ' Arrowhead wings go BACK from the tip
        Dim wingLength As Integer = 10

        Dim leftWingAngle As Double = tangentAngle - wingAngleOffset
        Dim rightWingAngle As Double = tangentAngle + wingAngleOffset

        Dim leftWingX As Integer = CInt(tipX - wingLength * Math.Cos(leftWingAngle))
        Dim leftWingY As Integer = CInt(tipY - wingLength * Math.Sin(leftWingAngle))

        Dim rightWingX As Integer = CInt(tipX - wingLength * Math.Cos(rightWingAngle))
        Dim rightWingY As Integer = CInt(tipY - wingLength * Math.Sin(rightWingAngle))

        ' Draw V-shaped arrowhead
        g.DrawLine(pen, tipX, tipY, leftWingX, leftWingY)
        g.DrawLine(pen, tipX, tipY, rightWingX, rightWingY)

        ' Label
        g.DrawString(label, SystemFonts.DefaultFont, Brushes.Black, x + radius + 5, y - 10)

        pen.Dispose()
    End Sub


    Private Sub ExitToolStripMenuItem_Click(sender As Object, e As EventArgs) Handles ExitToolStripMenuItem.Click
        If MessageBox.Show("Exit?", "Exit", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = vbYes Then End
    End Sub

    Private Sub ResetToolStripMenuItem_Click(sender As Object, e As EventArgs) Handles ResetToolStripMenuItem.Click
        ' Clear all input TextBoxes
        txtMagP.Clear()
        txtLocP.Clear()
        txtMagR.Clear()
        txtLocSR.Clear()
        txtLocER.Clear()
        txtMagT.Clear()
        txtLocST.Clear()
        txtLocET.Clear()
        txtMagM.Clear()
        txtLocM.Clear()
        txtMagP.Focus()

        ' Reset ComboBoxes to default index (e.g., 0 or -1 if none)
        cmbT.SelectedIndex = -1
        cmbM.SelectedIndex = -1

        ' Clear reaction output TextBoxes
        txtRA.Clear()
        txtRB.Clear()

        ' Clear the drawing area (PictureBox)
        picDiagram.Refresh()
    End Sub
End Class