Stepping through 3DFrame

Posted on 16/09/2017 by dougaj4

Following a recent comment this post looks at the code for setting up the stiffness matrix for a 3D frame, and how to step through any selected part of the code.

The general procedure for setting up a 3D stiffness matrix, and rotating it to the global coordinate system is given at the link above.  The 3DFrame spreadsheet (including full open-source code) can be downloaded from:

3DFrame.zip

The main program for the 3D analysis is the sub-routine p44, found in the mFrameP44 module in the Visual Basic Editor (VBE), which can be accessed by:

  • From the spreadsheet, press Alt-F11, or click the Visual Basic icon on the Developer tab*
  • Double-click the mFrameP44 module in the Project Explorer window.
  • Click the right-hand dropdown box above the editor window, and select P44

*  If the Developer tab is not visible, go to File-Options-Customize Ribbon, and select it as one of the main tabs.

The code for setting up the global stiffness matrix is:

    ' !---------------------global stiffness matrix assembly------------------------
elements_2:
' Range("kga").ClearContents
    For iel = 1 To Nels
        For i = 1 To nod
            Num(i) = g_num(i, iel)
            For j = 1 To NDim
                Coord(i, j) = g_coord(j, Num(i))
            Next j
        Next i

        ReDim km(ndof, ndof)
        i = BeamConER(iel, 6)
        If i = 0 Then
            ReDim R0(1 To 3, 1 To 3)
            Call rigid_jointed3(km, Prop, Gamma, Etype, iel, Coord, R0)
        Else
            For j = 1 To 12
                SpringA(1, j) = BeamHinge(i, j + 1)
            Next j
            Call spring_jointed3(km, Prop, Gamma, Etype, iel, Coord, R0, SpringA)
        End If

        For i = 1 To ndof
            g(i) = g_g(i, iel)
        Next i

        Call formkv(kv, km, g, neq, iel, g_coord, Num)
    If iel = Range("kmbeam").Value2 Then Range("km") = km
    Next iel    ' elements_2

This code loops through each beam element in the frame and calls either the rigid_jointed3 or spring-jointed3 routines for beams with fixed or spring end conditions respectively. The 12×12 matrix returned for each beam is then added to the global stiffness matrix with the formkv routine.

To step through the code in the p44 routine simply make sure that the cursor is somewhere within the body of the routine and press F8, or Debug-Step Into.  To run the routine to a selected point either:

  • Set a breakpoint at the required location by clicking in the left hand margin, then press F5 or Run-Run or
  • Select the line to run to, then press Ctrl-F8 or Debug-Run to cursor.

There is also a separate function, rigid_jointed3TT, that can be called from the spreadsheet for a specified beam, and returns the beam 12×12 stiffness matrix to the spreadsheet as an array function.  The instructions below show how to step through this function line by line.

To step through a VBA function it must either be called from a sub-routine, or initiated from the spreadsheet.  To do the latter:

  • Create a breakpoint somewhere within the VBA code by clicking in the left-hand margin.
  • Select a cell in the spreadsheet that calls the chosen function.  The screenshots below use cell C35 in the Matrix examples spreadsheet.
  • Press F2 (edit), then either enter for a function that returns a single value, or in this case Ctrl-Shift Enter to return an array.  The function will then run to the selected breakpoint:

You can now step through the code one line at a time by pressing the F8 key (or Debug-Step Into).  Note that the Locals Window, under the main Editor window displays the status and value of all variables, and you can also see the value of a variable by simply placing the cursor over the variable name anywhere in the code:

Procedures for stepping through the code are then the same as for a sub-routine.  To run to a selected line press Ctrl-F8 or right click and Run to cursor:

At the end of the function it will either return the end result (the km2 array), or one of the four intermediate arrays, depending on the value of the Out argument:

The Debug menu provides further options, for example allowing control to jump directly to a specified point, or for called routines to be run in a single step.

For more details of VBA debugging options see Chip Pearson’s Debugging VBA.

Posted in Beam Bending, Excel, Finite Element Analysis, Frame Analysis, Newton, UDFs, VBA | Tagged , , , , , | Leave a comment

Setting up UDF Applications

Posted on 09/09/2017 by dougaj4

Following a recent comment, this post looks at setting up a user defined function (UDF) on a blank worksheet, using the ConBeamU function as an example.

To use a UDF, the VBA code for the function must either be included in the active workbook, or another open file.  In most cases the VBA code can be copied from the master file to a new workbook, but in the case of the ConbeamU function the units related code refers to a database of units data in the master file.  The easiest way to set up a new file for this case is to save the master file with a new name, and delete all the unwanted sheets.  I have added a ConbeamU-template file to the ConbeamU zip file, that has all the required code and units data, two sheets with notes and instructions, and a single blank sheet.  The new zip file can be downloaded from:

ConbeamU.zip

The screen shots below illustrate how to set up a new application of the ConbeamU function, starting from a blank worksheet.

First copy details of the function arguments from the Functions sheet, and enter or copy and paste the input data.  Each data range may be placed in any convenient position.  For the ConbeamU function the required data ranges are:

  • Segments: details of each beam segment with different section properties, with distance of the segment end from the start (left hand end) of the beam, flexural stiffness (EI), and optionally shear stiffness (GA).
  • Outpoints: a single column with either the number of output sections for each span, or a list of output point positions (see below for more details).
  • Supports: position of each support, with optionally translational stiffness, rotational stiffness, and displacement.
  • Dloads: extent and magnitude of distributed transverse loads.
  • PLoads: location and magnitude of point transverse loads and moments.
  • OutUnits: single row with units for output results: position, shear force, bending moment, slope (leave blank), and deflection.
  • Out: output index, optional, default = 1 (output as listed above).
  • ListOutPoints, optional, default = False, output at specified number of sections/span.  See below for details of True option.

Note that for the ConBeamU function (and other unit aware functions) all data ranges with values that have a unit must be headed by a valid unit symbol:

After entering all required input data, enter the function in the top-left cell of the output range.  The easiest way to ensure that all arguments are provided, in the right order, is to enter the function name, including the opening bracket, then click the “insert function” button, just to the left of the edit bar, as shown below

As each function argument is selected the contents of the cell or range are shown to the right of the data box.  When all the required arguments are selected the function results appear under the data boxes.  In this example the default values are what we want for the two optional arguments, so we can leave them blank.  Click OK or press enter to enter the function:

At this stage only the first value of the results array is visible:

The standard Excel way to display all the contents of an array function is:

  • Select the required output range, with the array function in the top-left corner.
  • Press F2 (edit).
  • Press Ctrl-Shift-Enter

However the ConbeamU spreadsheet has a macro that will do this automatically, so with the cell containing the entered function still selected, just press Ctrl-Shift-S.

The default output option is to specify the number of output sections for each span.  An alternative is to list the position of each section where output is required.  In the example below two points are entered at each internal support, and each point with a point load or moment.  To display the output set the final “ListOutPoints” argument to True, and select the list of locations range as the “OutPoints” argument.  Having edited the function, press Ctrl-Shift-Enter to enter:

As before, to re-set the output range to display only the cells with valid output values, press Ctrl-Alt-S:

Note that the list of output point locations does not need to be adjacent to the output range, it can be anywhere in the workbook, or even in another workbook.

The procedures described above are applicable to any Excel function or UDF that returns an array function, except that resetting the output range to display the whole array by pressing Ctrl-Shift-S only works in those workbooks where the required macro has been added.

Posted in Arrays, Beam Bending, Excel, Finite Element Analysis, Newton, UDFs, VBA | Tagged , , , , | 2 Comments

UDF to replace cell references with values

Posted on 30/08/2017 by dougaj4

I recently posted an update to the Eval2 spreadsheet with a subroutine to display a cell formula as a text string, with the cell references replaced by the associated values.

I have now added three user defined functions (UDFs) to do the same job:

  • Addr2Val1 takes a text string as input and returns the formula with all cell references or range names converted to the value in the referenced cell.  Cell references may be anywhere on any spreadsheet.
  • The Eval function has been modified to work with cell references and range names, as well as optional lists of parameter symbols, and their associated values.
  • Addr2Val2 works the same as Addr2Val1, except the input is an active cell formula, rather than a text string.

The new file may be downloaded from:

Eval2.zip

Examples of each function are shown in the screenshot below, followed by source code for the Addr2Val2 function.  Full open-source code for the other functions is included in the download file.

Updated 3 Sep 2017: There seem to be issues with the WordPress system removing line breaks in some places, and inserting them in others. I have corrected the code below, but if you want to copy the code I recommend doing so from the download spreadsheet, rather than from the listing below, which probably still has some errors. 

Function Addr2Val2(FuncRng As Range, Optional CommaDec As Boolean = False) As Variant
 Dim NumChar As Long, ParamDict As Scripting.Dictionary, i As Long, CheckC As String, AscCheckC As Long, CheckP As String, NewFunc As String, iErr As Long
 Dim ParamRng As Range, NumParam As Long, PVal As Variant, IsRng As Boolean, CheckRng As String, Func As String

    ' Evaluate a cell formula (Func), replacing cell addresses or range names with the values in the referenced cells.

    'Func is a single cell containing the formula to be evaluated
    
    ' CommaDec = True to convert commas to decimal point and semi-colons to commas
    ' CommaDec = False (default) for no convertion.
    
    Func = Trim(FuncRng.Formula)
    Func = Replace(Func, "$", "")
    
    If CommaDec = True Then
    ' Replace all , with . and ; with ,
        Func = Replace(Func, ",", ".")
        Func = Replace(Func, ";", ",")
    End If
    
    NumChar = Len(Func)
    i = 1
    Do While i <= NumChar
        CheckP = "" 
            Do 
                CheckC = Mid(Func, i, 1) 
                AscCheckC = Asc(CheckC) 
                If (AscCheckC > 64 And AscCheckC < 91) Or (AscCheckC > 96 _               And AscCheckC < 123) Or AscCheckC = 95 Or AscCheckC = 33 Then
                CheckP = CheckP & CheckC
                i = i + 1

       ElseIf CheckP <> "" And Asc(CheckC) > 47 And Asc(CheckC) < 58 Then 
                CheckP = CheckP & CheckC
                i = i + 1
            Else
                ' Check if CheckP is a cell address or range name
                On Error Resume Next
                CheckRng = ""
                IsRng = False
                CheckRng = TypeName(Range(CheckP))
                If CheckRng = "Range" Then IsRng = True
                If IsRng Then
                    NewFunc = NewFunc & Range(CheckP).Value2 & CheckC
                                
                ' else leave it unchanged
                Else
                    NewFunc = NewFunc & CheckP & CheckC
                End If
                i = i + 1
                Exit Do
            End If
        Loop

    Loop

    Addr2Val2 = NewFunc
End Function
Posted in Excel, UDFs, VBA | Tagged , , , , | Leave a comment

Jansch and Renbourn live

Posted on 28/08/2017 by dougaj4

Three recently uploaded You Tube recordings of live performances by guitarists Bert Jansch and John Renbourn.  As further evidence that the quality of a You Tube video is inversely proportional to the number of views, none of the three have over 1000 views, and the first has just 6.

Bett’s Dance; Bert Jansch live at the 12 bar:

Bert Jansch and John Renbourn; un-named instrumental, live from Massachusetts, 1990

From the same concert, John Renbourn plays So Early in the Spring:

 

Posted in Bach | Tagged , , | 1 Comment

Scottish Fiddlers

Posted on 27/08/2017 by dougaj4

Yesterday I saw “Scotland the Brave” at the Sydney Opera House, featuring the Willoughby Symphony Orchestra and Choir, and fiddler extraordinaire Marcus Holden:

whose playing of Scottish fiddle music reminded me of Robin Williamson and the Incredible String Band:

and lead to the discovery that Marcus Holden also plays in a string band, The Jugalug String Band:

Posted in Bach | Tagged , , , , , | Leave a comment