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RE: Calculations
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- Subject: RE: Calculations
- From: "Conrad Harrison" <sch.tectonic(--nospam--at)bigpond.com>
- Date: Mon, 22 Nov 2010 11:23:24 +1030
I tend to prefer Excel/VBA combination. When ever I get a desire for Mathematical type and look at the MathCAD examples I always reach the same conclusion: presentation of far too much data to reach the conclusion. Most code requirements are dependent on large number of conditional requirements to select the appropraite formula to use. I find VBA code easier to read, than Excel cell formulae, and I don't see the need to present the various options in the printed calculations which tends to be the approach with MathCAD. I prefer hiding certain detail. Manually it would represent the difference between that presented in the main body of the report versus, that in the appendices, versus that on scrap paper kept for reference. For example in coldformed steel design calculation of effective section modulus can take several pages if all calculations were presented, and it needs calculating for each set of different conditions for phi.Mb. To automate the calculations in an Excel worksheet requires a circular reference to force iteration, and circular references are typically flagged as errors. By hiding the calculations away in VBA, the iteration procedure is more readable, and the worksheet just as a single cell formula, instead of several pages. Also when it comes to hot rolled design, most design is carried out using design capacity tables (DCT's), so simply having a value for phi.Mb with out the detail calculations is not typically a problem. My view is that the independent technical expert reviewing the design is meant to check the specification not my calculations nor my arithmetic, but rather conduct independent calculations. The codes of practice provide the formula and procedures, and all have reference numbers. It is the calculations not in the codes which need more disclosure. But once again here most hand written calculations do not present any algebraic formula or reference as to what is being calculated, just expressions with numbers, the person reviewing meant to understand and work out the procedure: or toss aside and conduct independent calculations. Calculations are a means of reaching decisions. In the main however, we are not conducting the calculations for such purpose, but to provide a record that some assessment was made: the design decision already made, for it is simply a repeat of the past. To me a lot of the calculations are a waste. A design-curve could be plotted, on this curve between any two points is an infinite number of other points: people seem to be spending entire careers calculting those other points, when the design-curve gives us the results we need, and a few points only are required to plot the curve. It all depends on the purpose of the calculations. With VBA can grab data from one program, pull into excel transform and write out for use by another program. With Excel can also build larger and larger models, which reference a common parameter list. With Excel can develop simple calculators, which just give the results, which can then be hand written into reports. For example I print moment diagrams from frame analysis software, then hand write the phi.Mb values obtained from Excel calculators, I don't print Excel reports out. With VBA functions I also have a choice between calling the functions in the worksheet cells, or writing a larger VBA application which writes results to the Worksheet. Basically writing an application in say Delphi or C++, requires a lot of effort to get data into the program, edit the data, and to produce and format a report, and also storing and retrieving data from a file. With Excel and MathCAD these aspects of the application are eliminated. I tend to spend as much time in the VBA editor of Excel as I do working in the worksheets. I find Excel a useful all round general purpose data processing tool, though for large amounts of data MS Access is better, though the most of the VBA code is reusable across applications. My first priority is to reach the design decisions quickly, by automating as much as possible. So wind loads for example calculated in Excel used to automatically generate an input file for say MicroStran or Multiframe. But it depends on the extent of the repetitiion that your projects present. If have a high level of repetition then getting the resulst quickly and a compact report are desirable. If really novel and unique, then a more formal and complete presentation of all calculations becomes more important. With pencil and paper typically being the fastest way to find the solution: once found then it could be written up in MathCAD or Excel (using XLC) for presentation and experimentation with changes of parameter. Choice therefore depends on the purpose of the calculations. Also I tended to prefer Quattro Pro spreadsheet, but working on contract, most places had Excel, so for that reason and the benefit of VBA I changed over to Excel. Plus IT managers tend to oppose running *.exe applications that they have not checked, but otherwise permit running VBA macros. So whilst wouldn't let me run Turbo C programs for generating ACAD scripts (*.scr), would allow me to run Excel/VBA macros. MathCAD, TEDDS etc, are not that readily available, the libraries and templates are also short on Australian Codes. Whilst MS Office tends to come preloaded on most computers. So making the best of the tools readily available tends to be my first choice rather than acquiring additional tools. For example I do everything I can to avoid using Multiframe, the need to use puts a bottleneck in the whole exercise. If can do everything in Excel then have a high level of productivity. Basicaly Excel can do all the calculations in less than a minute, double the number of calculations and still less than a minute. The major time consumer is adjusting the input parameters. So that for simple repetive type structures can complete the entire calculations in less than 5 minutes. Using out of the box tools, it takes longer because have to step through individual tasks, rather than process the entire structure from a few simple parameters. But does require that using Excel with the intent of identifying, separating out and listing the parameters which define the system. Rather than running through a ritual of producing calculations. If want the presentation then MathCAD or Excel with XLC add-in (from ExcelCalcs) is the way to go. If want diagrams to illustrate the calculations, then TEDDS or similar software templates is the option to choose. If the calculations are just a component of the over all task then Excel/VBA is my first choice. Central VBA library also reduces inconsistency between multiple worksbooks conducting similar calculations. What I do however does have a lot of repetition, and I work for manufacturers and builders who want standard designs. So I am more interested in maximum capabilities (design-curves and other compact presentations) rather than one-off point-value custom calculations. The choice really comes down to a matter of personal preference. Some people type their presentation calculations up in MS Word. Masterseries PowerPAD structural software is also built around the use of WORD rather than Excel. Regards Conrad Harrison B.Tech (mfg & mech), MIIE, gradTIEAust mailto:sch.tectonic(--nospam--at)bigpond.com Adelaide South Australia ******* ****** ******* ******** ******* ******* ******* *** * Read list FAQ at: http://www.seaint.org/list_FAQ.asp * * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to: * * http://www.seaint.org/sealist1.asp * * Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: http://www.seaint.org ******* ****** ****** ****** ******* ****** ****** ********
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