Daily Challenge Day 56

Started out with intent of creating yet another purlin design spreadsheet and got side tracked creating yet another spreadsheet for getting loads on surfaces of building from pressure coefficients. Including conditionals which change direction of arrows depending on sign of pressure coefficient and loads.

Then moved onto creating worksheet for purlin design, and largely ignored the pressure coefficients calculated in the above. The idea for the new spreadsheet is to show more of the detail calculations. Not finished it yet [23:37], just about to set up calculations for wind direction theta=90. Not entirely sure how much clearer I can make it. At the end of the day, no matter how much detail is presented, the reader needs to put effort into understanding the calculations and that takes time. My current detailed presentation explains the approach, and then presents the required partial loads in a table and combines them together: so no mathematical expressions are shown.

My new approach is showing the mathematical expressions for calculating the moments for the partial loads. Such an approach requires significantly more pages to present the calculations, and the current detailed approach already uses more pages than or routine purlin worksheet. For example our routine design spreadsheet uses a single A4 sheet, either landscape presentation or portrait presentation. The current detail presentation  extends to 5 sheets of A4 paper. Not sure how many sheets the new approach will take, but looking like 4 or more sheets.

Now whilst the new approach shows the mathematical expressions, it doesn’t necessarily make it easier to follow. The problem of the detailed approaches is the step by step calculations get in the way of the final result. So whilst looking at a summary table we may have the question: where did the numbers in the table come from? It doesn’t mean we get rid of the summary table and present pages and pages of calculations showing how every value in the table was calculated.

The detailed calculations are useful for checking. Detailed calculations can also be included in the appendices of formal reports. However, in the main detailed presentation of calculations is not necessary.

As I have mentioned before if you are doing a true independent check, then you do the calculations yourself, you don’t read the calculations, you do the calculations. If you want to check software, create your own spreadsheet or use something like FreeMat or SMath. If you want to check electronic calculation pads, then use pencil, paper and pocket calculator (P3). If want to check the calculator, use a slide rule, log tables, abacus,  or pencil and paper.

So electronic calculation pads (eCalcPads), save time when used on a regular basis and up until such point as start to forget what the eCalcPad actually does, and then have to refresh understanding of the calculations. Which is why it’s beneficial to have multiple eCalcPads, with differing resolutions on the presentation of the calculations. Such assists checking that each version produces the same results for the same inputs. It also provides different presentations to suit the needs of different audiences.

In the main calculations are a means to an end. The main purpose is to assist making decisions and taking action. Or to assist others to make decisions and take action. Or possibly more commonly to make decisions for others, so that they can take action.

As an example the only way I can check ASI design capacity tables (DCT’s) for steel sections is to do the detailed calculations to AS4100 myself. Likewise to check load capacity tables for cold-formed c-sections, do the detailed calculations to AS4600.

Similarly if want to check the span tables and connection resistances to the timber framing code AS1684.2, then need to do calculations to AS1684.1 and AS1720. And thats not overly simple as AS1684.1 still leaves questions unanswered. But that is not an issue about the presentation or availability of calculations: its an issue about the completeness of the documented evidence of suitability, and the ability of others to confirm or refute the contents of AS1684.

The timber framing code is a foundation for becoming familiar with the structural design of buildings and with the timber structures code AS1720, and the loading codes AS1170. Thus open source eCalcPads which permits students to validate AS1684 would be extremely useful for quality assurance, education and training.


  1. [10/06/2017] : Intended publication.
  2. [11/06/2017]: 00:06 Actual.