Calculations presentation skills

Introduction

I am practiced at developing and presenting ideas including the maths carrying-forward that idea.

That as I understand it is rather like "MathCAD" [Wikipedia] [Mathcad] but for basic engineering calculations (eg. Euler-Bernoulli beam) I can do it in my text-processor ("emacs" [Wikipedia] [Free Software Foundation] ).

General idea seen in explained examples

AcmeCorp tundish pour - quantitative prediction in design
(using "Bernoulli equation" conservation-of-energy in fluid-flow)
(background - here ).

Cantilever drilling platform - analysis using beam calculations

You will see these are where I needed to convey that the solution is very exact, highly interdependent and one feature cannot be arbitrarily altered unless unfortunate other outcomes are welcomed.

Crucial point - calculations quick

In all cases I have ever met, the calculation, which is what would be shared between engineers, is "time-efficient". Presenting the case developed for a wider audience takes many-fold longer time. Something like 10-fold to 40-fold longer?

The original workings for the drilling platform are provided here (text file)

As the welder, I ran-though this calculation in 2 minutes with the project manager concerned, who had done Mechanical Engineering at University.

The same applies to Finite Element Analysis [Wikipedia] [WeldingInst.] models. The model which is informative to an engineer takes much less time that an explanation of what the FEA model shows.

Like examples

This from 2019 - pile-driving

Did calcs re. shallow water piling.  Conversation for another day if
interested.
Punchline is - seems achievable.
A 19m high shearleg ("A-frame") on a 5m-wide barge would enable a full
305x305x118kg/m 12.2m UC with vibropiler attached (taking ICE 815C - 8
tonnes & 2.6m high) to pass under the apex.  I get the legs as being
SHS 200x200x8thk (very economical), so the entire "A-frame" weighs
about 2 tonnes.  Then blocks, winches, etc.  Fit and demount at will.
Chat if interested.

This has to be a Structural Hollow Section because the much lighter lattice structure would be too vulnerable to damage in this "very rough and ready" ad-hoc. application.

Beam calculation example

Take a 300x200x17.5RHS (Rectangular Hollow Section)(dimensions in mm).
It's S355 steel (355MPa yield strength).
You can find that in "The Blue Book" and check my answer.

It spans an 8m-wide hatch. The deck-beams are "strong".
What central load will it carry?

Firstly explaining - my functions take a "simple" sharp-cornered rectangle shape - so they will very closely but not exactly match the "Blue Book" values. However, they allow you to quickly "sketch" through stages and arrive at plausible solutions which can be "given the full treatment".

(/
(beam-fmax-rhs-simple-cload 200e-3 300e-3 17.5e-3 8 355e6) ;; 229705.8932291666 ;; N
9.81 ;; gravity - N/kg
1e3 ;; kg -> Tonnes
) ;; 23.415483509599042 ;; Tonnes

There you have it - 23.4Tonnes central lifted at onset of bending - eg by a chain-hoist stropped around the beam-centre.

Steps-along-the-way values which can be checked against "Blue Book" tabulated values:

;;; Second moment of area
(*
(ma2nd-plt-ibeam 200e-3 300e-3 17.5e-3 17.5e-3) ;; 0.00016697861979166658 ;; m^4
1e8) ;; 16697.861979166657 ;; cm^4
;;; lower than the "Blue book" value of 18600cm^4 - unusually different

;;; beam moment bear capacity
(beam-moment-capacity 355e6 (z-rhs-b-h-t 200e-3 300e-3 17.5e-3)) ;; 459411.7864583332 ;; Nm (Newton-metres)
;;; taking Blue Book values as double-check
(* 355e6 1240e-6) ;; 440200.0 ;; Nm ;; M=sigma.Z

The reason for this "trivial" example is you can see already the "important" point(s):

• the function which did the calculation is seen named (and its name gives a reasonable hint to any onlooker what it does)
• the values ("arguments") fed to that function are permanently recorded in this flat-text (ie teeny, readily archived) message
• the answer given by that function when fed those values outputs the answer into the text buffer at the cursor location -- which is efficient of human effort and encourages full exposition of the path to the answer

Another "by-the-way"; the function "beam-fmax-rhs-simple-cload" is

(defun beam-fmax-rhs-simple-cload
  (shs-width
   shs-depth
   shs-thk
   shs-length
   shs-stl-sigmamax ;; typically yield stress
   )
  "for an RHS - max.force it will bear in central load simple beam
best if all dimensions & values in SI / metres, etc
Order of args matches order going into ma2nd calc / fn"
  (simple-support-dblbeam-loadcap
   (beam-moment-capacity
    shs-stl-sigmamax
    (beam-sect-mod-z-d
     (ma2nd-rhs-b-h-t shs-width shs-depth shs-thk)
     shs-depth))
   shs-length))

Closing comment

My colleagues feel very confident and on a sound footing given my revealing of the thought-processes leading to the proposed solution(s).

(R. Smith, 23May2023> 27Jun2023)