Need help “Describing Structural Components to a Layman”. 1

[Ron247]

I have a case I am working on that I already see that I have to describe the possible structural components used to assemble a structure. The description has to be able to be understood by a typical layman (i.e. juror).

I have chosen to approach it as “ All structures consist of 3 possible components, Stick-like, Sheet-like and String-like. I intend to then outline the entire set of possible distortions (strains) you can do to these 3 possible components. The list I present may have items that are not needed or may have missing items. I need input on both. Being blind-sided in court because of poor preparation really sucks. If you would like to help, please see the attached document for the full scope.

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/raw/upload/v1555132088/tips/Distortions_k4q9du.docx[/url]

 

[TehMightyEngineer]

If you get involved with wood then idealize it as a bundle of straws. Showing how wood works great in compression and tension along the grain using a bundle of straws to represent the grain, but how it's weak perpendicular to the grain, is a very good visual way to explain wood failures.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[3DDave]

For sheet-like I'd look at a stretch fabric with a rubber/silicone frame. This would show the way that distortions lead to buckling.

There's also the ever popular polarization cell with a transparent plastic model sandwiched in between.

 

[SlideRuleEra]

"Everything is a Spring" and the Modulus of Elasticity (E) is the spring constant.

Put a reasonable load on a column or a pile... it "squashes", but returns (rebounds) to full length when the load is removed.

"Pull" on a cable or tension member... same thing as a column / pile... in reverse.

Put a reasonable load on a beam... it bends (deflects), but returns to original shape when the load move on.

"Twist" a beam (with lateral torsional bucking), if not too severe, it "straightens" out when load is relieved.

Edit: Mentioned your thread to my wife; she reminded me of one analogy:
Poisson's Ratio: As a person gets fat, their pants get shorter.

Another that I used successfully explained to regulators (accountants) why our 500+ megawatt turbine-generator foundations should not be taxed:
The large, complex inertia block, including piling/drilled piers, is properly sized to be an active part of the machine. It acts as an "anti-tuning fork" to intentionally vibrate at exactly the right frequencies which cancel and/or reduce the machine's characteristic vibration.

http://www.SlideRuleEra.net

 

[kipfoot]

Since you're breaking down structures in terms of geometry, I'd consider explaining it in two groups:
1) linear (your stick analogy, but also includes a string)
2) planar (your sheet analogy, but may also include a membrane, like a trampoline)

Within each of these groups, a structure has rigidity in various directions (or axes). A linear stick can be a column, but if it lacks rigidity in compression, it might be a rope. A planar structure could be a concrete slab, but if it can't resist bending, then it could be a trampoline or a net.

I could also imagine that support conditions might come into the discussion of how you put these elements together to create a structure. Hopefully this covers the structure in question, and you don't need to explain domes, shells, arches, compression rings. Wishing you juror faces of intense interest and not blank stares.

 

[oldestguy]

You can do the best job by visual demonstrating, as with a cardboard box, an umbrella, a camp chair, or other simple things that people see every day. I once saw an engineer bring in kids building blocks. All that complicated language will go over the heads of average folks.

 

[BUGGAR]

I have found that whenever you are demonstrating something structural, it is best to demonstrate it by breaking it. Set up your demo and make them guess if the bar will bend and drop the (baby*) or if the string will break and drop the knife onto the (baby*).
(*pick something that will affect the audience)

 

[Ron]

Mentioned your thread to my wife; she reminded me of one analogy:
Poisson's Ratio: As a person gets fat, their pants get shorter.

Great Analogy!

Wives of engineers pick up more than we know! My wife was riding around with one of her friends once and they got behind a transit mixer. The friend said "I don't like driving behind a cement truck".....my wife corrected her by saying it's a concrete truck, not a cement truck!

Ron247....as a veteran of many trials and having to explain technical stuff to juries, I've found that they are not as dumb as the lawyers will lead you to believe. They understand basics as long as you don't use jargon and simple visual aids are helpful. I tend to use a flip chart and draw things simply. It works for my students and a respected construction attorney once told me that when I stood up to draw on the flip chart the jury collectively moved forward in their seats and paid close attention....certainly our goal when explaining stuff!

OG's advice is exactly on point as usual!

 

[Ron247]

Thanks a lot for all the ideas. I knew this was a good place to get input.

I later realized that on a stick like component, you cannot visually show shear, what I am actually showing is bending as it relates to shear. For shear, not so easy to visually show. As stated, I am also confident a jury can understand most structural concepts because we all experience them, especially when something actually breaks. What is tough for me, is finding the visual aids. I am trying to show the distortions and I am getting them mixed up with the forces. So I definitely need to work on that.

The round eraser covers most stick/linear distortions. I like graham crackers for brittle concrete and block. You never see it bend, it just breaks. The basic yard stick is still the best axial demonstration except I rarely see new yard sticks. Has that gone away with rotary dial phone?

and Ron, while the pants get shorter would be a great visual, I do not think a jury is going to wait around for me to gain any more weight. So I will stay with squeezing a marshmallow for poissions.

This case will have no need for a catenary, but I though I would include it since I really have had little exposure to design of one.

I would appreciate additional ideas. Thanks

 

[BAretired]

I would appreciate highly critical comments on what I am intending to present to a jury.

It may be better to confine your presentation to structural elements and forces which are relevant to the jury's deliberations rather than attempting to cover the entire gamut of structural engineering.

BA

 

[Ron247]

Right BA, I should only cover the ones pertinent to our position. As I stated, there is no catenary and some of the plane type deformations will not be needed but I did want to compile a really good overall list for future reference. I also see by my post here, that I need to keep forces and deformation separated in my mind. I need to show deformations visually. The reason I want the entire list, is a good attorney will try to ask you a question you either do not know the answer to or have to "fish" for the answer. That is what I meant by poor preparation. If their expert witness is doing his job, he will give him the questions to ask.

Sticks/Linear, Sheet/Planar and strings were the only 3 generic items I could come up with that are used to assemble a structure. Can anyone thing of any others? I include a wooden shear wall with studs as a planar or sheet item.

 

[SlideRuleEra]

...realized that on a stick like component, you cannot visually show shear...

Take a few dry spaghetti noodles, hold them in both hands, hands close together. Then move one hand straight down... the noodles will suddenly (as in real life) shear.

http://www.SlideRuleEra.net

 

[BAretired]

Fasteners might be considered in a category of its own.

BA

 

[Ron247]

Thanks BA, I totally forgot about them. One issue in this project, is how some parts got connected. Take the same arrangement of components, connect them differently and you have a totally different structure.

Thanks Sliderule, that is probably the easiest way to illustrate shear. We have all done that at least once.

 

[BUGGAR]

A deck of cards is easier the sphagetti noodles (and easier to spell).

 

[hokie66]

I don't know about your approach. My approach has always been closer to that of Ron's with flip charts and marking pens. You want to be careful not to talk down to jurors, as most of them are intelligent.

Instead of "stick-like, sheet-like, and string-like", why not just use our own terms, beam, column, tie, etc. and demonstrate those by simple illustrations?

Perhaps I don't understand your motives, but I know you don't want to confuse jurors...unless you do.

 

[JStephen]

I think you'd get halfway through that page and a lot of people's eyes would just glaze over.

 

[WARose]

I used a Jim Mora line with a contractor: You think you know, but you DON'T-KNOW, and you never WILL, okay?

 

[Ron247]

hokie, it is a matter of them more rapidly and accurately visualizing items. In the short amount of time these things take place, I could get 1 or 2 people up to speed maybe but 12 people is harder. This post had 2 goals. The first was did I have a complete list of possible distortions and forces? The 2nd was a good visual way to communicate those distortions and forces. Beam and column is a good example. In engineering, orientation does not determine beam or column, loading does. In everyday life, it is orientation and most people do not have agreement on that.

 

[BridgeSmith]

I think if you assume that the jurors are smart, but not versed in the engineering terminology, you'll be most of the way to your goal. Just use common terms, such as "bending force" instead of "moment". Get too technical, or use words they've never heard, and they'll think you're trying to trick them. OTOH, if you 'dumb it down' too much, you'll come off as patronizing. They don't necessarily have to understand everything, they just have to find you credible and not condescending.