How Cables Work - With Diagrams! (Structures 1-2)

Here we understand how cables work using diagrams! How they change shape with changing load, how that means we can understand the tension in the cable and where/how it changes.
I also go through how this relates to suspension bridge cables too!
This is a follow-on video from the one I did with a fun cable demonstration you can find here: • How Do Cables Work? (w...

[@sambarlow3226]

great video, super clear, thank you!

[@siangibby5771]

I subscribed because of the "Funiculi', Funicula'" reference. Good work, all of it. Thanks for this great instruction.

[@PaulKassabian]

Awesome, thank you!

[@wisternykesilva5582]

this is channel is very very very good!

[@roctrader]

I like your teaching method Paul, very intuitive. You got a new subscriber, keep on this great work!

[@PaulKassabian]

Thanks! 15 years of teaching at MIT then Harvard...so something must be useful!

[@xingchenghuang5324]

Amazing structure intuition!

[@nathanshields6585]

These videos are well done! I love a good catenary

[@PaulKassabian]

Best. Thing. Ever.

[@user-hk6pj9qn2r]

amazing!!! thank you very much!!

[@PaulKassabian]

You're welcome!

[@gokulsatyasriram4614]

I love it. I want much more content from you sir.

[@PaulKassabian]

new one just posted!

[@gokulsatyasriram4614]

@@PaulKassabian 😀😀😀

[@iceman7298]

Brilliant!!

[@anandjamdade9156]

Excellent Sir

[@johnjaccob6419]

Keep going and thanks

[@wisternykesilva5582]

this is channel is very very very good1

[@PaulKassabian]

Thanks!

[@mohammadrezaranjbar2475]

very good🤩

[@TheEldho]

Hi Paul, How do we calculate the tension on a catenary cable held between two points ? Adding another cable on top of the existing one, trying to figure out whether it is going to hold

[@engsan710]

Hi Paul, when do you have to consider the weight of the cabel?

[@FoxRiverBridge]

If only we had been shown this video while learning math in grade school

[@belaczako1102]

High Paul. It's seems clear, that bridges deck is curved because of heat dilatation but how the cables can folow the deck when it shrink in cold? It looks to me that the deck, and the cable shrink in the oposite direction, wich leads to heavy tension. And which direction the support needs to handle forces in a suspension bridge?

[@PaulKassabian]

Good question, when the temperature reduces both the deck and cable shrink so it's not an opposite problem..due to geometry there are differences which are analyzed as temperature loadcases for all bridges. Thanks!

[@daultimateknight1539]

You helped me a lot :) may I use these diagrams? I would appreciate it if I could have a soft copy to use in my presentation

[@PaulKassabian]

Of course. They are from an iPhone/iPad app I used to have. I had help making them. I will be doing a video on them soon and, as part of that, I will include a link to all the images...so stay tuned!

[@bouzoukistudent8180]

are there any formula as to , and take the first examle here were we added a second string , if we take as a point o reference a vertical line passing thrught the middle of our weight , in what angle while increasing the span of the "hands" holding the line , the load ( tension) each hand is holding is equal as the tension when we holding the weight with one string ? i am guessing 45 degrees . but when we add a second or third or more loads the that said angle changed based the distance between loads ?( lets say that they are equaly destributed ) . Thank you !

[@PaulKassabian]

You're asking when the tension in a V-shaped string equals the force of a single central weight...for that it's 30degrees to the horizontal. Because half the vertical weight goes to each hand and sine(30)=0.5. For the rest, you just keep solving using basic trigonometry from the weights going up to the supports!

[@hadeelhabeeb3100]

hello mr Paul. can you help me to find the equation of the catenary curve when add e weight

[@hadeelhabeeb3100]

hello can you help me to find the equation when I add the weight

[@SharlsRS]

Im a little confused about how a free body diagram would be when the cable reaches the fully horizontal position while carrying a vertical load, as there is no vertical component to counterweight the downward load.

[@PaulKassabian]

Thanks for your note. With any vertical load (including self-weight from gravity) a cable cannot be perfectly horizontal. It may look like it (or essentially be so close as to be negligible) but there will always be some vertical displacement.

[@rockapedra1130]

Isn't it a catenary instead of a parabola?

[@PaulKassabian]

Thanks for your note. A catenary is the shape of a cable under its own weight (and nothing else), whereas a parabola is the shape of a cable under a constant horizontal load.

[@hugbearsx4]

@@PaulKassabian ... in a system where the weight of the cable itself is negligible compared to the external load that shapes it.

[@errishavsingh3767]

Hey Mr Paul Kassabian i am watching it from India 🇮🇳 but i wanna khow how Cable staying Extradosed cantilever bridge work...... would you please 🙏 make presentation upon it for me 😊.How should i connect with you sir?

[@archaeopteryx7405]

The shape of the cable is not a parabola; it is a catenary, a function of cosine hyperbolic.

[@PaulKassabian]

Thank you...a cable under its own weight is a cosine hyperbolic as you said...when point loads are added that are heavier than the cable then it becomes a parabola. The difference being how the the weight distributed: when it is along the curve of the cable itself it's a cosine hyperbolic ...whereas when the loads are distributed along the horizontal the shape becomes parabolic.

[@archaeopteryx7405]

@@PaulKassabian thank you for the clarification. I found your videos are pretty interesting and instructive.

[@hadeelhabeeb3100]

catenary curve