SA62: Cables - Introduction

This lecture is a part of our online course on introductory structural analysis. Sign up using the following URL: courses.structure.education/
In addition to updated, expanded, and better organized video lectures, the course contains quizzes and other learning content.

[@user-gq8xd8bx5q]

Best structural analysis channel on KZbin. Your mathematics are sound. Thanks for the video

[@McPlaySpot]

4:28 loved how that stick extended to such length out of the blue lmao

[@nasir0214]

Hats off Dr structure! God bless.

[@notetaker1141]

Very informative, and well done! Thanks!!!

[@uzairahmed4725]

which software you are using for animation and text writing? Good to know

[@DrStructure]

It is done using a script/program in Adobe Illustrator.

[@mashambashonhai4901]

Good day Dr Structure.. Thanks for the wonderful video on cables. I don't know if i might have missed the part for solutions or maybe they are not available yet

[@DrStructure]

Thanks for the feedback. The exercise problem solutions are going to be a part of the next lecture which will be made available within the next few days.

[@mashambashonhai4901]

@@DrStructure Alright, Thank you

[@ishaqmatin4721]

that is nice, are you going to add more lecture about analysis of cables?

[@DrStructure]

Thanks! Yes, more lectures on cables will be added in due time.

[@caoxuanhung4708]

10:39 Could you tell me reasons why is h1=0.45m? In the case, we don't know about this How do we solve problem?

[@DrStructure]

At a street intersection, the traffic light has a certain configuration determined/decided by the engineer during the design stage. The heights of the lights/wires are determined based on experience and the design specifications in use. Without knowing h1, we end up having too many unknowns to be able to solve the problem using basic equilibrium equations. This is similar to static determinacy in beams and trusses. If we end up with too many unknowns, we cannot solve the problem with the available equilibrium equations. In such a case, we have to resort to more advanced techniques for analyzing the system.

[@caoxuanhung4708]

@@DrStructure Thank you very much!

[@Eng.Ahmed_Gamal]

Can you tell me what the defence between cable, wire and rob ? Get my dfination on the cable

[@DrStructure]

For the purpose of structural analysis, cables and wires are treated the same way, they can take only tensile force. The difference between a wire and cable is often one of size. Wires are significantly smaller in diameter compared to cables. Cables are generally made of strands of wires. Unlike wires and cables, a rod is a rigid member that can undergo both tension and compression.

[@Eng.Ahmed_Gamal]

@@DrStructure I did not mean the rod but rather the rope

[@DrStructure]

From the structural analysis perspective, there is no difference between a rope and a cable. They both are tension members. Although they are made of different materials, hence offer different strength properties.

[@Eng.Ahmed_Gamal]

Thanks

[@SK-cs5pk]

Sir please cover the topic *how to find fixed end moment*

[@32_rivaldosihaloho37]

how do we get the height assumption in 10 : 44

[@DrStructure]

Height h1 is a geometrical dimension of the system. It can be determined by directly measuring it once the traffic lights have been assembled. Alternatively, knowing the material properties of the cable used to hang the lights, we can employ advanced analysis techniques to determine the displacement of the cable under the load.

[@Eng.Ahmed_Gamal]

10:37 Why is this distance assumed with this value

[@DrStructure]

They are obtained by measuring the distances between the (hypothetical) traffic lights. For the analysis purposes, one can use other values for those distances. The focus of the exercise is the notion of static equilibrium and how to compute forces using equilibrium equations. The actual determination of the number and location of traffic lights at an intersection is well outside the scope of this lecture.

[@Eng.Ahmed_Gamal]

@@DrStructure My other daughter. How can you assume an unknown thing and is not uncontrollable in the problem

[@DrStructure]

@@Eng.Ahmed_Gamal In engineering analysis, mathematical modeling methods are often invariant with respect to certain dimensions of the system that is being modeled and analyzed. For example, the analysis techniques used for structures are not a function of the dimensions of the structure. A beam can be analyzed using the same technique (the application of the equilibrium equations) regardless of the length of the beam. Whether the beam has a length of 5 meters, 6 meters, … the same principle applies. So, if the objective is to discuss the method, the specific number that we use for the length of the beam is irrelevant. The same idea applies in this case too. The specific distances between the traffic lights are irrelevant with regard to the principle of equilibrium being demonstrated in this lecture.

[@user-du2ps3fx2t]

Why the flexible structural element can't resist bending like cable

[@DrStructure]

That has to do with the properties of the material. Some material are not sufficiently rigid to handle certain types of loads.

[@user-du2ps3fx2t]

@@DrStructure why!?

[@DrStructure]

You need to look into mechanics of materials to better grasp how certain materials behave. There are an abundance of textbooks and other resources on that topic.

[@user-du2ps3fx2t]

@@DrStructure Show me a book to refer to

[@DrStructure]

A visit to a library or even an extensive internet search is the right course of action in conducting your research on the topic.

[@violetdzvuke1509]

why did we assume 0.45 on the second example am now confused

[@DrStructure]

We would not be able to analyze the system using the static equilibrium equations without knowing the shape that the cable assumes. The value of h1 completes the definition of the system’s geometry, enabling us to solve the equilibrium equations. If h1 is not know, the system remains statically indeterminate. To analyze such systems, we need to use more advanced techniques that are well beyond the scope of our lectures on cables.

[@violetdzvuke1509]

@@DrStructure ok If l come across a new question and the value of h1 is not known like in this example, how do l assume a value or l just use 0.45 like you did here?

[@DrStructure]

If the problem is a real-life one, you can measure the distance. If the problem is on a school test, you need to ask for more information.

[@violetdzvuke1509]

@@DrStructure thank you so much👏👏👏

[@Eng.Ahmed_Gamal]

I want to communicate with you on Facebook

[@DrStructure]

We are not on facebook. Please feel free to post your technical questions pertaining to each lecture on the comment section. We will respond accordingly.

[@Eng.Ahmed_Gamal]

@@DrStructure What if I want to display an image of a problem? Does KZbin support that?

[@DrStructure]

If you need to send us an image, send e-mail to [e-mail]

[@Eng.Ahmed_Gamal]

Thanks