Trusses: Method of Sections

Trusses: Method of Sections

[@AnthonyLevine007]

Never seen the "force polygon" method. Very cool.

[@whatdahek4120]

what is this amazing thing called a force polygon and how do I use it??????????

[@edwinlyakwipa7325]

Hello have you ever discovered what isthat force polygon!?

[@sarahals2268]

everything was perfect until he used force polygon and skipped the part I came for

[@MeTaLcOrE1616]

Sarah AlS its just basically drawing the forces to scale

[@dw8402]

Thank you so much, I finally learned this an hour and a half before my final because of this video

[@brandonxu9278]

everything was perfect up until the force polygon....couldn't understand that

[@dmurray1200]

You can replace the "force polygon" part of this solution with sum of the forces in the x and y directions and solving for them. Hope that helps someone

[@flyergeorges3619]

i would still have 2 unknowns..........

[@alas3640]

@@flyergeorges3619 then do 2 equations 2 unknowns :)

[@flyergeorges3619]

@@alas3640 thanks man but I already graduated 🤣

[@jake7472]

Don't just use force polygon without explaining how it works

[@WarriorOfHonor16]

Ya that force polygon method is fricken awesome

[@engissol]

ENGISSOL 2D Truss Analysis software features a powerful finite element solver to analyze trusses consisting of elements with rotational releases at their both ends. The deformed configuration under external loads is calculated and the axial force diagram of the structure provided by the user is represented. The creation of the model is an easy and quick task as the user can take advantage of the intelligent user interface of the software. Its versatile graphical user interface, the predifend libraries and many other available features can save you time and effort. Moreover, the program also supportes non-linear static analysis (second order analysis) for the consideration of P-Delta effects.

[@funshop7865]

5 years later before 2 days of my exam he introduced magic polygon I will just put the answer from my friends copy and will write force polygon method. Thanks

[@angelus_solus]

I wish I had a maths teacher like this when I was in school.

[@johnkupa8885]

thank you so much Intro Part is what i needed to hear..thanks sir

[@gloryk8277]

can you please tell how or show me how you got CD AND CJ after polygon method

[@Champagnepipa]

you lost me when you used magic to find the remaining members after JK

[@arjaylomuntad1247]

How did you get the forces CJ and CD sir? I'm still confused on how you got them. I just need clarification

[@graysongrzybowski943]

yea can you please explain to me how clockwise is positive and anti-clockwise is negative!!!! cause im looking in my book and its the opposite

[@ceebowone]

Grayson Grzybowski So your book says that the moments is anti clockwise for positive?

[@sharinganMRDBZ]

frank white Same thing with mine; textbook states the moment is positive for counterclockwise and negative for clockwise

[@ceebowone]

sharinganMRDBZ Well i assume you are from the US? its just a case of you drive on the right side while we drive on the left side. You use Fahrenheit we use celsius.

[@sharinganMRDBZ]

Yeah I'm the US ( Yeah we drive on the right side, while you drive on the left, but when it comes to weather, I use only Celsius since my parents come from a heirtage affected by the Europeans and its easier since we mainly use Celsius for scientific functions) Using this will allow me to come to the same result, as long as the rules are follow?

[@nrshar0n]

Grayson Grzybowski it doesnt matter which way is positive . Because it will give you the same result .

[@ayadhoussemeddin9143]

sir you were amazing wile you were explain until you said force polygon

[@Sjsime827]

I don't understand how you got all the force values at 7:40

[@Nelster]

They figured out the angles of the force vectors from the height and length of the truss, then since a force polygon in equilibrium is closed, they just drew everything to scale and measured the lengths of the vectors.

[@taylorinase2148]

Thank you for this explanation. I will now proceed to use force polygons on every one of my statics exams.

[@dielaughing73]

@@taylorinase2148 He would have solved it by using trig. If you complete the triangle containing the two unknowns you can solve easily since you know the length of the horizontal side and all angles. Sine rule lets you solve for CD and CJ. Simples.

[@seanpettee2821]

So he gets to the polygon, any directions on how he calculates past that? I followed up to the polygon then I'm lost...

[@yorenton]

At the end of the video he said that this is the Method of Joints which made it confusing. But, thanks anyway!

[@Sivise_fishtank]

wow powerful....apreciated

[@abbasmuhammadd.7090]

Love this....thank you Sir.

[@tanmay.agarwal89]

Superbbbbb!!!....lovin it😘😘

[@dipankarlaskar6875]

How to use force polygon method ?

[@deej6611]

Thank you! Nice explanation :)

[@davidkim0678]

I think I understand how this force polygon method works but how is this reliable on a test?

[@dennistwabona8691]

interesting but i would like to know how vertical distances of 2,2,2 come about. like how are those distances calculated

[@mj-pe5wl]

Thank you you did a great job

[@saeedAhmed-ck3ot]

Thanks a lot, you really helped me.

[@dylanloo6276]

How to find whether the unknown forces are in tension or compression?

[@karatillo10]

I learned that Clockwise Rotation is Negative and Counterclockwise is Positive!

[@Niloufasay]

How to assign the directions for forces (compressive and tensile) especially on trusses?

[@freshbeans1608]

you assume it however you like for any truss. Upon calculation ull discover ur answer to be either positive or negative. If for a certain truss u got a positive force and ur assumption for its direction was tension, then ur assumption is correct and it is indeed tension. If ur answer turned out to be negative, then it is the opposite of what u assumed, therefore compression.

[@edwinlyakwipa7325]

Wonderful 🙏

[@Milkisu_u]

why is the perpendicular distance of force 10kN 4m at point B? I thought it was 2m?

[@Milkisu_u]

oh whoops my bad. I used the vertical distance lmao it always confuses me.

[@ntonyjaime_]

Do you have more questions on it

[@AllForTheBetter]

I wish you where my professor.

[@littlelion1801]

Can anybody teach me about the detail of force polygon like that?

[@waheedx97]

great video

[@udekk2r867]

How u did the value of force CD??

[@ahammedbappy8091]

force polygon is unknown to me. could you please describe it in another one.

[@raffyfuertes5332]

how to use force polygon method?

[@BRianG1017]

what in the heck is a force polygon

[@hongcesoo4358]

mah boi saved my gpa

[@alessandromarchetti6672]

You put CJ in tension but is actually COMPRESSION

[@daniaazzahra1698]

sir can i get the pdf/the file on the projector please?:(

[@ianjaydelosangeles3173]

better tha my instructos

[@niderdelacruz3218]

How did you do that force polygon method? ha

[@niderdelacruz3218]

Awtsu Er Er I really dont get it? you have the values already.

[@ceebowone]

Awtsu Er Er If you have Autocad it will make the force polygon so much easier. As you can see, he first solved JK using the Moment equation but he still needed to solve CJ and CD. You convert the Forces magnitude into mm or cm so 10KN will be 10mm. When you draw up the force polygon you draw up each force into millimeters at the exact same angle shown on the diagram. With CD and CJ you complete the loop only using the angle of these two values and trimming off the excess where the two meet. Then the measurements of CD and CJ will be the magnitude of force.

[@trexinvert]

+Awtsu Er Er The fact that you are confused/asking is telling. You are not alone. The force polygon is basically a short cut(like identifying a zero force member by "eye"). The real method is just a simple FBD: ΣFx=0 and ΣFy=0.

[@chinurock8669]

thank u

[@vkvivek1633]

i am getting Fcd = 17.69 kn.. can anybody explain me why. ? its a differance of 1 kn..which is large.. well i used the moment eq at J.

[@immortaleddie]

you have to take the perpendicular distance of CD to point J. Its not 6m. I took 6cos(26.565) for that distance which is 5.366. that gave me a force close to his answer. not sure why though :)

[@chriswass1176]

am i the only one who got a negative Fcd= -18.55 and Fcj= -14.14, which means both are in compression.

[@chriswass1176]

i used sum Fx and sum Fy to get that answer.

[@gloryk8277]

how did you get FCD AND FCJ ? did you use the polygon method?

[@viky7344]

how to give directions for end lines of divided section?

[@lyodlepiten2369]

just an opposite direction dude. suppose u have upward force on the first part on the second part to make it balance u should make it downward

[@bandiogouwack7064]

force polygone, whats that

[@abhionyoutube]

why did u neglect Force from C to K?

[@lyodlepiten2369]

because there is no perpendicular distance when taking a moments from point C but he include it in force polygon .

[@abhionyoutube]

+lyod lepiten we can find perpendicular distance though

[@lyodlepiten2369]

+Abhishek Poudel nope. when taking a moments to a specific point. any force that intersect to that point have no perpendicular distance from that force.

[@osmundmorrison4786]

Wtf is polygon method

[@kartik5073]

Thanks nice

[@bryanlloydpallega6856]

its like a jedi, the Force Polygon Method, wtf is that?

[@esraasand842]

good

[@thanos9346]

anti clockwise is positive and clockwise is negative right??

[@Tnbizzkits]

Yup, thats what I was thinking. Ultimately it does not matter as you symbol will tell you which was it is at the end. Its about assumptions to start with. Im UK, he is AUS so it must be a world hemisphere thing!!!

[@UpperXEgo]

thank you so much

[@erzcav4793]

Thank you!!!!!

[@vangelissfs434]

god bless you

[@gagandeepsingh2925]

thanks sir

[@OneWIngyBoi]

I just used a system of equations.

[@wanted1729]

all the comments about the hell force polygon:)

[@tutingrubena1584]

or we could take moment at J and solve for CD

[@princechukwuma9686]

Yeah, it would work if and only if there wasn't a 10kn force at c

[@tutingrubena1584]

that would just cancel ou wouldn'tt it?

[@vaughnsigal4560]

he didn't specify what he was using as a positive direction for the moments. You always have to write what you're stating as positive

[@thabisiledladla6857]

MY CD IS 63.35 KN

[@user-lm8ql4mx5r]

กิตติพล ขาวงาม

[@LinnSpin]

Thank you :)

[@ayracullano9121]

How to use force polygon?

[@srakeshgowda]

It's from kinematics of machinery.

[@AlphaAussies]

Great