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
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.
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 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.
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
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.
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?
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.
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.
+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.
+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.
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!!!
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 :)
Sorry sir. Seemed good in the beginning and then it went crazy. Seems like you are talking to yourself. Be more clear and precise. Students are waiting for clarity & that is precisely what is missing here.
Never seen the "force polygon" method. Very cool.
what is this amazing thing called a force polygon and how do I use it??????????
Hello have you ever discovered what isthat force polygon!?
Thank you so much, I finally learned this an hour and a half before my final because of this video
everything was perfect until he used force polygon and skipped the part I came for
Sarah AlS its just basically drawing the forces to scale
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
i would still have 2 unknowns..........
@@flyergeorges3619 then do 2 equations 2 unknowns :)
@@alas3640 thanks man but I already graduated 🤣
Ya that force polygon method is fricken awesome
everything was perfect up until the force polygon....couldn't understand that
Don't just use force polygon without explaining how it works
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.
I wish I had a maths teacher like this when I was in school.
I don't understand how you got all the force values at 7:40
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.
Thank you for this explanation. I will now proceed to use force polygons on every one of my statics exams.
@@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.
thank you so much Intro Part is what i needed to hear..thanks sir
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
can you please tell how or show me how you got CD AND CJ after polygon method
How did you get the forces CJ and CD sir? I'm still confused on how you got them. I just need clarification
Superbbbbb!!!....lovin it😘😘
you lost me when you used magic to find the remaining members after JK
wow powerful....apreciated
Thank you! Nice explanation :)
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
Grayson Grzybowski So your book says that the moments is anti clockwise for positive?
frank white Same thing with mine; textbook states the moment is positive for counterclockwise and negative for clockwise
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.
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?
Grayson Grzybowski it doesnt matter which way is positive . Because it will give you the same result .
Love this....thank you Sir.
Wonderful 🙏
Thank you you did a great job
Thanks a lot, you really helped me.
sir you were amazing wile you were explain until you said force polygon
How to use force polygon?
It's from kinematics of machinery.
Great
Do you have more questions on it
better tha my instructos
interesting but i would like to know how vertical distances of 2,2,2 come about.
like how are those distances calculated
So he gets to the polygon, any directions on how he calculates past that? I followed up to the polygon then I'm lost...
great video
At the end of the video he said that this is the Method of Joints which made it confusing. But, thanks anyway!
How to find whether the unknown forces are in tension or compression?
How to assign the directions for forces (compressive and tensile) especially on trusses?
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.
I wish you where my professor.
I think I understand how this force polygon method works but how is this reliable on a test?
How did you do that force polygon method? ha
Awtsu Er Er I really dont get it? you have the values already.
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.
+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.
thank u
How u did the value of force CD??
how to use force polygon method?
mah boi saved my gpa
why is the perpendicular distance of force 10kN 4m at point B? I thought it was 2m?
oh whoops my bad. I used the vertical distance lmao it always confuses me.
what in the heck is a force polygon
You put CJ in tension but is actually COMPRESSION
Can anybody teach me about the detail of force polygon like that?
thank you so much
sir can i get the pdf/the file on the projector please?:(
Thanks nice
good
why did u neglect Force from C to K?
because there is no perpendicular distance when taking a moments from point C but he include it in force polygon .
+lyod lepiten we can find perpendicular distance though
+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.
Thank you!!!!!
force polygon is unknown to me. could you please describe it in another one.
how to give directions for end lines of divided section?
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
I learned that Clockwise Rotation is Negative and Counterclockwise is Positive!
god bless you
force polygone, whats that
its like a jedi, the Force Polygon Method, wtf is that?
thanks sir
anti clockwise is positive and clockwise is negative right??
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!!!
or we could take moment at J and solve for CD
Yeah, it would work if and only if there wasn't a 10kn force at c
that would just cancel ou wouldn'tt it?
am i the only one who got a negative Fcd= -18.55 and Fcj= -14.14, which means both are in compression.
i used sum Fx and sum Fy to get that answer.
how did you get FCD AND FCJ ? did you use the polygon method?
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.
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 :)
I just used a system of equations.
all the comments about the hell force polygon:)
Thank you :)
Wtf is polygon method
กิตติพล ขาวงาม
Sorry sir. Seemed good in the beginning and then it went crazy. Seems like you are talking to yourself. Be more clear and precise. Students are waiting for clarity & that is precisely what is missing here.
MY CD IS 63.35 KN
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
How to use force polygon method ?