Truss analysis by method of joints: worked example #1
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- เผยแพร่เมื่อ 18 มิ.ย. 2016
- This engineering statics tutorial goes over a full example using the method of joints for truss analysis. You first need to solve for the reaction forces by drawing a FBD of the entire structure. Once you have the reactions, you then need to draw a FBD of every joint. It’s the standard convention to draw unknown forces in tension, so that if you get a positive value for their magnitude, you know you have correctly assumed tension, and if you get a negative value, it just means that the member is in compression. Once you calculate an internal force in a member, it will be a known value for the next joint it touches. So if it’s found to be in compression, then just draw it in compression when you do the next FBD (meaning it’s pushing on the joint rather than pulling on it).
There is a typo in this video: The truss is 0.866m tall, not 1m. It's 1m*sin(60)=0.866m. Doesn't actually affect anything in the problem, it was just labelled wrong.
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Thanks for watching, I hope it helps!
What am I even going to college for? lol. You explained analysis of trusses better in 15 minutes than my prof did in 2x 2 hour lectures
That's a good question.
College? Is for us to know that there are many things we don't know...
That's true
what if do not change directions of truss at any specific joint at all(in other words leave all forces at every joint going outwards(tensile) no matter what and just while substituting the force while solving the next joint put a minus sign i.e if got a force as compressive the ans is -ve so instead of changing the direction of force just substitute the given -ve force directly while solving next joint.
How to calcute the reaction at support(im not sure whether its positive or negative)
Very helpful. This chapter has been the hardest for me yet and I believe I finally have this stuff figured out. I appreciate you explaining the "why" aspect of what you're doing rather than assuming that the audience knows as much in Statics as you do. I think some professors need to remind themselves that this stuff is going to be obvious to them when they've been doing this stuff for 20+ years, and not so obvious for the students learning this for the first time.
Yessss glad that my explanation worked. What you described is exactly what I try to accomplish in the videos. Cheers 🤜🤛
This is the one topic I have struggled to grasp and you sir have explained it and presented it flawlessly. I cannot thank you for how much you have improved my chances of getting a better grade.
Thanks for letting me know Venya.. really happy to hear that I could help!! I made several other truss and statics videos here: engineer4free.com/statics =)
Best "method of joints" tutorial I could find on youtube. it really helps thanks for sharing. I hope u r doing great wherever you are now.
Thanks for the kind words Max! Hope you are doing great too :)
+Engineer4Free I also agree! Thank you so much for helping me
True
Is the same true if i get -350 for my ay?
my mans a literal life saver, amazing work diving into topics specific to an engineering course. you explain it heaps better than my lecturers with thick accents and the long tangents they go in mid class
Very clean presentation, straight to the point, no time wasted drawing all it out in real time. very useful video
Yo Freaky Banana, thanks for the feedback...glad you like it =)
I missed the exam last year for this topic, and now when I'm about to retake it I knew i could just come back here to refresh my memory. Excellent video
this is the best video on TH-cam for the analysis of truss, short, simple, straightforward, clean, exact and has got the best explanation.
Thank you so much for the amazing video.
Thx bro. Please share my vids with some other classmates!
@@Engineer4Free sure, will do the same
This video has really explained things to my understanding. In fact I'm speechless. This video has just made me pass my elementary structures tomorrow... I'm really grateful
Amazing!!! Thanks for letting me know!!! If you have more left in the course, you might want to check out the other examples @ engineer4free.com/statics =)
I’m in the middle of taking my final and I think it’s safe to say you’ve saved my grade i wish you were my professor
Thanks!! Glad you like the video.
Also.... you are in the middle of your final and on YT? Zoom University lol
I am so doing this tomorrow lol
Very good demonstration, thank you d’or sharing. With your nodes analysis this covers it all. So helpful!
Thank u so much for teaching this for free! I watched most of ur videos whenever i hv trouble understanding something and in need of more examples to solve a problem. Theyve helped me a lot and u make it so easy to understand 😁
Awesome!! Thanks for the great feedback 😁😁
Hi :-)
Thank you for your time to making this video!
this is really helpful!!!
I hope u r doing great wherever you are now ;-)
This is hands down the best video I have ever seen . Thank you!!
Wow, thanks Aaron! =)
i have to say this is the best lesson out of the south sahara , you explained a whole 4 hour lecture in two simple videos , ps ive subscribed to the channel and ready for more engineering videos
Awesome, thanks Kelvin!!! =) =)
You explain better than my uni Lecturer will do in 1hr without even hearing him not to talk of understanding how he's going about it
Thanks so much
Thanks sir for this great tutorial on 'The analysis of Truss'....
because of you I got the simple method to solve problems without any confusion....
Glad to hear it man! Thanks for watching, and if you haven't seen the rest of my statics tutorials, then do check them out at engineer4free.com/statics :)
This is the best TH-cam I've ever watched..
Wow...you got good stuff
Best "method of joints" tutorial I could find on youtube!
Thanks man! That's awesome to hear!!
You literally saved my day, thankyou!
I've been told this 3 times before but didnt understand it.
Really glad I could help. Check out all the videos I did at engineer4free.com/statics , I have a few more on this method there too
Your explanation made these problems much easier to solve. Thanks
Thanks for letting me know David, cheers!
Well hats off to Engineer4Free for still replying to comments and keeping people updated even after 4 years. You're amazing
Thanks Atharva! Still trying🤜🤛
Thank you very much.....God will surely bless you for helping us understand
My problem was the direction of the forces in the members at first and now you've helped me understand it
I'm Soo happy ....thanks!
omg. finally a video that actually makes sense. youve made this so easyyyy. oh god thank you so much
This video is always a life saver the night before exams
clear and straight to the point. amazing explanation.
Thanks for watching!!! =)
I have a solid mechanics exam today and this just helped me understand this topic so quickly! Thanks!
Good luck!!! Plenty more vids btw at engineer4free.com/statics and engineer4free.com/mechanics-of-materials 👌
i got one in 3 days lol
@@anask4052 good luck
Thank you so much, literally saved me from hours of frustration.
This... this is amazing. You just earned another sub!!
Awesome!! Welcome 😊😊
Yo!
This video has helped me out alot, you are great at making things clear. However i still struggle with a similar problem. It looks more or less the same but the main difference is that if u look at point "B" you have a force that is coming from southwest aswell as southeast and one that is perfectly horisontel. If u instead change the horisontel one to a force that is pointing northeast, at say 25 degrees how would you go about solving that? For me the problem is that when im about to calculate the resulting force to be zero i get 2 unknown integers wich makes the equation unsolvable. Im really confused here and would appriceate any help i could get!
watched this legit 20 minutes before my exam and it helped so much
Glad to hear it! Now you know where to come before your next exam too
This is totally a breakthrough .... Good job.
Awesome!! Make sure you check out the rest of my statics vids at engineer4free.com/statics , the truss videos are numbers 42-51
yo thanks a lot at first I wasn't understanding then later I actually did understand keep doing your thang god bless
Word glad to hear it. Check out all the truss videos at engineer4free.com/statics if you haven’t already, they are numbers 42-51 ✌️
this guy explained it better than my lecturer, thanks man
You're welcome, thanks for watching! Check out the full playlist at engineer4free.com/statics 👌
Grear refresher for me since we've been in quarantine here in the Philippines for about 2 months now, I forgot my statics😂, I'm now in my Deformable, I'm trying to remember how to solve indeterminates using stress/strain. GOOD WORK SIR THANK YOU🙏
Glad I can help!!! Keep it up my friend 🤜🤛
PS I’ve got tutorials on indeterminates in these other courses: engineer4free.com/mechanics-of-materials and engineer4free.com/structural-analysis ... if you haven’t seen them already!
THANK YOU FOR MAKING THIS VIDEO, IT HELPED ME A TON!
Hi. the video and explanation is great but i keep getting negative values when you get positive ones. I was wondering how you decide on the direction of the components of the force before finding out the direction of the force itself (compression or tension)
Auto subscribe, this tutorial so far is the best for me. Thank you sir!
Thanks for the sub!! =)
@Engineer4Free. Thank You for the video. I was just wondering, how did u get Absin60 at around 3.30 minutes in. I just don't understand that part.
All angles in this problem are 60 degrees. That is because all members are the same length, so every triangle is equilateral, so every angle is 180/3=60 degrees. So AB is 60 degrees off the horizontal. We use the SOH CAH TOA trig functions to find its x and y components. Draw a right angle triangle such that AB is the hypotenuse, and the 60 degree angle is included. ABx = ABcos(60) and ABy = ABsin(60). See this diagram for help, it's a slightly different orientation, but the same idea: i.imgur.com/Dvdqf2t.jpg
Well this helps can’t wait to learn more when I’m done middle school
Keep on it!!! 🤜🤛
So when you are talking about compression of AB is it in terms of compression on the joint? because a compressive force has two forces of the same magnitude directing at one another
Honestly mate, you're a legend!!!!!!
this is really help, thanks for the lession sir
so neatly explained :) thank you sir!
Most welcome!!! More truss vids @ engineer4free.com/statics =)
Wow thank you i've always been confused with what arrow to draw thanks a lot 💯🙏
Awesome, glad I could help! You can check out all the statics videos I did over at engineer4free.com/statics if you haven't already, I have a whole section on trusses
what about when we dont have the applied forces only a few of the internal forces for instance AB,BC,BD...how do we go about figuring out those applied forces?
Thank you for the good job. you made the course simpler for me
You're welcome Kamohelo, I'm glad I could help you 🙂
thank you for this and saving me for my final coming up!
I've got it clearly, thank you very much.
Great!!! Thanks for letting me know =)
oh my god, this is so so helpful. Thank you so much
You're welcome Phạm!
Its perfect! but forces acting at a joint or node vertically (ex :- absin60) acting towards the node. Similarly , why dont abcos60 dont act towards the node?. Any explanation?
If the 200N would be going horizontally at B (to the right), would both moment at A and E still be positive?
Thank you very much for the in-depth explanation
Glad it was helpful! thanks for watching =)
My man just explained this better in 15 min than my lecturer managed to in 5 hours.
😏
You just saved my exam for tomorrow, god bless you
Awesome, glad to hear it! How did the exam end up going?
and here i am ..saved for my exam for tomorrow..LMAO
u saved me for tomorrow's exam too lol
@@Engineer4Free I guess we’ll never know
got a test tomorrow too lol
this guy is always saving me in the day before the exam, god bless you brother
when I did sin60 my ti-84 gives me -.3048 is there a reason our numbers are different?
@@dram906 maybe ur calculator, reset it because sometimes its on radian system change it to degree
@@ahmedothman6642 thankyou got it now!
@@dram906 no need, good luck
th-cam.com/video/fRyUf-GY754/w-d-xo.html
man, you're a life saver!
Happy to help! You should check out the rest of the statics vids I did here too: engineer4free.com/statics =) =)
Your video helped a lot, thank you!
Awesome Allan, glad I could help!! 🙂
I think I've forgotten how to do basic trig lol. Can anyone explain to me why sin is used when it is, and why cos is used when it is?
Haha all good. Take an angle that you know. Construct a right angle triangle such that the two members on each side of the angle are two of the sides of said triangle. Draw the third side in a way that makes it a right angle triangle. Identify which side is the hyp, opposite, and adjacent from the perspective of the known angle, then just plug and chug with SOH CAH TOA to find any unkniwn sides that you need. Example drawing is here: imgur.com/a/YCT6I1a 👌
Thank you Sir, this video was so helpful.
Awesome thanks for the feedback =)
Simple and effective!
Great content! quick question though, when solving for joint B on the Y axis, you used AB as 57.7 instead of -57.7. Why?
Cuz the vector is headed up and to the right. Remember that up right and an anti-clockwis moment are all the 3 positive directions that he is using. If he was using down left and clockwise as positive directions then that would be -57.7
AB is in compression meaning it is pushing out internally a force of 57.7 towards B
It feels like i have wasted my whole semester classes by listening to boring professor. Many Thanks for saving my paper. Cheers!
Sorry to hear, but you’re not alone. Glad I could help 🤜🤛
Sorry to hear, but you’re not alone. Glad I could help 🤜🤛
this tutorial explains everything I cant learn in school, I dont know why some teachers in universities dont have this kind of talent when it comes to teaching.
Thanks Darryl! In case you haven't seen the rest of the playlist too, its here: engineer4free.com/statics There are more truss tutorials in videos 42-51👌
@@Engineer4Free Thank you! 💙
When doing the FBD for each joint, the problem im doing, asks me to find member forces for more of the right side of the truss, so can i start doing it from the right side???
Yep, same either way. I just tend to start on the left out of habit. If you only need to find the force in one single member, use the method of sections. See videos 49 - 51 here: engineer4free.com/statics 👍
The best methods of joint you real elaborate whoever coming to cross these tutorial, the easy way of getting all forces acting at X-direction and Y-direction just you need to dismantle the Truss by FBD
Thank you so much for your explain..
It's really help me to understand.
Great, glad to hear that!! You can find all of the other statics videos that I did here: engineer4free.com/statics
thankyou, you're a lifesaver.
You’re welcome Syari!!!!!
Great tutorial, thank you.
Thanks Thomas!
why when drawing the whole trusses free body diagram do u not include Ax anymore, while including it in the second drawing?
I draw it on the first FBD of the entire structure, and then at 0:40 I acknowledge that Ax=0 because there are no horizontally applied loads acting on the structure. Once you know a force is zero, you don’t need to draw it again, it would just be distracting, so its acceptable to not draw it on the FBD of only joint A.
You are the best saved me alot of time
Awesome!! Check out engineer4free.com/statics for the rest of the statics videos =) =)
Great video! Helped me alot on my exam.
Awesome really glad to hear it!!! Thanks for letting me know :)
Thanks a lot this video helped me a lot in understanding joint method. Love from India. You are doing a great job.
Thanks Saket!! I have more tutorials at engineer4free.com/statics see #42-51 for more truss examples👍
@@Engineer4Free You are welcome. I will surely watch those videos. I have issue with section method
Thank you sir,that has really helped ❤❤👏👏💯
in choosing the joing do younhave to follow some pattern or any joint can be chosen as much as is has max of two forces to be determined
Generally you want to start at a support with known reaction force, but as long as you have enough info to solve at the joint, feel free to start wherever
While solving for joint D why was CD taken as positive evne though it is in compression and was found out to be negative? Someone please clear this confusion.
CD is found to be in compression so we change its orientation on the fbd of joint D to be pointing towards the joint with RTs known magnitude. Up is considered positive y direction and right is considered positive x direction for the fbd. CD is pointing up and to the right so its y conponent points up and its x component points right, both of which are considered positive for the respective sum of forces equations used. Does that clear it up?
can i ask? where did the 1.5m and 2.5m came from in the first fbd of the entire structure?
Is this alawys sin for forces in y direction and cos for forces in x direction is all the sums???
I don't understand where do you find 2 m and 1.5m
you dont find it, it's just an example if it is
Wow. This is much understandable than my 2-hour class. I hope you’d do videos in all my engineering subjects too. Hahaha Thanks!
I'm working on it! Check out engineer4free.com for all the courses, new vids and courses are always being added!!
Can i use this method on 45 ^ triangles??
I was wondering when you took the over all net moment which is the sum of the moment by Ey and the 200N force, why you did not include the moment from Ay.
Thanks
bcoz we are taking moment about Ay so we cant include Ay
thank you very much sir...
I find this as best method for doing problems... thanks again.. ☺☺
Glad to hear it! Thanks for letting me know :)
Thank you for existing used this to study
Excellent video, thank you so much :)
You're welcome!!
for joint c, why is the horizontal force of AC not -28.85 cos60?
Hey, i have a warren truss question with just a single triangle and a force acting on the top of the truss a size of 15kN to an angle of 60°. Can you help me with this?
If a member is oriented at 60 degrees and has an internal force of 15kN, then the x component of that internal force will be 15kN*(cos60)=7.50kN and the y component of that internal force will be 15kN*(sin60)=12.99kN. If the member is in tension, it will pull on each joint, and if it's in compression it will push. You can use those numbers and directions to find the sum of forces in x and y at each joint individually. More tutorials on trusses are also here: engineer4free.com/statics (videos 42-51)
Ah the problem is that when i tried to draw it as exactly as you say, all members 1m long and the 60 degree using AutoCad. The height of truss isn't 1m.
Yeah, that 1m vertical measurement is a typo, the height of the truss is 0.866m. But it never impacts or is used in the calculation. Sorry if that confused you. Every member is 1m long, and the angled ones are all at 60 degrees from the horizontal.
I really try to see this comment relating to this since all my calculations are different bec at start it uses the wrong dimension. But gladly the lesson didnt affect the essence of knowing the method.
good video helped me understand
You just explained in 15mins what engineer hamzat couldn't make me understand in 2years ...hamzat
Oh my god thank you, i get it now, a little more clear but just as tedious, thank you
You're welcome =). Method of joints is always tedious. It's the worst when you get to the end and it doesn't add up, and you then know there is a math problem buried in all the calculations some where!
I still hate statics but you did a great job explaining this. Thanks!
🤣🤣 glad I can help!
Thanks sir, you video is really helpful
Thank you so much for making this video,
You're welcome, thanks for watching!
With the 200N pointing down from the top, what if the arrow was pointing down but from underneath the truss??
No change whatsoever. Each represents the exact same thing: just a downward force acting on the truss at that joint!
YOU ARE AMAZING! Why didn't I find you last year! 😭
ahaha SORRY I don't know, but thanks!! =). Maybe tell some friends that could use the vids too so they don't miss out ;)
I hve an excellent teacher, but on trusses i missed the class, so i m watching u thanks
PLS POST MORE CONTENT, RELYING ON U TO SURVIVE THROUGH MY COLLEGE !!! MUCH THANKS!
Able to post content such as Autocad/Solidworks tutorials, Python and other contents like engineering materials pls. Much thanks! U're a lifesaver
Working on it!! Check out all the courses I've completed so far at engineer4free.com 👌
this is real helpful,thank u for sharing
+josef leonard glad to hear it, thanks for watching!! You can find the rest of the statics videos I made here engineer4free.com/statics
Those your answer change if the X's were bigger then 0?