ST06: Free Body Diagram for Rigid Body Equilibrium (III)

[@ridvanrizvanoglu5800]

The forces directions are matter here? Because I did not understand why on 1:47, Fr going toward pushing hydraulic liquid direction, but on 2:59 its going like pulling liquid direction. Hope I explained my problem

[@DrStructure]

Except in trivial cases where we are certain about the direction of an unknown force, when drawing the free-body diagram, the direction of unknown forces can be assumed. In this case, since the axial force in the cylinder is unknown; we can assume the force to be tensile or compressive. If the calculated force magnitude comes out to be negative, then the actual direction of the force is opposite to the assumed direction.

[@ridvanrizvanoglu5800]

@@DrStructure oh, I was thinking this rule is working only by inner forces analysis. Thanks for explaining 🙏

[@marxregis]

Your videos are much appreciated! Please keep up the good spirit and keep enlightening us!

[@mervealtunel1993]

IS THERE ANY CONTINUE QUESTION SOLUTION?

[@DrStructure]

The aim of this lecture is to illustrate the process of constructing and using free-body diagrams. We do not have a lecture that covers a complete analysis of the system. It may be worthwhile to prepare such a lecture as a continuation of this presentation.

[@jacobthomas785]

Hi,Your videos are all excellent.Can you please upload a real design example with static and dynamic analysis of the same.Also I would like to know how to find the dimensions of the system or detailed design by stress analysis.

[@DrStructure]

Our lecture series focus on static analysis of structures. We don’t yet have any lectures on dynamics or detailed stress analysis of mechanical systems. You may be able to find lectures on the topics of your interest on KZbin. Else, you there are ample (introductory to advance) textbooks on those subjects.

[@engrmasroorkhan2407]

i really like your way of explanation.. i have a question for you.. how you make such videos. i mean which software you use to make such videos?? if you have a tutorial video of making such videos then please paste it here in the comment. Looking for a positive reply from your side

[@DrStructure]

Thank you! There is no single software for this. We use Adobe Illustrator, and Illustrator scripts to generate the animations. We then put the entire video together, and synchronize audio and video using Camtasia Studio. Unfortunately we do not have any tutorial for this.

[@engrmasroorkhan2407]

Thank you Please make a tutorial video on this.. i really need it.

[@mussavirshaikh8925]

if there were more details on how to find the components of the moment, it would be great. Thanks!

[@DARVESHKAUSHIKHR09]

please please provide free body diagram of pulley system .and stress and strain alaysis of SOILD MECHANICS.

[@notetaker1141]

is there any bending moment in the system?

[@DrStructure]

Yes, bending moment can be found in the links/arms away from the pins.

[@evergreen160]

Good explanation thank you

[@DOTA2MAJISTRATE]

hi Dr.Structure, i have problem balancing this frame ibb.co/j4LF8JG ibb.co/wNHsvQM base on a force of 5 kN, my bracing should have a force of 3.5 kN, and it all seems good as the corner part have 0 force ( zero force member ), but when i try to do a global moment balancing i notice the summation of force at any of the support leg to ground is not = 0, please enlighten me :D

[@DrStructure]

You must have make a mistake in your calculations somewhere. How did you get the force in the diagonal members?

[@DOTA2MAJISTRATE]

@@DrStructure well, i did a balancing around Point B, cause Point C is zero force member, so a simple balance ibb.co/2NLhCCn

[@DrStructure]

You cannot analyze this as a truss. Why? because it is unstable, unless you add a diagonal member to the lower level connecting one of the support points to the upper joint of the other column.

[@DOTA2MAJISTRATE]

@@DrStructure Ok i get what you mean, it is because there are moments in the lower column member ?

[@DOTA2MAJISTRATE]

@@DrStructure for frame design by hand calculation, can i calculate the force of 5 kN like what i did ? 1. Base on the horizontal force of 5 kN apply at top of frame, distribute it to the diagonal member by doing a total force=0 at point B 2. Since point C is zero force member, each of diagonal member will carry 3.5kN and when we convert it into x direction it will transmit horizontal force of 5kN into 2 unit of 2.5 kN at left and right side of the column. 3. Then since the height of column to the diagonal bracing is 2m, we calculate the moment to be 2m x 2.5 kN = 5 kN m 4. And check the bending stress of column and see if it can take 5 kNm

[@Maaraktiengineering]

Why fm is negative There is no components of fm

[@DrStructure]

Not sure what you mean by "Fm has no component". Fm acts perpendicular to the central axis of the arm. So, it is going to have a non-zero moment about point B. Furthermore, on the free-body diagram, Fm is assumed to cause a clockwise moment about point B. But, the moment equilibrium equation tells us that for the total moment about B to be zero (for the arm to remain in the state of equilibrium), Fm must cause a counterclockwise rotation, hence, the negative value for Fm.