FE Exam Review - FE Civil - Structural Engineering - Determinacy and Stability - Frames

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[@sylvesterj95]

Finally someone who explains this perfectly. Thank you kind sir.

[@SubashBhandari-ps8mn]

amazing content that made the concept clear. thank a lot man. looking at your other videos as well. very helpful

[@servewithsmile3243]

Passed FE. Got a similar question. Thanks for all videos

[@directhubfeexam]

Congratulations! I'm glad these videos helped!

[@achillesprocorpio1936]

Thank you! You explain it very simple and clear 👍👍👍💯

[@directhubfeexam]

@@achillesprocorpio1936 you’re welcome!

[@robinnombrado1631]

Your explanation sir is clear thank u

[@ahulse78]

Why is 4 a hinge in the first example but not in the second?

[@directhubfeexam]

Hi Adam, the goal for determinacy and stability is to find the number of joints. The type of connection isn't really relevant to the question but for the first example the joint at 4 is assumed to act like a pin (i.e a hinge) and for the second example the joint acts as a fixed joint. At point 4, it will still be considered a "joint" for both cases. I hope this helps a little. Note: on the Other Disciplines FE exam determinacy and stability are not tested.

[@quintonmarsalis5902]

DIRECTHUB FE EXAM PREP why is "c" for example 2 equal to zero?

[@andreahodge5679]

Hi! Great Video. Why is there no reaction at the hinges but were counting them as different members?

[@directhubfeexam]

Hello Andrea, when using the method in the FE Handbook for Frames, the reactions (r) are always the external reactions. The tricky part is the c value. This is the number of condition equations. I'll save you a headache by giving you this hint - THE NUMBER OF CONDITION EQUATION (c) IS ALWAYS DETERMINED BY THE FOLLOWING EQUATION: c= Number of members meeting at a hinge -1

[@andreahodge5679]

@@directhubfeexam I understand that c is typically the number of hinges right? But I’m confused as to why in the problem we don’t include the reactions in the hinges but on other problems we do?

[@directhubfeexam]

@@andreahodge5679 Hi Andrea, I see the confusion there. The only time you would consider the reactions at the hinges is for BEAMS. For trusses and frames, you only count the external reactions when determining the r-value.

[@andreahodge5679]

@@directhubfeexam Okay thank you!

[@megtea]

why is c = 0? shouldn't it be 5? not sure why you counted the ones in the last video, but not these ones.

[@directhubfeexam]

c is always number of members meeting at hinge minus 1 c = n -1 If you do that you’ll always get it right

[@mienge2177]

Can you please do more complicated problem with 3 column 2 stories frame with hinges in the middle of beams. Do you count as 2 beams or 1 beam when there is hing in the center of beam? or is there 2 different ways to do it thanks.

[@directhubfeexam]

mie nge if there’s is a hinge at the center of the beam it will be 2 beams. So n=2. Please refer the the determinancy for beams videos.

[@TaraNathPoudel]

Can I Get This Book link??

[@chrischiaramonte1400]

Do pinned supports count as towards the C value? My problem has pinned supports instead of fixed supports, and this seems to be the only way I can get the correct answer

[@directhubfeexam]

Hi Chris, I think you are referring to the hinges? Yes, they do contribute to the C value. The fixed supports do not. So in this case since there are 3 hinges with only two members meeting at each hinge - C = 3. If you apply this equation to any pins (hinges) - it always works out. C= Number of members meeting at a hinge -1 Let's say we had 3 members meeting at a hinge: C = 3 - 1 = 2 Hope this helps!

[@cradleblaze8798]

Can you also apply this for trusses ass well ? By the way thanks a lot for sharing this method ! Edit - : Found it the starting of the video

[@directhubfeexam]

Hi Cradle, Actually trusses are a lot easier to analyze for determinacy. You would apply the rules under "Plane Truss" in FE Handbook 10.1 on page. 271. Apply this approach only for frames.

[@learncivilwithparam170]

Do above Check is sufficient to check stability ?

[@directhubfeexam]

Hi, this method does not. Checking for stability is not discussed in the FE Handbook but will depend on two major conditions. 1) If the reaction forces are all parallel the structure is classified as being "unstable". In this case, the reaction forces are not all parallel so we are ok. 2) If the reaction forces are concurrent (the line of action for each reaction force intersect) then the structure is classified as "unstable". In this case, the lines of actions for all the reaction forces do not intersect (i.e. not concurrent) therefore the structure is stable. I hope this helps!