Q BgQuestion:

Scholar
Karma Points: 261
Respect (80%):
posted by  bankai001 on 5/21/2008 11:59:17 PM  |  status: Live  

Finding Ra,Rb, and Ma (Prob 10.4-1)

Course Textbook Chapter Problem
N/A N/A N/A N/A
Question Details:
A propped cantilever beam AB of length L carries a concentrated P acting at the position shown in the figure. Determine the reactions Ra, Rb, & Ma for this beam. Also draw the shear force and bending-moment diagrams, labeling all critical ordinates.
Bonus Point Alert! Earn +4 additional karma points for helping this annual member.

AAnswers:

Answer Question
Mentor
Karma Points: 617
posted by jayborre on 5/25/2008 6:08:05 AM  |  status: Live
Asker's Rating: This answer has not been rated. If you asked this question, then please login.   
Response Details:
This propped beam can be simply analyzed using  different deflection methods, but  for a much simpler and easy-to-understand solution, we will be using the Moment-Area Method.

By the second theorem of M-A method, it states that (with respect figure below which i mark the roller support as point A and the fixed as point B, anyway its just a designation, the results will be the same) the deviation of A with respect to B (t B/A) is equal to the area of the moment diagram between A and B, multiplied by the distance from A to the centroid of the area of moment diagram.

By formula:



But if you notice, since there is roller support at point A, we can say that:


For the moment diagram by parts:


Hence,


= 0












Solving for Ra:





But if you notice, a + b = L and therefore, b = L - a, substitute this  in the working equatiion:

 

Finally,

(Note: this Ra is the value of the reaction at the roller support)


I will not spoil the fun here, the reaction on the fixed end as well as its moment can be computed by summing forces at point A and point B respectively (with respect to my figure). But I will give you the answers for Rb and Mb.

Here it is:







Also, here's the shear and moment diagram:



 
Note: Please bear with me for I have reversed the figure as well as its letter designation, but anyway, the results are the same.


If you still have questions regarding this problem, feel free to message me. And please don't forget to rate me. Thanks and GOD bless

If you still have some questions regarding this topic, Please don't hesitate to ask me. Also, please don't forget to rate me. Thank you and GOD bless



JAY ROBIN B. BORRE

BS Civil Engineering
Technological Institute of the Philippines - Manila
jayborre@yahoo.com
0917-9137085
Answer Question
Ask New Question

Join Cramster's Community

Cramster.com brings together students, educators and subject enthusiasts in an online study community. With around-the-clock expert help and a community of over 100,000 knowledgeable members, you can find the help you need, whenever you need it. Join for free today » How Cramster is different than tutoring »