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Wednesday, 27 November 2019

REACTIONS AT SUPPORT AND CONNECTION IN ENGINEERING MECHANICS

We have started a new topic in our previous post i.e. engineering mechanics. We have seen there the basics of engineering mechanics such as concept of force systemprinciple of transmissibility of forces and its limitations, classification of force systembody force and surface force, moment of a force, Varignon’s theorem, concept of a couple, resultant of a force system acting on a body and how to draw the Free body diagram with the help of our recent posts. 

Now, we will be interested here to understand reactions at support and connection in engineering mechanics with the help of this post. 

Reactions at support and connection in engineering mechanics 

This topic i.e. reactions at support and connection in engineering mechanics for solving any kind of mechanics problems involving the different types of forces. 

We will understand here the different types of supports, connections and their reactions here with the help of this post. 

So, let us start now without wasting your time. 

In structural arrangements, support is basically defined as a member that helps other members to resist the loads. 

Support condition that restrain translation in one direction 

Support condition that restrain translation in one direction, what we will understand after reading this? 

Its means, support condition that does not permit the motion in one direction.   

Roller support, friction-less surfaces, rockers and wall edges are the best example for support condition that restrain translation in one direction. 

There will be only one unknown term and that will be the magnitude of the reaction force normal to the contact surface. We will have information here the direction of this reaction force but we will have to find out here the magnitude of this reaction force in such type of support conditions. 

Let us see here few examples for supports that restrain translation in one direction with the help of following figure. 

Roller support

Support condition that restrain translation but permit the rotation 

Support condition that restrain translation but permit the rotation, what we will understand after reading this? 

Its means, support condition that does not permit the translation motion but it permits the rotation. Translation or linear movement will be restricted here at such types of supports. 

Hinges support, rough surfaces, frictionless thin bearings and frictionless pin connections are the best example for support condition that restrain translation in one direction but permit the rotation. 

Let us think the case of a door which will be supported with the help of hinges. If we think it, we will be able to say that only rotational motion will be possible and there will not be any possibility for the translation or linear motion. 

There will be two unknown terms and that will be the magnitude and the direction of the reaction force at support. 

As we will not have any information about the magnitude and the direction of the reaction force at support, we will write the reaction forces for such types of supports as Rx and Ry. We will have to find out here the magnitude as well as the direction of the reaction force in such type of support conditions. 

Let us see here few examples for supports that restrain translation in one direction but permit the rotational motion with the help of following figure. 



Hinge support

Support condition that restrain translation and rotational motion 

Support condition that restrain translation as well as rotational motion, what we will understand after reading this? 

Its means, support condition that does not permit the translation motion and rotational motion. 

Translation or linear movement and rotational motion will be restricted here at such types of supports.  

Fixed supports such as simply supported beams, welded ends and two closely spaced pin joints are the best examples for support condition that restrain translation and rotation both. 

There will be three unknown terms and that will be the magnitude and the direction of the reaction force at support and the moment. 

As we will not have any information about the magnitude and the direction of the reaction force at support, we will write the reaction forces for such types of supports as Rx (horizontal reaction force, F) and R(vertical reaction force, V). We will have to find out here the magnitude as well as the direction of the reaction force and moment too in such type of support conditions. 

Let us see here few examples for supports that does not permit the translation motion and rotational motion with the help of following figure. 


Fixed supports

Therefore, we have seen here the meaning of supports, various types of supports and connections and their reactions and finally we have also looked here the practical examples of different types of supports in various engineering equipment with the help of this post.   

Do you have any suggestions? Please write in comment box and also drop your email id in the given mail box which is given at right hand side of page for further and continuous update from www.hkdivedi.com.   

Further we will find out, in our next post, concept of force system and Trusses in engineering mechanics.  

Reference:  

Engineering Mechanics, By Prof K. Ramesh 
Image courtesy: Google   

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