Module 2 : Analysis of Statically Determinate Structures
Lecture 6 : Internal Force Diagrams
2.6

Internal Force Diagrams

 

Let us consider the beam-column AB of the previous example with the same loading condition, but a different cross-section b - b (Figure 2.11). Following the same procedure as in the previous example we can find the internal forces at b - b . The values of internal forces at b - b are not same as of those at a - a.

   
                          
                          
                          
                           
 

Thus, internal forces vary according to the cross-section under consideration.

                           
 

Figure 2.11 Cross-section b - b of beam column AB

   
  A structural member should be able to carry the internal forces at each section without failure so as to perform its intended function. So, in order to check the integrity or effectiveness of a structural member, one needs to check its capacity against internal forces at its each and every cross-section. This makes the study of the variation of internal forces in a member very important to Structural Mechanics. Such a study is best done through internal force diagrams, which provide, at one glance, several critical information on these internal forces.
   
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