Module 5 : Force Method - Introduction and applications
Lecture 4 : Three Moment Equation

Example 5.25 Analyze the continuous beam show in Fig. 5.29(a) by the three moment equation method if support B sinks by an amount of 10 mm. Draw the shear force and bending moment diagram. Take flexural rigidity .

 

 

Solution: Since support A and D are simply supported, .

 

Applying the three moment equation for span AB and BC : ( )

 

                    

 

or                                                                                                                                                                                (i)

 

Span BC and CD :

                      
 

or                                                                                                                                                                             (ii)

 

Solving Eqs. (i) and (ii), and .

 

The bending moment diagram is shown in Figure 5.29(b).

 
   
   
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