Calculate deformation of node 4 of the isostatic system below, using the Virtual Work Method manually.


Hint for solution

 

According to the method; Integral should be considered separately for bars between 1-2 and 2-4 nodes.

Detailed solution


E= Modulus of elasticity A= Cross-sectional area I= Cross-section moment of inertia M= Moment on the element due to external loading M'= Moment on the element due to unit loading Δ= Deformation

 

Step 1: Finding Moment Function Based on Unit Load

1: Unit loading D 1 , D 2 , D 3 : Support responses M 12 : 1-2 bars 2 DN moment value
M 24 : 2-4 bars 2 DN moment values ​​L 12 : 1-2 bars length L 24 : 2- Length of 4 bars
M 12 (x): 1-2 bars moment function M 24 (x): 2-4 bars moment function ΣM 1,dn : Total moment about 1 DN ΣM4,dn: Total moment about 4 DN ΣD: Total equilibrium

Moment Function :,


Step 2: Finding the Moment Function Based on the Given Load

D 4 , D 5 , D 6 : Support responses M'12 : 1-2 bars 2 DN moment value M'24 : 2-4 bars 2 DN moment values
​​L 12 : 1-2 bars length L 24 : 2-4 bars length M'12 (x): 1-2 bars moment function
M'24 (x): 2-4 bars moment function ΣM1,dn : 1 Total moment relative to DN
ΣM4,dn: 4 Total moment relative to DN ΣD: Total equilibrium

Moment Function : ,


Step 3: Multiplying the M and M' Moment Functions in the Previous Steps and Getting the Integral

Integral for 1-2 Bar

Integral for 2-4 Rod

Deformation of node 4 = 0.91 m