# Structural Analysis Questions and Answers – Qualitative Influence Lines for Indeterminate Structures

This set of Structural Analysis Multiple Choice Questions & Answers (MCQs) focuses on “Qualitative Influence Lines for Indeterminate Structures”.

1. Muller Breslau’s principle gives a quantitative analysis of indeterminate structures.
a) True
b) False

Explanation: Muller Breslau’s Principle gives only a qualitative analysis of ILD for indeterminate structure. ILD co-ordinates cannot be quantified and hence the statement is incorrect.

2. Which one the following is the ILD for the vertical reaction at A for the given fixed beam?

a)
b)
c)
d)

Explanation: For the indeterminate structures as like Fixed Beam, the ILD for the vertical reaction cannot be linear and option A, B and C have a linear variation of ILD Therefore, option D is the correct. Also, Vertical reaction at A would be maximum if the load is placed at support A itself.

3. Which one the following is the ILD for the bending moment at A for the given fixed beam?

a)
b)
c)
d)

Explanation: ILD for the bending would be 2nd-degree curve i.e. parabolic curve. The maximum value for bending at support A would occur if the load is placed closer to support A. To draw ILD for support A, assume pin joint at joint A and hence bending moment co-ordinate would be zero at support A itself.

4. Which one the following is the ILD for the bending moment at section C for the given fixed beam?

a)
b)
c)
d)

Explanation: For the drawing ILD for the shear force at a particular section, we assume roller hinge in between and provide unit displacement in upward and downward direction alongside. Since it is an indeterminate structure, variation would not be linear as indeterminate cases.

5. Which one the following is the ILD for the bending moment at section C for the given fixed beam?

a)
b)
c)
d)

Explanation: For the bending moment at a particular section, ILD will be maximum at that particular section itself. Thus, option b is eliminated. Also, since there’s no external moment acting on the beam, there’ll only be sagging moment and hence option d eliminated. For ILD of bending moment at a section, assume pin joint at section C and giving it unit upward displacement.

6. ILD for the shear force at section C for the continuous beam is ____

a)
b)
c)
d)

Explanation: To draw ILD for the shear force at section C, assume roller at the section and provide a unit displacement in upward and downward alongside the section. Therefore, displacement at section C in the opposite direction would eliminate options A, C and D.

7. ILD for the bending moment at section C for the continuous beam is _______

a)
b)
c)
d)

Explanation: For drawing ILD at section, we assume internal hinge at that section and apply unit rotation in an upward direction and let the remaining beam follow the course of the suite.

8. ILD for any stress function in a structure is represented by its deflected shape obtained by removing the restrained offered by the stress function and applying a unit displacement.
a) True
b) False

Explanation: Muller Breslou’s principle is helpful for developing qualitative ILD for determinate as well as indeterminate structures. ILD for any stress function in a structure is represented by its deflected shape obtained by removing the restrained offered by the stress function and applying a unit displacement.

9. Which one of the following is the correct combination of loading for the maximum negative moment at section C for the given continuous beam?

a)
b)
c)
d)

Explanation:
Drawing ILD for bending moment at section C gives us as

Therefore, Maximum negative Moment for section C is obtained when loading is placed at the second and fourth span. Thus, the correct answer is as follows

10. Which one of the following is the correct combination of loading for the maximum negative moment at section C for the given continuous beam?

a)
b)
c)
d)

Explanation:
Drawing ILD for bending moment at section C gives us as

Therefore, Maximum positive Moment for section C is obtained when loading is placed at first, third and fifth span.

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