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All questions of Influence Lines for Civil Engineering (CE) Exam

The bed of an alluvial channel along the flow will always be
  • a)
    flat
  • b)
    way
  • c)
    duned and rippled
  • d)
    and of the above is possible
Correct answer is option 'D'. Can you explain this answer?

Avinash Mehta answered
The correct answer is 'D', all of the above is possible. The bed of an alluvial channel along the flow can take on different forms depending on the specific conditions of the channel and the flow. For example, in a stable channel with a relatively low sediment load, the bed may be relatively flat. However, in a channel with a high sediment load or with high velocity flow, the bed may be rippled or even duned. Additionally, in meandering channels, the bed may be way. The bed morphology of an alluvial channel is a constantly changing and influenced by many factors such as sediment load, discharge, channel slope, and channel width.

What will be the value of Rda?
  • a)
    1
  • b)
    0
  • c)
    0.481
  • d)
    0.681
Correct answer is option 'C'. Can you explain this answer?

Kirti Sharma answered
Answer: c
Explanation: It will be the ration of Δda and Δaa. Δaa is 1944/EI and Δca is 936/EI. Join all these point for ILD.

The most important shape parameter in sediment analysis is
  • a)
    sphericity
  • b)
    Shape factor
  • c)
    roundness
  • d)
    form factor
Correct answer is option 'A'. Can you explain this answer?

Yes, that is correct. Sphericity is the most important shape parameter in sediment analysis. It is a measure of the degree to which the shape of a particle approximates a perfect sphere. Sphericity is typically expressed as a dimensionless ratio, with a value of 1 indicating a perfect sphere and values less than 1 indicating a particle that is more elongated or irregular in shape.
Sphericity is an important parameter in sediment analysis because it can affect the behavior of particles in a number of ways. For example, more spherical particles tend to roll more easily and may be more resistant to abrasion than more elongated particles. Sphericity can also affect the way that particles settle out of a suspension and the way that they pack together.

So, the correct answer is:

a) Sphericity

Three wheel loads 10t, 26t and 24t spaced 2m apart roll on a girder from left to right with the 10t load leading. The girder has a span of 20 meter. For the condition of maximum bending moment at a section 8 meter from the left end.
  • a)
    The 10t load should be placed at the section.
  • b)
    The 26t load should be placed at the section.
  • c)
    The 24t load should be placed at the section.
  • d)
    Either the 26t load or the 24t load should be placed at the section.
Correct answer is option 'B'. Can you explain this answer?

Ishani Basu answered
Maximum bending moment at a section occurs when a particular load is on the section which changes the ratio 
as the load passes over the section . 

where R1, → resultant of load on left sid e of section Resultant of all loads (R)
= 10 + 26 + 24 = 60t

When 10t load crosses section C. 

When 26t load crosses the section C, 

It means that maximum bending moment is obtained when 26t load is on the section.

A uniformly distributed line load of 60 kN per metre run of length 5 meters on a girder of span 16 metres. What is the maximum positive shear force at a section 6 metres from the left end.
  • a)
    140.625 kN
  • b)
    65.625 kN 
  • c)
    90.625 kN
  • d)
    45.625 kN
Correct answer is option 'A'. Can you explain this answer?

Puja Sharma answered
We must first draw the influence line diagram for the SF at the section D,

For maximum positive SF at D, the loading should be applied as shown in the figure.
Maximum positive = load x area of ILD SF at D intensity covered by the load

 What will be the value of Rca?
  • a)
    1
  • b)
    0
  • c)
    0.652
  • d)
    0.852
Correct answer is option 'D'. Can you explain this answer?

Ishani Basu answered
Answer: d
Explanation: It will be the ration of Δca and Δaa. Δaa is 1944/EI and Δca is 1656/EI

A Warren truss is supported as shown in the given figure. Which one of the following diagrams represents the influence line for the force in member U3U4?
  • a)
  • b)
  • c)
  • d)
Correct answer is option 'D'. Can you explain this answer?

Sahil Mehra answered
Introduce a cut through U3U4, U3L4and L3L4. The member forces of L3L4 and U3L4 pass through support at L4 . So w hen load is at L0, L1 L2, L3 and L4. the total moment of all the force except force in U3U4 on the right part of cut section is zero. So from moment equilibrium the force in U3U4 will remain zero when load is between. L0 and L4.
When load is at L5, the force in member U3U4

What will be the shape of overall ILD?
  • a)
    straight line
  • b)
    parabola
  • c)
    hyperbola
  • d)
    arbitrary curve
Correct answer is option 'D'. Can you explain this answer?

Answer: d
Explanation: ILD will be basically(approximately) a line passing through all above points but it will be a type of curve as slope near A will be zero and then slope will change.

For the continuous beam shown in figure, the influence line diagram for support reaction at D is best represented as
  • a)
  • b)
  • c)
  • d)
Correct answer is option 'C'. Can you explain this answer?

Athira Pillai answered
The ILD for support reaction at D can be obtained by:giving unit displacement in the direction of reaction. The deflected shape of beam will represent ILD as in figure (c).

The Muller-Breslau principle can be used to
1. Determine the shape of the influence line
2. Indicate the parts of the structure to be loaded to obtain the maximum effect
3. Calculate the ordinates of the influence lines
Which of the these statements is/are correct? 
  • a)
    only 1
  • b)
    both 1 and 2
  • c)
    both 2 and 3
  • d)
    1, 2 and 3
Correct answer is option 'D'. Can you explain this answer?

Tarun Shah answered
The Muller-Breslau principle is a method used for calculating influence lines for determining the effects of moving loads on a structure. It is based on the principle that the displacement of a structure due to a unit load at any point is proportional to the area of the influence line.

The principle can be used to:

1. Determine the shape of the influence line: The shape of the influence line can be determined by considering the structure as a continuous beam and calculating the deflection at any point due to a unit load moving along the beam. The influence line is then plotted by taking the ratio of the deflection to the length of the beam.

2. Indicate the parts of the structure to be loaded to obtain the maximum effect: The Muller-Breslau principle can also be used to determine the position of the load on the structure that will produce the maximum effect. This is done by finding the point along the influence line where the product of the load and the area under the influence line is maximum.

3. Calculate the ordinates of the influence lines: The Muller-Breslau principle can also be used to calculate the ordinates of the influence lines at any point along the beam. This is done by dividing the area under the influence line up to that point by the length of the beam.

Therefore, all three statements are correct and the correct answer is option 'D'.

Which one of the following equations represents influence line of fixed end moment at B of the fixed beam AB of length l with origin at A?
  • a)
  • b)
  • c)
  • d)
Correct answer is option 'A'. Can you explain this answer?

For the influence line of fixed end moment at B, release the moment at B and give unit rotation, the deformed shape will represent the influence line.

due to unit load at x distance from A.

A uniformly distributed load whose length is shorter than the span, crosses a simply supported beam from left to right. The maximum bending moment at a section occurs when
  • a)
    the load remains only on the left of the section
  • b)
    the load is only on the right of the section
  • c)
    the section divides the load in the same ratio as it divides the span
  • d)
    half of the load remains to the left of the section and other half on the right of section
Correct answer is option 'C'. Can you explain this answer?

Srestha Tiwari answered
Explanation:

When a uniformly distributed load crosses a simply supported beam from left to right, the maximum bending moment at a section occurs when the section divides the load in the same ratio as it divides the span. Let's understand this concept in detail.

Uniformly Distributed Load:

A uniformly distributed load is a load that is spread evenly over a given length or area. In the case of a simply supported beam, a uniformly distributed load is a load that is distributed evenly over the entire length of the beam.

Maximum Bending Moment:

Bending moment is the moment that is developed in a beam due to the external loads applied to it. The maximum bending moment in a simply supported beam occurs at the mid-span of the beam.

Section Divides the Load:

When a section is taken in a simply supported beam, it divides the load into two parts: the load on the left side of the section and the load on the right side of the section. The ratio of these two loads is determined by the distance of the section from the left support and the distance of the section from the right support.

When the section is at the mid-span of the beam, the load on the left side of the section is equal to the load on the right side of the section. Therefore, the section divides the load in the same ratio as it divides the span.

The maximum bending moment in a simply supported beam occurs when the load on one side of the section is greater than the load on the other side of the section. This is because the bending moment is directly proportional to the load and the distance from the load to the section.

Conclusion:

In conclusion, the maximum bending moment at a section in a simply supported beam occurs when the section divides the load in the same ratio as it divides the span. Therefore, option 'C' is the correct answer.

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