In a 10 m long simply-supported prestressed concrete beam, if prestressing force = P;eccentricity = e; area of cross-section = A; section modulus = Z; bending moment due to dead load = Mg; bending moment due to live load = Mq, the resultant stress due to dead load and live load at top fiber at mid-span is given by

\(\left( {\frac{P}{A} + \frac{{P.e}}{Z}} \right) + \left( {\frac{{{M_g}}}{Z}} \right) + \left( {\frac{{{M_q}}}{Z}} \right)\)

\(\left( {\frac{P}{A} - \frac{{P.e}}{Z}} \right) + \left( {\frac{{{M_g}}}{Z}} \right) + \left( {\frac{{{M_q}}}{Z}} \right)\)

\(\left( {\frac{P}{A} + \frac{{P.e}}{Z}} \right) + \left( {\frac{{{M_g}}}{Z}} \right) + \left( {\frac{{{M_q}}}{Z}} \right)\)

\(\left( {\frac{P}{A} - \frac{{P.e}}{Z}} \right) - \left( {\frac{{{M_g}}}{Z}} \right) - \left( {\frac{{{M_q}}}{Z}} \right)\)

\(\left( {\frac{P}{A} + \frac{{P.e}}{Z}} \right) - \left( {\frac{{{M_g}}}{Z}} \right) - \left( {\frac{{{M_q}}}{Z}} \right)\)

According to IS 1343, the limit state of serviceability of prestressed concrete sections shall satisfy

Cracking, deflection and minimum compression

Cracking and maximum compression

Cracking, deflection and maximum compression

Cracking, deflection and minimum compression

Deflection and maximum compression

Pre-stressed concrete is more desirable in case of

Cylindrical pipes subjected to external fluid pressure

Cylindrical pipes subjected to internal fluid pressure

Cylindrical pipes subjected to external fluid pressure

Cylindrical pipes subjected to equal internal and external fluid pressures

Cylindrical pipes subjected to end pressures

Loss of stress due to relaxation of steel is influenced by

Elastic deformation of concrete

In a pre-tensioned prestressed concrete cross-section,Statement 1: The stress in wires is assumed to be zero at the end supports and increases to its final maximum value over its transmission length.Statement 2:The bond stress between concrete and prestressed wires is maximum near the end supports and decreases to nearly zero over its transmission length.

Statement 1 is true and statement 2 is false

Statement 2 is false and statement 2 is true

24 + Mcqs in Prestress Concrete in Prestressed Concrete Structures Page 1 McqOptions

1.	A concrete beam is pre-stressed by a cable carrying an initial pre-stressing force of 300 kN, the area is 300 mm2. What is the percentage of loss of stress due to shrinkage in pre-tensioned members?
A.	6.3 %
B.	2.3 %
C.	4 %
D.	5.3 %
Answer» B. 2.3 %

Discussion

2.	A post-tensioned concrete beam is prestressed by means of three cables each 100 mm2 area and stressed to 1100 MPa. All three cables are straight and located at an eccentricity of 50 mm. If modulus modular ratio (m) = 6 and stress in concrete at the level of steel (Fc) = 5 MPa, then what is the loss of stress in cables due to elastic shortening if all cables are simultaneously tensioned and anchoring?
A.	90 MPa
B.	60 MPa
C.	30 MPa
D.	0 MPa
Answer» E.

Discussion

3.	A simply supported rectangular prestressed concrete beam is subjected to uniformly distributed live load over its entire span, such that the resulting stress at the midspan at bottom fibre is zero. The eccentricity at that section is d/6 below the C.G., where d is the depth of the beam. Location of the thrust line at that section is
A.	At C.G.
B.	d/6 above C.G.
C.	d/6 below C.G.
D.	d/3 below C.G.
Answer» C. d/6 below C.G.

Discussion

4.	Prestressing in a concrete beam with sloping or curve profile
A.	Increases shear strength
B.	Increases flexural strength
C.	Decreases shear strength
D.	Both 1 and 2
Answer» E.

Discussion

5.	A system usually adopted in the production of pre-tensioned members like railway sleepers, poles, etc. on large scale is ______.
A.	Magnel - Blato system
B.	P. S. C. Monowire system
C.	Hoyer system
D.	Gifford-Udall system
Answer» D. Gifford-Udall system

Discussion

6.	High tensile bars threaded at the ends are used in
A.	Freyssinet system
B.	Gifford-Udall system
C.	Lee-MeCall system
D.	Magnel-Blaton system
Answer» D. Magnel-Blaton system

Discussion

7.	In a 10 m long simply-supported prestressed concrete beam, if prestressing force = P;eccentricity = e; area of cross-section = A; section modulus = Z; bending moment due to dead load = Mg; bending moment due to live load = Mq, the resultant stress due to dead load and live load at top fiber at mid-span is given by
A.	\(\left( {\frac{P}{A} - \frac{{P.e}}{Z}} \right) + \left( {\frac{{{M_g}}}{Z}} \right) + \left( {\frac{{{M_q}}}{Z}} \right)\)
B.	\(\left( {\frac{P}{A} + \frac{{P.e}}{Z}} \right) + \left( {\frac{{{M_g}}}{Z}} \right) + \left( {\frac{{{M_q}}}{Z}} \right)\)
C.	\(\left( {\frac{P}{A} - \frac{{P.e}}{Z}} \right) - \left( {\frac{{{M_g}}}{Z}} \right) - \left( {\frac{{{M_q}}}{Z}} \right)\)
D.	\(\left( {\frac{P}{A} + \frac{{P.e}}{Z}} \right) - \left( {\frac{{{M_g}}}{Z}} \right) - \left( {\frac{{{M_q}}}{Z}} \right)\)
Answer» B. \(\left( {\frac{P}{A} + \frac{{P.e}}{Z}} \right) + \left( {\frac{{{M_g}}}{Z}} \right) + \left( {\frac{{{M_q}}}{Z}} \right)\)

Discussion

8.	Friction loss depends on
A.	type of jack
B.	type of anchorage
C.	type of tendons
D.	type of jack and anchorage
Answer» E.

Discussion

9.	In post-tensioning, the elastic loss in a stressed tendon resulting from the shortening of the member when additional tendons are stressed is called as
A.	Loss of prestress
B.	Bond less
C.	Sequence- stressing loss
D.	Anchorage loss
E.	Shrinkage loss
Answer» D. Anchorage loss

Discussion

10.	As per IS 1343, at the time of initial tensioning, the maximum tensile stress immediately behind the anchorages shall be limited to p percent of the ultimate tensile strength of the wire, wherein p is
A.	85
B.	67
C.	50
D.	76
E.	75
Answer» E. 75

Discussion

11.	A prestressed concrete rectangular beam of size 300 × 900 mm is prestressed with an initial prestressing force of 700 kN at an eccentricity of 350 mm at midspan, stress at top fibre at midspan due to prestress alone is :
A.	3.46 MPa (tension)
B.	8.64 MPa (compression)
C.	2.59 MPa (compression)
D.	Zero
Answer» B. 8.64 MPa (compression)

Discussion

12.	A 4.8 m long post-tensioned prestressed concrete beam is prestressed by a parabolic cable with eccentricity of 15 mm above C.G at the both supports and 45 mm below C.G. at the midspan. The beam is tensioned from one end. In the estimation of maximum loss due to friction, what should be the cumulative angle turned by the parabolic profile?
A.	0.01 radians
B.	0.1 radians
C.	0.15 radians
D.	0.02 radians
Answer» C. 0.15 radians

Discussion

13.	Deflection of beams in pre-stressed concrete structures w.r.t. RCC structures is:
A.	Equal
B.	Less
C.	More
D.	Less or more
Answer» C. More

Discussion

14.	A simply supported prestressed beam of span 10 m is subjected to a point load of 10 kN at center. A prestressing force of 2000 kN is applied through the inclined tendon, Zero eccentricity at support, and ‘ e ’ at Midspan. To nullify the external point load effect, how much ‘ e ’ should be provided? Neglect the self-weight of the beam.
A.	12.5 mm
B.	50 mm
C.	70 mm
D.	85 mm
Answer» B. 50 mm

Discussion

15.	According to IS 1343, the limit state of serviceability of prestressed concrete sections shall satisfy
A.	Deflection and cracking
B.	Cracking and maximum compression
C.	Cracking, deflection and maximum compression
D.	Cracking, deflection and minimum compression
E.	Deflection and maximum compression
Answer» D. Cracking, deflection and minimum compression

Discussion

16.	Pre-stressed concrete is more desirable in case of
A.	Cylindrical pipes subjected to internal fluid pressure
B.	Cylindrical pipes subjected to external fluid pressure
C.	Cylindrical pipes subjected to equal internal and external fluid pressures
D.	Cylindrical pipes subjected to end pressures
Answer» B. Cylindrical pipes subjected to external fluid pressure

Discussion

17.	A post tensioned prestressed concrete beam is having a cross-section of 300 × 300. The area of end block is 100 × 100 mm. Instead of 100 × 100 mm end block, 150 mm × 150 mm end block is provided. What will be the reduction in bursting forces? Let the load in tendons be Po
A.	0.03 Po
B.	0.04Po
C.	0.045Po
D.	0.05Po
Answer» E.

Discussion

18.	Loss of stress due to relaxation of steel is influenced by
A.	Elastic deformation of concrete
B.	Anchorage slip
C.	Friction
D.	Initial stress in steel
Answer» E.

Discussion

19.	In a pre-tensioned prestressed concrete cross-section,Statement 1: The stress in wires is assumed to be zero at the end supports and increases to its final maximum value over its transmission length.Statement 2:The bond stress between concrete and prestressed wires is maximum near the end supports and decreases to nearly zero over its transmission length.
A.	Statement 1 and 2 are true
B.	Statement 1 is true and statement 2 is false
C.	Statement 2 is false and statement 2 is true
D.	Statement 1 and 2 are false
Answer» B. Statement 1 is true and statement 2 is false

Discussion

20.	A simply supported beam of span 9 m is subjected to two-point loads, each of 10 kN acting at, 1/3 of the span as shown in the figure. If the self-weight of the beam is neglected, then how much prestressing force is required to counter-balance the external loads if θ = 30°?
A.	5 kN
B.	10 kN
C.	20 kN
D.	30 kN
Answer» D. 30 kN

Discussion

21.	At the time of initial tensioning, the maximum tensile stress fpi immediately behind the anchorage shall not exceed ______ of the ultimate tensile strength fpu of the wire of bar or stand.
A.	55%
B.	69%
C.	76%
D.	85%
Answer» D. 85%

Discussion

22.	Prestressing force transmitted to concrete as initial internal stress to counteract the internal stress developed due to external loads is called
A.	Stress concept
B.	Strength concept
C.	Force concept
D.	Load balancing concept
Answer» B. Strength concept

Discussion

23.	A concrete beam is post-tensioned by a cable carrying initial stress of 1000 N / mm2, the slip at jacking end was observed to be 5 mm, modulus of steel is 210 kN / mm2 and span of beam is 30 m; what is % of loss of stress due to anchorage?
A.	3.5%
B.	2.5%
C.	1.5%
D.	4.0%
Answer» B. 2.5%

Discussion

24.	For a pre-tensioned beam, young’s Modulus of steel and concrete are 200 GPa and 35.35 GPa. if ultimate shrinkage strain and Ultimate Creep Coefficient are 200 microns and 1.6, respectively, what is the level of sustained stress in concrete at the level of ‘steel if the loss due to creep is three times the loss due to shrinkage?
A.	9 MPa
B.	13 MPa
C.	11 MPa
D.	15 MPa
Answer» C. 11 MPa

Discussion

Explore topic-wise MCQs in Prestressed Concrete Structures.

A concrete beam is pre-stressed by a cable carrying an initial pre-stressing force of 300 kN, the area is 300 mm2. What is the percentage of loss of stress due to shrinkage in pre-tensioned members?

Prestressing in a concrete beam with sloping or curve profile

A system usually adopted in the production of pre-tensioned members like railway sleepers, poles, etc. on large scale is ______.

High tensile bars threaded at the ends are used in

Friction loss depends on

In post-tensioning, the elastic loss in a stressed tendon resulting from the shortening of the member when additional tendons are stressed is called as

As per IS 1343, at the time of initial tensioning, the maximum tensile stress immediately behind the anchorages shall be limited to p percent of the ultimate tensile strength of the wire, wherein p is

A prestressed concrete rectangular beam of size 300 × 900 mm is prestressed with an initial prestressing force of 700 kN at an eccentricity of 350 mm at midspan, stress at top fibre at midspan due to prestress alone is :

Deflection of beams in pre-stressed concrete structures w.r.t. RCC structures is:

According to IS 1343, the limit state of serviceability of prestressed concrete sections shall satisfy

Pre-stressed concrete is more desirable in case of

A post tensioned prestressed concrete beam is having a cross-section of 300 × 300. The area of end block is 100 × 100 mm. Instead of 100 × 100 mm end block, 150 mm × 150 mm end block is provided. What will be the reduction in bursting forces? Let the load in tendons be Po

Loss of stress due to relaxation of steel is influenced by

A simply supported beam of span 9 m is subjected to two-point loads, each of 10 kN acting at, 1/3 of the span as shown in the figure. If the self-weight of the beam is neglected, then how much prestressing force is required to counter-balance the external loads if θ = 30°?

At the time of initial tensioning, the maximum tensile stress fpi immediately behind the anchorage shall not exceed ______ of the ultimate tensile strength fpu of the wire of bar or stand.

Prestressing force transmitted to concrete as initial internal stress to counteract the internal stress developed due to external loads is called

A concrete beam is post-tensioned by a cable carrying initial stress of 1000 N / mm2, the slip at jacking end was observed to be 5 mm, modulus of steel is 210 kN / mm2 and span of beam is 30 m; what is % of loss of stress due to anchorage?