Category: Prestressed Concrete Structures Objective Questions

250+ TOP MCQs on Importance and Factors Influencing Deflections and Answers

Prestressed Concrete Structures Interview Questions and Answers on “Importance and Factors Influencing Deflections”.

1. The philosophy of design is termed as ______________
a) Limit state approach
b) Limit area method
c) Limit design approach
d) Limit elasticity approach
Answer: a
Clarification: The philosophy of design termed as “Limit state approach” adopted by the Russian code in 1954 and the American and British codes in 1971, it requires a proper knowledge of the behavior of structural concrete members at the multiple limit states, of which deflection forms an important criterion for the safety of the structure.

2. The structural concrete members if not designed to have adequate stiffness, it affects ____________
a) Serviceability
b) Local conditions
c) Aggregates
d) Cement
Answer: a
Clarification: In general, according to various national codes, the structural concrete members should be designed to have adequate stiffness to limit deflections, which may adversely affect the strength or serviceability of the structure at working loads.

3. The large deflections under dynamic effects may cause ____________
a) Likely appearance to users
b) Discomfort to users
c) High bending
d) Requires more construction materials
Answer: b
Clarification: Large deflections under dynamic effects and under the influence of variable loads may cause discomfort to users, the members of structural concrete are designed in such a way that it possess adequate stiffness to control the deflections or it may leads to a very great impact on serviceability conditions and strength of a structure at working loads.

4. The excessive deflections are likely to cause damage to ____________
a) Partitions
b) Footing
c) Column
d) Beam
Answer: a
Clarification: Excessive deflections are likely to cause damage to finishes, partitions and associated structures, the principal structural members which resulted in excessive sagging condition makes the floor area not suitable for further use.

5. Which of the following influence the deflections of prestressed concrete members?
a) Cable profile
b) Wall profile
c) Type of aggregates
d) Type of cement
Answer: a
Clarification: The deflections of prestressed concrete members are influenced by the following salient features: imposed load and self weight, magnitude of the prestressing force, cable profile, and second moment of area of cross section, modulus of elasticity of concrete, shrinkage, creep, relaxation, span, and fixity conditions.

6. Which type of deflections is solved by Mohr’s theorem?
a) Instantaneous
b) Long
c) Middle span
d) End span
Answer: a
Clarification: The computations of short term or instantaneous deflections, which occur immediately after the transfer of prestress and on application of loads is conveniently done by Mohr’s theorem from certain surveys it is concluded that the maximum deflection should be noted including with limiting deflection span ratio.

7. In the pre cracking stage, the deflections are computed by ____________
a) Prestressing force
b) Sectional area
c) Diameter
d) Second moment of area
Answer: d
Clarification: In the pre cracking stage the whole cross section is effective and the deflections in this stage are computed by using the second moment of area of the gross concrete section, as the length of the structural member increases the deflections can be controlled to a maximum extent possible.

8. In a post cracking stage, a prestressed concrete beam behaves in a manner similar to ____________
a) Reinforced concrete beam
b) Flexural beam
c) High strength of concrete
d) Soffit beam
Answer: a
Clarification: In the post cracking stage, a prestressed concrete beam behaves in a manner similar to that of a reinforced concrete beam, these beams undergo cracking under working loads, they undergo large deflections and reinforced concrete beam require shear reinforcement in this testing of steel and concrete cannot be done.

9. The computations in post cracking stage are by considering ____________
a) Moment of inertia
b) Moment curvature
c) Moment design
d) Moment area
Answer: b
Clarification: The computations of deflections in this stage are made by considering moment curvature relationships which involve the section, properties of the cracked beam, based on prestressing forces and live loads the deflections of prestressed concrete members can be calculated if the longitudinal distribution of curvatures and magnitude of beam can be known at that particular time.

10. In both pre and post cracking stages the effect of creep and shrinkage of concrete is to increase the ____________
a) Short term deflections
b) Middle span deflections
c) Long span deflections
d) Edge span deflections
Answer: c
Clarification: In both pre and post cracking stages the effect of creep and shrinkage of concrete is to increase the long term deflections under sustained loads, which is estimated by using empirical methods that involve the use of effective (long term), modulus of elasticity or by multiplying short term deflections by suitable factors.

250+ TOP MCQs on Transverse Tensile Stresses and Answers

Prestressed Concrete Structures Multiple Choice Questions on “Transverse Tensile Stresses”.

1. The transverse tensile stress in transmission zone is developed due to concentration of ____________
a) Anchorages
b) Tendons
c) Jacks
d) Prestressing
Answer: b
Clarification: Transverse tensile stresses of considerable magnitude develop in the transfer zone due to the concentration of tendons at the ends and these stresses are influenced by jacking and the method of releasing the tendons from the prestressing beds.

2. The transverse tensile stresses are found to be maximum near ____________
a) Centroidal section
b) Mid span section
c) End zone section
d) Shaft cracking
Answer: b
Clarification: The area at or near centroidal sections of the end faces of beams have maximum tensile stress and if the tensile stresses exceed the tensile strength of concrete, horizontal cracking occur, mid span of the section effects the deflection parameters of the structural member.

3. The method of distributing tendons at the ends has a greater influence on ____________
a) Mid zone cracking
b) End zone cracking
c) Equivalent cracking
d) Shaft cracking
Answer: b
Clarification: A number of cases of cracks developed in precast pretensioned members are reported by foundation and it has been found that the method of distributing tendons at the ends have a greater influence on the end zone cracking.

4. The problem of end zone cracking in pretensioned I beams has been experimentally investigated by ____________
a) Warren Hastings
b) Albert
c) Mattock
d) Thindle
Answer: c
Clarification: The problem of end zone cracking in pretensioned I beams has been experimentally investigated by Marshall, Mattock, Arther and also Ganguli at the centroid of cast in situ slab the compressive force applied is equivalent to direct compressive force acting at composite section together bending moment.

5. The tensile stress is determined by the empirical equation of the type?
a) fv = KM/bwd2
b) KR/bwd2
c) KE/bwd2
d) KW/bwd2
Answer: a
Clarification: The transverse tensile stress is determined by the empirical formula fv = KM/bwd2
fv– Transverse tensile stress at centroid of the end face, M – Resulting bending moment between the prestress force and internal prestress developed in the concrete on the centroidal axis, bw = thickness of web, d = overall depth of beam, K = constant depending upon the slope and distribution of tendons at the ends.

6. The transverse tensile stress distribution in transfer zones can be computed by an expression of the type?
a) 10M/bwhLt (1-x/Lt) e-3.5xLt
b) 10M/bwhLt (1-x/Lt)
c) 10M/bwhLt
d) M/bwhLt
Answer: b
Clarification: Investigations by Marshall and Krishna Murthy involving extensive tests on pretensioned I beams indicate that the transverse tensile stress distribution in transfer zone can be computed by an expression of the type: 10M/bwhLt (1-x/Lt) e-3.5xLt
Lt = transmission length, x = distance from end face.

7. The magnitude of maximum tensile stresses found to occur at the centroid of end face when x is zero is ____________
a) 10M/bwhLt
b) 10M/bwhLt
c) 20M/bwhLt
d) 30M/bwhLt
Answer: a
Clarification: The magnitude of the maximum tensile stress which is found to occur at the centroid of each end face when x = 0 is given by:
fv(max) = 10M/bwhLt,
M = moment, Lt = transmission length.

8. The creep coefficient of the concrete varies from ____________
a) 1 to 6
b) 1 to 3
c) 1 to 9
d) 1 to 12
Answer: b
Clarification: The creep coefficient varies from 1 to 3 and it is denoted by ϕ, the composite section carries all the applied loads when the effect of creep is more and on the precast element the cast in situ slab is casted in which the slab has already undergone shrinkage and creep, but creeping starts only after thee in situ slab is casted and is larger due to wet concrete and both precast beams and cast insitu slabs contains differential creep and shrinkage which induced stresses from one element to the another element.

9. The term iw in a section of I beam is termed as ____________
a) Thickness of web
b) Depth of web
c) Self weight of I section
d) Total weight of I section
Answer: a
Clarification: The term iw is thickness of web and this is used in problems of end zone cracking in pretensioned I beams, on applying compressive forces of equal magnitude along the same line the tensile forces can be balanced.

10. A time dependent deformation of concrete is termed as ____________
a) Shrinkage
b) Creep
c) Final stress
d) Strain
Answer: b
Clarification: A time dependant formation of concrete is termed as creep, this deformation is seen due to loadings and applied stress or strain failures and the main effects of creep are it decreases the effects due to shrinkage strain; there is a mutual transfer of loads from beam to the composite section.

250+ TOP MCQs on Design of Pretensioned Beams and Answers

Prestressed Concrete Structures Multiple Choice Questions on “Design of Pretensioned Beams”.

1. Design a pretensioned roof pull-in to suit the data Fcu, concrete cube strength = 50n/mm2, effective span = 6m, applied load = 5kn/m, dead load = 1.4, live load = 1.6, β = 0.125, k = 7.5, Dc = 2400, and determine ultimate moment and shear?
a) 42 and 27.75
b) 54 and 27.75
c) 34 and 27.75
d) 20 and 28
Answer: a
Clarification: Wmin/Wud = KDcgβ(L/h)L/fcu(d/h)2 = 7.5×2400 x 9.81 x 0.125×25 x 6/50x 106x(0.85)2 = 0.094
Fcu, concrete cube strength = 50n/mm2, effective span = 6m, applied load = 5kn/m, dead load = 1.4, live load = 1.6, β = 0.125, k = 7.5, Dc = 2400, fcu = 50n/mm2, wmin = (0.094)(9.25) = 0.86kn/m, mu = (0.125×9.25×62) = 42knm, vu = (0.5×9.25×6) = 27.75kn.

2. Design cross sectional dimensions of pretensioned roof pull given that b is 0.5d?
a) 250
b) 260
c) 270
d) 280
Answer: c
Clarification: Mu = 0.10fcubd2 and if b = 0.5d
D = (42×106x2/0.10×50)1/3 = 270mm.

3. Find the approximate thickness of web if b is 0.5d, d is 270mm, d/h ratio is 0.85, h is 315mm, adopt effective depth, d = 275mm overall depth , h is 320mm, width of flange of 160mm and Average thickness of flange is 70mm since sloping flanges are used, increases the flange thickness by 20 percent?
a) 45mm
b) 43mm
c) 41mm
d) 42mm
Answer: b
Clarification: b = 0.5d, d = 270mm, d/h = 0.85, h = 315mm, adopt effective depth, d = 275mm overall depth , h is 320mm, width of flange of 160mm and Average thickness of flange is 70mm since sloping flanges are used, increases the flange thickness by 20 percent:
Thickness of flange = (0.2×275) =55mm Approximate thickness of web = (0.85vu/fth) = (0.85×27.75×103/1.7×320) = 43mm.

4. Find minimum range of stresses if fct is 15n/mm2, fcw is 17, ftw is zero, fu is -1n/mm2, ɳ is 0.8?
a) 12 and 18n/mm2
b) 13 and 14n/mm2
c) 12 and 15n/mm2
d) 10 and 16n/mm2
Answer: a
Clarification: Range of stress fbr = (ɳfct-fcw) = (0.85×15-0) = 12n/mm2, ftr = (fcw – ɳfu) = (17-0.8x(-1)) = 17.8n/mm2, fct = 15n/mm2, fcw = 17, ftw = 0, fu = -1n/mm2, ɳ = 0.8.

5. Find minimum section modulus given data is mg is 3.86×106, mq is 22.50×106, fbr is given as 12 and the loss ratio is 0.8?
a) 134×104
b) 182×104
c) 123×104
d) 120×104
Answer: b
Clarification: mg = 3.86×106, mq = 22.50×106, fbr = 12, loss ratio = 0.8
Zb > or equal (mq+(1-ɳ)mg/fbr) > or equal ((22.50×106)+(1-0.8)3.86×106)/12)
Greater than equal to 182x104mm3.

6. Find the supporting force if given characteristic strength is -1, moment of gravity is 3.86×106, zt = 230×104?
a) -2.68n/mm2
b) -3.45n/mm2
c) -1.23n/mm2
d) 13.56n/mm2
Answer: a
Clarification: p = (A(finfZb+fsubZt)/Zt+Zb)
Finf = ((ftw/ɳ+(mq+mg)/ɳzb)) = (0+ (26.36×106/0.8x230x104))
Fsup = (fu – mg/zt) = (-1 – (3.86×106)/(230×104)) = -2.68n/mm2.

7. Check for ultimate flexural strength if given Aps is 154mm2, fpu is 1600n/mm2, b is 160mm, fcu is 50n/mm2and diameter is 265mm?
a) 9.65
b) 0.116
c) 3.442
d) 2.345
Answer: b
Clarification: Aps = (38.5xy) = 154mm2, fpu = 1600n/mm2, b = 160mm, fcu 50n/mm2, d = 265mm
(Apsfpu/bdfcu) = (154×1600/160x265x50) = 0.116.

8. Find ultimate shear strength (check it for safe against shear failure) if vu is 27.75kn, Loss ratio is 0.8, prestressing force is 182000, area is 31400, breadth is 50 where height is 320, prestressing force is 1.7, fcp = 4.65, ft is 1.7?
a) Safe
b) Unsafe
c) Zero
d) Collapse
Answer: a
Clarification: Fcp = (ɳp/A) = (0.8×182000/31400) = 4.65n/mm2
Vcw = 0.67bh(f12+0.8fcpft)1/2 = (0.67x50x320(1.72+0.8×4.65×1.7)1/2/103) = 33.2kn
Vcw > Vu hence safe against shear failure.

9. Check for deflection due to prestressing force if given data is Prestressing force is 182×103 eccentricity of cable is 105, Length of the cable is 1000, elastic modulus of concrete is 34×103, Moment of inertia is 3200×105?
a) 9.4
b) 4.5
c) 6.8
d) 9.8
Answer: c
Clarification: P = 182×103 e = 105, L = 1000, elastic modulus of concrete = 34×103, I = 3200×105
PeL2/8EcI = (182×103x105x62x10002/8x34x103x3200x105) = 6.8mm.

10. Find the deflection due to self weight given that ϕ = 1.6, Ee = 2.6Ece, elastic modulus of concrete is 34×103, gravity is given as 6, self weight is 0.76, Length of the cable is 1000, elastic modulus of concrete is 34×103 , Moment of inertia is 3200×105?
a) 1.66mm
b) 5.3mm
c) 23.4mm
d) 1.02mm
Answer: d
Clarification: Ece = Ec/1+ϕ, ϕ = 1.6, Ee = 2.6Ece
Deflection due to self weight g = (5gL4/384EcI) = (5×0.76×64x10004/384x34x103x3700x105) = 1.02mm.

250+ TOP MCQs on Prestressing of Shell and Folded Structures and Answers

Prestressed Concrete Structures Interview Questions and Answers for freshers on “Prestressing of Shell and Folded Structures”.

1. The concrete shell roof has been widely used to cover __________
a) Small floor spaces
b) Large floor spaces
c) Middle span spaces
d) Edge floor spaces
Answer: b
Clarification: The concrete shell roofs have been widely used to cover large floor spaces of industrial structures and they are generally preferred to other structural forms as they use a minimum amount of materials yielding maximum structural advantage, the cross section being optimally used to resist the forces.

2. Reinforced concrete shells are ideally suited to cover floor spaces of up to __________
a) 15m
b) 25m
c) 30m
d) 40m
Answer: c
Clarification: Reinforced concrete shells are ideally suited to cover floor spaces over medium to long range spans of up to 30m and in the case of longer spans, the tension develops in the edge beams of cylindrical shells is very high and results in congestion of reinforcement and improper compaction of concrete in these zones.

3. Long spans exceeding 30m necessitate is?
a) Welding
b) Blocking
c) Anchoring
d) Spinning
Answer: a
Clarification: Longer spans exceeding 30m necessitate the lapping or wielding of reinforcement in addition, the structure may be rendered unfit for its intended use at the serviceability limit states due to excessive deflections and objectionable cracking and most of these problems are eliminated by prestressing the edge beams of long span shell structures.

4. The parabolic profile of the cables in the edge beam counteracts the __________
a) Compression
b) Tension
c) Deflection
d) Deformation
Answer: c
Clarification: The parabolic profile of the cables in the edge beam counteracts the deflections due to the dead and live loads, so that the resulting deflection is well within the safe permissible limits and prestressing the shell considerably reduced the quantity of reinforcement in the structure as demonstrated by Goldstein.

5. The investigations by Marshall have shown that prestressing considerably reduces __________
a) Sagging moment
b) Transverse moment
c) Hogging moment
d) Longitudinal moment
Answer: b
Clarification: The investigations by Marshall have shown that prestressing considerably reduces transverse moments and the development of cracking due to high tensile stresses at the soffits of edge beams can be completely eliminated by eccentric prestressing and in addition precompression in concrete inhibits the formation of temperature and shrinkage cracks.

6. The compressive state of stress in the shell membrane results in which construction?
a) Airtight construction
b) Water tight construction
c) Lever construction
d) Soffit construction
Answer: b
Clarification: The compressive state of stress in the shell membrane results in which construction water tight construction and according to Haas prestressing has a favorable influence in providing adequate safety against the limit state of collapse by inelastic bulking India in 1941 over spans of 36m, with a chord width of 10.5m, the thickness of the shell being 63mm and the prestressed shell roof of the aircraft hangar at Karachi was built in 1942 over spans of 40m and as these shells gave satisfactory performance and were also economical in France, U.K, Germany and other countries.

7. In general, concrete shells have thin cross sections, which prectude the use of large diameter?
a) Cables
b) Wires
c) Bars
d) Lens
Answer: a
Clarification: In general, concrete shells have thin cross sections, which prectude the use of large diameter Cables and the tendons consisting of 5 to 8mm diameter wires accommodated in narrow sheaths are conveniently used in post tensioning the lower parts of the shell membrane to overcome the problem of correctly positioning the curved cables along the space curves at the junction of the shell and edge beam, it is general practice to impart prestress by post tensioning the curved cables that housed entirely in the deep edge beams and the edge beams being invariably deep, it is convenient to arrange the cables one over the other so that maximum eccentricity is available at the centre of span.

8. The analysis of circular cylindrical shells with prestressed edge beam is more or less similar to __________
a) Prestressed concrete beam
b) Reinforced concrete beam
c) Chemically prestressed beam
d) Partially prestressed beam
Answer: b
Clarification: The analysis of circular cylindrical shells with prestressed edge beam is more or less similar to Reinforced concrete beam however, the effect of prestressing is to be considered in formulating the boundary conditions at the junction of the shell and the edge beam and in addition to the normal boundary conditions such as zero horizontal displacement and rotation of the shell edge, which are also applicable for reinforced concrete shells.

9. The rigorous methods generally involve computations to estimate the __________
a) Transverse reactions
b) Longitudinal reactions
c) Redundant reactions
d) Span reactions
Answer: c
Clarification: The rigorous methods generally involve lengthy computations to estimate the redundant reactions between the shell and the edge beam and in the case of long shells with span/radius ratio exceeding 3, the beam theory developed can be conveniently used for the preliminary analysis of prestressed shells without the loss of much accuracy and in this method the shell is considered or a beam of curved cross section and the flexural and shear stresses are computed using the well known beam formulas.

10. The general bending theory of thin curved shells is governed by a __________
a) Differential equation
b) Parabola equation
c) Ellipse equation
d) Moment equations
Answer: a
Clarification: The general bending theory by thin curved shells is governed by a differential equation of eighth order involving the main shell parameters and deformations and solution based on simplifying approximations have been developed by several investigators and a comparative analysis of various analytical approximations.

11. The hyperbolic parabolic shells, grouped under the category of __________
a) Singly curved shells
b) Doubly curved shells
c) Three curved shells
d) Four curved shells
Answer: b
Clarification: Hyperbolic paraboloid shells, grouped under the category of doubly curved antielastic sells were first successfully used as roofing units by silberkuhl in germany and parts of one shear hyperboloid units, with a geometric from closely following a circular curve in the length(span) direction and hyperbolic curve in the direction of width are well suited for mass production since they are ruled surfaces.

12. Fold plates are widely used for __________
a) Roofs
b) Beams
c) Stress
d) Foundation
Answer: a
Clarification: Folded or hipped plates are widely used for roofs of industrial structures, coal bunkers and cooling towers and the simplicity of the form used for casting folded plates makes them competitive shell construction for covering large floor space and the plates have a triangular or trapezoidal zig-zag cross sectional shape and prestressing is generally done by curved cables or straight tendons lying within the plate in the longitudinal direction to counteract the beam action.

13. The folded plate is also analyzed for __________
a) Longitudinal
b) Transverse
c) Straight
d) Reverse
Answer: b
Clarification: The folded plate is also analyzed for transverse moment by considering the plate as a continuous slab with imaginary supports at the junctions and the transverse reinforcement are designed to resist these moments and according to IS:224 nominal reinforcements consisting of 10mm bars are to be provided in the compression zones at 200mm centers and the maximum spacing of reinforcements in any direction is limited to five times the thickness of the member and minimum reinforcement in the section should conform to the provisions in various national codes.

14. The spherical domes are supported by a ring beam at the __________
a) Base
b) Middle
c) Start
d) Edge
Answer: a
Clarification: Concrete domes are generally preferred for covering circular tanks and for roofs of large span circular structures, such as sports arenas and churchus where an uninterrupted floor space is desirable and a prestressed concrete hemispherical dome of 40m diameter has been used for the roof of the atomic reactor at Kota, Rajasthan, India and the spherical domes are supported by a ring beam at the base, which can be conveniently prestressed by winding tensioned wires or by cables to counteract the hoop tension developed in the ring beam and the main disadvantage of the reinforcement becoming congested in large diameter reinforced concrete ring beams is overcome by prestressing the ring beams in addition there are significant savings in cost, when compared with other equivalent roofs of conventional design.

15. The peripheral ring beam is prestressed by which type of wire winding?
a) Circular
b) Trapezoidal
c) Elliptical
d) Curved
Answer: b
Clarification: The peripheral ring beam is prestressed by which type of wire winding Trapezoidal similar to that of tank walls, or by cables housed in the ring beams with anchorage points at 90 degrees spacing, opposed and phased at 45 degrees and in the case of cables, due provisions should be made be about 10 to 15percent due to the large curvature of the cables.

250+ TOP MCQs on Structural Forms for Irrigation and Answers

Prestressed Concrete Structures Multiple Choice Questions on “Structural Forms for Irrigation”.

1. The concrete, aqueducts and siphons are required for ____________
a) Storage of water
b) Transportation of water
c) Distribution of water
d) Blockage of water
Answer: b
Clarification: Reinforced concrete is ideally suited and widely adopted for the construction of large gravity dams like Bhakra dam, Hirakud dam, Rihand dams and canals, aqueducts and sympones are generally required for transportation of water for irrigation purposes over long distances.

2. The concrete tabular aqueducts prestressed both longitudinal and transversal serves how many purposes?
a) One
b) Three
c) Dual
d) Five
Answer: c
Clarification: Prestressed concrete box sections with longitudinal deep girders and cross girders with slab between the girders and concrete tabular aqueducts prestressed both longitudinally and transversely with diameter in the range of 3-5m and spans varying from 30-50m and this structural form serves the dual purpose of water transportation in the tabular duct and the top portion is used for the road way and prestressed concrete circular sections wit loop cables for transverse prestressing to resist water pressure as in the case of siphons.

3. An example of the application of prestressed concrete in aqueducts in India is?
a) Yamuna
b) Gomati
c) Krishna
d) Penna
Answer: b
Clarification: An example of the application of prestressed concrete in aqueducts in India is Gomati aqueduct having 12 equal spans of 31.8m and the structure is designed as a box section of 12.8m by 6.7m and carries a discharge of 357 cumecs and the depth of the two main prestressed concrete girders is 9.9m and weights as much as 550 tones per girder per span.

4. The girders are supported on which type of well foundations?
a) Double D shaped
b) Trapezoidal shaped
c) T shaped
d) Dome shaped
Answer: a
Clarification: The girders are supported on double D shaped well foundations having a size of 12m by 27m sunk to a depth of 32m below the low water level and Gomati aqueduct as the distinction of being the biggest and the longest aqueduct in India constructed by Hindustan construction company ltd and Bombay for the Uttarpradesh irrigation department and the top of the aqueduct has been planned to serve as a roadway.

5. The circular shape was planned at Bhima aqueduct reduced ____________
a) Factor of safety
b) Rugosity coefficient
c) Tension coefficient
d) Deflection
Answer: b
Clarification: The Bhima aqueduct constructed near solapur, Maharashtra has a continuous precast concrete circular tube prestressed both longitudinally and circumferentially and the circular shape was planned to reduce the Rugosity coefficient facilitating easy passage of water and the aqueduct is 947m long with spans of 41.5m having a truncated circular cross section of 4.8 diameter with 3.75m roadway at top and the average thickness of the circular tube is 200mm and this aqueduct is an excellent example of planning hydraulic and highway elements in a single structure.

6. Virendeel girders are widely used in ____________
a) America
b) Singapore
c) Europe
d) France
Answer: c
Clarification: Virendeel girders developed by Arthur Virendeel in 1896, is an open web trussed girder with horizontal top and bottoms with vertical web members and rigid joints and these girders have been widely used in Europe and particularly in Belguim, where free unobstructed space is required between the top and bottom chords such as in clerestory lighting in churches and also for main girders on factories and warehouse sheds.

7. Prestressed concrete domes with which type of beam provides an ideal solution to cover such large containment vessels are ____________
a) Ring beam
b) Trapezoidal beams
c) Elliptical beams
d) Transverse beams
Answer: a
Clarification: Most of the atomic power plants have containment structures of circular shape having diameters in the range of 40m and prestressed concrete domes with a ring beam provides an ideal solution to cover such large containment vessels prestressed concrete circular tanks are widely used for the storage of water, oil, granular materials like cement and other liquids.

8. The capacity of prestressed concrete tanks may vary from ____________
a) 600 to 60000m3
b) 400 to 40000m3
c) 200 to 20000m3
d) 500 to 50000m3
Answer: b
Clarification: The capacity of such tanks may vary from 400 to nearly 40000m3 and economical dimensional proportions for water tanks as reported by the preload engineering company, Newyork and theses tanks are provided with reinforced concrete domes having a thickness ranging from 50-110mm with a prestressed concrete ring beam at the junction of the cylindrical tank walls and spherical dome.

9. The example of prestressed concrete reservoir is ____________
a) Ball tank built at trombay, Maharashtra
b) Ball tank built at trombay, Assam
c) Ball tank built at trombay, Goa
d) Ball tank built at trombay, Madhya pradesh
Answer: a
Clarification: Typical example of prestressed concrete reservoir having a capacity of 4 million liters can be found in the ball tank built at trombay, Maharashtra and the spherical tank was designed and built by STOP consultants and Gammon India ltd for the department of atomic energy and the diameter of the tank is around 10m and it is prestressed in the circumferential and meridional directions.

10. The prestressed concrete is ideally suited for the construction of ____________
a) Medium and long span bridges
b) Short span bridges
c) Lined span bridges
d) Curved span bridges
Answer: a
Clarification: Prestressed concrete is ideally suited for the construction of medium and long span bridges and at present the reinforcements and prestressed concrete bridge decks from a major percentage of the several types of bridges constructed throughout the world.

250+ TOP MCQs on Tensioning Devices and Answers

Prestressed Concrete Structures Multiple Choice Questions on “Tensioning Devices”.

1. In pre tensioning system, type of prestressing tendon used is ___________
a) Bars
b) Wires
c) Strands
d) Cables
Answer: c
Clarification: The strand tendons are used in both pre tensioning and post tensioning, they are made by winding seven cold drawn wires together on a stranding machine, the addition of strands in subsequent layers of wire forms strands of 19 or 37 wires, large post tensioning applications can cope with stressing requirements by use of these tendons.

2. The yield stress relieved in wires is about ___________
a) 620mpa
b) 1300mpa
c) 1250mpa
d) 600mpa
Answer: b
Clarification: The wire tendons are mainly used in post tensioning system for prestressed concrete, they are cold drawn and stress is relieved with a yield stress of about 1300mpa and the diameter generally ranges from between 5mm-8mm.

3. The use of bar tendons with threaded anchorages reduces the possibility of ___________
a) Push
b) Pull
c) Break
d) Bend
Answer: b
Clarification: The bar type tendons are used in certain post tensioning systems, the bars are of high strength alloy steel of yield strength about 620mpa and diameter up to 40mm and the use of bar tendons with threaded anchorages reduces the possibility of pull in at the anchorages and also anchorage cost.

4. The cables are formed by arrangement of wires or strands in ___________
a) Bundles
b) Rings
c) Ducts
d) Steel
Answer: a
Clarification: The cables are formed by arrangement of wires or strands in bundles and the performed duct in concrete member can be stressed and tensioned by appropriate post tensioning method by using cables, post tensioning is invariably used for strengthening concrete dams, circular prestressing of large concrete tanks and biological shields of nuclear reactors.

5. How many types of splicing arrangement are widely used in post tensioning systems?
a) 4
b) 5
c) 3
d) 2
Answer: a
Clarification: Screw connectors are normally employed to splice large diameter high tensile bars which can be threaded at ends, the torpedo splice consists of triple wedges for securing the wires and the entire unit is covered and protected by a sleeve, clamp splices are equipped with bolts and nuts with a series of clamp plates to house the tendons between them for splicing of small diameter wires of 3-6mm.

6. The commonly used mechanical devices used in the following statement.
a) Weight with lever transmission
b) Geared transmission without pulley blocks
c) Hydraulic jacks
d) Tendons
Answer: a
Clarification: The commonly used mechanical devices are weights with the level transmission, weight without lever transmission, geared transmission with pulley blocks; screw jacks without gear drives, wire winding machinery and the mechanical devices are generally used for imparting prestress in the concrete members which are prepared in large amounts in big factories.

7. The hydraulic jacks are the simplest and most widely used devices for providing prestress of ___________
a) High magnitudes
b) High discharges
c) High Bending moment
d) High tension
Answer: a
Clarification: Hydraulic jacks are the simplest and most widely used devices for providing prestress of high magnitudes and various hydraulic devices are prepared by different scientists from which the commonly used devices Freyssinet, Magnel Balton, Gifford Udall system, Baur Leonhardt, lee mc call system, Prescon system etc.

8. The applied force should be measured accurately in hydraulic devices while?
a) Tensioning the tendons
b) Tensioning the wires
c) Tensioning the cables
d) Tensioning the anchorages
Answer: a
Clarification: The prestressing members with hydraulic devices, the applied force should be measured accurately while tensioning the tendons and this can be achieved by providing pressure gauges with the jacks.

9. The electrical devices are commonly used for tensioning of ___________
a) Bend wires and steel wires
b) Deformed bars and steel wires
c) Torsion and steel wires
d) Compression wires and steel wires
Answer: a
Clarification: Electrical devices are used commonly for the tensioning of deformed bars and steel wires and the method of pre stressing involves the heating up of steel wires and anchoring them before filling the moulds with concrete.

10. The basic chemical substance used for pre stressing forces in concrete member is ___________
a) Aluminium
b) Sulphur
c) Shrinkage cement
d) Expanding cement
Answer: d
Clarification: Chemical substances are also used for developing pre stressing force in concrete members and the basic chemical substance used is expansive cement, when expansive cement is used in construction, the tendons are subjected to tension (while setting).