Category: Prestressed Concrete Structures Objective Questions

250+ TOP MCQs on Loss Due to Creep of Concrete and Answers

Prestressed Concrete Structures Multiple Choice Questions on “Loss Due to Creep of Concrete”.

1. Which of the following results in the reduction of stress in steel used for prestress?
a) Shrinkage
b) Friction
c) Creep
d) Anchorage slip
Answer: c
Clarification: The sustained prestress in the concrete of a prestressed members results in creep of concrete which effectively reduces the stress in high tensile steel and the progressive inelastic strains due to creep in a concrete are likely to occur under the smallest sustained stresses at ambient temperatures, shrinkage and creep of concrete are basically similar in origin, being largely the result of migration of water in the capillaries of cement paste.

2. The loss of stress due to creep of concrete can be estimated by ___________
a) Ultimate creep strain
b) Ultimate load
c) Ultimate creep stress
d) Ultimate creep tension
Answer: a
Clarification: The loss of stress in steel due to creep of concrete can be estimated if the magnitude of ultimate creep strain or creep coefficient is known and the values of creep coefficient which is the ratio of ultimate creep strain to the elastic strain is 2.2 at 7 days of loading, 1.6 at 28 days and 1.1 when the age at loading is 1 year.

3. The value of creep coefficient ‘f’ depends upon ___________
a) Humidity
b) Frost
c) Uv rays
d) Ice
Answer: a
Clarification: The value of creep coefficient ‘f’ depends upon various factors such as humidity duration of load applied, age of loading and effective section thickness and the effective section thickness is defined for uniform sections as twice the cross sectional area divided by the exposed perimeter, it can be assumed about 4060 and 80 percent, respectively of the final creep develops during the first, six and 30 months under load when concrete is exposed to conditions of constant relative humidity.

4. The creep coefficient varies from a minimum value of ___________
a) 2.0
b) 1.5
c) 2.5
d) 1.0
Answer: b
Clarification: The creep coefficient varies from a minimum value of 1.5(for wet conditions) to a maximum value of 4.0(for dry condition), for design purposes it is convention to differentiate between deformation due to externally applied stress generally referred as creep and the deformation which occurs without externally applied stresses referred as shrinkage as the increase in strain under a sustained stress is several times larger than the strain on loading, it is of considerable importance in prestressed structural members.

5. The creep coefficient is high for ___________
a) Pretensioned
b) Post tensioned
c) Chemical tensioned
d) Electrical tensioned
Answer: a
Clarification: Creep coefficient is generally low for post tensioned members and high for pre tensioned members, the various factors influencing creep of concrete are relative humidity, stress level, strength of concrete, age of concrete at loading, duration of stress, water cement ratio, and type of cement and aggregate in the concrete, for stress up to half of the crushing strength of concrete.

6. The creep coefficient equation is given as ___________
a) Creep strain/elastic strain
b) Creep stress/elastic stress
c) Elastic strain/creep strain
d) Elastic stress/creep stress
Answer: a
Clarification: The magnitude of the creep coefficient ϕ varies depending upon the humidity, concrete quality, duration of applied loading and the age of concrete when loaded,
Creep coefficient = (creep strain / elastic strain), ϕ = ℇc/ℇe, ℇc = ϕ ℇe = ϕ(fs/Ec),
Loss of stress in steel = ℇcEcϕEs = ϕ(fs/Ec)Es = ϕfcαe.

7. The loss of stress in steel due to creep of concrete is ___________
a) ℇcc fc Es
b) ℇc fc Ec
c) ℇc fe αe
d) ℇcc fc ϕ
Answer: a
Clarification: The loss of stress in steel due to creep of concrete is ℇcc fc Es,
ℇcc = ultimate creep strain for a sustained unit stress, fc = compressive stress in concrete at the level of steel, Es = modulus of elasticity of steel.

8. A concrete beam of rectangular section 100mm wide, area is 3×104, initial stress is 1200n/mm2 of 7mm diameter located at an eccentricity 50mm. Estimate the loss of stress due to creep of concrete using the ultimate creep strain method?
a) 88
b) 40
c) 50
d) 120
Answer: a
Clarification: Es = 210kn/mm2, I = 225×106mm4, Ec = 35n/mm2, a = 3×104mm2, p = (1200×38.5×5) = 23×104n, ℇcc = 41×10-6mm/mm per n/mm2, αe = (Es/Ec) = 6, ϕ = 1.6, fc = (23×104/3×104+23×104×50×50/225×106) = 10.2n/mm2, Ultimate creep strain method loss = ℇcc fc Es = (41×10-6)(10.2)(210×103) = 88n/mm2.

9. A post tensioned concrete beam of rectangular section 200mm wide and 300mm deep is stressed by a parabolic cable with eccentricity 50mm at centre of span, area is 3×104mm2, initial stress is 1200n/mm2 Find the stress in concrete at the level of steel?
a) 10n/mm2
b) 15n/mm2
c) 6n/mm2
d) 8n/mm2
Answer: d
Clarification: A = 3×104mm2, p = (200×1200) = 240000n, e = 50mm,
Stress in concrete at the level of steel: (240000/30000) = 8n/mm2.

10. The British code for structural concrete recommends design values of ultimate creep strain of pretensioning is ___________
a) 48×10-6
b) 53×10-6
c) 40×10-6
d) 38×10-6
Answer: a
Clarification: The British code for structural concrete recommends design values of ultimate creep strain of 48×10-6 for pretensioning and 36×10-6 for post tensioning and these values have to be increased in inverse proportion if the compressive strength of concrete at transfer is less than 40n/mm2.

250+ TOP MCQs on Torsion Members and Answers

Prestressed Concrete Structures Multiple Choice Questions on “Torsion Members”.

1. In case of structural concrete members subjected to torsion, shear stress develops depending upon the __________
a) Type of bending
b) Type of tendon
c) Type of anchorage
d) Type of cross section
Answer: d
Clarification: In the case of structural concrete members subjected to torsion, shear stresses develop depending upon the type of cross section and magnitude of torque, the shear stresses in association with the flexural stresses may give rise to principal tensile stresses, the value of which when it exceeds tensile strength of the concrete results in the development of cracks on the surface of the member.

2. The distribution of torsion shear stress is uniform in __________
a) Parallel sections
b) Rectangular sections
c) Trapezoidal sections
d) Circular sections
Answer: c
Clarification: The distribution of torsion shear stress is uniform in circular sections where the magnitude of the shear stress is proportional to the distance from the centre and in case of non circular sections involving warping of the cross section, approximate formula have been proposed based on elastic analysis.

3. The maximum shear stress of circular section is given as __________
a) 16T/πD3
b) 20T/πD3
c) 40T/πD3
d) 100T/πD3
Answer: a
Clarification: An analysis of principal stresses in prestressed concrete members should include the combined effect of shear stresses due to transverse loads and torsion, together with direct stresses due to flexure and prestress and the maximum stress of circular section is given as:
16T/πD3, D = diameter, T = torsion.

4. The failure of prestressed concrete member without additional un tensioned reinforcement, to that of plain concrete is?
a) Zero
b) Less
c) 1
d) 4
Answer: b
Clarification: The failure of a prestressed concrete member without additional un tensioned reinforcement, under pure torsion, is more or less similar to that of plain concrete where sudden failure is imminent almost simultaneously with the formation of first crack.

5. Which type of prestressing is advantageous for the members subjected to pure tension?
a) Concentric prestressing
b) Tangential prestressing
c) Circular prestressing
d) Overloaded prestressing
Answer: a
Clarification: The research by Humphery and Zia has shown that by suitably adjusting the value of the prestressing force the torsional resistance can be increased by as much as 2.5 times that for the corresponding plain concrete member and for members subjected to pure torsion; concentric prestress is more advantageous than eccentric prestress.

6. When both longitudinal steel and spirals are provided in prestressed members, the ultimate torsional resistance is?
a) Twp+Tws
b) Ttp+Tts
c) Tvp+Tvs
d) Tep+Tes
Answer: b
Clarification: The use of longitudinal steel or spirals independent of each other does not increase the ultimate torsional resistance but when both longitudinal steel and spirals are provided in prestressed members, the ultimate torsional resistance is enhanced and according can be expressed as Ttp + Tts, where Ttp is the torsional resistance moment of the prestressed concrete section and Tts is the additional torsional resistance moment of the non-prestressed reinforcement, which must consist of spirals and longitudinal steel.

7. The behavior of a prestressed concrete member is affected by the relative magnitude of __________
a) Internal actions
b) External actions
c) Zero
d) Constant actions
Answer: a
Clarification: The behavior of a prestressed concrete member is affected by the relative magnitude of the internal actions, such as torque, bending moment and shear force, in circular sections and if torsion is small, it has little effect on the overall behavior and the failure are controlled by either flexure or shear.

8. The members subjected to torque, bending and shear are generally reinforced with __________
a) Parallel and perpendicular reinforcements
b) Longitudinal and transverse reinforcements
c) Rectangular and trapezoidal reinforcements
d) Circular and square reinforcements
Answer: b
Clarification: Members subjected to torque, bending and shear are generally reinforced with longitudinal and transverse reinforcements in order to study the contribution of the longitudinal and transverse reinforcement in resisting flexure, torsion and shear forces, it becomes necessary to analyze the system of forces acting on the warped cross sections of the structural element at the limit state of failure.

9. The skew bending theory is based on the __________
a) Plane Elasticity
b) Plane Deformation
c) Plane Torque
d) Plane Strain
Answer: b
Clarification: The skew bending theory is based on the plane deformation approach to plane sections subjected to bending and torsion, the skew bending theory was initially proposed by Lessing with subsequent contributions from Collins, Hsu, Zia, GEsund, Mattock and Elfgreen, of the several researches in this field, Hsu has made the most significant contribution based on the experimental investigations, his work forms the basis of the American, Australian(AS 1481) and Indian code (IS: 1343) provisions.

10. The space truss, which is composed of longitudinal bars and diagonal concrete truss subjected to twist is known as __________
a) Skew bending theory
b) Space truss analogy theory
c) Space truss theory
d) Compression failed theory
Answer: b
Clarification: The space truss analogy theory, which is a modification of the planar truss analogy for shear and according to this theory the space truss, which is composed of longitudinal bars and diagonal concrete struts is subjected to twist in which the stirrups and longitudinal bars are considered the tension members and the diagonal concrete struts at an angle θ between the cracks and considered the compression members θ is idealized to 45 degrees.

250+ TOP MCQs on Design for Flexure and Axial Tension and Answers

Prestressed Concrete Structures Questions and Answers for Freshers on “Design for Flexure and Axial Tension”.

1. Which of failure is considered in the design of prestressed concrete members for the limit states of collapse?
a) Total failure
b) Shear failure
c) Ultimate failure
d) Collapse failure
Answer: c
Clarification: The distribution of compressive stress in the section at the ultimate failure stage is considered and the effective depth required is estimated by equating the total ultimate moment with the internal resisting angle.

2. The maximum design value of the moment of resistance of rectangular flanged section varies from ____________
a) 0.08fckbd2 to 0.2fckbd2
b) 0.11fcckd2 to 0.5fckbd2
c) 0.15fcckd2 to 0.8fckbd2
d) 0.21fcckd2 to 0.9fckbd2
Answer: a
Clarification: A comparative analysis of the various code recommendations indicate that the maximum design value of the moment of resistance of rectangular and flange of sections vary from 0.08fckbd2 to 0.2fckbd2, depending upon the recommendations of the stress block parameters.

3. It is often preferable to use a larger section, because it means a saving on ____________
a) Deflection
b) Cost
c) Stress
d) Strain
Answer: a
Clarification: The maximum ultimate moment of resistance of a resistance of a rectangular section rectangular section according to the Indian standard code IS: 1343-1980 is given by:
Mud = 0.21fckbd2, the dimension based on this expression are the minimum values and it often preferable to use a larger section because it means a saving on the costly prestressing tendons.

4. The area of high tensile and un tensioned reinforcement required to mobilize the desired flexural strength is computed using?
a) Tension equilibrium
b) Force equilibrium
c) Transverse equilibrium
d) Rotational equilibrium
Answer: b
Clarification: The area of high tensile and un tensioned reinforcement required to mobilize the desired flexural strength is computed using the force equilibrium at the limit state of collapse and the force equilibrium rather depends upon the pressures exerted in different conditions.

5. A pretensioned prestressed concrete beam of rectangular section is required to support a design ultimate moment of 100knm. Design the section if fck is 50n/mm2 and fp 1600n/mm2, xu/d is 0.5?
a) 300
b) 500
c) 600
d) 200
Answer: a
Clarification: Mu = 0.36fckbxu(d-0.42xu) = 0.14fckbd2, b = 0.5d, d3 = (mu/0.14fck0.5) = (100×106/0.15x50x0.5), d = 300mm, b = 150mm, xu = (0.5×300) = 150mm for (xu/d) = 0.5, fpu = 0.87fp, Ap = (mu/0.87fp(d-0.42xu)) = (100×1006/0.87×1600(300-0.42×150)) = 300mm2, adopt a section 150mm wide by 350mm deep with 300mm2 of high tensile steel located at an effective depth of 300mm.

6. A post tensioned beam of unsymmetrical I section is required to support a design ultimate moment of 1200 knm and determine the overall depth and thickness of the compression flange required if fck is 35n/mm2 and fp is 1500n/mm2?
a) 1000mm2
b) 1015mm2
c) 1030mm2
d) 1003mm2
Answer: d
Clarification: For flanged sections, mud = 0.08fckbd2 assuming b = 0.5d and bw = 0.25b, d3 = ((1200×106)/0.10x35x0.5)), d = 1000mm, b = 500mm, thickness of top flange = hf = 0.2d = (0.2×10000) = 200mm, thickness of web = bw = 0.25b = (0.25×500) = 125mm
Assuming the neutral axis depth, xu = hf = 200mm, mu = 0.87fpAp (d-0.42xu), Ap = (mu/0.87fp (d-0.42xu)) = (1200×106/0.87×1500(1000-0.42×200)) = 1003mm2.

7. Due to presence of precompression, prestressed concrete is ideally suited for the design of members subjected to ____________
a) Axial tension
b) Prestressed tension
c) Principle stress
d) Bonded stress
Answer: a
Clarification: Due to presence of precompression, prestressed concrete is ideally suited for the design of members subjected to axial tension and the axial tension in a member depends upon the direction of tension acting on a member and its reaction.

8. The design essentially considered for axial tension is to determine the ____________
a) Deflection
b) Eccentricity
c) Cross section
d) Loads
Answer: c
Clarification: The design essentially consists of determining the cross section area of the member and the required prestressing force to safely support the axial tensile load conforming to the limit state of serviceability and collapse.

9. According to Indian standard code IS: 3370 the load factors against cracking and collapse should not be less than?
a) 15
b) 1.5
c) 3
d) 0.3
Answer: b
Clarification: According to Indian standard code IS: 3370 1967 the load factors against cracking and collapse should be not less than 1.2 and 2 respectively and IS: 3370 code is used for design factors of load factors.

10. Design a suitable section for the tie member of a truss to support a maximum design tensile force of 500kn. The permissible compressive stress in concrete at transfer is 15n/mm2.
a) 41500
b) 4000
c) 22000
d) 1500
Answer: a
Clarification: Design tensile load, nd = 500kn, fct = 15n/mm2, ftw = 0, ɳ = 0.80
Area of concrete section = (Nd/ ɳ fct) = (500×103/0.8×15) = 41500mm2.

Prestressed Concrete Structures for Freshers,

250+ TOP MCQs on Ultimate Load Analysis and Answers

Prestressed Concrete Structures Multiple Choice Questions on “Ultimate Load Analysis”.

1. The reduction in the magnitude of prestressing force occurs due to __________
a) Re block
b) Restraint
c) Relock
d) Re tension
Answer: b
Clarification: According to Bennet the main effects due to axial deformation and tertiary moments are: Reduction in the magnitude of prestressing force in a particular member due to the restraint of the adjacent members, the development of tertiary moments due to bending deformation of the indeterminate structure due to axial contraction under the action of the prestressing force.

2. The ultimate load carrying capacity is controlled by __________
a) Tensile strength
b) Compressive strength
c) Flexural strength
d) Axial strength
Answer: c
Clarification: The ultimate load carrying capacity of a statically determinate prestressed concrete structure is mainly controlled by the flexural strength of a critical section in the member and in contrast to this, the ultimate load carrying capacity of an indeterminate prestressed concrete structure depends upon the flexural strength of several critical sections and their rotation capacity.

3. A conservative estimate of the ultimate resistance is obtained by assuming __________
a) Extra reinforcement
b) Tensile reinforcement
c) Factor of safety
d) Collapse
Answer: d
Clarification: However a highly conservative estimate of the ultimate resistance of the structure is obtained by assuming the collapse to occur when the moment, calculated by the linear elastic theory first reaches a value equal to the flexural strength at any section.

4. Due to large deformations at the critical sections which concentration develops?
a) Equilibrium
b) Curvature
c) Resultant
d) Loads
Answer: b
Clarification: Due to large deformations at the critical sections in a statically indeterminate structure a concentration of curvature builds up over a few clearly defined short length of the member, such as the interior supports and midspan points of a continuous beam and these plastic zones are idealized as hinges at which a rotation is considered to take place.

5. If the partial redistribution takes place by the limited hinge rotations, the ultimate strength of the structure lies between __________
a) Upper limit
b) Lower limit
c) Upper limit above and lower limit
d) Zero
Answer: c
Clarification: If the partial redistribution takes place due to the constraints imposed by limited hinge rotations, the ultimate strength of the structure lies in between the upper limit above and the lower limit corresponding to the computations based on the linear elastic theory.

6. The equilibrium between the internal forces and the external loads is maintained for __________
a) Stress combinations
b) Load combinations
c) Deformation combinations
d) Elastic combinations
Answer: b
Clarification: The redistribution of moments is permitted under the following conditions: equilibrium between the internal forces and the external loads is maintained for approximate load combinations, at sections where the moment capacity after redistribution is less than that from the elastic maximum moment diagram the following relationship should be satisfied ((xu/d) + δm/100)) < 0.8, xu = depth of neutral axis, d = effective depth, δm = percentage reduction in moment.

7. The ultimate moment of resistance provided at any section of a member is not less than?
a) 80%
b) 40%
c) 25%
d) 95%
Answer: a
Clarification: The ultimate moment of resistance provided at any section of a member is not less than:
80% of the moment at that section obtained from an elastic maximum moment diagram covering all appropriate combination of loads, the elastic moment at any section in a member due to partial combination of loads shall not be reduced by more than 20 percent of the numerically largest moment covering all appropriate combination of loads.

8. In the design of continuous prestressed concrete members, it is often necessary to determine a cable profile lying within __________
a) Distribution zone
b) Limiting zone
c) Edge zone
d) Span zone
Answer: b
Clarification: In the design of continuous prestressed concrete members, it is often necessary to determine a cable profile lying within the limiting zone of thrust and also satisfying the conditions of concordancy and a method based on the principle of virtual work is outlined for determining the concordant cable profile.

9. The difference of the maximum and minimum moments at a cross section in design of continuous prestressed beam is given as __________
a) Mt = Mmax-Mmin
b) Mf = Mmax+Mmin
c) Mt = Mmax
d) Mt = Mmin
Answer: a
Clarification: The maximum positive and negative moments due to the live and dead load moments at various sections of the member are calculated and hence computing the range of moment which is obtained as the difference of the maximum and minimum moments at a cross section, Mt = Mmax-Mmin In the design of statically indeterminate prestressed concrete structures involves computation of maximum and minimum moments at various cross sections of the members.

10. The overall cross sectional dimensions are fixed using the __________
a) Permissible tensile stresses
b) Permissible compressive stresses
c) Permissible principle stresses
d) Permissible strains
Answer: b
Clarification: The overall cross sectional dimensions are fixed using the permissible compressive stresses in concrete, fc by equation
Z = bh2/6 = My/fc assuming a suitable values of b = 0.4-0.5h, the overall depth this obtained so as obtain the range of moments which generally determines the cross sectional dimensions of the member.

11. In the design of unidirectional members like continuous beams, the axial contraction due to effect of prestressing is __________
a) Constant
b) Zero
c) Neglected
d) 1
Answer: c
Clarification: In the design of unidirectional members like continuous beams, the axial contraction due to effect of prestressing is: Neglected as it has very little influence on the force and moments in the structure but in the case of two dimensional structures, such as portal frames and bents, the axial contraction of the members significantly influences the primary and secondary moments in the structure.

12. The data that should be available for purpose of design is?
a) Overall shape
b) Overall area
c) Overall height
d) Overall depth
Answer: a
Clarification: The data available for purpose of design is the overall shape of the structure and the loading conditions and the computations of maximum and minimum live load bending moments require a knowledge of the stiffness of the members of the frame and the moments and thrusts determined by assuming a suitable stiffness ratio by the normal methods of structural analysis.

250+ TOP MCQs on Introduction and General Aspects and Answers

Prestressed Concrete Structures Multiple Choice Questions on “Introduction and General Aspects”.

1. The logical steps to be found before beginning the construction of any prestressed concrete structures are ____________
a) Planning analysis and design
b) Stress analysis
c) Strain analysis
d) Prestressed analysis
Answer: a
Clarification: Planning, analysis and design are the logical steps to be followed before beginning the construction of any prestressed concrete structures from ancient times; construction of a structure has always been one of the most fascinating challenges to man ingenuity.

2. The architectural capabilities constitutes the essence of the ____________
a) Conceptual aspects of structures
b) Chemical aspects of structures
c) Structural aspects of structures
d) Time aspects of structures
Answer: b
Clarification: Architectural capabilities constitutes the essence of the conceptual and aesthetic aspects of structures and the domain of construction activity involves several known and unknown features such as management of materials and labour, mobilization of suitable cost effective techniques, treacherous foundations problems adverse water conditions, planning and scheduling of the construction process to a time based frame, constant interaction with the design engineer, architect, site engineer, construction workers and ability to take sound and daring decisions at times of crisis.

3. Which type of engineers should be more conceptual and visual?
a) Construction engineers
b) Site engineers
c) Practical engineers
d) Workers
Answer: c
Clarification: Practical engineers must be more conceptual than mere perceptual, more creative than mere analytical and more visual than mere mathematical and construction engineers should have wide experience involving several types of structures rather than isolated narrow specialization and expertise and original skill are attained from relentless understanding and practice rather than mere theoretical knowledge and good and sound judgment are attained from wide practical experience and often experience comes from bad judgment.

4. The sub structure in every structure is known as ____________
a) Beam
b) Foundation
c) Slab
d) Column
Answer: b
Clarification: Every structure has a foundation(sub structure) which may either be shallow type, like isolated and combined footings, or a monolithic raft where the loads to be transferred on solids of low bearing capacity and large, as in the case of multistoried buildings.

5. Deep foundation depends upon the type of ____________
a) Super structure
b) Foundation
c) Span
d) Area
Answer: a
Clarification: Deep foundations are generally piles, caissons and walls depending upon the type of super structure and the soil conditions and the most common types of piles used are: Timber, Steel, Reinforced concrete and prestressed concrete.

6. The precast piles of reinforced concrete are widely used types for ____________
a) Plastic solids
b) Wet soils
c) Clayey soils
d) Hard soils
Answer: c
Clarification: Precast piles of reinforced or prestressed concrete are the most widely used types for clayey soils of low bearing capacity and well foundation also referred to as open caissons are the most common types generally adopted for major bridges in India, where the soil strata comprises sand or stiff clay.

7. The pneumatic caisson foundations consisting of ____________
a) Concrete cutting
b) Steel cutting
c) Aluminium cutting
d) Block cutting
Answer: b
Clarification: Pneumatic caisson foundations consisting of steel cutting base and concrete pier are adopted for deep foundations in watery situation and the reader may refer to the monograph design of bridges by the author for detailed descriptions and structural design of piles, wells and caissons.

8. One of the following elements of super structure is?
a) Aircraft hanger
b) Water vessels
c) Hydrogen container
d) Liquid container
Answer: a
Clarification: A super structure comprises a floor or roof of a building, bridge deck, large capacity liquid retaining structure, aircraft hanger, nuclear reactor containment vessel, offshore oil drilling platform and a host type of structures and there is no single form of design which would always be more economical.

9. There is no single form of design which would always be most?
a) Long lasting
b) Economical
c) Universal
d) Same
Answer: b
Clarification: There is no single form of design which would always be most economical and it is only by computing a few tentative with a knowledge of the site conditions, availability of skilled labour, materials and machinery, time frame fixed for completion of the project and purpose of the intended structure that one can reasonably arrive at an economical solution.

10. The specifications for batching and mixing of concrete are measured to an accuracy of ____________
a) 0.5%
b) 0.6%
c) 0.8%
d) 0.2%
Answer: a
Clarification: Concrete of uniform quality can be produced only when the ingredients are accurately measured for each batch and good specification requires that batching is done by weight rather than by volume weight batching ensures greater accuracy, simplicity and flexibility and specifications require that the materials – cement, aggregates and water measured to an accuracy of + or – 0.5%.

250+ TOP MCQs on High Strength Concrete and Answers

Prestressed Concrete Structures Multiple Choice Questions on “High Strength Concrete”.

1. The developments in the field of concrete mix design gave compressive strength ranging between ___________
a) 30-70
b) 70-100
c) 35-45
d) 30-80
Answer: b
Clarification: Recent developments in the field of concrete mix design have indicated that it is now possible to produce even ultra high strength concrete, of any desired 28 day cube compressive strength ranging from 70-100n/mm2 without taking resource to unusual materials.

2. High strength concrete resists ___________
a) Levelling
b) Bursting
c) Tangent moments
d) Trapezoidal moments
Answer: b
Clarification: The concrete in a prestressed concrete member is subjected to high bearing stresses due to anchoring at its ends and hence, high strength concrete is required to safely resist the bursting stresses at the end of the beam.

3. In high strength concrete, high modulus of elasticity in the beam is due to ___________
a) Elastic and creep strains
b) Principle tensile stresses
c) Reinforced beams
d) Vibration
Answer: a
Clarification: Low shrinkage, minimum creep characteristics and a high value of young’s modulus are generally deemed necessary for concrete used for prestressed members and the loss of prestress in steel reinforcement is minimum because the elastic and creep strain are very small due to high modulus of elasticity.

4. Which of the following is one of the standard codes used for designing high strength concrete mixes?
a) BS 8110-1985
b) BS 883-1974
c) BS 8113-1986
d) BS 886-1976
Answer: a
Clarification: The various methods adopted for designing high strength concrete mixes are Erntroy and Shack lock’s empirical method, American concrete institute method, British DOE method, Indian standard code and British code BS 8110-1985 stipulates that not more than 5 percent of the test results should fall below 28 days characteristic strength.

5. Which of the following is the Indian code used for high strength concrete mixes?
a) IS 1343-1980
b) IS 10263-1982
c) IS 384-1980
d) IS 457-1979
Answer: a
Clarification: Indian standard code IS 1343-1980 and IS 456-1978 stipulates that only controlled concrete should be used for prestressed concrete construction and the exact specifications with regard to the acceptance criteria for concrete generally vary from one code to another.

6. The cube strength of concrete required for both pre tensioning and post tensioning according to Indian standard codes are ___________
a) 30 and 20
b) 15 and 25
c) 40 and 30
d) 45 and 35
Answer: d
Clarification: The minimum 28 day cube compressive strength prescribed in the Indian standard code IS 1343-1980 is 45n/mm2 for pretensioned members and 35n/mm2 for post tensioned members with the development of vibration techniques in 1930, it became possible to produce without much difficult, high strength concrete having 28 day compression strength in the range of 30-70n/mm2.

7. The full form of ACI method for mix design proportion is ___________
a) American committee institute
b) American council institute
c) American concrete institute
d) American cement institute
Answer: c
Clarification: American concrete institute’s mix design procedure for no slump is one of the methods used for high strength concrete mix design and the American concrete institute in a non profit technical society and standards developing organization, ACI was founded in January 1905.

8. In which method, high strength concrete mixes are designed by relating compressive strength to reference number?
a) Erntroy and Shack locks
b) American concrete institute method
c) British DOE method
d) Indian standard code method
Answer: a
Clarification: In Erntroy and Shack lock’s empirical method high strength concrete mixes are designed by using empirical graphs relating the compressive strength to reference number for concrete made with crushed Granite, coarse aggregates and irregular gravel and the range of the degrees of workability varying from externally low to high corresponds to the compacting factor values of 0.65 and 0.95.

9. The water cement ratio used for British DOE method is ___________
a) 0.7
b) 0.5
c) 0.9
d) 0.7
Answer: b
Clarification: In British DOE method based on the type of cement and coarse aggregate provided evaluate the compressive strength of concrete mix made with water cement ratio of 0.5 and the durability requirements of mix design. Doe is design of experiments is a methodology that can be effective for general problem solving as well as for improving or optimizing product design and manufacturing and production process.

10. The degree of workability of Indian standard method is ___________
a) 0.80
b) 0.50
c) 0.60
d) 0.20
Answer: a
Clarification: The degree of workability relating to compaction factor value is 0.80 for Indian standard method design for high strength concrete mix, the steps involved in Indian standard method is target mean strength, water cement ratio, maximum size of aggregates, degree of workability, considering all the factors the cement content is obtained.