Category: Prestressed Concrete Structures Objective Questions

250+ TOP MCQs on Stresses in Tendons and Answers

Prestressed Concrete Structures Multiple Choice Questions on “Stresses in Tendons”.

1. The prestressed member undergoes deformation due to the action of ______________
a) Prestressing force and flexural loads
b) Prestressing force and combined loads
c) Prestressing force and transverse loads
d) Prestressing force and tangential loads
Answer: c
Clarification: A prestressed member undergoes deformation due to the action of the prestressing force and transverse loads acting on the member and the curvature of the cable changes which results in a slight variation of stresses in the tendons.

2. The rotation equation obtained by applying Mohr’s theorem considering a concrete beam of span l, force p, eccentricity e is?
a) θp = PeL/2EI
b) θp = PeL/4EI
c) θp = PeL/16EI
d) θp = PeL/20EI
Answer: a
Clarification: A concrete beam of span l is prestressed by a cable carrying an effective force p at an eccentricity e the rotation at the supports due to hogging of the beam is obtained by applying Mohr’s theorem as θp = Area of bending moment/flexural rigidity = PeL/2EI.

3. The cross section of a prestressed concrete beam is 100mm wide and 300mm deep and the initial stress in tendons are located at a eccentricity of 50mm is 1000n/mm2, the sectional area is 100mm2. Find rotation due to prestress (hogging moment)?
a) 0.00155
b) 0.00165
c) 0.00175
d) 0.00185
Answer: d
Clarification: Moment of area I = (100×3003/12) = 225×106mm4
Prestressing force p = (1000×100) = 105 = 100kn
Rotation due to prestressing force θp = PeL/2EI = (100×50×6×103/2×36×225×106)
Hogging moment = 0.00185radians.

4. In the elastic range, any increase in prestressed member does not show any effect on ____________
a) Steel stress
b) Compressive stress
c) Bending stress
d) Flexural stress
Answer: a
Clarification: In the elastic range any increase in loading on a prestressed member does not result in any significant change in the steel stress and in other words, the stress in steel is more or less constant in elastic range of prestressed concrete.

5. The rate of increase in stress in the tendons of a prestress concrete member depends upon ____________
a) Bond and breakage
b) Bond and surrounding concrete
c) Bond and elasticity
d) Bond and anchorage
Answer: b
Clarification: The rate of increase of stress in the tendons of a prestressed concrete member under loads depends upon the degree of bond between the high tensile steel wires and the surrounding concrete, the increase of stress in steel depends on the average strain in concrete at the level of steel.

6. A prestressed concrete beam used over a span of 6m is 100mm wide and 300mm deep, live load of 4kn/m, density of concrete is 24kn/m3, modulus of elasticity of concrete is 36 and steel is 210kn/mm2. Find rotation due to loads(sagging moment)?
a) 0.005
b) 0.00525
c) 0.0024
d) 0.0045
Answer: d
Clarification: E = 210kn/mm2, Self weight of the beam, g = (0.1×0.3×24) = 0.72kn/m
Live load on the beam (q) = 4kn/m, Total load on the beam, Wd = (q+g) = (4+0.72) = 0.00472kn/mm
Rotation due to prestressing force θp = PeL/24EI = (100×50×6×103/24×36×210×106)
Sagging moment = 0.00525radians.

7. The stress in tendons of bonded beams is ____________
a) αe (My/I)
b) αe (My/R)
c) αe (My/L)
d) αe (My/20)
Answer: a
Clarification: The stresses in tendons of bonded beams is αe (My/I), αe = Modular ratio of steel to concrete, y = vertical distance of a point from centroid of concrete section, M = bending moment, I = moment of area of the section, in cases of bonded members such as pretensioned elements or post tensioned grouted members, the composite action between steel and concrete prevails and the stresses in steel are computed using the theory of composite sections up to stage of cracking.

8. The rate of increase of stress is larger in case of ____________
a) Bonded beams
b) Un bonded beams
c) Tensioned beams
d) Anchorage beams
Answer: a
Clarification: The rate of increase of stress is larger in case of bonded beams than in un bonded beams both in the pre cracking and post cracking stages, in case of unbounded beams, the tendons are free to elongate independently throughout their length under the action of transverse loads on the beam.

9. The development of crack widths is comparatively larger in ____________
a) Bonded beams
b) Un bonded beams
c) Localized beams
d) Strengthened beams
Answer: a
Clarification: In post cracking stage, while the bonded beams are characterized by small cracks, which are well distributed in the zone of the larger moments, unbounded beams develop only a few cracks, which are localized at weaker sections and the crack widths are correspondingly larger in comparison with the bonded beams.

10. Which beams are preferred mostly due to their higher flexural strength?
a) Bonded beams
b) Un bonded beams
c) Exhaustive beams
d) Extended beams
Answer: a
Clarification: In general bonded beams are preferable due to their higher flexural strength and predictable deformation characteristics, after the onset of cracking the stress in steel increases at a faster rate in both types of beams since steel does not reach its ultimate strength in case of unbounded beams the ultimate load supported by the beam is smaller than that of bonded beam in which the steel attains its ultimate strength at the failure stage of member.

250+ TOP MCQs on Elastic Design of Sections and Answers

Tricky Prestressed Concrete Structures Questions and Answers on “Elastic Design of Sections”.

1. The code used for determining the ultimate flexural strength of the rectangular section?
a) IS: 1444
b) IS: 1440
c) IS: 1343
d) IS: 1543
Answer: c
Clarification: IS: 1343 code method is used for determining the ultimate flexural strength of rectangular sections and T sections, all the bending stresses and direct force shall remain compressive in any direction, in structures subjected to dynamic loading, under the same circumstances on the other structures a tensile stresses Ft may be allowed which is less than one tenth of maximum permissible compressive stresses.

2. If the neutral axis of the section lies within the flange, the moment of resistance of the section is given by the equation.
a) Mu = fp ap (d-0.42Xu)
b) Mu = fp ap (d+0.42Xu)
c) Mu = fp ap (0.42Xu)
d) Mu = fp ap (0.52Xu)
Answer: a
Clarification: If the neutral axis of the section lies within the flange, then the moment of resistance of the section is given by the equation, Mu = fp ap (0.42Xu), Mu = ultimate moment of resistance, fp= tensile stress developed in tendon at failure, ap = area of prestressing, d= depth, Xu = depth of neutral axis.

3. In pre tension & post tension members, the value of tensile stress fp and depth of neutral axis Xu is obtained based on __________
a) Shear reinforcement
b) Effective reinforcement
c) Edge reinforcement
d) Span reinforcement
Answer: b
Clarification: In pretension & post tensioned members, the value of tensile stress fp and depth of neutral axis xu is obtained based on effective reinforcement ratio (Apf/bdfera) and effective bond (or) un bond between concrete & tendon and these values are given in tables of IS: 1343 code.

4. If the neutral axis of the section lies outside the flange then the ultimate moment of resistance of flanged section is?
a) Mu = fp Apw (d-0.4 xu)+0.45fck (b-bw) Df (d-0.5Df)
b) Mu = fp Apw (d-0.4 xu)+0.45fck (b-bw)
c) Mu = fp Apw (d-0.4 xu)
d) Mu = fp Apw
Answer: a
Clarification: If the neutral axis of the section lies outside the flange, then the ultimate moment of resistance of flanged section is calculated by combining the moment of resistance of web & flange portion
Where Apw = area of prestressing steel for web (Ap-Apf), Apf = area of prestressing steel for flange (0.45fck (b-bw) (df/f), f = characteristic tensile strength of the prestressing steel, df = flange thickness, b = width of beam, bw = width of web after considering are the cases in the tendon, the effective prestress fpc should be greater than 0.45f.

5. The number of steps involved in designing a rectangular prestressed concrete beam are __________
a) 8
b) 14
c) 6
d) 1
Answer: c
Clarification: There are 6 steps involved in designing of a rectangular, prestressed concrete beam 6, moment (M1), section modulus z, width & depth, area amount of steel required As, self weight of beam Wd, Md, position of reinforcement.

6. The section modulus z, of designing a rectangular prestressed concrete beam is given as __________
a) Z = ML/FC
b) Z = Me/Fc
c) Z = MC/FC
d) Z = Md/Fc
Answer: a
Clarification: The required section modulus z from the equation Z= ML/FC fc is the permissible stresses for concrete, but section modulus, Z=bd2/6 where d- depth of beam and the beam should be equal to L/20 or L/25, b-width of the beam, which is given as, b=6z/d2.

7. The position of reinforcement of a recta ngular prestressed concrete beam is evaluated from the relations.
a) e = 2Md-Mc/2F
b) e = 2Md-Me/2F
c) e = 2Md+Mc/2F
d) e = 2Md+Me/2F
Answer: d
Clarification: From the moment due to live loads & dead loads, the position of reinforcement is evaluated from the relation e = 2Md+ML/2F,e = eccentricity, inoder to protect a member from collapsing suddenly after the development of shear cracks a minimum shear reinforcement is provided this minimum shear reinforcement (As) is provided in the form of stirrups which is obtained by satisfying following condition:
Asv/bsv = 0.4/0.8fy.

8. The number of steps are involved in designing a prestressed concrete beam of I section is?
a) 14
b) 10
c) 12
d) 8
Answer: a
Clarification: Following are step by step procedure adopted for designing the prestressed beam of I section stress ft, permissible stress of concrete at transferred fr, fc, allowable tensile stress ft, permissible tensile stress in steel, loss of prestress b/w 15 to 20%, moment due to super imposed load ML, total bending Mt over all depth d, final prestressing force f, area required A, thickness of flange & web in b/w 120mm to 150mm, width of the flange bf, area of tendons At, no of cables required after final dimensions check the beam for safety.

9. The overall depth in a beam of I section is given as?
a) d = k(me)1/2
b) d = k(mt)1/2
c) d = k(ml)1/2
d) d = k(ma)1/2
Answer: b
Clarification: The overall depth if beam d from the equation:
d = k(mt)1/2 k-coefficient,
The value ranges in between 30-45 adopt average value, this is the seventh step used in designing the I section.

10. The area of tendons` At` is given as __________
a) At = F/Safe tensile stress in steel
b) At = L/Safe tensile stress in steel
c) At = D/Safe tensile stress in steel
d) At = C/Safe tensile stress in steel
Answer: a
Clarification: The area of tendons `At` is given as At = F/Safe tensile stress in steel by considering this area, provide suitable diameter of wires & determine the required number of wires, find the number of cables required and in each cable provide 8 to 12 wires the spacing for cables should be 120mm, after adopting the final dimensions check the beam for safety.

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250+ TOP MCQs on Criteria for Limit States and Answers

Prestressed Concrete Structures Multiple Choice Questions on “Criteria for Limit States”.

1. In general, a satisfactory design must ensure the achievement of an acceptable is ____________
a) Life of structure
b) Curing
c) Design
d) Crack
Answer: a
Clarification: In general, a satisfactory design must ensure the achievement of an acceptable probability that the specified life of a structure is not curtailed prematurely due to the attainment of unsatisfactory conditions or limit state, which covers the various forms of failure.

2. The limit states at which the structure ceases to function the most important among them is?
a) Strain
b) Deflection
c) Stress
d) Deformation
Answer: b
Clarification: There are several limit states at which the structure ceases to function the most important among them being the limit state of collapse, excessive deflection and cracking, each of these limit states may be attained due to different types of loading configurations however in practice only one or two of these are of primary significance in design.

3. The failure of one or more critical sections in ____________
a) Flexure
b) Breakage
c) Bondage
d) Prestress
Answer: a
Clarification: Failure of one or more critical sections in flexure, shear, and torsion or due to their combinations is one of the criteria concerning prestressed concrete for ultimate limit state, the ultimate load analysis of slabs by the yield line theory also suffers from similar deficiencies in that the deformation characteristics of the slab at service loads cannot be predicted by ultimate loads.

4. One of the criteria considered for ultimate limit state is ____________
a) Bursting of midspan
b) Bursting of endblock
c) Bursting of edge block
d) Bursting of middle block
Answer: b
Clarification: Bursting of prestressed concrete end block is one of the criteria considered for ultimate limit state is bursting of end block, In erstwhile U.S.S.R as far back of 1930, problems were considered concerning the formulation of a design concept to take into account the variabilities inherent in the materials of construction and design process and building construction.

5. The bearing failure at which point is considered as criteria for ultimate limit state?
a) Bearing failure at edges
b) Bearing failure at midspan
c) Bearing failure at supports
d) Bending failure at edge
Answer: c
Clarification: The bearing at support, anchorages or under concentrated imposed load, bond and various types of failure are also considered as bearing failure at supports, basically limit state design is a method of designing structures based on a statistical concept of safety and the associated statistical probability of failure.

6. The failure due to which member is considered as criteria for ultimate limit state?
a) Elastic instability of members
b) Elastic stability of members
c) Deformation of members
d) Relaxation of members
Answer: a
Clarification: Bond and anchorage failure of reinforcement, failure of connections between precast and cast insitu elements and failure due to elastic instability of members are the factors which are considered in limit states due to their characteristics of sustain.

7. The limit state of collapse may be attained due to ____________
a) Friction
b) Attraction
c) Ductility
d) Vibrations
Answer: d
Clarification: The limit state of collapse may also be attained due to fatigue, vibrations, and corrosive environment impact as a consequence of explosions or earthquakes and disintegration due to fire or frost, a comprehensive and critical review of the limit states design concepts embodied in various codes was presented in his reports reinforced concrete and prestressed concrete.

8. The structure may be rendered unfit due to ____________
a) Collapse limit states
b) Nature limit states
c) Serviceability limit states
d) Loaded limit states
Answer: c
Clarification: The structure may be rendered unfit for its intended purpose due to various serviceability limit states being reached, there are six factors which effect the limit states and the different failures of the members are also considered in this factors in case of limit states.

9. The excessive deflection or displacement adversely affects the ____________
a) Finishes
b) Edges
c) Paintings
d) Beam detailing
Answer: a
Clarification: Excessive deflections or displacement, adversely affecting the finishes and causing discomfort to the users of the structure is serviceability limit states, the method of design for a structure must ensure an acceptable probability that the structure during its life will not become unfit for the intended purpose.

10. The excessive local damage resulting in cracking impairs the ____________
a) Efficiency
b) Deficiency
c) Capacity
d) Dead loads
Answer: a
Clarification: Excessive local damage resulting in cracking or spalling of concrete, which impairs the efficiency or appearance of the structure, the acceptable probability should give a satisfactory balance between the initial and maintenance costs during the life of the structure together with the cost of those insurance premiums that are based on the probability of the structure becoming unfit for the design purpose.

250+ TOP MCQs on Stresses at Serviceability Limit and Answers

Prestressed Concrete Structures Question Bank on “Stresses at Serviceability Limit”.

1. The maximum permissible stresses are mainly governed by ___________
a) Tensile stresses
b) Compressive stresses
c) Ultimate stress
d) Principle stresses
Answer: b
Clarification: The maximum permissible stresses in the precast prestressed concrete and the insitu cast concrete are mainly governed by the compressive strength of concrete in the respective elements and in general the permissible stresses in a precast prestressed concrete are governed by the normal rules for prestressed concrete.

2. Certain expectations in serviceability limits of British code are made regarding ___________
a) High stresses
b) Compressive stresses
c) Limited stresses
d) Elongation stresses
Answer: a
Clarification: Certain expectations are made regarding high stresses developed at the interface of the precast and insitu cast elements and in British code BS: 8110 provides for a higher value of compressive stress equal to 0.5fcu which is 50 percent higher than the normally allowable value in prestressed element.

3. The higher value of compressive stress is permissible only in ___________
a) I sections
b) Composite sections
c) L sections
d) Prestressed sections
Answer: b
Clarification: The higher value of compressive stress is permissible only in composite sections with the stipulation that the failure of the section is due to excessive elongation of steel and this requirement is to safe guard against the explosive compressive failure of the concrete at the limit state of collapse.

4. The permissible flexural tensile stress in the insitu concrete at the ___________
a) Contact surface
b) Longitudinal surface
c) Zig zag surface
d) Dump surface
Answer: a
Clarification: The permissible flexural tensile stress in the insitu concrete at the contact surface with the prestressed element, as prescribed in the British code BS: 8110 varies from 3.2 to 5.0n/mm2 corresponding to various grades of concrete.

5. The stresses may be increased up to 50 percent for prestressed unit by the use of ___________
a) Allowable tensile stresses
b) Permissible tensile stresses
c) Permitted tensile stresses
d) Constant tensile stresses
Answer: a
Clarification: Theses stresses may be increased by upto 50 percent, provided that the allowable tensile stresses for the prestressed unit is reduced by the same amount the higher values of flexural tensile stresses are permitted since it has been proved by experiments that the development of cracking which are visible is prevented by the uncracked prestressed concrete which is bonded to the insitu concrete.

6. The horizontal shear is generally governed by ___________
a) Shear limit state
b) Ultimate limit state
c) Principle limit state
d) Tensile limit state
Answer: b
Clarification: Horizontal shear is generally governed by the ultimate limit states the British code (BS:8110-1985) identifies three types of surfaces in the design provisions for the maximum permissible design ultimate horizontal shear stresses at the interface.

7. The horizontal shear force, at the interface of the precast and insitu components, are due to ___________
a) Design ultimate loads
b) Design shear loads
c) Design flexural loads
d) Design tensile loads
Answer: a
Clarification: The horizontal shear force at the interface of the precast and insitu components due to design ultimate loads is the total compression from that part of the compression zone above the interface calculated from the ultimate bending moment.

8. The average horizontal design shear stress is computed by dividing ___________
a) Horizontal principle force/Area
b) Precast force/Area
c) Horizontal shear force/Area
d) Load/Area
Answer: c
Clarification: The average horizontal design shear stress is computed by dividing the horizontal shear force by the area which is obtained as the product of the contact width of the bear and its length between the points of zero moments.

9. To obtain the horizontal shear stress the design shear stress are ___________
a) Calculated
b) Analysed
c) Distributed
d) Divided
Answer: c
Clarification: The average design shear stress is then distributed in proportion to the vertical design shear force diagram to obtain the horizontal shear stress at any point along the length of the members and the design shear stresses should not exceed the values compiled for different types of surfaces.

10. When the links are provided, their cross sectional area should be at least?
a) 0.20
b) 0.15
c) 0.20
d) 0.18
Answer: b
Clarification: When links are provided their cross sectional area should be at least 0.15 percent of the contact area and the spacing of the links in T beam ribs with composite flanges should not exceed neither four times the minimum thickness of the insitu concrete nor 600mm.

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250+ TOP MCQs on General Features and Answers

Prestressed Concrete Structures Multiple Choice Questions on “General Features”.

1. Which is more economical to use along precast reinforced concrete trusses?
a) Roller member
b) Hinge member
c) Tie member
d) Flange member
Answer: c
Clarification: It is more economical and convenient to use precast reinforced concrete trusses with a prestressed tie member covering roofs of industrial structures such as wave houses workshops having spans exceeding 15m.

2. The configuration of truss depends upon the shape of?
a) Beam
b) Roof
c) Foundation
d) Area
Answer: b
Clarification: The configuration of the truss depends upon the shape of the roof and its general layout and in Russia trusses are generally adopted for industrial buildings having spans greater than 18m and a central I girders and the deck is suspended by cable stays comprising parallel wire cables of BBR-HIAM type with their own anchorage system.

3. Which type of trusses in case of structure located in coastal areas?
a) Steel
b) Tensile trusses
c) Concrete trusses
d) Tensile & Concrete trusses
Answer: c
Clarification: In the case of structures located in coastal area where humidity and temperature are high, it is preferable to use concrete trusses in place of steel trusses which are vulnerable to rust and deterioration due to high humidity.

4. The use of concrete trusses will considerably reduce __________
a) Costs
b) Beams
c) Slabs
d) Layers
Answer: a
Clarification: The use of concrete trusses will considerably reduce the maintenance cost in comparison with steel trusses which require periodical painting at shorter intervals and the trusses in structural member are of circular, cylindrical, hollow etc used for various heavy structures the stress analysis is done by considering all the factors which influence the trusses.

5. Most favorable configuration of the top chord is obtained in __________
a) Bow strung truss
b) Elevated truss
c) Curved truss
d) Termed truss
Answer: a
Clarification: The most favorable configuration of the top cord is obtained in the bow strung truss and the web or diagonal members are subjected to very heavy tension and hence ideally suited for prestressing and top chords and bottom chords are considered in case of precast and insitu cast concrete assuming the pretensioned beam as unpropped and propped.

6. The cables strayed bridges are preferred to convential suspension bridges due to reduction of __________
a) Moments
b) Bending moment
c) Loads
d) Area
Answer: b
Clarification: Cable strayed bridges are preferred to convential suspension bridges for long spans mainly due to reduction in bending moment in the stiffening girder resulting in smaller section of the girders leading to considerable economy in overall costs highway bridges can be built of prestressed concrete with spans up 700m and rail bridges up to span range of 400m.

7. The suspension bridges require a stiffening girder for covering the span, with a __________
a) Flexural stiffness
b) Tensile stiffness
c) Compressive stiffness
d) Principle stiffness
Answer: a
Clarification: A comparative study also indicates that a suspension bridge requires a stiffening girder with a flexural stiffness which must be about ten times larger than that required for a cable stayed bridge covering the same span and suspension bridge requires additional heavy anchor blocks which can be prohibitively costly if the navigation clearance is high and foundation conditions poor.

8. The second Hooghly bridge (vidyasagar sethu) at Kolkata is an excellent example of this?
a) Cable strayed bridge
b) Cable tensioned bridge
c) Cable stressed bridge
d) Cable strained bridge
Answer: a
Clarification: The second Hooghly bridge (vidyasagar sethu) at Kolkata is an excellent example of: Cable strayed bridge comprising a main span of 457.2m and two side spans of 182.8m each and the deck is made of concrete slab 230mm thick two outer steel I girders 28.10m apart.

9. The bridge provides how many large carriage ways?
a) 2
b) 1
c) 4
d) 3
Answer: d
Clarification: The Bridge provides for two 3- lane carriage ways 12.3m each and 2.5m floor paths and the cable stayed bridge costing 600 million rupees was found to be cost effective in comparison with other types.

10. The world’s tallest and longest cable stayed bridge is located in?
a) America
b) France
c) Iraq
d) India
Answer: b
Clarification: The world’s tallest and longest cables stayed bridge is located in France and the French bridge is considered to be an engineering feat since some of the bridge pillars rise gracefully to a height of more than 300m and the bridge is located outside the French town of milliance and is 2.46km long and the bridge designed by the famous British architecture sir norman Foster, is currently the world’s tallest and longest cable stayed bridge and described by many as an astounding engineering feat.

250+ TOP MCQs on Prestressed Concrete Structures Basic Concepts and Answers

Prestressed Concrete Structures Multiple Choice Questions on “Basic Concepts”.

1. The phenomena of development of internal tensile stresses in a concrete member by means of tensioning devices are called as ____________
a) Pre-tensioning
b) Post-tensioning
c) Prestressing of concrete
d) Thermoelectric prestressing

Answer: c
Clarification: Prestressed concrete is basic concrete, in which internal stresses of a suitable magnitude and distribution are introduced so that the stresses resulting from external loads are counteracted to a desired degree.

2. In reinforced concrete members the prestress is commonly introduced by ___________
a) Tensioning the steel reinforcement
b) Tendons
c) Shortening of concrete
d) Rings

Answer: a
Clarification: In reinforced concrete members, the prestress commonly introduced is by tensioning the steel reinforcement while rings i.e stirrups are used while placing columns or foundation in structures, tendon is a stretched member of a prestressed concrete element which serves the purpose of transmitting the prestress to concrete and shortening of concrete phenomena occurs while placing of concrete.

3. Which of the following basic concept is involved in the analysis of prestressed concrete members?
a) Combined and bending stresses
b) Principle stresses
c) Shear stresses
d) Overhead stresses

Answer: a
Clarification: The basic concept involved in the analysis of prestressed concrete members is concept of combined direct and bending stresses used for columns whereas principle and shear stresses are formed in case of tensioning the prestressed and reinforced structures, overhead stresses are formed while the stresses in structures goes beyond safe limit provided by different codes.

4. The prestressing of concrete member is carried out to reduce ___________
a) Compressive stresses
b) Tensile stresses
c) Bending stresses
d) Shear force

Answer: a
Clarification: The prestressing of concrete members is done to reduce the compressive stresses developed in the concrete members to the required extent while tensile stresses is the stress state where the length of member tends to expand in tension side while the volume remains constant, shear forces and bending stresses occurs at the cross section of the beam as the unbalanced vertical force and algebraic sum of moment of forces to right or left of section.

5. The earliest examples of wooden barrel construction by force-fitting of metal bands and shrink-fitting of metal tiers of wooden wheels indicate the art of ___________
a) Prestressing
b) Tensioning
c) Stress
d) Straining

Answer: a
Clarification: Wooden barrel construction by force-fitting of metal bands and shrink-fitting of metal tyres on wooden wheels indicate the art of prestressing and it has been practiced from ancient times while the example of tensioning is bracing for building and bridges whereas stress occurs in a member at a force per unit area and strain phenomena occurs by change in length of a unstressed element.

6. The concept is used in many branches of civil engineering and building construction?
a) Reinforced concrete
b) Prestressed concrete
c) Steel concrete
d) Lump sum concrete

Answer: b
Clarification: Prestressed concrete is widely used in many branches of civil engineering and building construction and in recent days it is experiencing greatest growth in the field of commercial building because of its acoustic properties and its ability to provide long open space.

7. The attempt to introduce permanently acting forces in concrete to resist the elastic forces is ___________
a) Prestressing
b) Loading
c) Pre-straining
d) Bending

Answer: a
Clarification: Freyssinet attempted to introduce permanently acting forces in concrete to resist the elastic forces developed under loads and this idea was later developed under the name of prestressing while the loading and bending phenomena occurs in a member while placing and during excessive loads and pre-straining occurs in prestressed concrete structures.

8. In reinforced concrete members, the prestress commonly introduced is ___________
a) Tensioning steel reinforcement
b) Tensioning wood reinforcement
c) Tensioning rings
d) Tensioning plates

Answer: a
Clarification: In reinforced concrete members steel is commonly used by tensioning steel reinforcement and Steel was commonly used in reinforcement in earlier days and had several disadvantages in case of residential buildings.

9. Development of early cracks in reinforced concrete is due to ___________
a) Strains of steel
b) Stresses of steel
c) Ultimate load
d) Bending of steel

Answer: a
Clarification: Development of early cracks in reinforced concrete is due to incompatibility in the strains of steel and concrete and it was perhaps the starting point in the development of a new material like prestressed concrete.

10. Concrete is weak in?
a) Compression
b) Tension
c) Loading
d) Bending

Answer: b
Clarification: Concrete is not able to resist direct tension in comparison of its ability to resist direct compression because of its low tensile strength and brittle nature, it behaves non linearly at all times because it has essentially zero strength in tension it is always used as reinforced concrete, as a composite material and it is a mixture of sand, aggregate, cement and water whereas structures are highly vulnerable to tensile cracking due to very low thermal coefficient of expansion.