Generic selectors
Exact matches only
Search in title
Search in content
Search in posts
Search in pages
Filter by Categories
nmims post
Objective Type Set
Online MCQ Assignment
Question Solution
Solved Question
Uncategorized

Prestressed Concrete Structures MCQ Set 1

1. Which one of the following is the Indian standard regarded to the limit state of deflection:
a) IS: 1443-1950
b) IS: 1343-1980
c) IS: 1514-1941
d) IS: 1600-1948

View Answer

Answer: b [Reason:] It is the general practice in most of the codes to safeguard against excessive deflections under serviceability limit states, either indirectly by prescribing a minimum span to depth ratio for the member or directly by specifying a maximum permissible deflection expressed as a fraction of the span and recommendations of Indian standard code with regard to the limit state of deflections is IS: 1343-1980.

2. The final deflection due to all loads including the efforts of temperature, creep and shrinkage should normally exceed span up to:
a) Span/250
b) Span/300
c) Span/500
d) Span/800

View Answer

Answer: a [Reason:] The final deflection due to all loads including the effects of temperature, creep and shrinkage should normally not exceed span/250 is the first recommendations made by IS: 1343-1980 with regard to the limit state of deflection.

3. The deflection including the effects of temperature, creep and shrinkage occurring after the erection should not normally exceed:
a) Span/400
b) Span/350
c) Span/140
d) Span/100

View Answer

Answer: b [Reason:] The deflection including the effect of temperature, creep and shrinkage occurring after the erection of partitions and the application of finishes should not normally exceed span/350 whichever is less, creep is directly proportional to the stresses but above this value it increases more rapidly.

4. If the finishes are to be applied to the prestressed concrete members, the total upward deflection should not exceed:
a) Span/300
b) Span/450
c) Span/150
d) Span/350

View Answer

Answer: a [Reason:] If finishes are applied to the prestressed concrete members, the total upward deflection should not exceed span/300, unless uniformity of chamber between adjacent units can be ensured, span/350 or 20mm whichever is less for non brittle partitions or finishes.

5. The British code specifies a maximum deflection limit of span which the sag in the member usually become noticeable is:
a) Span /130
b) Span/250
c) Span/200
d) Span/150

View Answer

Answer: c [Reason:] The British code (BS: 8110-1985) specifies a maximum deflection limit of span/250 beyond which the sag in a member will be usually become noticeable and to prevent damage to non-structural elements, the code recommends that the deflection after the installation of finishes & partitions should not exceed the span/500 or 20mm whichever is less for brittle members.

6. The type of deflection of not supporting and non structural elements of flat roofs is:
a) Large deflection
b) Immediate deflection
c) Small deflection
d) Edge deflection

View Answer

Answer: c [Reason:] Floors roofs not supporting and not attached to non structural element likely to be damaged by large deflection such deflection is considered as immediate deflection due to the live load, deflection limitations are given as (span/180).

7. The floors not supporting and not attached to non structural elements are damaged by:
a) Large deflection
b) Column deflection
c) Span deflection
d) Beam deflection

View Answer

Answer: a [Reason:] Floors not supporting and not attached to non structural element likely to be damaged by large deflections and are carried by immediate deflection due to live load and deflection limitations are given as (span/360).

8. The FIP-1984 limits for total deflection below the level of supports up to:
a) Span/200 to Span/300
b) Span/150 to Span/250
c) Span/100 to Span/50
d) Span/175 to Span/280

View Answer

Answer: a [Reason:] The FIP-1984 recommends the following suitable deflection limits for floors, roofs and the other horizontal members in building as total deflection below the level of supports is Span/200 to Span/300.

9. The FIP-1984 limits for deflection that occurs after addition of partitions up to:
a) Span/200 to Span/300
b) Span/250 to Span/350
c) Span/500 to Span/1000
d) Span/170 to Span/320

View Answer

Answer: c [Reason:] The FIP-1984 recommends the following suitable deflection limits for floors, roofs and the other horizontal members in building limits for deflection that occurs after addition of partitions up to: Span/500 to Span/1000.

10. The French code limits the deflection of members carrying masonry and partition walls up to:
a) Span/600
b) Span/400
c) Span/500
d) Span/700

View Answer

Answer: c [Reason:] The French code limits the deflection of members carrying masonry and partition walls to span/500, which is the total increase in deflection due to short term and sustained loads over the instantaneous deflection due to self weight.

Prestressed Concrete Structures MCQ Set 2

1. The composite sections provide one monolithic action between:
a) Prefabricated units
b) Post fabricated units
c) Pasteurized units
d) Tensioned units

View Answer

Answer: a [Reason:] In a composite construction precast prestressed members are used in conjunction with the concrete cast in situ so that the members behave as monolithic unit under service loads and stirrups produced from the prestressed unit into the added concrete or by castellation on the surface of the prestressed unit adjoining the concrete which in cast in situ.

2. The high strength prestressed units are used in which zone?
a) Compression zone
b) Tension zone
c) Span zone
d) Beam zone

View Answer

Answer: b [Reason:] The high strength prestressed units are used in the tension zone while the concrete which is the cast in situ of relatively lower compressive strength is used in the compression zone of the composite members and the composite action between the two components is achieved by roughening the surface of the prestressed unit on to which the concrete is cast insitu thus giving a better frictional resistance.

3. The Composite construction was first tries for a motorway bridge:
a) 1940
b) 1945
c) 1960
d) 1980

View Answer

Answer: a [Reason:] The phenomenon of differential shrinkage between the concrete cast insitu and the prestressed units also contributes to the monolithic action of the composite members and composite construction was first tried for a way bridge in 1940 and detailed calculations were prestressed by morch in 1943.

4. Due to the effect of composite action sizes of precast prestressed units can be:
a) Increased
b) Reduced
c) Deducted
d) Serviced

View Answer

Answer: b [Reason:] The sizes of precast prestressed units can be reduced due to the effect of composite action and low ratio of size of the precast unit to that of the whole component member and appreciable saving in the cost of steel in a composite member compared with a reinforced or prestressed concrete member.

5. In many cases precast prestressed unit serve as:
a) Supports and dispences
b) Girders and dispences
c) Area and dispences
d) Beams and dispences

View Answer

Answer: a [Reason:] In many cases precast prestressed units serve as supports and dispense with the form work for placement of insitu concrete and composite members are ideally suited for constructing bridge decks without the disruption of normal traffic.

6. The efficient utilization of material in a composite section in which the low and medium strength concrete resists:
a) Tensile forces
b) Principal forces
c) Compressive forces
d) Axial forces

View Answer

Answer: c [Reason:] The efficient utilization of material in a composite member in a composite section in which the low and medium strength concentration of insitu construction resists compressive forces while the high strength prestressed units resist tensile forces.

7. The combination of light weight concrete for the cast insitu slab results in reduced:
a) Live loads
b) Dead loads
c) Constant loads
d) Limited loads

View Answer

Answer: b [Reason:] Combination of light weight concrete for the cast in situ slab results in reduced dead loads leading to economy in the overall costs and the precast prestressed units which require skilled labour and workmanship can be cast in a factory or casting yard and conveyed to the site of construction.

8. In case of conventional method there will be a steel beam and slab construction in which the components carries their:
a) Entire load
b) Half load
c) Span load
d) Deflection

View Answer

Answer: a [Reason:] In case of conventional method, there will be a steel beam and slab construction in which the components carries their entire load transmitted by the slab and there will be no composite action between the members when compared than conventional method of construction the precast unit’s method facilitates a greater structural efficiency.

9. The main components of the composite beam are prestressed precast stem and:
a) A cast insitu flange
b) A cast insitu beam
c) A cast insitu slab
d) A cast insitu column

View Answer

Answer: a [Reason:] The main components of the composite beam are prestressed precast stem and a cast insitu flange and the prestressed precast stem of higher grade concrete is prepared in a factory while the flange having a concrete of lower grade is used for casting is done at the site.

10. To attain the composite action the precast stem and the flange is:
a) Laced together
b) Tied together
c) Keyed together
d) Cutted together

View Answer

Answer: c [Reason:] To attain the composite action the precast stem and the flange is keyed together and facilitates in carrying the heavier loads effectively between the prefabricated beam and cast in situ slab shear connection should be provided in which they act as one unit and resist the loads by composite action as in reinforced concrete T beams.

Prestressed Concrete Structures MCQ Set 3

1. The equivalent moment of given loading is:
prestressed-concrete-structures-questions-answers-concept-load-balancing-q1
a) Pe
b) 4Pe/L
c) Pe/L2
d) Pe/aL

View Answer

Answer: a [Reason:]prestressed-concrete-structures-questions-answers-concept-load-balancing-q1a

2. The tendon profile of given equivalent loading is:
prestressed-concrete-structures-questions-answers-concept-load-balancing-q2
prestressed-concrete-structures-questions-answers-concept-load-balancing-q2a

View Answer

Answer: a [Reason:] prestressed-concrete-structures-questions-answers-concept-load-balancing-q2b Equivalent moment M=4Pe/L Camber provided is WL2/48EI.

3. The cable provided for the given loading is:
prestressed-concrete-structures-questions-answers-concept-load-balancing-q3
a) ML2/8EI
b) WL3/48EI
c) 5WL4/384EI
d) 12WL4/384EI

View Answer

Answer: c [Reason:] Equivalent moment for cable provided for the given loading condition is W= 8Pe/L2 and Camber provided for the cable is 5WL4/384EI.

4. The moment profile for given loading is:
prestressed-concrete-structures-questions-answers-concept-load-balancing-q4
a) W=Pe/aL
b) W=Pe/4aL
c) W=Pe/16aL
d) W=Pe/24aL

View Answer

Answer: a [Reason:] The moment profile for the given loading Equivalent moment is W=Pe/aL and Camber provided is a(3-4a2)WL2/24EI.

5. A rectangular prestressed beam 150 mm wide and 300mm deep is used over a effective span of 10m and the cable with zero eccentricity at the supports, linearly varying to 50mm at the centre carries an effective prestressing force of 500kn(Z=225×104). Evaluate stress due to prestressing?
a) 22.2n/mm2
b) 42.2n/mm2
c) 32.2n/mm2
d) 52.2n/mm2

View Answer

Answer: a [Reason:] b=150mm, d=300mm, l= 10m, e=50mm, p=500kn Self weight of beam g = (0.15×0.3×24)=1.08kn/m, Moment due to self weight = (0.125×1.08×102=13.5knm, Stress due to self weight = (13.5×106/225×104) = 6n/mm2, Stress due to prestressing = (P/A+Pe/A) = (500×103/45×103)+(500×103×50/225×104) =22.22n/mm2.

6. A rectangular beam of 300mm wide and 800mm deep supports two concentrated loads of 20kn each at a span of 9m.Calculate the prestressing force and suggest a suitable cable profile if the eccentricity is 50mm?
a) 600kn
b) 500kn
c) 200kn
d) 800kn

View Answer

Answer: a [Reason:] Q = 20kn, e = 100mm, L = 9m, Z = 32×106mm3 Pe = QL/3 , P = (QL/3e) = (200×9000/3×100) = 600kn.

7. A beam of symmetrical I-section spanning 8m has a flange width of 250mm and flange thickness of 80mm, overall depth is 450mm, eccentricity of 150mm, g = 1.57kn/m, q = 2.50kn/m. Determine effective force?
a) 250
b) 217
c) 320
d) 200

View Answer

Answer: b [Reason:] The bending moment at the centre of the span is Mg = (0.125×1.57×82) = 12.56knm Mq = (0.125×2.50×82)=20knm, Total moment M = (Mg+Mq)=32.5knm P = (M/e) = (32.5×103/150) = 217kn.

8. The shape of the bending moment diagram results from:
a) Tendon profile
b) External loads
c) Cable profile
d) Compression

View Answer

Answer: b [Reason:] The cable profile in a prestressed member corresponds to the shape of the bending moment diagram resulting from the external loads, in a prestressed concrete member external type of loads are balanced by transverse component of suitable cable profile.

9. When the beam supports two concentrated loads, the cable follows which profile?
a) Straight
b) Bent
c) Curved
d) Trapezoidal

View Answer

Answer: d [Reason:] If the beam supports two concentrated loads, the cable should follow a trapezoidal cable because of the concentrated loads the cable bends in a trapezoidal shape, the reactions are obtained by replacing the forces acting on concrete with tendons.

10. If the beam supports uniformly distributed load the tendon follows:
a) Straight
b) Ellipse profile
c) Random profile
d) Parabolic profile

View Answer

Answer: d [Reason:] When the beam supports uniformly distributed load, the corresponding tendon should follow a parabolic profile, when a prestressed a concrete beam AB of span l it is subjected to an external load of w/m length the prestressing force p, the prestress is imparted to the beam with the help of parabolic tendon with the dip of h at the centre due to parabolic profile the beam is subjected to upward uniform force We is given as px = p = wel2/8h.

11. The concept of load balancing is useful in selecting the:
a) Anchorage profile
b) Bending profile
c) Tendon profile
d) Jack profile

View Answer

Answer: c [Reason:] The concept of loading balancing is useful in selecting the tendon profile, which can supply the most desirable system of forces in concrete, straight portion of cable profile does not produce any reactions at the end, while the curve and sharp angles of cable develop uniformly distributed and concentrated load respectively.

Prestressed Concrete Structures MCQ Set 4

1. The width of cracks that developed in prestressed members is governed by how many factors:
a) 3
b) 4
c) 5
d) 7

View Answer

Answer: b [Reason:] ACI committee and Nawy have indicated that the width of cracks that develops in prestressed members is governed by: the average strain at the level at which cracks are considered, the minimum cover to the tension steel, the overall depth of the member in the neutral axis depth.

2. The formula recommended by the British code BS: 8110 – 1985 for the estimation of surface crack width Wcr is:
a) Wcr = 3acrεm / 1+2(acr – Cmin/h-x)
b) Wcr = 3acrεm
c) Wcr = 3acrεm / 1+2(acr + Cmin/h-x)
d) Wcr = 5acrεm

View Answer

Answer: a [Reason:] Wcr = 3acrεm / 1+2(acr – lmin/h-x) is recommended by the British code BS: 8110 – 1985 for the estimation of surface crack width based on the work of beedy, acr = distance from the point considered to the surface of the nearest longitudinal area, εm = average strain at the level where cracking is being considered, Cmin = minimum cover to the tension steel, h = overall depth of member, x = neutral axis.

3. The reason for smaller crack widths in slabs under service loads is:
a) H – x is large
b) H + x is small
c) 0
d) Constant

View Answer

Answer: b [Reason:] In structural members, εm is a maximum at the tension face if h-x is sufficiently small for the crack width at the tension face not to exceed the permissible limit of 0.3mm, it will not exceed the limit anywhere, this is the reason for smaller crack widths in slabs under service loads, provided the thickness does not exceed about 200mm.

4. The stabilized mean crack spacing acs can be expressed as:
a) C (A1/Ʃ0)
b) C (A1/Ʃ8)
c) C (A1/Ʃ5)
d) C (A1/Ʃ7)

View Answer

Answer: a [Reason:] Nawy based on extensive research work, have developed empirical relations to predict the maximum width of cracks and their mean spacing in pre tensioned and post tensioned beams and according to the investigations the stabilized mean crack spacing, acs can be expressed as C (A1/Ʃ0) At = effective concrete area in tension, Ʃ0 = sum of the circumferences of the reinforcing elements, C = empirical constant.

5. The width of cracks is influenced by:
a) Hollow stress
b) Linear stress
c) Net stress
d) Shear stress

View Answer

Answer: c [Reason:] The widths of cracks are influenced by the net stress in the tendons, their surface characteristics and the effective area in tension. Width of crack of Case 1: directly over a bar, the distance acr is equal to the concrete cover Cmin equation then reduces: Wcr = 3acrεm and Case 2: when distance acr is large: Wcr = 1.5(h-x) εmin.

6. The British and Indian standard codes on prestressed concrete maximum limiting crack for members exposed to aggressive environment is:
a) 0.1mm
b) 0.3mm
c) 0.6mm
d) 0.4mm

View Answer

Answer: a [Reason:] The British and Indian standard codes on prestressed concrete prescribe maximum limiting crack widths of 0.1mm for members exposed to aggressive environment and 0.2mm for all other members.

7. A nano polymer range which meets wider expectations as aesthetics is known as:
a) Refit
b) Break
c) Struck
d) Collapse

View Answer

Answer: a [Reason:] A nano polymer range which meets wider expectations as aesthetics, economics, durability and performance of manufactured concrete products and the application of nano technology in the production of nano polymers has revolutionized the concrete industry.

8. The construction joints should be located at points of:
a) Maximum shear
b) Minimum shear
c) Total shear
d) Average shear

View Answer

Answer: b [Reason:] Construction joints should be planned in advance and preferably they should be located at points of minimum shear and they should be nearly perpendicular to the principal lines of stress and construction joints are generally either vertical or horizontal.

9. When the work is resumed the surfaces of the concrete previously placed should be cleaned of:
a) Ash
b) Mud
c) Dirt
d) Soil

View Answer

Answer: c [Reason:] When the work is resumed the surface of the concrete previously placed should be thoroughly cleaned of dirt, scum, laitance, loosely projecting aggregates and other soft material using stiff wire brushes and the surface should then be thoroughly soaked with clean water for two to three hours before further concreting using a thin layer of cement slurry.

10. In roadway slabs, construction joints should be formed:
a) Vertical
b) Horizontal
c) Aligned
d) Loaded

View Answer

Answer: a [Reason:] In roadway slabs, construction joints shall be formed vertical and in true alignment and shear layers in construction joints should be constructed as shown in working site plans and in the case of box girders webs, theses shear keys are normally shown on the plans to the full width.

Prestressed Concrete Structures MCQ Set 5

1. The soffit of the beam after the transfer of prestress to concrete will be under:
a) Tension
b) Compression
c) Breakage
d) Bondage

View Answer

Answer: b [Reason:] The bending moment at which visible cracks developed in prestressed concrete members is generally referred to as the cracking moment after the transfer of prestress to concrete, the soffit of the beam will be under compression.

2. The compressive and tensile stresses developed in cracking moments are due to:
a) Bending loads
b) Transverse loads
c) Tensile loads
d) Compressive loads

View Answer

Answer: b [Reason:] These compressive stresses are balanced by the tensile stresses developed due to the transverse loads on the beam, so that the resultant stress at the bottom fiber is zero, a further increase in loading results in the development of tensile stresses at the soffit of beam.

3. The micro cracks develop as soon as the tensile strain in concrete exceeds about:
a) 80-100×10-6 units
b) 100-150×10-6units
c) 150-300×10-6 units
d) 300-500×10-6 units

View Answer

Answer: a [Reason:] As concrete is weak in tension, micro cracks develop as soon as the tensile strain in concrete exceeds about 80-100×10-6 units and the parameters in concrete are influenced by various materials and their permissible values according to Indian standard codes.

4. When the loads in a concrete member are further increased than permitted, the crack widths are of an order of limit:
a) 0.01-0.02mm5
b) 0.05-0.10mm5
c) 0.03-0.05mm5
d) 0.07-0.08mm5

View Answer

Answer: a [Reason:] If the loads are further increased, than 80-100×10-6 units visible cracks appear in the tension zone and at this stage, it is estimated that the crack widths are of an order of 0.01-0.02mm5 and these width of cracks are considered from a value of minimum to maximum not excess till permitted.

5. A rectangular concrete beam of cross section 120mm wide and 300mm deep is prestressed by a straight cable, effective force of 180kn at an eccentricity 50, area of 36×103mm2(z=18×105mm3). Find the total stress due to prestress?
a) 10
b) 25
c) 35
d) 45

View Answer

Answer: a [Reason:] P = 180kn, A = 36×103mm2, e = 50mm, b = 120mm, d = 300mm, z = 18×105mm3 Stresses due to prestress = (p/a) = (180×103/36×103) = 5n/mm2, (pe/z) = (180×103×50/18×105) = 5n/mm2

Total stress = ((p/a)+(pe/z))=(5+5) = 10n/mm2.

6. A rectangular concrete beam of cross section 100mm wide and 400mm deep is prestressed by a straight cable of span 6m, imposed load is 3.14kn/m, area is 36×103mm2(Z=18×105mm3). Calculate working moment assuming the self weight of concrete as 24kn/m3?
a) 10.25
b) 2.25
c) 3.25
d) 4.25

View Answer

Answer: a [Reason:] Z = 18×105mm3, A= 36×103mm2, G = (0.1×0.4×24) =0.96kn/m Total load W = (g+q) = (0.96+3.14) = 4.1kn/m, Maximum working moment = (0.125×4×62) = 18.45knm (M/Z) = (18.45×106/18×105) = 10.25n/mm2.

7. When the tensile stresses are developed in the cracks, they are visible at:
a) Hoop stress of beams
b) Soffit of beams
c) Sagging of beams
d) Hogging of beams

View Answer

Answer: b [Reason:] The tensile stresses are developed when cracks become visible at the soffit of beams depend upon the type and distribution of steel reinforcement and the quality of concrete in beam, at the soffit of the beam concrete behaves according to influencing parameters of steel reinforcement.

8. The cracks appear when the tensile stresses at the soffit are equal to:
a) Modulus of elasticity
b) Modulus of rupture
c) Tension modulus
d) Reinforcement modulus

View Answer

Answer: b [Reason:] It is generally considered that visible cracks appear when the tensile stresses at the soffit are approximately equal to modulus of rupture of the material, it is an ultimate strength pertaining to failure of beams by flexure equal to the bending moment at rupture divided by the section modulus of beams.

9. The widths of the cracks are influenced by:
a) Degree of bond
b) Stress
c) Strain
d) Tension

View Answer

Answer: a [Reason:] The widths of the cracks are highly influenced by the degree of bond developed between concrete and steel and stress corrosion cracking results from the combined action of corrosion and static tensile stress which may be either residual or externally applied.

10. The formulae for load factor against cracking is:
a) Cracking moment/Working moment
b) Cracking moment/Bending moment
c) Cracking moment/Tensile moment
d) Cracking moment/Aerial moment

View Answer

Answer: a [Reason:] The beam at which visible cracks developed in prestressed concrete members is generally referred to as the “cracking moment” and their formula for load factor against cracking is cracking moment/working moment.