Prestressed Concrete Structures MCQ Set 1
1. One of the structural forms used for bridges are:
a) Solid slabs
b) Dense slabs
c) Rigid slabs
d) Open slabs
Answer: a [Reason:] For medium and long spans prestressed concrete is ideally suited for the super structure of bridges and the structural forms generally used for bridges are listed as follows solid slabs(10-15m), voided or hollow slabs(15-25m), rigid frame bridges(15-30m), Tee beams and slabs(20-40m), two cell box girders(30-70m), multi cell box girders(40-80), balanced cantilever type bridges(20-30m), continuous girders of variable depth(30-40), cable stayed bridges(100-500m).
2. Prestressed concrete has more or less replaced:
a) Reinforced concrete
b) Prestressed concrete
c) Aluminium concrete
d) Voids concrete
Answer: a [Reason:] Prestressed concrete has more or less replaced reinforced concrete as the most suitable material for bridge construction due to its inherent advantages of high strength coupled with durability, energy absorption under dynamic loads, ability to resist repetitive loads, freedom from cracks, easy mould ability to desired shape, economy and ease of maintenance.
3. The floors and girders of through type structures should be placed in:
a) Two continuous
b) One continuous
c) Span continuous
d) Limit continuous
Answer: b [Reason:] The floor and girders of through type structures should be placed in one continuous unless otherwise specified in which case a special sear anchorage should be provided to ensure monolithic action between the girders and floor and the case of tee beam slab floors, it is preferable to deposit concrete first up to the top of the girder ribs followed by concreting of the slab in one continuous operation and if the slab concrete is delayed, suitable shear keys should be formed by roughening the top of the girder before depositing the centre in the slab.
4. Prestressed concrete members should be compacted by which type of vibration:
a) Mechanical vibration
b) Structural vibration
c) Internal vibration
d) External vibration
Answer: a [Reason:] Prestressed concrete members should be compacted by mechanical vibrations expect when certain types of extrusion machines are used which consolidate the concrete by tamping and depending on the type of structural members, internal, external or surface type vibrators are used and normally vibrators having frequencies in the range of at least 3200-3600 cycles per minute are used.
5. The vibrations should be used only for:
Answer: b [Reason:] Vibration should be well distributed so that the concrete reaches a state of plastic mass with uniform density and vibrators should be used for compaction only and not for moving concrete horizontally along the forms.
6. When vibrators are used for horizontal and vertical operation, the spacing should :
d) Made wet
Answer: a [Reason:] When vibrators are used for horizontal and vertical operation, the spacing of points of vibration should be such that their zones of influence overlap and when concrete is deposited in layers such as that in column, the vibrator should be inserted vertically.
7. When concrete is deposited in layers it should be allowed to:
Answer: a [Reason:] When concrete is deposited in layer it is allowed to sink due to its own weight to the bottom of the layer and then slowly withdrawn and during vibration of succeeding layers, the vibrator should preferably penetrate the surface of the preceding layer by at least 150mm and good vibration should result in a surface without honey combing, aggregate or mortar pockets or excessive air bubbles.
8. The self compacting concrete (SCC) is generally referred as:
a) Spatial concrete
b) Pores concrete
c) Rheodynamic concrete
d) Flexible concrete
Answer: c [Reason:] Rheodynamic concrete generally referred to as self compacting concrete (SCC) is able to flow under its own weight and completely fill the formwork, even in the presence of dense reinforcements without the need for any vibration whilst maintaining homogeneity and resulting in concrete of high early strength and durability.
9. Degussa-MBT construction chemicals (INDIA) have developed revolutionary type of admixtures based on:
a) Micro science
b) Nano science
c) poly science
d) Animal science
Answer: b [Reason:] Degussa-MBT construction chemicals (INDIA) have developed revolutionary type of admixtures using nano polymers which can be used to bring together functional groups aimed at targeted performances in concrete and based on nano science.
10. A system of polymers with longer side and shorter side chains is called:
a) Zero energy system
b) Elastic energy system
c) Bonded energy system
d) Force energy system
Answer: a [Reason:] A system of polymers with longer side chains and shorter main chains to facilitate high early strengths in concrete without steam curing and with specific applications in precast reinforced and prestressed concrete units manufacturing industry.
Prestressed Concrete Structures MCQ Set 2
1. The structural forms generally used for aircraft hangers are compiled of:
a) 3 types
b) 2 types
c) 4 types
d) 6 types
Answer: a [Reason:] Over the last few decades, increased airway traffic has necessitated the development and use of large aircraft like Boeing-747 and Airbus-320 and the servicing of these aircraft requires large aircraft hangers with unrestricted space for easy movement of aircraft and the structures forms generally used for aircraft hangers are compiled as follows: prestressed concrete barrel shells, prestressed concrete folded plates, twin cantilever folded plate roofs.
2. The cantilever folded plate roof requires significantly lower quantities of materials like:
a) Concrete and prestressing cables
b) Shortcrete and prestressing cables
c) Fabric and prestressing cables
d) Reinforcement and prestressing cables
Answer: a [Reason:] Twin cantilever folded plate roofs with a central service complex and the continuous folded plate roof is stayed by prestressed concrete ties and this type of planning provides and unrestricted clear space of 60-90m on either side of the central service complex and the cantilever and folded plate roof complex requires significantly lower quantities of materials like concrete and prestressing cables due to the unique feature of the structural form.
3. The prestress concrete aircraft hangers normally require free spaces for:
Answer: d [Reason:] Prestressed concrete aircraft hangers normally require large column free spaces and the introduction of prestressed concrete in India in the year 1939 resulting in larger spans of column free structures suitable for aircraft hangers such as that planned for the Karachi airport in 1942.
4. In Karachi airport at that time in 1942 which were used:
a) High tensile steel wires
b) High compression wires
c) Normal wires
d) Long span wires
Answer: a [Reason:] At the time, the high tensile steel wires were imported from France and the cables were made by covering the wires with bitumen wrapped in sisal craft paper and the cables comprised 32 numbers of 5mm diameter wires providing a prestressing force of 660kn and prestressed reinforced concrete trusses of spans in the range of 18m with asbestos covering were planned to provide large column free space for the integral coach factory built at perambur madras as early as 1956.
5. An example to plan aircraft hanger using prestressed concrete which is ideally suitable for large spans:
a) Indian airlines airbus hanger
b) Spain airlines airbus hanger
c) American airlines airbus hanger
d) Africa airlines airbus hanger
Answer: a [Reason:] The present method is to plan aircraft hangers using prestressed concrete which is ideally suitable for large spans with reduced maintenance costs due to superior durability characteristics of prestressed concrete and an excellent example of this type is the roof of the Indian airlines hanger in Bombay.
6. The Indian airlines airbus hanger which was considered as world record:
a) Structure construction
c) Long cantilever span
Answer: c [Reason:] The structure comprises prestressed concrete folded plates cantilevering on opposite sides from the main service complex and the long cantilever span can be considered as world record for this type of construction which was chosen to achieve flexibility of lateral expansion without distributing the existing facilities.
7. The inclined struts supporting the prestressed concrete ties are provided with:
Answer: b [Reason:] The roof is formed by a very thin folded plate of 7.62m module with webs inclined at 45 degrees and the continuous folded plate is stayed by prestressed concrete ties and the inclined struts supporting the prestressed concrete ties and provided with Freyssinet hinges at the junction with the roof in order to permit free rotations.
8. The hanger provides a clear uninterrupted space of:
Answer: a [Reason:] The hanger provides a clear uninterrupted space of 91.4m long with an average height of 13m so that two airbus aircrafts can easily be parked in the hanger and also an expansion joint planned and provided at the centre divides the roof into two units of 45.7m each.
9. As the side walls are independent of the roof so that the hanger can be:
Answer: a [Reason:] The cantilever roof is estimated to deflect by 280mm near the tip under maximum wind effects and the safe movements of the sliding door is ensured by the provision of a concrete channel section of adequate depth at the tip of the roof and the hanger has been planned and designed to withstand the dynamic effect of wind gusts of the coastal zone during cyclonic wind reaching a speed of 160knmph and the hanger can also be widened whenever required as the side walls are independent of the roof and the airbus hanger was designed by STOP consulting engineers for the Indian airlines corporation.
10. Another planning example of planning an aircraft hanger is Boeing hanger at santa curv airport is in:
Answer: c [Reason:] Another planning example of planning an aircraft hanger is Boeing hanger at santa curv airport is in: Bombay the prestressed hanger provides an uninterrupted area of 101m by 45.73m and the roof consists of 10 barrel shells of 45.75m span with 12.2m chord width supported on longitudinal prestressed concrete edge beams and the frontal beams are also prestressed and the span over clear door openings is 48.8m and the overall depth of the beam is 6.1m the soffit of the beam and the aircraft hanger was planned and designed and constructed by gammon Indian limited for the international airports authority of India.
Prestressed Concrete Structures MCQ Set 3
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 [Reason:] 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:
Answer: c [Reason:] 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:
Answer: b [Reason:] 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 [Reason:] 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
Answer: b [Reason:] 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:
Answer: c [Reason:] 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:
a) Ring beam
b) Trapezoidal beams
c) Elliptical beams
d) Transverse beams
Answer: a [Reason:] 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 [Reason:] 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 [Reason:] 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 [Reason:] 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.
Prestressed Concrete Structures MCQ Set 4
1. In pre tensioning system, type of prestressing tendon used is:
Answer: c [Reason:] 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:
Answer: b [Reason:] 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:
Answer: b [Reason:] 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:
Answer: a [Reason:] 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?
Answer: a [Reason:] 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:
a) Weight with lever transmission
b) Geared transmission without pulley blocks
c) Hydraulic jacks
Answer: a [Reason:] The commonly used mechanical devices are weights with 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 [Reason:] 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 [Reason:] 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 [Reason:] 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:
c) Shrinkage cement
d) Expanding cement
Answer: d [Reason:] 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).
Prestressed Concrete Structures MCQ Set 5
1. The repair and rehabilitation of damaged or spalled concrete is done by removing the:
a) Loose concrete
Answer: a [Reason:] Repair and rehabilitation of damaged or spalled concrete is done by removing the unsound or loose concrete by providing temporary supports to the girder to relieve dead load stresses and the case of pretressed concrete bridge decks, special stress check up is essential before starting the repair works.
2. In many cases of heavily loaded girders, shear distress is observed near the:
Answer: b [Reason:] In many cases of heavily loaded, girders shear distress is observed near the supports in the form of diagonal tension cracks and shear cracks may arise due to improper detailing or compaction of concrete near the support zone in such cases holes are drilled diagonally and rebars are placed and grouted to arrest the shear cracks.
3. Bridge girders located in zones of very severe exposure conditions suffer:
Answer: a [Reason:] Bridge girders located in zones of very severe exposure conditions are like it to suffer: Spalling extensive spalling of concrete exposing the reinforcements and in such cases the unsound or loose concrete around the girders is removed and repairing against the loss of concrete section is done by jacketing the girders using a steel form.
4. The crack propagation in the concrete girders can be arrested by using the principles of:
a) Pre tensioning
b) Post tensioning
Answer: b [Reason:] Crack propagation in the concrete girders can be arrested by using the principles of post tensioning and in this tensile cracking in the girder are arrested by including compression using tension ties forced to the sides of the girder at locations of tensile cracks.
5. In some cases of repairs of girders damaged by collision, the damage is severe what are used:
a) Trusses and bars
b) Struts and pins
c) Links and dowels
d) Lace and anchores
Answer: c [Reason:] In some cases, the damage is more severe deeper so that the high tensile wires and strands are exposed and in such cases, the damaged portion is repaired by using links ad dowels along with wire mesh tied to the reinforcements and the entire damaged part is repaired using mortar or non shrink grout.
6. The corrosion of reinforcement due to extreme exposure is common for structure located in:
a) Dry conditions
b) Costal zones
c) Regional zones
d) Hot condition
Answer: b [Reason:] Due to various reasons such as corrosion of reinforcements due to extreme exposure conditions, especially when un bonded tendons are used, the high tensile strands may get damaged resulting in loss of prestresss in the girder.
7. In case of damaged prestressed concrete I girders which are used for restoring strength?
b) Post tensioning
Answer: b [Reason:] Post tensioning rods ( one on either side of the web) in conjugation with jacking (concrete) corbels located outside the damaged areas can be used to restore the strength of the prestressed girder and to start with the calculated preload is applied and the damaged concrete is repaired.
8. In restoration of strength by adding external reinforced concrete the damages concrete is first repaired by applying:
b) Tensile load
c) Compressive load
Answer: a [Reason:] In this method the damaged concrete is first repaired by applying the required preload and the concrete a corbels are constructed with the required conventional steel reinforcement and it shows adding external reinforcement concrete to restore the strength of the damaged girder.
9. In method 3 the restoration is done y addition of:
a) Metal sleeve jacket
b) Aluminium jacket
c) Steel jacket
d) Water proof jacket
Answer: a [Reason:] In this methods preload is applied prior to the repair of the damaged concrete and removed after the completion of repairs and a metal sleeve jacket is installed around and beyond the damaged area and the gap between the metal sleeve girders is filles with epoxy grout by pressure injection.
10. The depth of structural element is increased by adding:
a) Excess concrete
b) Low concrete
c) Prestressed concrete
Answer: a [Reason:] The depth of structural elements is increased by adding an new layer of concrete on top of an existing cross sections and bonding the old and new elements with modern epoxy resin adhesives and the total reinforcement in the cross section is increased by epoxy bonding of thin steel plates on the tension face of the beam to increase the flexural and shear strength.