Explanation: If the direct stresses are compressive, then the magnitude of principal stresses in prestressed concrete member acts reduced considerably and therefore under working loads, these principal stresses have to be compressive in nature in order to eliminate diagonal cracks in concrete.

Explanation: The ultimate shear resistance of prestressed concrete sections with web shear cracking but without flexural cracks, is mainly governed by the limiting value of the principal tensile stress developed in concrete, the failure is assumed to take place when the principal tension exceeds the tensile strength of concrete.

Explanation: 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.

Explanation: In the anchorage zone or the end block of a post tensioned prestressed concrete element, the state of stress distribution is complex and three dimensional in nature, in most post tensioned members the prestressing wires are introduced in cable holes or ducts, preformed in the members, and then stressed and anchored at the end faces.

Explanation: Short term deflections of prestressed members of class-1 and class-2 types under service loads are influenced by: magnitude of the prestressing force and its profile, applied load and self weight of the member and flexural rigidity of the Un cracked concrete sections.

Explanation: 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.

Explanation: 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.

Explanation: 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.

Explanation: Long span continuous prestressed concrete bridges are built of which type of box girders multi celled box girders segments of variable depth using the post tensioning system, and typical cross sections of post tensioned prestressed concrete bridge decks and salient features of the cantilever construction method using cast insitu segments and precast concrete elements.

Explanation: 11 storied cast in situ reinforced concrete structure which has the upper 8 stores resting on reinforced concrete arched girders with prestressed concrete ties spanning nearly 18m this is suited for large columns free space for conference halls, auditoriums, sports stadiums, industrial structures and in such cases prestressed concrete is invariably selected due to its inherent high strength durability and economy.

Explanation: The most important consideration in the construction of prestressed concrete structures is the design, production and control of high strength concrete with desirable properties the minimum grade specified in the Indian standard code IS: 1343: 2005 for post tensioned concrete is M30 and for prestressed concrete work it is M40, the code also specifies the only Design mix concrete should be used to ensure the desired strength and durability.

Explanation: 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.

Explanation: 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.

Explanation: 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.