This set of Advanced Prestressed Concrete Structures Questions and Answers focuses on “Principles and Classifications of Prestressing”.
1. Which one of the following is the basic assumption involved in designing of prestressed concrete members:
a) Plane member remains plane before and after bending
b) Variation of stresses in tensile reinforcement
c) Development of principle stresses
d) Hooke’s law is not valid for prestressing
Explanation: The basic assumption involved in analysis and designing of prestressed concrete members are the plane cross-section of beam remains plane before and after bending, there is no variation of stresses in the tensile reinforcement, Hooke’s law is valid for both concrete and steel.
2. The compression in concrete and tension in steel are developed by:
a) Joint cements
b) Expansion cements
c) Water cement ratio
d) Hardened cements
Explanation: Compression in concrete and tension in steel is developed by use of expanding cements due to its elastic property or expanding property, joint cement is an adhesive used primarily for attaching the joint tape that is placed over the beams whereas water cement ratio is the ratio of the weight of water to weight of cement used in a concrete mix.
3. The distortion principle of statically indeterminate structures is subjected by:
Explanation: Distortion principle of statically indeterminate structures is used by rotation or by displacement and in statistics a structure is statistically indeterminate when the static equilibrium equation are insufficient for determining the internal forces and reactions on that structure.
4. The prestressing used for arches and pavements involves the application of:
a) Direct forces
b) Compressive forces
c) Tensile forces
d) Axial forces
Explanation: The prestressing used for arches and pavements is the application of direct forces between abutments, whereas to impart the desired forces, flat jacks are used and axial force is the compression or tension force acting in a member, if the axial force acts through the centroid of the member it is called concentric loading.
5. The classification of prestressed concrete is based on the method of:
b) Bending moments
d) Stresses acting
Explanation: Classification of prestressed concrete is based on the method of design like externally, internally, partial, moderate, axial, eccentric, concordant, uni-axial, biaxial, tri-axial, non distortional, linear, circular, post and pre tensioning, prestressed concrete has considerable increase resilience due to its capacity for completely recovering from substantial effects of overloading without undergoing any serious damage.
6. The concrete members which are prestressed by providing the tensioned tendons are termed as:
a) Externally prestressed members
b) Internally prestressed members
c) Linear prestressed members
d) Circular prestressed members
Explanation: The concrete member which is prestressed by providing the tensioned tendon are termed as internally prestressed members and the existing space between the edge of beam and abutments is filled with concrete using expanding cement.
7. The linear prestressing is mostly applicable for:
a) Bent members
b) Straight members
c) Cracked members
d) Overloaded members
Explanation: Linear prestressing is mostly applicable for straight members such as slabs, beams etc and the members are prestressed in a linear manner, tendons are spliced in case of continuous prestressed concrete members to gain continuity and the various types of splices used as tendons are screw connector, torpedo splices, clamp splice and wrapped splice.
8. In pre-tensioning system, after curing and hardening of concrete the reinforcement is set:
Explanation: In pre-tensioning system, the tendons are tensioned first and then the casting of concrete is carried out and the edge of the tendon at its either side is fixed to an abutment and its other edge is pulled with the application of jack and then the reinforcements are set free after curing and hardening.
9. The method of prestressing the concrete after it attains its strength is known as:
a) Pre tensioning
b) Post tensioning
c) Chemical prestressing
d) Axial prestressing
Explanation: The method of prestressing the concrete after it attains its strength is known as post tensioning and ducts are made in the member at the time of placing the concrete, the suitability of post tensioning is good for medium to long span-insitu work, where the cost of tensioning is very less.
10. In which method the prestress is developed due to bond between the concrete and steel?
a) Pre tensioning
b) Post tensioning
c) Thermo electric prestressing
d) Prefix beam prestressing
Explanation: The prestress developed in pre tensioning is due to the bond between concrete and steel tendons, a method of prestressing concrete in which the tendons are tensioned before the concrete is placed at the work site.
Sanfoundry Global Education & Learning Series – Prestressed Concrete Structures.
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