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.