# Prestressed Concrete Structures Questions and Answers – Principles of Optimisation

This set of Prestressed Concrete Structures Multiple Choice Questions & Answers (MCQs) focuses on “Principles of Optimisation”.

1. The primary aim of structural optimization is to determine the __________
a) Design variables
b) Design parameters
c) Design constants
d) Design limits

Explanation: The primary aim of structural optimization is to determine the most suitable combination of design variables, so as to achieve satisfactory performance of the structures subjected to the behavior and geometric constraints imposed with the goal of optimality being defined by the conditions and the three basic features of the structural optimization problem are:
The design variables, the objective function, the constraints.

2. The process of optimum design of prestressed concrete structures may be looked as __________
a) Computer programming problem
b) Mathematical programming problem
c) Diagram
d) Algorithm

Explanation: Basically the process of optimum design of prestressed concrete structures may be looked upon as a mathematical programming problem in which the total cost or consumption of materials is minimized, subject to certain functional constrains such at serviceability limit states and flexural and shear strength requirements at the limit state of collapse.

3. The optimization problem involves __________
a) Short computations
b) Zero computations
c) Long computations
d) Span computations

Explanation: Generally optimization problems involve long and tedious computations and as such manual computations are limited to simple problems comprising a few design variables and however the development of high speed electronic digital computer has revived the interest in optimization problems and significant advances have been made in the field of structural optimization.

4. The design variables are generally grouped under which parameters?
a) Dimensional variables
b) Span variables
c) Foundation variables
d) Constant variables

Explanation: The design variables are generally grouped under which parameters dimensional variables represented by the member sizes such as the thickness of a plate, cross sectional area of a member and moment of inertia of a flexural members, configuration or geometric variables represented by the coordinates of element joints, variables involving the mechanical or physical properties of the material, such as the variable modulus of elasticity.

5. In the sequential unconstrained minimization techniques, which problems are converted?
a) Un constrained
b) Constrained
c) Designed

Explanation: In the sequential unconstrained minimization technique, the constrained minimization problem is converted into an unconstrained one by introducing an interior or exterior penalty function and this method introduced by Carroll and amplified by Fiacco and Mc cormick has proved to be highly advantageous in practical structural design problems.
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6. In sequential linear programming, the non-linear objective functions and constrains are __________
a) Linearized
b) Parralized
c) Straightened
d) Divided

Explanation: In sequential linear programming, the non-linear objective function and constrains are linearized in the vicinity of the starting point and a new design point is obtained by solving the linear programming problem and the sequence of line arising in the neighborhood and solving by linear programming is continued from the new point till the optimum is reached.

7. The further improvement method of sequential linear programming is?
a) Beam limit method
b) Rise limit method
c) Move limit method
d) Fall limit method

Explanation: Further improvements in these methods are due to pope, who suggested the move limit method and more recently Ramakrishna and Bhavikati has improved and used this method for the optimum design of mechanical components under stress.

8. Dynamic programming developed in optimization techniques are widely applied in __________
a) Research
b) Structures
c) Entertainment
d) Mathematics

Explanation: Dynamic programming developed by Bellman in the early 1950s and widely applied in operations research and economics is basically a mathematical approach for multi stage decision problems and this approach is well suited to the optimal design of certain kinds of structure, in general those in which the interaction between different parts is rather simple.

9. The limitation of dynamic programming is that it does not lend itself for __________
a) Construction general purpose computer programmes
b) Machine design
c) Graphic design
d) Architectural design

Explanation: The limitation of dynamic programming is that it does not lend itself to the construction of general purpose computer programmes suitable for a wide range of distinct problems and dynamic programming has been used for optimizing the shape of pin jointed structures and for the optimal design of transmission towers by palmer and Sheppard.

10. In geometric programming, the emphasis is on __________
a) Optimal distribution
b) Single distribution
c) Variable distribution
d) Linear distribution

Explanation: Reliability of prestressed concrete structural systems like beams and frames has been examined by Ranganathan while the reliability design of prestressed concrete beams has been reported by chandrashekhar and dayaratnam and application of geometric programming to structures optimization problems has been attempted by temple man and of the total cost among the various terms in the objective function instead of on the values of the variables.

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