Optimum Design
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1. Criterion function
Maximize performance
Minimize weight
Minimize cost (lastly)
2. Functional
All the equations to properly define the vehicle function. This
can be several computer programs, or analysis of structural
vibrations and response which present stiffness requirements
3. Regional constraints
Vehicle weight is a maximum value often dictated by their
runway capacity
Must fit in a prescribed space
Crew size
Travel a given speed
Design life
B. Petro or Chemical Plants
These plants function for 30-50 years and are expected to survive major
earthquakes and explosions with as little damage as possible. The criterion
here is a process to produce a product and the design of pressure vessels,
pipes, and physical containment of the parts of the process. When vessels
are welded a proof test of 140% of the operating pressure is applied to cause
a failure should a critical crack size exist. Corrosion allowance of 1/16 to
1/4 inch on one or both sides of a vessel are added to the design thickness.
Thin wall vessels (which are optimal) are a minimum weight structure
for the applied loads.
1. Criterion function
Maximize profitable life
Minimum cost
2. Function constraints
All equations to define a process or vessel being designed
3. Regional constraint
Weight and size of vessels or components being designed as they
must be sent by trucks over roads, barged down waterways, or
on railroad flatbeds over existing railroads. Bridge clearance
and total land area are also problems here
C. Main and Auxiliary Power and Pump Units
The criterion here is high reliability and excellent performance. The strength
of the parts, cavitation, and creep are prime considerations. Means of fab-