214
C. Bacotiu et al.
Table 6.1 Criteria and weights used for the choice of water pipe material
No.
Criterion name
Abbreviation
Weight
1
Hydraulic smoothness
HYDRA
1
2
Mechanical strength
MECH
2
3
Chemical stability
CHEM
1
4
Diameter range
DIAM
1
5
Handling and installation
INST
2
6
Operational problems and service life
LIFE
3
7
Environmental aspects
ENV
1
8
Costs/financial effort
COSTS
3
– Ductile cast iron pipe (DCI);
– Fiberglass pipe (FG);
– Pre-stressed concrete pipe (PC).
They are the so-called “actions” (or alternatives or options).
In the next step, the decision maker has established what are the criteria that
should be used in order to compare the potential actions (competitors). As a general
rule, those criteria should be coherent, comprehensive and non-redundant. For our
case, Table 6.1 summarizes the eight criteria taken into account and their weights.
It is important to point out that each criterion may include other sub-criteria, so
the discussion is far more complicated than it seems. An aggregation procedure may
take place. Regarding the weights, they represent the importance of a certain criterion
for the decision maker, in this case, the privileged ones are “Life” and “Costs”.
Apparently, the number of criteria, their exact meaning and their weight come from
a negotiation process with all the actors involved in the decision process. Each decision maker has some degree of subjectivity when it comes to choosing the weights.
Every MCDA procedure needs as input data, the evaluation of the alternatives
against the criteria. Therefore, the next step was to evaluate each option with respect
to each criterion. Depending on the criterion, the assessment may be objective with
respect to some scale of measurement (e.g. money) or, it can be subjective, reflecting
the personal opinion of the evaluator. In the end, a so-called performance matrix was
obtained.
The performance of each alternative with respect to each criterion is usually
expressed by a grade, e.g. very good, good, medium, satisfying, unsatisfying. The
entire procedure for converting the grades into numbers which are then used for
computing the concordance and discordance indexes is detailed in Schärlig [15].
Based on Schärlig [15], we developed in our department a software tool called
AMEL1 [1], which was used to make all the needed indexes calculations and to perform sensitivity analysis in order to identify the “best” water pipe material (Fig. 6.11).
The ELECTRE 1 method can be used to construct a partial ranking and finally
choose one of the most promising alternatives. Using the concordance and discordance indexes followed by a sensitivity procedure, this method is based on “common
C. Bacotiu et al.
Table 6.1 Criteria and weights used for the choice of water pipe material
No.
Criterion name
Abbreviation
Weight
1
Hydraulic smoothness
HYDRA
1
2
Mechanical strength
MECH
2
3
Chemical stability
CHEM
1
4
Diameter range
DIAM
1
5
Handling and installation
INST
2
6
Operational problems and service life
LIFE
3
7
Environmental aspects
ENV
1
8
Costs/financial effort
COSTS
3
– Ductile cast iron pipe (DCI);
– Fiberglass pipe (FG);
– Pre-stressed concrete pipe (PC).
They are the so-called “actions” (or alternatives or options).
In the next step, the decision maker has established what are the criteria that
should be used in order to compare the potential actions (competitors). As a general
rule, those criteria should be coherent, comprehensive and non-redundant. For our
case, Table 6.1 summarizes the eight criteria taken into account and their weights.
It is important to point out that each criterion may include other sub-criteria, so
the discussion is far more complicated than it seems. An aggregation procedure may
take place. Regarding the weights, they represent the importance of a certain criterion
for the decision maker, in this case, the privileged ones are “Life” and “Costs”.
Apparently, the number of criteria, their exact meaning and their weight come from
a negotiation process with all the actors involved in the decision process. Each decision maker has some degree of subjectivity when it comes to choosing the weights.
Every MCDA procedure needs as input data, the evaluation of the alternatives
against the criteria. Therefore, the next step was to evaluate each option with respect
to each criterion. Depending on the criterion, the assessment may be objective with
respect to some scale of measurement (e.g. money) or, it can be subjective, reflecting
the personal opinion of the evaluator. In the end, a so-called performance matrix was
obtained.
The performance of each alternative with respect to each criterion is usually
expressed by a grade, e.g. very good, good, medium, satisfying, unsatisfying. The
entire procedure for converting the grades into numbers which are then used for
computing the concordance and discordance indexes is detailed in Schärlig [15].
Based on Schärlig [15], we developed in our department a software tool called
AMEL1 [1], which was used to make all the needed indexes calculations and to perform sensitivity analysis in order to identify the “best” water pipe material (Fig. 6.11).
The ELECTRE 1 method can be used to construct a partial ranking and finally
choose one of the most promising alternatives. Using the concordance and discordance indexes followed by a sensitivity procedure, this method is based on “common