FORMACIÓN COMPLEMENTARIA SISTEMAS CONSTRUCTIVOS INDUSTRIALIZADOS

SENA

OSWALDO HURTADO FIGUEROA INSTRUCTOR DE CONSTRUCCIÓN SENA

Email: ohurtado@misena.edu.co Cel: 314-3026758

TIPOS DE CONCRETOS UTILIZADOS LOS CONCRETOS UTILIZADOS PARA LAS CONSTRUCCIONES CON SISTEMAS INDUSTRIALIZADOS

Mediante ensayos de laboratorio se llevó a cabo una caracterización físico - mecánica de los diferentes concretos que se utilizan en los sistemas industrializados de construcción de edificaciones, haciendo un análisis comparativo del comportamiento de este tipo de mezclas a diferentes edades (horas y días). Adicionalmente se contrastaron las principales propiedades mecánicas de estos concretos especiales con las del concreto convencional (bombeable) usado en la construcción de placas de sistemas tradicionales. Por otro lado se llevaron a cabo ensayos de calorimetría sobre los concretos usados en los sistemas industrializados con el fin de relacionar el diferencial máximo de temperatura (ETmax), tomado del perfil térmico, con la resistencia máxima esperada de la mezcla. Finalmente se desarrolló un prototipo para determinar el esfuerzo de adherencia entre el acero de refuerzo y el concreto con el fin de establecer la evolución de este esfuerzo en el tiempo. En los sistemas industrializados de vivienda de muros de concreto se requieren dos tipos de mezclas dependiendo si son usadas para los muros o para las placas. En particular, los criterios de diseño de las mezclas de concreto usadas para los muros están asociadas con la fluidez y los tiempos de fraguado debido a la alta resistencia al bloqueo que se presenta al interior de los muros (espesores entre 8 y 17 cm) generada por la presencia de tuberías, refuerzos de acero v accesorios. Por su parte la principal característica que se busca en las mezclas usadas en las placas de concreto está asociada con la resistencia a edades tempranas sin perder de vista la fisuración plástica, Las características mencionadas anterior mente han evolucionado desde los primeros años de la década de los 90's cuando se introdujo al país el sistema Outinord y el Contech . En los primeros años de esta década se usaba un único tipo de concreto que cumplía con las características deseables tanto para placas como para muros. Sin embargo es claro que el uso de una única mezcla de concreto no garantiza un adecuado aprovechamiento de las propiedades físicas y mecánicas de las mezclas, dado que un muro no requiere de tanta resistencia inicial como una placa de concreto y una fluidez muy alta puede alargar los tiempos para poder llevar acabo el allenado ("finishing") de las placas. El concreto usado en los muros estructurales de los sistemas industrializados ha evolucionado desde mezclas fluidas con asentamientos de 7" (17,5 cm) hasta los concretos autocompactantes que no requieren vibrador de inmersión y que garantizan un adecuado llenado en todos los espacios al interior de los muros.

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Table 8 shows the various types of profile which can be obtained at the end of this test and the

conclusion for each of them.

Conclusion

There is no relation between the activities of the management part and no relation between the activities of

the operational part of the processes.

The processes are probably managed in a similar way and the activities considered as significant are not the same for the two processes.

There is no relation between the activities of the management part of the processes and the activities

considered as significant for a process are the complete opposite for each of the two processes.

The processes are probably managed in a similar way and the activities considered as significant for a process are the opposite for the two processes.

The processes are probably managed in a completely different way and there is no relation between the

activities of their operational parts.

There is no relation between the activities of the management part and the activities considered as significant

are the same for the two process.

The processes are managed in a completely different way and the activities considered as significant are the

same for the two processes.

The processes are managed in a similar way and the activities considered as significant are the same for the

two processes.

The processes are managed in a completely different way and the activities considered as significant for a

process are the complete opposite for each of the two processes.

Table 8 - Comparison of the OMP matrixes: types of profile

A comparison of the activities of the processes can then be carried out. Given A the POM matrix of

the reference process and given B the POM matrix of the process to be improved, the matrix C of the

differences is built in the following way:

- If A[i, j] = 1 and B[i, j] = 0 then C[i, j] = 2

- If A[i, j] = 0 and B[i, j] = 1 then C[i, j] = -2

- If A[i, j] = 0 and B[i, j] = 0 then C[i, j] = 0

- If A[i, j] = 1 and B[i, j] = 1 then C[i, j] = 1

We then calculate three points:

- the centre of gravity for the activities the two processes have in common (values of C equal to

1),

- the centre of gravity for the activities which exist for the reference process but not for the

process to improve (values of C equal to 2),

- the centre of gravity for the activities which exist for the process to improve but not for the

reference process (values of C equal to -2).

To show how these points are calculated, let us consider (Table 9) the following example of a matrix

C, reduced here to 4 lines and 4 columns.

N° 1 2 3 4 1 1*N° 2 2*N° -2 -2*N°

4 1 2 1 0 2 8 1 4 0 0

3 0 -2 0 2 0 0 1 3 1 3

2 1 1 2 2 2 4 2 4 0 0

1 2 1 2 1 2 2 2 2 0 0

1 2 2 1 1 1*N° 2 4 3 4

2 1 1 2 2

2*N° 1 2 6 8

-2 0 1 0 0

-2*N° 0 2 0 0

1 : numbers of cells equal to 1; 2 : numbers of cells equal to 2 ; -2 : numbers of cells equal to -2

Table 9

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We can now calculate the co-ordinates of the centres of gravity with the following relation:

XG =

n

i

i

n

i

i N

1

1

* YG =

n

j

j

n

j

j N

1

1

* (8)

For the example given above, the co-ordinates of the three points are:

XG YG

Activities in common 2.16 2.33

Additional activities in the reference process 2.83 2.16

Additional activities in the process to be improved 2 3

These points can then be represented graphically by a correlation graph (Figure 3). The size of each

circle is proportional to the number of values used to calculate the point. We thus have a graphic tool

which allows us to quickly understand the differences between the two processes. In the example

given, the activities the two processes have in common refer to technical as well as to organisational

and human factors. The reference process is characterized by a significant effort on strategic actions

(axis function) while the process to improve concentrates on support activities (assistance function).

Figure 3 – Correlation graph

The representation in Figure 4 offers additional information to that shown in Figure 3 by locating the

activities at the origin of the differences between the two processes. The additional activities of the

reference process (in blue on the figure) represent potential actions to be undertaken to improve the

process.

Figure 4 – Comparison of activities

1 1 1 -2 -2 1 1 1 -2 1 -2 1 1 1 1 1 1 1 1 1 1 -2 2 1 1 -2 2 2 2 2 1 -2 1 1 1 1 1 -2 -2 1 1 -2 -2 2 2 2 -2 -2 1 -2 -2 1 -2 -2 2 2 2 2 2 -2 1 1 1 1 -2 2 2 2 2 2 2 1 2 1 1 -2 2 2 2 1 2 -2 -2 -2 2 -2 2 2 1 -2 2 1 1 1 1 -2 1 2 2 2 2 -2 1 -2 -2 2 2 2 2 2 2 1 1 -2 2 2 2 2 2 2 -2 -2 2 2 2 2 2 2 2 2 2 1 1 -2 1 2 2 2 2 -2 -2 2 2 2 1 2 1 2

Activities in common

Additional activities in

the reference process

Additional activities in

the process to improve

OR

GA

NIS

AT

ION

HU

MA

INT

EC

HN

IQU

E

AXE ACTION ASSISTANCE

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

0 1 2 3 4 5 6 7 8 9 10 11 12 13

Activities in common

Additional activities in the

reference process

Additional activities in the

process to improve

Org

an

izatio

nal

Hu

man

T

echn

ical

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2.3. Output data of the comparison

The output data of the comparison which is carried out (comparison of the ISC matrixes and the OMP

matrixes) are thus:

- the striking contrasts resulting from the comparison of the two ISC matrixes

- the formulation of the causes at the origin of these striking contrasts

- the relative position of the activities in each process

- the vision of the activities privileged in the two processes

These data are obtained with a study requiring only some structured interviews compatible with the

time the manager has available. With these output data, it is easy to structure an effective action plan

to make progress on the process to improve.

Conclusion

It is the difficulty of SME to carry out a benchmarking which led us to propose tools and methods:

- to describe the processes, the process to improve and the reference process,

- to compare these processes with the objective of defining actions to carry out on the process to

improve.

The description of the process which we proposed is based on some recommendations of the system

theory. We thus stressed the need, not only to identify the good practices of a process, but also, and

especially, to identify the interactions between these practices which mean that the process is in a

position to be maintained and to improve over time.

The comparison of these matrixes aims at leading very quickly to an action plan to improve the

process. This comparison is based on the description of striking contrasts which exist in the history,

the structure and the execution of this process compared to a reference process. The tool proposed thus

highlights the differences in the practices implemented, either in the way of carrying out these

processes, or in the way of managing it.

Our current work aims to develop the OMP matrix (Operative and Management Part) by giving the

possibility of providing answers, different from binary ones (0 or 1), but founded on more structured

information (for example, with the use of semantic scales whose treatment could be carried out by

fuzzy logic). This information would enable us to reveal subtleties in the positions of the centres of

gravity. Another topic of research relates to the identification of the good practices. In this paper, this

identification is currently based on a description of the differences observed between a reference

process and the process to be improved. Our research is now to determine how just one interview

could be carried out instead of two.

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