An assessment-based process for modifying the built fabric of historic centres: the case of Como in...

Sixth International Workshop on "Geographical Analysis, Urban Modeling, Spatial Statistics"

GEOG-AN-MOD 11 in conjunction with

The 2011 International Conference on ComputationalScience and its Applications (ICCSA 2011)

June 20 th to June 23 th, 2011, University of Cantabria, Santander, Spain

Pier Luigi Paolillo(1), with Alberto Benedetti, Umberto Baresi, Luca Terlizzi, Giorgio Graj (1) Polytechnic of [email protected] - http://webdiap.diap.polimi.it/paolillo/

mailto:[email protected]

http://webdiap.diap.polimi.it/paolillo/

1. Why the historic centres: a preliminar consideration

2. The methodological process: from the selection of descriptor and variables to the final synthesis in the

“suitability for change” map

3. Method for analysing and assessing the characteristics of centrality and socioeconomic

vitality

4. Assessing the values of the built fabric

5. The final step: the map of suitability for change

and the relative types of change for the single built fabrics

Estimate:(α) residenzial vitality

(β) commercial distribution(γ) services accessibility

ASSUMPTION OF THE BEST SCENARIO FOR SUITABILITY FOR CHANGE OF BUILT FABRICS

ASSUMPTION OF THE BEST SCENARIO FOR SUITABILITY FOR CHANGE OF BUILT FABRICS

Results:

Socio/economic characterizationSocio/economic characterization

5 scenarios derived from “f” function

5 scenarios derived from “f” function

Regional Laws

Support to administratio

n

Identify types of change in built fabrics

(art. 27 Lr.12/05)

Classify priority of intervent in historic

centre

Goal:Define degrees of suitability for change

of single buildings

Goal:Identify and quantify demographic,

economic, social tendency

Suitability for changeSuitability for change Social and economic phenomenaSocial and economic phenomena

Database organised to develop Gis analysis

Multi/dimensional analysis

Comparison between scenarios and socio/economic aspects, and selection of the best-one

),,,,,( FEDCBAf

Use an algorithm to create scenarios of suitability for change

0. The framework assumed

Urban Planning Discussion-ANCSA:

Growing importance (since 50’s) of “historic centres” issue, related today with a generalised decay:-RELATIONAL (population and vacancy)-STRUCTURAL (appeal and economy)-PHYSICAL (built fabrics)

1. Why the historic centres: a preliminar consideration

REGULATION assessment in LOMBARDY:

-LR.12/2005: NEW PLANNING INSTRUMENT, PGT

Goals:-identify HISTORIC CENTRES-recognize Types of change for each fabric

Structuring the method:Necessity of a different approach based on quantitative analysis

Preliminar analysis of the case-study: territorial phenomena and planning instruments;

Use of the database to develop analysis and evaluations with Gis software

Como historic centre:

Worsening in terms of: -weakness in human relations

-lost of attractivity-Growing decline and vacancy in

built fabrics

Change of approach:

60’s * conservation of historic fabricsToday * re-use of built fabrics, in order to: - not use further free-soil - use fabric nowadays vacant

Identifying the variables

Grouping the variables into summary indicesSocio/

economical aspects

Identifying the spatial units of investigation

Historic/architectural

aspects

Multidimensional/algorythm analysis

Areas of iso-problematicity

Scenarios for change

Identifying the descriptor blocks

Selecting the most

suitable scenario for change in this specific place

Spatialising the phenomena (thematic mapping)

2. The methodological process: from the selection of descriptor and variables to the final synthesis in the “suitability for change” map

3. Method for analysing and assessing the characteristics of centrality and socioeconomic vitality

Function indicating how various phenomenical

aspects flow together into the socio/economical analysis

where:A = tendency to accumulated centrality of the historic centre;B = instability of the fabric due to monofunctionality;C = density of localisation of the most strongly attractive activities;D = stability of the inter-relating residential fabric;E = urban landscape importance of buildings

Innovative tools and applications

Multiple centrality assessment

- Porta et al., 2006; Cardillo et al., 2006; Crucitti et al., 2006; Scellato et al., 2006

- Similar approach to configurational analysis (Bill Hillier and the UC London school)

- Moving from space configuration to recognize structure and caracteristics of open urban spaces

Viewshed

- Viewshed analyses: common function of most Gis software. The analysis uses the elevation value of each cell of the Dem to determine visibility to or from a particular cell

- Application of viewshed to built fabric with specific carachteristics (constraints, facades, uniformity of a specific built-area)


Indices and variables

A) Mca (Multiple centrality assessment)

Goal: recognize the inclination towards transformation of built fabrics

Indices:Betweenness -> traffic long-radiusLocal closeness -> traffic short-radiusLand use density -> concentration of extra-residential buildingsFunctional heterogeneity -> application of Shannon index to calculate heterogeneity

Basis:- Connectionfrom point topoint to create Axial map (ecuclidean axis) with Mcatools

Betweenness (x) Local closeness (y)

Network interaction (a1)

2

yx

Land use density (x)

Functional heterogeneity (y)

Vitality of the economic fabric

(a2)

2

yx



B) Instability of the fabric due to monofunctionality

Goal: Recognize areas with potential risk of becoming monofuncional and central “banlieue”

Indices:Index of ageing -> areas with old inhabitantsResidential density -> areas with inhabitantsIndex of heterogeneity of non-residential activities -> monofuncional areas

Basis:- Make residential and economical data interacting toghether using Kernel Density

Index of ageing Residential density

Index of heterogeneity

of non-residential activities

Thematic activities



C) Density of localisation of the most strongly attractive activities

Goal: Recognize the competitive areas from the economic point of view

Indices:Density of commercial activities Density of service sector activities

Density of commercial activities

D) Stability of the inter-relating residential fabric

Goal: Recognize problematic residential areas

Indices:Incidence of the non-Italian resident populationIncidence of residential vacancyDistribution of the population within buildings (underoccupation – overcrowding)

Density of service sector

activities

Vacancy

Indices

Variables

Residentnationality

Residential buildings size

Roots

Census of built fabric

Residential dataset

Census of built fabric



E) Urban landscape importance of buildings

Goal: Recognize buildings with particular landscape values

Indices:Building perception -> is the building seen from relevant points of observation?Characterisation of the perception -> how is the building perception?

Basis:- Advanced applications in Gis softwares: * building the (Digital Elevation Model);* selecting points of observations;* building Viewshed

Building DEM(DTM+Built fabrics)

Building VIEWSHED

Points of observation

Fabrics with positive elements

Fabrics with negative elements

Quantity of fabric percepted

Urban landscape importance of buildings


Viewshed procedure

Decomposing the observation points into a number of different

viewshed analyses (e.g.: access points to the historic centre, busiest historic streets,

open spaces for public socialising, and so on)

Selecting observation

points

Sifting informational

strata

Summarising, referring as necessary to the qualitative

characterisation of the particular building (E)

Quantifying and summarising the

degree of visibility of any given building

Refining the analysis as appropriate (e.g.: distinguishing between buildings seen in

perspective and buildings seen in the round)

Analysis:if k = 1

the building is visible


Applied multidimensional geostatistic analysis

i) correlational analysis, aimed at reducing the number of variables to be tested and used in the subsequent stages;

ii) non-hierarchical analysis, which makes it possible to identify the spaces that are homogeneous in terms of the variables adopted for describing the model

From variables and indices to Multidimensional analysis

Use of dedicated software Addawin (prof. Griguolo, IUAV of Venice) in the GIS environment: from aggregated indicators derived estimating f (A, B, C, D, E), to application of geostatistics procedures, in particular multivariate analysis:

Facplan image:step that analyses the distribution of the centres of the stable profiles with respect to the two axes that most effectively explain the multivariate situation under investigation

Phenomena

Clusters


Function indicating how various phenomenical

aspects flow together into the built fabrics analysis

where:F = suitability for retention, intrinsic in the building itselfG = suitability for retention, in the relationship between building and urban blockH = the urban landscape importance of the context in which the building standsI = suitability for increases in volume

Assumption of descriptors block and variables


F) Suitability for retention, intrinsic in the building

Goal: recognize the inclination towards transformation of built fabrics

Indices/variables:F1 - presence of environmental and historic/architectural constraintsF2 - persistence of buildings over timeF3 - the state of conservation of buildingsF4 - presence of facades to be retainedF5 - presence of excrescences

F1 - Contraints F2 - Datation

F3 - Conservation F4 - Facades

F5 - Excrescences



G) Suitability for retention, in the relationship between building

and urban block

Goal: recognize the inclination towards transformation of built fabrics, in the relation with the urban blocks

Indices/variables:G1 - presence of transformed areas (causing discontinuities in the urban fabric)G2 - degree of uniformity in respect to the first historic threshold adoptedG3 - degree of uniformity in respect to the number of storeys

G1 – Transformed areas

G3 - Uniformity (number of storeys)

G2 – Uniformity (first historic threshold)



H) Urban landscape importance

Goal: recognize the built fabrics impact on perception

Indices/variables:H1 – presence of quality elementsH2 – presence of elements of contrastH3 – index of perception of the buildingH4 – incidence of the building on the public space

H4 – Perception from public spacesH3 – Index of perception (from historic roads, points of access, public places)

H2 – Contrast factors

H1 – Quality factors



I) Suitability for increases in volume

Goal: recognize the building that can be raised as number of storeys

Indices/variables:I1 – character of the existing built frontageI2 – possibility of adding extra storeys

1 – Built-front with at least 50% fabrics with

same height

3 –Buildings useful for raising storeys

4 –Buildings unuseful (as reference) for raising storeys

2 – Buildings with specific characteristics


Algorhythm for assessing suitability for change


Assumption of an algorithm to classify the built fabrics

Classification of the result values

Aggregation of variables and indices in thematic

blocks

Assumption of different classes of suitability for

change, for every built fabrics of the historic centre

Devising the basic algorhythm of suitability

for change

Creatingscenario 1

Types of change permitted by the

regulations

Correlating the classes of suitability for change to the consented methods of changes to buildings

Preparing the map of suitability for change

Devising different

scenarios

Territorial

socioeconomic configurations

Comparing scenarios and selecting the scenario

that is most compatible with these territorial configurations


Building and selecting scenarios of suitability for change


Classifying and comparing different

scenario outputs

i) internal consistency: correlation between suitability for change and the datasetof variables adopted, identifying excessively high interdependencies that would indicate a flattening of the outcomes of the multivariate analysis

ii) external consistency is the correspondence between the general character of the scenario, in terms of suitability for change, and the real social, economic, and demographic characteristics of the territorial configurations of the historic core

Building and selecting scenarios of suitability for change

5. The final step: the map of suitability for change and the relative types of change for the single built fabrics

Final scenario of suitability for change

Cartography

From classes to types of change on built fabrics

5. The final step:Comparison between prescriptions of the old Prg and the new assessment recognized by Pgt

From a homogeneous classification of buildings

To a new one, coherent with the specific

characterization of the single built fabrics

Previous planning instrument:Prg -General regulator plan

(1975-1993)

New planning instrument:

Pgt -Plan for territorial government (2010)

References

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