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DECivil ICIST Urban Rehabilitation in Southern Europe The Seismic Problem and the Portuguese Case Rita Bento Instituto Superior Técnico, TECHNICAL UNIVERSITY.

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Presentation on theme: "DECivil ICIST Urban Rehabilitation in Southern Europe The Seismic Problem and the Portuguese Case Rita Bento Instituto Superior Técnico, TECHNICAL UNIVERSITY."— Presentation transcript:

1 DECivil ICIST Urban Rehabilitation in Southern Europe The Seismic Problem and the Portuguese Case Rita Bento Instituto Superior Técnico, TECHNICAL UNIVERSITY OF LISBON December 2005 INTERNATIONAL WORKSHOP CITY OF TOMORROW AND CULTURAL HERITAGE POMERIA OUTLOOK DECEMBER 2005

2 DECivil ICIST INSTITUTO SUPERIOR TÉCNICO

3 DECivil ICIST Urban Rehabilitation in Southern Europe New central, eastern and southern EU states face the need to rehabilitate building stock; Common causes: lack of maintenance in the past; Different causes due to physical environment: Central and Northern Europe – the heating systems; Southern Europe – earthquake resisting rehabilitation

4 DECivil ICIST TOPICS Overall view of the importance of earthquake rehabilitation building stock in southern EU states: Detailed discussion of Lisbon downtown and 1755 earthquake; Proposals of the Portuguese and European scientific communities; Emphasis on common actions at European level: common strategy for central, northern and southern countries to negotiate EU financial support for rehabilitation of the building stock.

5 DECivil ICIST 1. Introduction Earthquakes still remain a severe threat in Southern Europe; It is impossible to predict dates of occurrence of earthquakes. Nevertheless the inadequate seismic resistance of the building stock, lifelines and industry is well understood and can be avoided Build and Strengthen structures Most critical issue: the problem of older vulnerable structures, built before current regulations and still perform vital functions; Different initiatives developed at European level. In Portugal, SPES has proposed new initiatives for the reduction of the seismic risk: Workshop Reducing Earthquake Risk in Europe – organized by EAEE and SPES, in October 2005

6 DECivil ICIST 1. Earthquakes in Europe - occurrence The SESAME Map of Seismic Hazard in the European Area – uneven distribution of earthquake distribution in Europe

7 DECivil ICIST The main different types of earthquake effects at the earths surface are: Fault rupture; Landslides and liquefaction; Tsunami; Fires; Ground motion /ground shaking. Ground motion is the cause of the vast majority of human and economic losses due to earthquake. 2. Earthquakes in Europe - effects

8 DECivil ICIST Several actions have to be performed against the effect of ground motion: 1.Evaluate the seismic resistance of existing buildings and strengthen the weakest ones; 2.Ensure the quality of construction; 3.Evaluate de seismic resistance and strengthen where necessary the industrial facilities and lifelines (power, gas, water,…); 4.Protect built heritage, by strengthen monuments and buildings of high cultural heritage. 2. Earthquakes in Europe - effects

9 DECivil ICIST Several decisions and policies can be suggested [Spence et al., 2005]: 1.Pursuing and strengthening the policies already enforced: Support of research on seismology and earthquake engineering; Development of Structural codes (EC8); Establish a centre for coordination of emergency aid; 2.Defining recommendations for Member States minimum standards of Earthquake safety; 3.Creating a structure to coordinate tasks better performed at European level. 3. What can be a European Risk Reduction Programme?

10 DECivil ICIST Two different components can be referred in urban rehabilitation of buildings: 1.Associated with conservation and improvement of living conditions; 2.Related with improving of safety conditions Evaluation and strengthening of existing buildings and monuments The criterion should be to strength buildings where the cost of strengthening is less than the expected losses and buildings that do not possess minimum safety levels.

11 DECivil ICIST To support this action the main available resource is the European Regional Development Fund (ERDF). It was recently proposed [Spence et al., 2005]: i.The regulation of ERDF be changed to allow supporting interventions on the housing stock, with specific objectives to provided minimum levels of safety; ii.That upper limits for the EU financial support should be established. The EU has already recognized the importance of strengthening monuments and buildings of high cultural value Evaluation and strengthening of existing buildings and monuments

12 DECivil ICIST To the reduction of the seismic risk is fundamental to ensuring the quality of construction to: New buildings and another infrastructures; To the design and execution of the rehabilitation of existing structures. The proposed is: EU would incentive the process by demanding guarantees from the Member-States: The responsible by the construction process should present external revision documents, assuming the responsibility for the quality of the final product and, if possible, insurance covering seismic risk Ensuring the quality of construction

13 DECivil ICIST Portugal is a seismic prone territory. 1755s Lisbon Earthquake was very strong (M=8.7): Destroyed large areas in Lisbon and Algarve. In Lisbon it was followed by a tsunami and a fire, out of control for several days Lisbon was rebuilt following an urban plan. The fear of another earthquake led of the enforcement of new construction rules Pombalino Buildings 4. The Portuguese Case: 1755 Earthquake and the Pombalino buildings

14 DECivil ICIST Old Masonry buildings in Lisbon LEGENDA: A - EDIFÍCIOS DE ALVENARIA (<1755) B - EDIFÍCIOS POMBALINOS E SEMELHANTES (1755 a 1880) C - EDIFÍCIOS ALTOS DE ALVENARIA COM PAVIMENTOS DE MADEIRA OU DE BETÃO E PAREDES RESISTENTES DE ALVENARIA (1880 a 1940) D – EDIFÍCIOS DE ALVENARIA, COM PAVIMENTOS EM BETÃO OU COM ESTRUTURA PORTICADA DE BETÃO (1940 a 1960) E – EDIFÍCIOS RECENTES DE BETÃO ARMADO (>1960) [in Mendes-Victor et al, 1993] Downtown

15 DECivil ICIST After 1755 Lisbon Earthquake, masonry buildings were built with a 3D wood structure named gaiola pombalina. The gaiola structure is like a cage made of vertical and horizontal elements braced with diagonals Pombalinos Buildings ( ) Gaiola Pombalina [Mascarenhas, 1997]

16 DECivil ICIST Pombalino Building Gaiola 3-D wood structure St Andrews Crosses Different geometries Maximum number of floors: 3 + ground-floor Foundations – short and small diameter woodpiles connected by a timber grid System of vaults made of blocks of ceramic masonry and stone arches Floors – timber slabs [Mascarenhas, 1997]

17 DECivil ICIST Gaiola Pombalina: Scheme of an interior wall with St Andrews crosses The walls are filled with masonry, so the wood elements can not be seen. Partition walls 3D wood structure Floors

18 DECivil ICIST Gaioleiros Buildings (1800–1940) [Mascarenhas, 1997] As time went by, the wood elements were progressively removed in new constructions The diagonal elements gradually disappear Interior walls were replaced with masonry or wood-partitions In time, masonry becomes the only structural material. Partition walls

19 DECivil ICIST Placa Buildings ( ) Thin concrete slabs [Mascarenhas, 1997] Masonry walls At the most recent masonry buildings, wood floors were replaced with thin concrete slabs. Selft weight was increased. As the result of construction evolution, old masonry buildings became less resistant to horizontal loads

20 DECivil ICIST Pombalino Building analysed Rua da Prata, 210 a 212 Roof/Penthouse Main Entrance

21 DECivil ICIST Pombalino Building analyzed in [Santos, 2000] Main Façade Plan of a typical floor

22 DECivil ICIST Numerical Model (SAP2000 ® ) Vaults (crosses) Floors bars Floors Shell Elements (2D) of masonry walls Beam elements MasonryInterior wall of gaiola

23 DECivil ICIST Numerical Model (SAP2000 ® ) - Quarter

24 DECivil ICIST Building Analysis sis = 0.20 sis = 0.25 sis = 0.30 Evolution of Damage Levels in masonry elements from main façade in 1 st step of iterative procedure – evolution of tension damaged masonry Deformed main façade

25 DECivil ICIST COLAPSE Mechanism: Bending of the front façade out of its plane 1998 Azores Earthquake Collapse Mechanism obtained

26 DECivil ICIST 1998 Azores Earthquake Collapse Mechanism according to original conception Fall out the plane of exterior walls without complete collapse – it depends on de number of floors [Mascarenhas, 1997]

27 DECivil ICIST Strengthening Solutions Solution 1 Strengthening of the connections gaiola- façades The overturning of the façades can only occur after the rupture of its connections to the exterior masonry walls. Steel connectors

28 DECivil ICIST Solution 2 Inclusion of a R.C. beam ( m 2 ) on the top Beam around the exterior perimeter Solution 3 Inclusion of R.C. beams ( m 2 ) in all the floors Beams at the pavements level

29 DECivil ICIST Actual Conservation State of Pombalino Buildings Buildings that mantain their original conception Main problems result from deficient/no maintenance: roof broken ceramic tiles that allow water inflitration causing masonry and timber degradation, etc. Buildings that suffered structural changes In most of the cases are critical as they reduce the seismic resistance and therefore are not advisable

30 DECivil ICIST Influence of the structural modifications Vertical continuity is not interrupted People may go around The open larger shop windows Vertical continuity is interrupted Increase the building vulnerability to shear base collapse Demolition of interior walls and introduction different structural elements Redistribution of the internal forces

31 DECivil ICIST Introduction of more stories at the top of the building Mass and F inertia increase at the top

32 DECivil ICIST Changes in Gaiola structure: removing timber elements or cutting elements for pipe solution Timber section was cut/reduced Bad solution Better solution Stiffness and bracing capacity of this timber structure

33 DECivil ICIST The Portuguese Association for Earthquake Engineering (SPES) has been working actively for the reduction of the Seismic Risk in Portugal. In 2001, it was presented a programme with 7 tasks: 1.Surveying and seismic evaluation of the building stock; 2.Definition of more efficient strategies of intervention; 3.Improvement of seismic strengthening solutions; 4.Formation of a legal framework for rehabilitation actions; 5.Civil and technical education and spread of information; 6.Creation of master-plans for seismic rehabilitation; 7.Interventions. 5. Portuguese Programme for the Reduction of the Seismic Vulnerability

34 DECivil ICIST Albeit the importance of the programme, it is not yet effectively supported by any member of the government, group of municipalities or politicians or by any private sector entity; For all these groups it is important: to decide in view of very short-terms horizons; To have some immediate return of their investment. The last initiative of SPES was the definition of the European Risk Reduction Programme; This cooperation seems to be the right way to the seismic risk reduction at all levels: local, national and European. 5. Portuguese Programme for the Reduction of the Seismic Vulnerability

35 DECivil ICIST Old masonry buildings are an important part of the building stock of most European cities and have to be preserve; The rehabilitation and strengthen should be promoted and coordinated at a European level; Because of the large number of structures evolved it is necessary to define priorities: start in regions of high seismic intensity and be directed at vital and weaker buildings; The European Regional Development Fund (ERDF) could support this action, although urban rehabilitation programmes supported by ERDF aimed essentially the regeneration of socially degraded areas. 6. Final Comments

36 DECivil ICIST It is herein suggested to negotiate a global programme in the EU to support the following components of the interventions on the rehabilitation of building stock: The heating conditions in the central and northern European countries; The earthquake rehabilitation of the weakest and strategic buildings from southern European countries. 6. Final Comments

37 DECivil ICIST Urban Rehabilitation in Southern Europe The Seismic Problem and the Portuguese Case Rita Bento Instituto Superior Técnico, TECHNICAL UNIVERSITY OF LISBON December 2005 INTERNATIONAL WORKSHOP CITY OF TOMORROW AND CULTURAL HERITAGE POMERIA OUTLOOK DECEMBER 2005

38 DECivil ICIST More Information: SPES – Sociedade Portuguesa de Engenharia Sísmica EERI – Earthquake Engineering Research Institute World Housing Encyclopedia www. world-housing.net (Pombalino Buildings)


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