INTERNATIONAL WORKSHOP CITY OF TOMORROW AND CULTURAL HERITAGE

INTERNATIONAL WORKSHOP CITY OF TOMORROW AND CULTURAL HERITAGE POMERIA OUTLOOK 2005 DECivil 8 -9 DECEMBER 2005 ICIST Urban Rehabilitation in Southern Europe The Seismic Problem and the Portuguese Case Rita Bento Instituto Superior Técnico, TECHNICAL UNIVERSITY OF LISBON December 2005

INSTITUTO SUPERIOR TÉCNICO DECivil ICIST

Urban Rehabilitation in Southern Europe DECivil ICIST • 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

TOPICS • DECivil ICIST 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.

1. Introduction DECivil • 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 ICIST 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

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

2. Earthquakes in Europe - effects DECivil • The main different types of earthquake effects at the earth’s surface are: ICIST • 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 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.

3. What can be a European Risk Reduction Programme? 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 (EC 8); • 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. 1 Evaluation and strengthening of existing buildings and monuments 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. 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.

3. 1 Evaluation and strengthening of existing buildings and monuments 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.

3. 2 Ensuring the quality of construction DECivil • To the reduction of the seismic risk is fundamental to ensuring the quality of construction to: ICIST • 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.

4. The Portuguese Case: 1755 Earthquake and the ‘Pombalino’ buildings • Portugal is a seismic prone territory. 1755’s Lisbon Earthquake was very strong (M=8. 7): DECivil ICIST • 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

Old Masonry buildings in Lisbon DECivil ICIST Downtown [in Mendes-Victor et al, 1993] 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)

Pombalinos Buildings (1755 -1880) DECivil ICIST • After 1755 Lisbon Earthquake, masonry buildings were built with a 3 D wood structure named gaiola pombalina. The gaiola structure is like a cage made of vertical and horizontal elements braced with diagonals Gaiola Pombalina [Mascarenhas, 1997]

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

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

‘Gaioleiros’ Buildings (1800– 1940) DECivil ICIST • 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 Partition walls • In time, masonry becomes the only structural material. [Mascarenhas, 1997]

‘Placa’ Buildings (1940 - 1960) DECivil ICIST • At the most recent masonry buildings, wood floors were replaced with thin concrete slabs. Selft weight was increased. Thin • As the result of construction evolution, old masonry buildings became less resistant to horizontal loads concrete slabs Masonry walls [Mascarenhas, 1997]

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

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

Numerical Model (SAP 2000®) Floors DECivil ICIST Floors bars Vaults (crosses) Masonry Interior wall of ‘gaiola’ Shell Elements (2 D) of masonry walls Beam elements

Numerical Model (SAP 2000®) - Quarter DECivil ICIST

Building Analysis DECivil Evolution of Damage Levels in masonry elements from main façade in 1 st step of iterative procedure – evolution of tension damaged masonry ICIST sis= 0. 20 sis= 0. 25 sis= 0. 30 Deformed main façade

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

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

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

Solution 2 Inclusion of a R. C. beam (0. 4 0. 25 m 2) on the top DECivil ICIST Beam around the exterior perimeter Solution 3 Inclusion of R. C. beams (0. 4 0. 25 m 2) in all the floors Beams at the pavements level

Actual Conservation State of ‘Pombalino’ Buildings DECivil ICIST w 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. w Buildings that suffered structural changes In most of the cases are critical as they reduce the seismic resistance and therefore are not advisable

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

• Introduction of more stories at the top of the building Mass and Finertia DECivil ICIST increase at the top

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

5. Portuguese Programme for the Reduction of the Seismic Vulnerability 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 DECivil • Albeit the importance of the programme, it is not yet effectively supported by any member of the government, group of ICIST 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.

6. Final Comments DECivil • Old masonry buildings are an important part of the building stock of most European cities and have to be preserve; ICIST • 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 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.

INTERNATIONAL WORKSHOP CITY OF TOMORROW AND CULTURAL HERITAGE POMERIA OUTLOOK 2005 DECivil 8 -9 DECEMBER 2005 ICIST Urban Rehabilitation in Southern Europe The Seismic Problem and the Portuguese Case Rita Bento Instituto Superior Técnico, TECHNICAL UNIVERSITY OF LISBON December 2005

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