| Summary: |
Construction with raw earth still has an important presence around the World, where it constitutes one of the most ancient methods for building. This importance is confirmed by the fact that about one third of the world population lives in earthen constructions. Furthermore, this type of construction shows a large world distribution, which includes even regions with important seismic hazard [1]. The construction of housing is its main use. However, several military, religious and monumental buildings built with earth exist and present an important cultural, historical and architectonic value. Such importance is proven by the fact that about 10% of sites and monuments classified as World Heritage by UNESCO are built with earth. The great availability and low-cost of earth as a building material explains the great popularity of this type of construction in developing countries. On the other hand, nowadays the use of earthen construction in developed countries is marginal, being supported mainly by the high sustainability and architectonic interest of this type of construction. The Portuguese case is an example of this situation, but where a large earthen built heritage still exists. Adobe construction was mainly used in the region "Litoral-Centro", namely in buildings of the "Art Nouveau" style, whose cultural, historical and architectonic value is relevant [2]. Rammed earth construction was mainly used in the regions of "Alentejo" and "Algarve" both in the construction of dwellings [3] and of millenary fortresses with great historical importance [4].
Earthen constructions are known for presenting poor seismic performance [5], evidenced in important earthquakes, such as El Salvador, in 2001, Bam, in 2003 and Peru, in 2007. In Portugal, there is a general lack of knowledge on the seismic behaviour of the local earthen heritage. This unawareness relative to safety becomes critical, since this heritage is built on regio  |
Summary
Construction with raw earth still has an important presence around the World, where it constitutes one of the most ancient methods for building. This importance is confirmed by the fact that about one third of the world population lives in earthen constructions. Furthermore, this type of construction shows a large world distribution, which includes even regions with important seismic hazard [1]. The construction of housing is its main use. However, several military, religious and monumental buildings built with earth exist and present an important cultural, historical and architectonic value. Such importance is proven by the fact that about 10% of sites and monuments classified as World Heritage by UNESCO are built with earth. The great availability and low-cost of earth as a building material explains the great popularity of this type of construction in developing countries. On the other hand, nowadays the use of earthen construction in developed countries is marginal, being supported mainly by the high sustainability and architectonic interest of this type of construction. The Portuguese case is an example of this situation, but where a large earthen built heritage still exists. Adobe construction was mainly used in the region "Litoral-Centro", namely in buildings of the "Art Nouveau" style, whose cultural, historical and architectonic value is relevant [2]. Rammed earth construction was mainly used in the regions of "Alentejo" and "Algarve" both in the construction of dwellings [3] and of millenary fortresses with great historical importance [4].
Earthen constructions are known for presenting poor seismic performance [5], evidenced in important earthquakes, such as El Salvador, in 2001, Bam, in 2003 and Peru, in 2007. In Portugal, there is a general lack of knowledge on the seismic behaviour of the local earthen heritage. This unawareness relative to safety becomes critical, since this heritage is built on regions with important seismic hazard and is often found in poor conservation condition [6]. Nowadays, the rehabilitation of earthen heritage assumes great interest, namely in what concerns its housing and touristic valorisation. However, the experience of the aforementioned earthquakes shows that a sustainable rehabilitation must address seismic strengthening.
The seismic behaviour of adobe construction is a topic which has been studied, namely in Peru, where shaking table tests have been performed [7]. Nevertheless, the development of specific methodologies for seismic safety assessment, including adequate performance parameters, is still required. The seismic strengthening of adobe constructions is still a topic deserving more study [8], but like for the safety assessment, the development of reliable design is lacking. The case of rammed earth is even more critical, since the seismic study of these constructions is still very limited [9].
Taking into account the described scenario, this project intends to contribute critically to the development of the national and international knowledge related with the seismic behaviour of adobe and rammed earth construction. Furthermore, the development of an integrated approach for the seismic strengthening of these constructions with geo-mesh reinforced coatings is also intended due to the good effectiveness and low cost presented by this solution [10]. In this way, it will be possible to harmonize the rehabilitation of the earthen built heritage, or even strengthening requirements, with adequate seismic safety needs.
The proposed objectives will be achieved using a methodology based on the following steps:
- Identification of the parameters with influence on the seismic performance and evaluation of their level of importance, making use of data mining techniques;
- Characterization of the seismic behaviour of adobe and rammed earth constructions through quasi-static and dynamic experimental tests (on the shaking table);
- Evaluation of the efficiency of seismic reinforcement with geo-mesh reinforced plasters through quasi-static and dynamic experimental tests;
- Calibration of numerical models to simulate the dynamic behaviour of adobe masonry and rammed earth elements, complemented with parametric analysis for the identification and definition of critical seismic performance parameters;
- Development of recommendations for the evaluation of the seismic safety of adobe and rammed earth structures and for the design of reinforcements with geo-mesh plasters.
The methodology presented herein is implemented by an extremely motivated team of researchers, active in the areas of earthen construction, dynamics of structures and numerical modelling. The final results of the project will be very useful for the scientific and technical community interested in the earthen construction theme and will support the rational rehabilitation of the earthen built heritage.
[1] Houben H, Guillaud H. (2008) Earth Construction: A Comprehensive Guide. 3rd Edition, Intermediate Technology Development Group.
[2] Silveira, D., Varum, H., Costa, A., Lima, E. (2010) Survey and characterization of the adobe built park in Aveiro city, In proceedings 6º Seminário de Arquitectura de Terra em Portugal and 9º Seminário Ibero-Americano de Construção e Arquitectura com Terra, Coimbra, Portugal, 20-23 February 2010. (in Portuguese)
[3] Correia, M. (2007) Rammed Earth in Alentejo. Argumentum, Lisbon.
[4] Correia, M. (2004) Fortificações islâmicas em taipa Militar, Pedra & Cal, 24, 16.
[5] Tolles, E.L., Kimbro, E.E., Ginell, W.S. (2002) Planning and Engineering Guidelines for the Seismic Retrofitting of Historic Adobe Structures. The Getty Conservation Institute, Los Angeles.
[6] Oliveira, D.V., Silva, R.A., Lourenço, P.B., Schueremans, L. (2010) The rammed earth constructions and the earthquakes. In proceedings Congresso Nacional de Sismologia e Engenharia. SÍSMICA 2010, 20-23 October; Aveiro, Portugal. (in Portuguese)
[7] Tolles, E.L., Kimbro, E.E., Webster, F.A., Ginell, W.S. (2000) Seismic Stabilization of Historic Adobe Structures: Final Report of the Getty Seismic Adobe Project. The Getty Conservation Institute, Los Angeles.
[8] Oliveira, C., Varum, H., Vargas, J. (2012). Earthen structures research and standards: seismic reinforcement. In proceedings XI Conferencia Internacional sobre el Estudio y Conservación del Patrimonio Arquitectónico de Tierra. Terra 2012. Lima: Pontificia Universidad Católica del Perú.
[9] Lacouture, L., Bernal, C., Ortiz, J., Valencia, D. (2007) Studies on seismic vulnerability, rehabilitation and strengthening of adobe and rammed earth houses. Apuntes, 20(2), 286-303. (in Spanish)
[10] Blondet, M., Vargas, J., Velásquez, J., Tarque, N. (2006) Experimental study of synthetic mesh reinforcement of historical adobe buildings. In: Lourenço PB, Roca P, Modena C, Agrawal S (eds) Proceedings of Structural Analysis of Historical Constructions, New Delhi, India. |