Seismic Stabilization of Historic Earthen Buildings
 

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Earthen buildings, typically classified as unreinforced masonry structures, are extremely vulnerable to earthquakes and subject to sudden collapse during a seismic event—especially if a building lacks proper and regular maintenance. Historic earthen sites located in seismic areas are at high risk of being heavily damaged and even destroyed.

During the 1990s, the Getty Conservation Institute carried out a major research and laboratory testing program—Getty Seismic Adobe Project (GSAP)—which the GCI and the field are now building upon. GSAP investigated the performance of historic adobe structures during earthquakes, and then developed cost-effective retrofit methods that substantially preserve the authenticity of these buildings. Results of this research have been disseminated in a series of publications, both in English and Spanish (see Related Materials).

In 2006 the Earthen Architecture Initiative convened two meetings: the Getty Seismic Adobe Project Colloquium and New Concepts in Seismic Strengthening of Historic Adobe Structures. Held at the Getty Center, the meetings focused on implementation of the Getty's seismic research and on identification of further research needed in the study of historic earthen architecture in seismic zones. Papers presented at the GSAP colloquium, as well as the main conclusions of colloquium's round table discussions, can be found at Proceedings of the Getty Seismic Adobe Project 2006 colloquium.

The participants in the colloquium concluded that the GSAP methodology was excellent and effective. However, the methodology's reliance on high-tech materials and professional expertise was a deterrent to it being more widely implemented.

The Seismic Retrofitting Project

To address this, the GCI has joined with the Ministerio de Cultura del Perú (MDC), the School of Architecture and Civil Engineering of the University of Bath (BATH), and the Escuela de Ciencias e Ingeniería of the Pontificia Universidad Católica del Perú (PUCP) to form the Seismic Retrofitting Project (SRP). The project—building on GSAP, the conclusions of the Pisco Peru 2007 earthquake assessment carried out by the GCI and its consultant engineers (see below), and a detailed structural assessment of four Peruvian historic earthen buildings as prototypes found in seismic regions of South America—will combine traditional construction techniques and materials with high-tech methodologies to design and test easy-to-implement seismic retrofitting techniques and maintenance programs to improve the structural performance and safety of earthen buildings while minimizing loss of historic fabric.

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The project will also provide guidance for those responsible for implementation (e.g., architects, engineers, and conservators), and work with authorities to gain acceptance and to facilitate the implementation of the designed techniques. The project's results are intended to be widely applicable across Latin America.

The project objectives are to:

  • design low tech seismic retrofitting techniques—using locally available materials and expertise for Peruvian historic building types—that have potential for wider application in other countries;
  • test and obtain data that demonstrates the validity of the designed techniques;
  • acquire recognition, approval, and promotion of the techniques by local authorities,
  • develop a methodology to structurally assess earthen historic sites as a tool for decision making regarding site maintenance and interventions that has a potential for wider application;
  • produce suitable manuals for site managers describing the retrofitting techniques and their implementation;
  • develop guidelines for the conservation community to carry on site assessments and the implementation of retrofitting techniques, highlighting the significance of constant monitoring, maintenance, and repair;
  • develop a model conservation project that demonstrates the implementation of the techniques.

The project's activities can be divided in four phases: 1) feasibility and research; 2) methodology; 3) testing; and 4) dissemination and implementation.

Phase I - Feasibility and Research

  • Test the project feasibility, goals, and outcomes by consulting different professionals with expertise in the field of conservation and seismic retrofitting at the national and international level, and establish an external peer review group.
  • Gather information based on modes of failures of the identified prototypes. This research study analyzes existing historic data regarding the way earthen buildings behave during a seismic event using the findings from the damage assessments performed after the 2007 Pisco earthquake (see Pisco earthquake below), as well as after the 1996 Northridge earthquake (conducted as part of GSAP).
  • In collaboration and partnership with local authorities, PUCP, and BATH, identify and structurally assess up to four building typologies that are priorities for application of seismic retrofit techniques based on level of significance, where solutions are most needed, and where the reinforcement techniques used will have the greatest application in Peru and other countries in Latin America.
  • Develop in collaboration with PUCP and BATH static and dynamic testing and numerical modeling analyses, respectively, of the identified building prototypes for the study of their structural performance during an earthquake.

Selected Prototype Sites

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Phase II - Methodology

  • Collect historical information on low tech/alternative/vernacular/historic materials and techniques used as seismic reinforcements in Peruvian buildings, including information from Peruvian conservators regarding the seismic performance of existing/implemented repairs on historic earthen buildings.
  • In collaboration with Peruvian national institutions, develop workshops focused on structural assessment methodologies and non-destructive techniques for structural diagnosis.

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Phase III - Design and Testing

  • In collaboration with project partners and consultants, design retrofitting systems suitable to the selected building prototypes using new and/or existing techniques.
  • Carry on static and dynamic testing and numerical modeling of scale retrofitted and non-retrofitted models and/or structural components at PUCP and BATH, respectively.

Phase IV - Dissemination and Implementation

  • Develop in collaboration with local partners and international consultants a project proposal for the implementation of the designed and tested retrofitting techniques in at least one of the selected building types.
  • Develop peer reviewed guidelines for the implementation of retrofitting design and techniques that could be considered as a part of the Peruvian National Building Code and that could be widely applied to Latin American countries.
  • Develop on-site guidelines for site managers to practically explain the implementation of retrofitting techniques and including principles for site maintenance that together form the basis of preventive approaches to the conservation of earthen historic buildings in seismic areas.
  • Develop workshops with national institutions to train site managers and building officials to disseminate the retrofitting guidelines and manuals.
  • Partner with a local organization to implement the retrofitting techniques as part of a comprehensive conservation project, supervising the different phases of the implementation project and documenting the process for further dissemination.

The 2007 Pisco Earthquake

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Post-earthquake assessments offer an opportunity to understand why buildings fail and provide information that can serve as the basis for the improvement of seismic performance. For centuries, lessons learned from earthquakes and other natural disasters have been used to advance construction techniques; more recently, such lessons have fostered the development of the engineering and historic preservation disciplines, as well as the testing and review of current building codes and disaster management policies and procedures. The history of Peruvian architecture exemplifies this process. In response to their understanding about the effects of seismic activity on earthen structures, early Peruvian cultures developed reinforcement techniques to enhance construction systems. That tradition continues with the inclusion of the NTE-80 Norma Técnica del Adobe, which regulates new adobe construction in the country and is part of the Peruvian National Building Code.

On August 15, 2007, a Moment Magnitude (Mw) of 8.0 and a maximum local Modified Mercalli Intensity (MMI) of VII-VIII earthquake hit the southern coast of Peru. Preliminary reports indicated that a large number of historic earthen sites located in the communities of Cañete, Chincha, Pisco, Ica, and Huancavelica were severely damaged.

After the 2007 earthquake, a multidisciplinary team of national and international earthquake engineers, preservation architects, and conservators—convened by the GCI—visited a total of fifteen historic earthen sites, rapidly documented them, and evaluated the damage to these sites. The team concentrated on recording existing conditions such as abandonment, deterioration, or structural alterations over time with the ultimate objective of understanding the impact of such conditions on the buildings seismic performance. The assessment was organized in response to a request from the former Instituto Nacional de Cultura del Perú (INC, Peruvian National Institute of Culture, now the Ministerio de Cultura del Perú–MDC).

The selection of the four prototype structures selected to be studied as part of SRP—the Hotel El Comercio, the Cathedral of Ica, the Church of Kuño Tambo, and Casa Arones—grew out of this earthquake assessment process.

Last updated: March 2013