Seismic Evaluation and Retrofit for Reducing the Vulnerability of Housing in Colombia: Development and Implementation

Abstract eng:
Regions of low to high seismicity exist throughout Colombia, with major cities like Bogotá and Medellin falling within zones of intermediate seismicity according to the Colombian Earthquake Resistant Standards (Normas Sismo Resistentes or NSR). In urban centers, like Bogotá or Medellin, informal housing construction is prevalent as the population in these areas grows. According to CENAC (Centro de Estudios de la Construcción y el Desarrollo Urbano y Regional), of every 5 new homes built in Colombia today, 3 are of “informal origin”, meaning they are built spontaneously without any legal procedures nor formal design. These houses are commonly built in confined masonry and, although this system is well defined in NSR-10, informal construction does not typically adhere to the standard. As a result of the increased growth of these informal neighborhoods in Colombia, millions of people are vulnerable to death, injury or homelessness as a result of housing collapse in the design earthquake. To help address this risk, cities such as Bogotá have developed programs to support housing improvements in the most vulnerable areas. These programs allocate subsidies for home improvements to the most vulnerable households and provide them with technical assistance through the process. Build Change is working with the municipal agency, Caja de la Vivienda Popular (CVP), which is focused on providing technical assistance for subsidized home improvements, to develop an efficient approach for implementing seismic evaluation and retrofit of the large vulnerable housing stock. With partners and local professionals, Build Change developed a manual with simplified procedures for the seismic evaluation and retrofit design of low-rise confined masonry and unreinforced masonry houses in Bogotá. These procedures are based on a similar manual developed for the Haitian context in partnership with Degenkolb Engineers, which in turn is based on the U.S. standards ASCE 31 and 41. The latter are approved references for building evaluation and rehabilitation, respectively, in accordance with the NSR-10. Adaptations were made to simplify the procedures for use in housing and for applications to confined masonry construction in Colombia, which is a building system not explicitly addressed in the U.S. standards. The procedures are outlined in this paper. This manual was reviewed and approved for use by the national Comisión Asesora Permanente Para el Régimen de Construcciones Sismo Resistentes in Colombia (Permanent Advisory Commission for the Regime of Seismic-Resistant Construction). Following the approval of the manual, Build Change, the Habitat Secretary of Bogotá, and CVP initiated a pilot project to provide technical assistance to seismically retrofit approximately 50 homes in El Amparo and other neighborhoods located in the south of Bogotá, in accordance with the manual procedures. Local engineers who have received training from Build Change performed the evaluations and retrofit designs based on the manual. This paper shares the experiences of this pilot project to date, including a specific case example, and how these experiences have informed potential improvements to the manual procedures and their implementation in a retrofit program. Next steps are identified for implementing a housing retrofit program at scale.

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