Fragility assessment of traditional wooden houses in Madagascar subjected to extreme wind loads

Abstract

Cyclones are a common hazard in Madagascar, each year causing fatalities and damage to the physical and socioeconomic infrastructure. Residential infrastructures are a critical sector within the built environment and studying their performance under natural hazards is a significant step for assessing the risk and resilience of a community. In the coastal regions of Madagascar, more than 80% of houses are self-built, non-engineered traditional wooden houses constructed based on heritage practices and using low or no-cost materials collected in nearby areas or forests. These traditional wooden houses are particularly vulnerable to cyclonic winds, and in this paper, a novel approach is used to evaluate their structural performance and to predict their likelihood of failure under extreme wind conditions. The structural systems and their damage due to extreme winds were first evaluated based on field surveys and collected information such as post-disaster reports. A range of field tests was then carried out at two coastal sites to evaluate the strength of the members and connections identified as commonly used for constructing traditional wooden houses in Madagascar. Damage fragility curves were subsequently developed based on the performance of the connections of roof coverings, wall claddings, the roof structural system, and the performance of columns embedded into the ground and combined to predict the structure's performance. The experimental methods and results presented in this study can be exploited to improve the existing Malagasy guidelines for cyclone resistance of traditional wooden houses published in 2016. The developed fragility curves can also be used to represent traditional wooden houses within a community for risk or resilience assessment under cyclonic wind conditions.