Self-Built Houses in a Peruvian Andean City: Seismic Vulnerability and Seismic Behavior

The Mantaro Valley in Peru has experienced a seismic silence lasting 54 years, indicating a significant likelihood of a major seismic event occurring. Moreover, the rapid increase in the problematic practice of self-construction, mainly using clay frame structures with infill masonry walls materials, has rendered the area highly susceptible to a seismic disaster, raising concerns specifically for the Huancán district. Thus, the main aim of this study was to assess the seismic vulnerability of 30 houses in the Huancán district by employing a questionnaire based on the INDECI methodology. The structural program (ETABS) was employed. Additionally, the seismic behavior of each house was evaluated through analytical analysis using structural calculation software. The findings revealed that 40% of the houses exhibited a very high vulnerability, 50% demonstrated an increased exposure, and 10% displayed a moderate vulnerability. The most influential factors contributing to this vulnerability were irregularities in the floor plan, height, and mass distribution of the houses. Furthermore, it was observed that the homes suffered from inadequate wall density in the X direction, negatively impacting compliance with standards related to wall density, maximum axial stress, crack control, and inter-story drift. Ultimately, the Huancán district exhibits a 90% vulnerability level classified as "high" and "very high", highlighting significant structural deficiencies such as house wall flexibility. It underscores the urgent need for authorities to implement preventive measures, including structural reinforcements and enhanced control in risk management practices.