Sismicidade em Moçambique e a sua relevância no dimensionamento estrutural de edifício: caso de Manica

Abstract

This study assesses seismicity in the province of Manica, Mozambique, and its influence on the structural design of buildings. The country’s geographical location, traversed by the Great Rift Valley, exposes it to significant seismic activity, making it essential to evaluate the impact of earthquakes on construction. The 7.0 magnitude earthquake recorded in 2006 in Machaze emphasized the need to understand seismic risks and adopt effective strategies to minimize their impact on structures. In this study, a hypothetical building model was analyzed from three perspectives. First, it was designed and sized without considering seismic action (Case A), following traditional methods. Then, the same building was subjected to seismic analysis, revealing significant structural deficiencies and the need for reinforcement (Case B). Finally, a new design of the building was developed, now considering seismic action from the outset (Case C). Comparing the three cases demonstrated that buildings originally designed without seismic consideration may require costly interventions to ensure structural safety. In contrast, proper seismic design from the beginning improves the structure's resistance and reduces additional costs. To validate the findings, three additional models with different structural and geometric configurations were developed (Cases D, E, and F). These models were designed both without seismic consideration and with seismic consideration, allowing for an evaluation of the influence of different structural typologies on the earthquake response. The comparative analysis reinforced that the introduction of seismic criteria from the initial project phase leads to more efficient and safer structures, minimizing the need for future reinforcement. It also highlighted that seismic vulnerability is not uniform and depends on variables such as height, stiffness, arrangement of structural elements, and load distribution. Different reinforcement solutions for buildings that did not account for seismicity in their initial design were also evaluated. Reinforcement with steel and reinforced concrete proved to be a robust option, significantly increasing the structure’s resistance capacity, although with a relatively high construction impact. Alternatively, the use of carbon fibers proved to be an effective and less invasive solution, providing structural reinforcement with minimal interference in the building's use. The choice between solutions depends on the specific conditions of the structure and available resources.