Health monitoring of civil engineering infrastructures with optical fiber sensors

Structural health monitoring is a fundamental tool to guaranty the civil infrastructure lifetime. In this paper, the monitoring of an adobe structure with optical fiber sensors is reported. Static and dynamic measurements were made during a destructive test on a full-scale wall, with an optical fiber accelerometer and a network of thirteen multiplexed displacement sensors. The measured values shown a decrease of 47.8 % in the first natural frequency value, between the initial situation (structure undamaged) and after the cyclic test (structure damaged). The results show very good agreement (maximum relative error in terms of structural frequency of 2.08 %) between the results obtained using electronic sensing technology and the optical sensing technology

An accurate formula for the period of a simple pendulum oscillating beyond the small-angle regime

A simple approximation formula is derived here for the dependence of the period of a simple pendulum on amplitude that only requires a pocket calculator and furnishes an error of less than 0.25% with respect to the exact period. It is shown that this formula describes the increase of the pendulum period with amplitude better than other simple formulas found in literature. A good agreement with experimental data for a low air-resistance pendulum is also verified and it suggests, together with the current availability/precision of timers and detectors, that the proposed formula is useful for extending the pendulum experiment beyond the usual small-angle oscillations.Comment: 15 pages and 4 figures. to appear in American Journal of Physic

Sensor óptico para monitorização do comportamento dinâmico de estruturas

Este trabalho centra-se no desenvolvimento de um sistema, baseado em tecnologia óptica, que permite a identificação das frequências naturais de estruturas especiais de engenharia e que vai de encontro às necessidades de uma monitorização eficaz e de baixo custo. O sistema óptico implementado foi validado através de testes de campo numa ponte pedonal, comparando a resposta medida com a obtida com sensores baseados em tecnologia electrónica. Os resultados alcançados confirmam a viabilidade da solução implementada nas medidas dinâmicas pretendidas para estruturas

Regeneração de algarobeiras em área de mata ciliar do rio de Contas, em Manoel Vitorino-BA.

O estudo teve como objetivo analisar a estrutura vegetal de áreas da Caatinga com a presença da algaroba