Abstract

Civil engineering constructions like pedestrian footbridges are structures increasingly slender, ambitious and complex in which the dynamic effects caused by the loads to which they are subjected (pedestrians) may induce service problems and / or significant or repetitive amplifications of the efforts and deformations. This fact together with the current social demands related to the perception and comfort raise the need to integrate the analysis and computer-aided design in the evaluation of the vibrations generated by the loads this type of structures supports. In the specific case of finite element commercial programs, their use has not proliferated as much as in other engineering fields due to the existence of simplified methodologies in numerous national and international guidelines and regulations and the difficulty of making realistic models in the case of complex structures. However, the knowledge generated by the analysis of this type of numerical models would be especially useful in the earlier phases of the design of similar structures, so much initial as of the necessary modifications to solve existing dynamic problems, since it is in these stages when the best solution could be applied from both a technical and an economic point of view. This article describes the process of generation and updating of the mechanical finite element model (FEM) of a footbridge in service and the simulation of two types of load: an excitation generated by a shaker and a pedestrian load, contrasting the results generated by the numerical model with those obtained experimentally.

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his paper proposes a new vibration-based structural health monitoring method for the identification of delamination defects in composite bulkheads used in small-length fiber-based ships. The core of this work is to find out if the variations of vibration energy can be efficiently used as a key performance indicator for the detection and quantification of delamination defects in marine composite bulkheads. For this purpose, the changes of vibrational energy exerted by delamination defects in sandwich and monolithic composite panel bulkheads with different types of delamination phenomenon are investigated using a non-destructive test. Experiments show that the overall vibration energy of the bulkheads is directly dependent on the damage conditions of the specimens and therefore, the variations of this parameter are a good indicator of the incorporation of delamination defects in composite bulkheads. Additionally, the overall vibration energy changes also give interesting information about the severity of the delamination defect in the panels. Hence, this methodology based on vibratory energy can be used to accurately determine delamination defects in medium-sized composite bulkheads with the advantages of being a simple and cost-effective approach. The findings of this research possess important applications for the identification of delamination failures in composite components such as bulkheads, turbine blades, and aircraft structures, among others.

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This experiment investigated how the sound of stream water affects the growth of ''Cucumis sativus'' plants under drought stress. Plants can recognize vibrations (sounds). Additionally, plants limit their growth when they receive suboptimal amounts of water to preserve resources. The purpose of this study was to determine how the sound of stream water affects plants under drought stress, in order to determine if it will affect their growth. Four groups of 10 plants were germinated, with 3 experimental groups treated with the sound of stream water for different amounts of time (0.5, 2, or 3 hrs; control group had 0 hr). Once plants were germinated, drought stress began in all groups, but each group’s respective amount of treatment stayed the same (0, 0.5, 2, 3 hrs). During all stages of the experiment, the plants were watered during the period of sound treatment to develop a correlation. At the end of the experiment, it was found that growth significantly increased corresponding to increasing treatment time. Group 4 (3 hr) had the largest increase in growth compared to control, while group 2 (0.5 hr) had the least improvement over control. Subsequently, the sound of stream water treatment beneficially impacts plant growth, directly correlated to exposure.

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