The important advances achieved in the modal identification, sensors, and structural monitoring of bridges have motivated the bridge engineering community to develop damage detection methods based on vibration monitoring. Some of these methods have already been demonstrated under certain conditions in bridges with deliberate damage. However, the performance of these methods for damage detection in bridges has not been fully proven so far and more research needs to be done in this direction. In this article, six damage detection methods based on vibration monitoring are evaluated with two case studies. First, the dynamic simulation and modal parameters of a cracked composite bridge are obtained. Here, the damage detection methods are evaluated under different crack depth, extension of the damage, and noise level. Second, damage is identified in a reinforced concrete bridge. This bridge was deliberately damaged in two phases. In this example, damage detection methods, which do not require comparison between different structural conditions, were applied. In the first case study, evaluated damage detection methods could detect damage for all the damage scenarios; however, their performance was notably affected when noise was introduced to the vibration parameters. In the second case study, the evaluated methods could successfully localize the damage induced to the bridge.

The use of concrete in civil infrastructure is highly demanded in structural and nonstructural elements. However, the high production of concrete could lead to severe pollution in the world. This pollution can be decreased using sustainable materials mixed with cement to obtain sustainable concrete. These sustainable materials include reinforcing fibers (e.g., steel, polypropylene, carbon fibers), recycled materials (e.g., tire rubber, crushed glass, plastic, industrial waste) as well as organic and inorganic elements as concrete aggregates and reinforcement elements. The sustainable construction materials can reduce the amount constitutive elements of concrete required for civil constructions. In addition, some sustainable materials added to cement could improve some properties of the concrete, like the compressive and flexural strength of concrete structural elements. Thus, the maintenance requirements or early replacement of these structural elements could be decreased. This review presents recent investigations about the performance of different sustainable concrete types. In addition, we include the effects on the mechanical properties of the concrete caused by the incorporation of several sustainable materials. In addition, recommendations for the use and testing of sustainable concrete are reported. These materials have potential applications in the sustainable concrete infrastructure in future smart cities.

Footbridges are structures that may experience vibration amplification problems caused by pedestrian and/or wind actions. Design codes deal with these phenomena limiting the natural frequencies and the maximum accelerations expected. Aiming at taking into consideration these dynamic phenomena, current procedures to evaluate the structural performance of light-weight bridges based on experimental dynamic analysis are evaluated in this study. To achieve this, the dynamic response of three pedestrians walking, running and jumping was obtained. Maximum comfort limits of dynamic responses were then determined. The results indicate that codes could overestimate the level of vibration in this kind of footbridge.

In this document, the performance of damage detection methods used for the evaluation of bridge structures was determined. To do that, these methods were applied to the experimental dynamic parameters obtained from cracked steel I beams. Different damage scenarios were simulated in the steel I beams through saw-cuts perpendicular to the longitudinal axis of the beams. The damage detection methods were evaluated under different damage scenarios tried to represent fatigue damage in bridge structures. Ambient vibration tests, before and after damage, were performed on analyzed beams and the obtained dynamic parameters were used for the damage detection procedure. For all the evaluated scenarios, only the first three mode shapes were taken into account. Results indicated high possibility of damage detection when the severity of damage increase, damage is close to a measuring point and far away from an inflexion point and/or the boundary conditions. It was found that Level I methods (just detection) are not confidence to detect damage. On the other hand, level II methods (location) had good performance for the most severe damage scenarios. It was found out that Wavelet based methods are the best choice for their application to bridge structures.

Resonators based on micro and nanoelectromechanical systems (MEMS/NEMS) are used in many applications, including biological and gas sensors, magnetic field sensors, RF switches, accelerometers, piezoelectric micro and nanogenerators, and viscosity sensors. The design of these resonators requires analytical models to predict their mechanical behavior and optimize the sensitivity and resolution. However, most of these models are only applied to resonators with rectangular and uniform cross-sections. In this paper, we present the analytical modeling to determine the first bending resonant frequency, out-of-plane deflections, and normal stresses of MEMS/NEMS-based multilayered resonators with variable cross-sections and multiple fixed supports. The proposed modeling is derived using the well-known Rayleigh and Macaulay methods, as well as the Euler-Bernoulli beam theory. This analytical modeling is applied to four multilayered resonators with different clamped supports and non-uniform cross-sections. The results of our analytical modeling agree well with respect to those of finite element method (FEM) models and experimental data reported in the literature. The proposed analytical modeling can be used to estimate the frequency shift of resonators due to variations of their geometric parameters, number of clamped-supports or mechanical properties of the materials. Furthermore, this modeling can be used to obtain optimal designs of resonators that ensure safe operations and enhanced performance for sensors and energy harvesters in telecommunications, automotive sector, aerospace industry, consumer electronics, non-destructive testing, and navigation.