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The current trend toward lighter and slender pedestrian structures, with new aesthetic requirements and highperformance materials, has resulted in structures with increased susceptibility to vibration. Notable vibrations under human-induced excitations might appear, and the vibration serviceability requirements might not be accomplished. The Valladolid Science Museum Footbridge (Spain) is an example of a lively structure that might achieve excessive vertical acceleration under walking or running excitation. The control of excessive footbridge vibrations via passive and active devices is dealt with in this work. More specifically, this paper is concerned with the design and experimental implementation of a passive tuned mass damper (TMD) and an active mass damper (AMD) to mitigate human-induced vibrations on this in-service footbridge. The TMD, with a mass ratio of 1%, is designed by a numerical method based on H ∞ controllers. The AMD consists of a proof-mass actuator, with a mass ratio of approximately 0.2%, controlled by a strategy based on acceleration feedback with a phase-lag network. The performance of both devices has been assessed. structure to reduce the human influence, a proportional increase of stiffness being also necessary; and (iv) increasing the damping of the structure with special devices. Taking into account that stiffening the structure and increasing the mass are usually complicated and involve significant structural and non-structural changes, the alternative option of including damping devices to the structure seems to be the easiest way of improving the vibration performance of footbridges. Typical passive damping systems [6] are metallic dampers, friction dampers, visco-elastic dampers, viscous dampers, tuned mass dampers (TMDs) and tuned liquid dampers (TLDs). Among passive control devices available for implementation in footbridges, TMDs [7,8] (including parallel multiple TMDs [9] and series multiple TMDs [10]), TLDs [11] and fluid-viscous dampers are the most effective and, hence, the usual adopted solution [12].An alternative procedure to cancel footbridge vibrations is the use of active devices. Moutinho et al. [13] have recently implemented an active vibration control (AVC) on a stress-ribbon footbridge using a proof-mass actuator together with direct velocity feedback control (DVFC) with saturation. This actuator generates inertial forces in the structure without need for a fixed reference. The velocity output, which is obtained by an integrator circuit applied to the measured acceleration response, is multiplied by a gain and feeds back to a collocated actuator. The term collocated means that the actuator and sensor are located physically at the same point on the structure. The merits of this method are its robustness to spillover effects due to high-order unmodelled dynamics and that it is unconditionally stable in the absence of actuator and sensor (accelerometer with an integrator circuit) dynamics [14]. Nonetheless, when such dynamics are considered, the stability for high gai...

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This paper presents the design, development and testing of a low-cost Structural Health Monitoring (SHM) system based on MEMS (Micro Electro-Mechanical Systems) triaxial accelerometers. A new control system composed by a myRIO platform, managed by specific LabVIEW software, has been developed. The LabVIEW software also computes the frequency response functions for the subsequent modal analysis. The proposed SHM system was validated by comparing the data measured by this set-up with a conventional SHM system based on piezoelectric accelerometers. After carrying out some validation tests, a high correlation can be appreciated in the behavior of both systems, being possible to conclude that the proposed system is sufficiently accurate and sensitive for operative purposes, apart from being significantly more affordable than the traditional one.