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Human-induced vibration has become a serious serviceability problem due to the larger opening of girder, lighter floor systems and longer spans designed and used in practice. Vibration tests were undertaken in laboratory to research the vibrational characteristics of the arch pre-stressed concrete truss (APT) system spanning 16.0 m. Results from ambient vibration, impulse excitations (heel-drop and jumping) and steady-state incentives (walking and running) were presented. Dynamic characteristics such as natural frequencies, damping ratios, mode shapes and acceleration responses were studied and checked against the existing codes. Experimental results show that the investigated APT girder possesses high fundamental frequency and low damping ratio. Moreover, the perception factors based on the root-mean-square acceleration, vibration dose value (VDV) and psychological comfort data were obtained. Lastly, the threshold accelerations and VDVs were suggested for evaluating the human-induced vibration.

Inertial micro-switches have great potential in the applications of acceleration sensing, due to the integrated advantages of a small size, high integration level, and low or even no power consumption. This paper presents an overview of the recent advancements made in research on the sensitive direction, threshold acceleration, contact effect, and threshold accuracy of inertial micro-switches. The reviewed switches were categorized according to the performance parameters, including multi-directional switches, multi-threshold switches, persistent closed switches, flexible-electrode switches, and low-g high-threshold-accuracy switches. The current challenges and prospects are also discussed.

This paper describes the design and construction of a new pedestrian walkway extension to the Principe Umberto bridge in Legnago (Italy), testing of vibration, and work carried out to improve its performance in serviceability condition. This walkway showed a marked responsiveness to repetitive horizontal forces, which tended to excite transversal and torsional vibration around the longitudinal axis of the structure. To overcome this problem a new static condition was created. This was based on analysing the response of the structure to human-induced dynamic loading by pedestrian movement (walking, running or jumping). Vibrations derived from such human-induced loads can cause disturbance to pedestrians (the serviceability problem) or, in more severe cases, resonance of the structure. According to technical literature and various design codes, there are two factors to be considered in overcoming these phenomena: the natural frequencies of the structure must be made to fall outside the range of human-pacing frequencies, and the maximum acceleration at any point of the structure must be not greater than a threshold value. On that basis, both modal and dynamic analyses were performed on the Legnago Bridge and the results made it possible to identify the cause of the excessive deformability. These analyses were then used to develop a design solution and to re-verify the structural project, which consisted of a variation to the static design. (A)

Squeeze-film damping and acceleration load are two major issues in the design of inertial micro-switches. In order to deeply and systematically study these two issues, this paper proposes a typical vertically-driven inertial micro-switch, wherein the air and electrode gaps were chosen to design the required damping ratio and threshold value, respectively. The switch was modeled by ANSYS Workbench, and the simulation program was optimized for computational accuracy and speed. Transient analysis was employed to investigate the relationship between the damping ratio, acceleration load, and the natural frequency, and the dynamic properties (including contact bounce, contact time, response time, and threshold acceleration) of the switch. The results can be used as a guide in the design of inertial micro-switches to meet various application requirements. For example, increasing the damping ratio can prolong the contact time of the switch activated by short acceleration duration or reduce the contact bounce of the switch activated by long acceleration duration; the threshold value is immune to variations in the damping effect and acceleration duration when the switch is quasi-statically operated; the anti-jamming capability of the switch can be improved by designing the sensing frequency of the switch to be higher than the acceleration duration but much lower than the other order frequencies of the switch.

The equation of motion of a one way (vertical) spanning strip wall, as an assembly of two rigid bodies, is presented. Only one degree of freedom is needed to completely describe the wall response as the bodies are assumed to be perfectly rectangular and are allowed to rock but not to slide horizontally. Furthermore, no arching action occurs since vertical motion of the upper body is not restrained. Consequently, the equation of motion is nonlinear, with non constant coefficients and a Coriolis acceleration term. Phenomena associated with overburden to self weight ratio, motion triggering, impulsive energy dissipation, amplitude dependency of damping and period of vibration, and scale effect are discussed, contributing to a more complete understanding of experimental observations and to an estimation of system parameters based on the wall characteristics, such as intermediate hinge height and energy damping, necessary to perform nonlinear time history analyses. A comparison to a simple standing, or parapet, wall is developed in order to better highlight the characteristics of this assembly.

At present, the Newmark Sliding Block Method is adopted as a seismic evaluation method of embankments in Japan. The threshold acceleration during shaking is supposed to be a constant in the Newmark Sliding Block Method. However, threshold acceleration can be varied during strong earthquake motions. In this study, several dynamic centrifuge model tests were carried out to investigate the threshold acceleration of embankments during the shaking. The compensation in the Newmark Sliding Block Method was proposed considering variations in threshold acceleration. The test data indicate that the threshold acceleration of the embankments has a tendency to decrease during an earthquake.

At present, the Newmark Sliding Block Method is adopted as a seismic evaluation method of embankments in Japan. The threshold acceleration during shaking is supposed to be a constant in the Newmark Sliding Block Method. However, threshold acceleration can be varied during strong earthquake motions. In this study, several dynamic centrifuge model tests were carried out to investigate the threshold acceleration of embankments during the shaking. The compensation in the Newmark Sliding Block Method was proposed considering variations in threshold acceleration. The test data indicate that the threshold acceleration of the embankments has a tendency to decrease during an earthquake.