Post-Breakage Vibration Frequency Analysis of In-Service Pedestrian Laminated Glass Modular Units

The vibration performance of pedestrian structures has attracted the attention of several studies, especially with respect to unfavourable operational conditions or possible damage scenarios. Specific vibration comfort levels must be commonly satisfied in addition to basic safety requirements, depending on the class of use, the structural typology and the materials involved. Careful consideration could be thus needed at the design stage (in terms of serviceability and ultimate limit state requirements), but also during the service life of a given pedestrian system. As for structural health monitoring purposes, early damage detection and maintenance interventions on constructed facilities, vibration frequency estimates are also known to represent a preliminary but rather important diagnostic parameter. In this paper, the attention is focused on the post-breakage vibration analysis of in-service triple laminated glass (LG) modular units that are part of a case-study indoor walkway in Italy. On-site non-destructive experimental methods and dynamic identification techniques are used for the vibration performance assessment of a partially cracked LG panel (LGF), compared to an uncracked modular unit (LGU). Equivalent material properties are derived to account for the fractured glass layer, and compared with literature data for post-breakage calculations. The derivation of experimental dynamic parameters for the post-breakage mechanical characterization of the structural system is supported by finite element (FE) numerical models and parametric frequency analyses.

Arrangement Method of Vibration Dampers Considering Frequency Response Physical Characteristics and Stiffness of Conductor

In order to study the calculation method of installation distance of vibration dampers with higher precision, so as to maximize its anti-vibration performance on the conductor. The arrangement method of dampers based on the frequency response characteristics of conductors is proposed, the dynamic model of conductor considering stiffness is established. The model is solved by finite difference method, the natural frequency and vibration mode of conductor in case of Aeolian vibration are obtained, and the wavelength of conductor vibration is obtained according to its mode, so as to calculate the installation distance of vibration dampers. The calculation results of the new method are compared with those of the traditional method, which proves the advantage of the new method in calculation accuracy. The new method has a good effect on improving the calculation accuracy of the installation distance of the vibration dampers on the conductors, which is greatly influenced by its stiffness. At the same time, the frequency response of the conductor should be considered as much as possible in the calculation of the installation distance of the damper.

Calculation Method of Working Rotational Angle of Automobile Transmission System and Its Applications

The working state and operating parameters of the automobile transmission system play a key role in the vehicle noise and vibration performance. Based on the basic calculation method of relative rotational angle, this paper proposes two methods for calculating the working rotational angle and torsional stiffness of the transmission system, which can effectively obtain the key information of the transmission system under the vehicle operating state. The working rotational angle, whose initial angle should be corrected by the average angle in the neutral gear coasting condition, can reflect the actual working state of the torsional vibration damper effectively. And the accuracy of the linear torsional stiffness obtained will be above 90%. Both simulation and experimental analysis results show that these two proposed application methods have high calculation accuracies and engineering feasibility.

Experimental Investigations and Numerical Simulations of the Vibrational Performance of Wood Truss Joist Floors with Strongbacks

This paper provides an experimental study and computer modeling analysis of vibration performance of full-scale wood truss joist floors, related to the static deflection and vibration mode/frequency and single-person-induced vibration. The vibration behavior of full-scale truss joist floors was investigated and the influences of the strongbacks on the vibration behavior were assessed. The results showed that the simulated predictions agreed well with the measured results. Strongbacks do not significantly affect the fundamental frequency of the truss joist floors but influence the second and third modal frequencies. The use of strongback rows at mid-span effectively decreased the maximum deformation of point loading at floor center. The effect of adding strongbacks at one-third of each span on decreasing maximum deformation at the floor center was minimal. The case of walking parallel to the joist produced higher acceleration response at the floor center than that of walking perpendicular to the joist. The closer the placements of strongbacks were to the mid-span, the more significant reduction of the vibration at floor center was. Two strongback rows at mid-span performed the best effect on reduction of vibration response at floor center. However, the use of strongbacks had limits of reduction peak acceleration of the sheathing between the joists. The study provides a valuable guide for future vibration serviceability study and design optimization of wood truss joist floors.

Nonlinear Parametric Resonance Behavior of Cables in a Long Cantilever Bridge for Sightseeing Platform

In order to study the parametric vibration of stayed cables in a long cantilever bridge for a sightseeing platform, nonlinear parametric vibration equations of the stayed cables excited by the vibration of bridge deck and tower are derived. Then, a second-order differential equation is transformed into a first-order ordinary differential equation, which is solved by using the Runge–Kutta method. A finite element model of cables was also built to verify the solution of the Runge–Kutta method. Then, the inherent dynamic characteristics of the full structure and all the cables with different lengths were analyzed to discuss the potential risk of parametric vibration. The longest and shortest cables were taken as examples to explore their nonlinear vibration performance. The effects of damping ratio, excitation position, and amplitude on cables’ nonlinear vibration performance were investigated. The results show that it will be more efficient and convenient to use the Runge–Kutta method to calculate cables’ nonlinear vibration amplitude without loss of accuracy. In addition, short cables have more resonance zones compared to long cables. Especially, with the cable length shortening, the dominant frequencies of the dynamic response and its amplitude increase significantly, and the number of resonance zones also increases. However, excessive excitation amplitude will also cause multiple resonance zones in the cable. The parametric analysis results show that it is effective and efficient to mitigate the nonlinear vibration by adjusting the frequency relationship between the bridge and the cables, rather than by increasing the damping ratio.