Xugang Hua

Numerical modeling and experimental study on a novel pounding tuned mass damper

Owing to its easy implementation and robustness, the pounding tuned mass damper (PTMD), which uses viscoelastic materials to cover the pounding boundary to increase the energy dissipation during impact, has been studied in recent years. The conventional PTMD design includes a gap between the pounding mass and the viscoelastic material; the value of this gap should be optimized. In this paper, a novel PTMD is proposed to control structural vibrations. In the proposed PTMD, the pounding boundary covered by viscoelastic materials is simply added to one side of the tuned mass when the tuned mass is in the equilibrium position. Unlike the conventional PTMD, the gap between the tuned mass and the pounding boundary is zero in the proposed design and is no longer a design parameter. A new analytic model is proposed to accurately predict the impact force between viscoelastic materials and steel. Through comparison with the impact force and the indentation from impact experiments, the accuracy of the proposed impact force model is validated. To verify the control performance of the proposed PTMD, an experimental study on a frame with the proposed PTMD is carried out to investigate the control performance in free vibration and forced vibration cases. Both experimental and numerical results show that the proposed PTMD can effectively reduce the response of the frame structure and that the damping ratio of the frame is significantly increased.

Monte Carlo Study of the Effect of Measurement Noise in Model Updating with Regularization

Finite-element (FE) model updating aims at the parametric identification of a structure by correcting model parameters in an initial FE model of the structure to reconcile FE predictions with experimental counterparts. However, experimental data inevitably contain a certain level of measurement noise, and the measurement noise will further generate error and uncertainty in updating results. This paper presents a Monte Carlo (MC) simulation study of the effect of measurement noise on updating parameters in FE models updating with regularization, attempting to quantify the distribution functions of updating parameters in face of measurement noise, and evaluating the adequacy of moment-based stochastic FE model updating algorithms. Taking a numerical study of model updating of a simple truss bridge as an example, a series of artificial measurement noise generated with the normal distribution of zero mean and varying variance is introduced into the simulated modal parameters to quantify the effect of measurem...

Advanced Impact Force Model for Low-Speed Pounding between Viscoelastic Materials and Steel

AbstractViscoelastic (VE) materials, which have a lower value for their coefficient of restitution, are widely used in vibration control and reduction of structural pounding. Even if an impact occu...

Wind loads and effects on rigid frame bridges with twin-legged high piers at erection stages:

This article presents a procedure for analyzing wind effects on the rigid frame bridges with twin-legged high piers during erection stages, taking into account all wind loading components both on the beam and on the piers. These wind loading components include the mean wind load and the load induced by the three turbulence wind components and by the wake excitation. The buffeting forces induced by turbulence wind are formulated considering the modification due to aerodynamic admittance functions. The buffeting responses are analyzed based on the coherence of buffeting forces and using finite element method in conjunction with random vibration theory in the frequency domain. The peak dynamic response is obtained by combining the various response components through gust response factor approach. The procedure is applied to Xiaoguan Bridge under different erection stages using the analytic aerodynamic parameters fitted from computational fluid dynamics. The numerical results indicate that the obtained peak structural responses are more conservative and accurate when considering the effect of each loading component on the beam and on the piers, and the roles of different loading components are different with regard to bridge configurations. Aerodynamic admittance functions are source of the important part of the error margin of the analytical prediction method for buffeting responses of bridges, and buffeting responses based on wind velocity coherence will underestimate the results.

Modal parameter identification of a long-span footbridge by forced vibration experiments

Performing forced vibration tests on full-scale structures is the most reliable way of determining the relevant modal parameters in structural dynamics, such as modal frequencies, mode shapes, modal damping, and modal masses. This study describes the modal identification of a double-level curved cable-stayed bridge with separate deck systems for pedestrians and vehicles via forced vibration tests. The steady-state structural responses to sinusoidal excitations produced by an electrodynamic shaker are recorded under varying excitation frequencies, and the frequency response functions are established. The measured frequency response functions are curve fitted to estimate the modal parameters. The numerical simulation of frequency response function–based modal parameter identification of an elastically multi-supported continuous beam structure is carried out, and the emphasis has been placed on the evaluation of the effect of an additional shaker mass, excitation frequency step and range, multi-mode vibration, and noise on identification results. Finally, the modal parameters for the first lateral mode of a double-level curved cable-stayed bridge are identified by forced vibration experiments, and the results are compared with those from ambient vibration tests and free vibration tests. The effect of the unmeasured wind excitation on identification is discussed. It is shown that the effect of ambient vibration is minor for wind velocity of 3–5u2009m/s. The damping ratios identified by forced and free vibration tests are comparable, while those from ambient vibration are subject to large variations. The modal mass obtained from forced vibration tests is in good agreement with finite element prediction, which provides design basis for mass-type dampers.