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Roller doors are popularly used in cities due to their compact design, low cost, and ease of use. However, roller doors are made of thin metal sheets and have low inherent damping, which causes roller doors in their closed configuration to experience strong vibration when subjected to external excitations, such as wind and passing vehicles. These vibrations also result in severe noise radiation. It is therefore necessary and important to minimize the vibrations and the noise emanating from the roller doors. This research develops a novel application method to suppress the vibration of existing roller doors and to mitigate the induced noise, and the main principle is using the high damping property of viscoelastic materials through retrofit to increase the damping of the roller door. The key component of the retrofit is a viscoelastic stripe of three layers: a self-adhesive layer, a viscoelastic layer and a constraining metallic layer. The proposed method can be easily applied to the existing roller doors and has nearly no negative impact on its daily usage. To validate the feasibility of this method, shaking table tests were conducted and investigated on a roller door model with and without viscoelastic retrofit, and the experimental results demonstrate that the proposed retrofit method can effectively mitigate the vibration and therefore reduce the induced noise for an existing roller door.

The nonlinear characteristic of vibration control systems has attracted increasing attention for its advantage in improving structural performance. In this paper, a new type of viscoelastic damping limb-like-structure (VE-LLS) device is proposed by combing the viscoelastic (VE) damper and limb-like-structure (LLS) together, which possesses coupling nonlinearity characteristic caused by geometric and material factors, as well as a remarkable advantage in improving the control performance. First, to explore the nonlinear geometrical effects on the static stiffness of the VE-LLS device, a formula is derived from static stiffness, and the results are discussed. Second, dynamic analysis is performed of the proposed device considering the coupling geometrical and material nonlinearities in frequency domain, with the real-time effect of frequency and temperature on the mechanical properties of the viscoelastic damper considered in solving the nonlinear vibration equation. The harmonic balance method (HBM) is used to solve the nonlinear dynamic equation. Then, the displacement transmissibility of the VE-LLS device is calculated and assessed. The results indicate that the proposed device possesses excellent vibration isolation performance, and the geometric parameters of the viscoelastic damper have significant nonlinear effect on the performance. Finally, an experiment is carried out of the VE-LLS device to verify the accuracy of the static stiffness analysis. The results show that the theoretical results agree well the experimental ones, and that the theoretical results have high accuracy and reliability.

When subjected to excessive shear deformation, viscoelastic (VE) dampers may inevitably suffer from damages, due to their VE material layers with limited thickness. Under the circumstance, their stiffness and energy dissipation capabilities may deteriorate but not totally vanish. To estimate the seismic performances of viscoelastically damped structures, the beyond design and residual performances of damaged VE dampers are crucial to protect structures from severe failure during the following main shock or aftershocks. On the other hand, for new viscoelastically damped structures under the normal design earthquakes, neglecting the residual performance of damaged VE dampers may result in nonconservative design. Thus, this study aims to provide approaches to analytically characterize the beyond design and residual performances of damaged full-scale VE dampers. Based on the simplified fractional derivative model, the analytical predictions have been compared with the experimental results. The proposed model works well for the design performance of the intact full-scale VE dampers. Particularly, it can also reproduce the beyond design and residual performances of damaged full-scale VE dampers, if due consideration is taken of the effects of excitation frequencies, ambient temperatures, temperature rises, softening, and hardening.

This study proposes a novel viscoelastic bio-inspired multi-dimensional vibration isolation device (VBM-VI). The viscoelastic (VE) damper and the limb-like-structure (LLS) are first installed into the vibration device to make it simultaneously reveal excellent vibration isolation performance at three directions. First, the dynamic equations of the proposed device are established, and the significant coupling nonlinear characteristics caused by material and geometric factor together are discussed. Then, the harmonic balance method (HBM) is used to solve the nonlinear dynamic equation, and the geometrical parameters of the VE damper and LLS device are studied to assess the influence of coupling nonlinear characteristic on the vibration isolation performance. The results indicate that the coupling nonlinear characteristics have an excellent advantage on vibration control, and the proposed VBM-VI device can achieve different vibration isolation performances by adjusting the parameters of the VE damper or LLS. The study also shows that the vibration isolation performances at the horizontal and vertical directions are coupled and restricted with each other, showing different levels of sensitivity to parameter variation. Finally, a comparative study is performed between the traditional vibration isolation device (TV-VI) and the VBM-VI device, indicating that the coupling nonlinear characteristic caused by the VE damper and LLS possesses remarkable advantage of improving the vibration isolation performance of the VBM-VI device.

Traditional physics-based mathematical models of viscoelastic (VE) damper often exhibit different degrees of prediction errors under complex working conditions, whereas data-driven approaches have shown significant potential for overcoming such problems, and have not been introduced into any study to describe the dynamic mechanical properties of VE damper. In this paper, the architecture of microsphere model is adopted to represent the spatial distribution of molecular chain structure of VE damping material, which is categorized into free chains and elastic chains. Then, the physics-informed neural network surrogates are introduced to describe the statistical stress–strain behaviors of free chains and elastic chains. Finally, by constructing the physics-constrained loss function based on the combination of physics-based model and data-driven model, a physics-constrained data-driven model is proposed to characterize the dynamic mechanical behaviors of VE damper used for structure vibration control. Based on the existing experimental data, the prediction ability and robustness of the proposed model are comparatively verified, the results reveal that the proposed model can accurately reflect the stiffness and energy dissipation of VE damper under different ambient temperatures, excitation frequencies, and deformation conditions. This study proves the potential of physics-informed neural network theory in characterizing the complex mechanical behaviors of VE damper.

The high-damping viscoelastic (VE) materials are widely used to reduce unwanted vibrations in civil structures. However, the significant frequency and temperature dependences from high-damping VE materials cause a challenge in efficiently analyzing the structural dynamic behaviors. The aim of this study is to propose a generalized dynamic analysis method for the linear structural system with VE elements. The implementation steps and advantages of the dynamic analysis method are presented. In this method, the frequency-dependent matrices and non-proportional damping induced by VE elements are fully considered in modal coordinates, and then the state-space representation converted from the modal-based transfer function is adopted to implement the time-domain simulation. Any popular VE constitutive models which accurately describe frequency-dependent matrices can be applied to the method. The number of the state-space representation can be adjusted according to the interested frequency range. Numerical applications performed on a viscoelastically damped structure, a VE base-isolated structure, and a structure with a VE tuned mass damper (TMD) demonstrate the numerical accuracy, efficiency, and generality of the proposed dynamic analysis method.

The objective of this paper is to introduce a Rational Polynomial Approximation (RPA) method for modelling the response of structures that contain discrete elements with linear frequency-dependent stiffness and damping characteristics. The RPA method consists of two steps: First, system identification is performed to obtain a rational polynomial approximation for the system's transfer functions. Then, a time-domain model for the system is realised. The main advantage of the RPA method is that the resulting model is a system of ordinary differential equations, facilitating time history analysis of both linear and nonlinear structures using standard time-step integration algorithms and procedures.

Viscoelastic (VE) dampers comprise one of the primary classes of frequency-dependent dampers with both frequency-dependent stiffness and damping. VE dampers are used for mitigation of seismic- and wind-induced structural vibration. When using VE dampers in analysis, effective modelling of the frequency-dependent characteristics of the VE damper plays a key role in accurate simulation of structural responses.

Following a description of the theory behind the RPA method, the efficacy of the method is verified through several numerical examples employing VE damped structures. The results are compared with Kasai's fractional derivative model for VE dampers. Application of the RPA method to nonlinear structures is also given. The RPA method is shown to be effective and efficient for modelling VE damped structure.