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This study aims to reveal the control mechanism of viscoelastic (VE) energy dissipation braces with strong mechanical nonlinear characteristics on the seismic response of reinforced concrete (RC) frame structures. Firstly, a new STM32-Matlab-OpenSees joint hybrid test platform is developed by introducing OpenSees, which is convenient for structural modeling and fast for structural calculation. The overall architecture and operation of the hybrid test platform are comprehensively analyzed. Then, a series of simulated seismic hybrid tests on three-dimensional (3D) RC frame structures with VE energy dissipation braces under different seismic waves are successfully carried out. Lastly, the hybrid test results of this structure system at different working conditions are compared and analyzed comprehensively. The research results show that the developed platform breaks the boundary limitation that OpenSees relies on the framework software OpenFresco and can only be connected to specific control systems in the hybrid test. Thus, it greatly expands the application scope of flexible configuration controller and actuator categories for the hybrid test platform, and it also provides a good reference value for the establishment and implementation of similar hybrid test platforms. Under the action of various seismic waves, VE energy dissipation braces has good universality for the shock absorption of RC frame structures. The damping control effect and energy dissipation efficiency of VE energy dissipation braces are significantly different under various seismic waves. In the design of RC frame structures with VE energy dispersion braces, it is very necessary to conduct the seismic analysis of the structures under multiple ground motions with wide frequency domain. The additional position of VE energy dissipation braces should be an important analysis indicators in the optimization design of the structures. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The isolation technologies are adopted to protect the long-span space structures from serious damage under the action of earthquakes. When the isolation system is applied to the space structures, both horizontal and vertical vibration control effects on the structures should be concerned. In this paper, a two-dimensional earthquake isolation and mitigation device (TEIMD) composed of a high-damping viscoelastic (VE) core pad and VE dampers is proposed. Based on the dynamic shear experiment results of the VE damper, the energy dissipation capability of VE material is preferable. Then, the nonlinear equivalent stiffness and equivalent damping ratio of the TEIMD in horizontal and vertical directions are evaluated by using the numerical simulation method. The TEIMDs are arranged on the column top of a double-layer grid structure to assess the isolation effectiveness of the novel device. The dynamic analysis results of the double-layer grid structure with and without TEIMD reveal that this novel device can significantly reduce the acceleration response of the upper grid by relying on the strong energy dissipation performances in the horizontal and vertical directions. This research also verifies the feasibility of applying the TEIMD to the double-layer grid structure, which can effectively dissipate the vertical vibration energy of the structure. [ABSTRACT FROM AUTHOR]

Based on the low cost and superior damping performance of viscoelastic dampers, the new structural system strengthened with viscoelastic energy dissipation braces (VEDB) is proposed to upgrade the reinforced concrete frame structures with insufficient seismic capability. For the dynamic performance researches and damage evolution predictions of this structure system during earthquakes, the dynamic performance of six RCFs (reinforced concrete frames) and six VEFs (another six special reinforced concrete frames with VEDB) are studied under sinusoidal wide frequency range loading excitation horizontally. On this basis, the qualitative and quantitative relations on the damage growing at the material-level and the member-level performance deteriorating about the frame structures are conducted. Furthermore, the empirical calculation model on the cross-level damage evolution of VEFs are established and verified. Finally, a set of useful and robust cross-level judgment criteria for damage performance rates is proposed. The research found that, the installation of VEDB can significantly improve the load bearing capacity, the lateral stiffness and the energy dissipation capacity of the structures. The damage pattern of the structures is improved by VEDB, and it ensures the design criteria of "strong joints and weak members." The empirical calculation model on the cross-level damage evolution and judgment criteria for damage performance rates proposed in this paper are useful and stable in practical engineering. [ABSTRACT FROM AUTHOR]

This study aims to develop a high-performance acrylate viscoelastic damper (HAVED), which is suitable for the low-frequency vibration control of building structures. To reveal the influence of ambient temperature, excitation frequency, and displacement amplitude on the dynamic mechanical performance and energy dissipation capacity of a HAVED, a series of dynamic mechanical performance tests were performed on a HAVED within the extensive temperature (10°C–50°C), frequency (0.1–3 Hz), and displacement (0.5–4 mm) range. The analysis results show that a HAVED has excellent energy dissipation capacity and good adaptability to the external environment. The loss factor of a HAVED can reach up to 1.85, and it remains above 0.28 even in a high-temperature environment of 50°C. The dynamic mechanical properties and energy dissipation capacity of a HAVED show strong dependences and obvious coupling effects on temperature, frequency, and displacement amplitude. Based on the experimental research of a HAVED, the micromechanical properties of viscoelastic materials are analyzed, and the high-order fractional derivative model is used to comprehensively describe the mechanical characterization of microscopic molecular chains. The Kraus theory is introduced to consider the influence of filler particles, and the high-order fractional derivative micro–macro cross-scale mathematical model is proposed by combining with the temperature-frequency equivalence principle. Through the experimental results, the prediction capabilities of the model that have been established have been verified. The analysis results show that the proposed model can comprehensively describe the influence of ambient temperature, excitation frequency, displacement amplitude, microscopic molecular chain structure, and filler particles on the mechanical properties of a HAVED. [ABSTRACT FROM AUTHOR]

The bionics design method has been proverbially applied at vibration control field, and how to make bionic vibration control device possess excellent mechanical property and stable energy dissipation capacity is an important subject. In this paper, a bionic viscoelastic limb-like-structure (VE-LLS) device is proposed in conjunction with the viscoelastic (VE) damper and the limb-like-structure (LLS) device together, and the proposed device simultaneously possesses excellent mechanical propriety and energy dissipation capacity. Firstly, the mechanical property test of the VE-LLS device is conducted to investigate the effect of ambient temperature, excitation amplitude and frequency on its dynamic mechanical property and energy dissipation capacity. The energy dissipation contribution caused by the LLS joint friction for the VE-LLS device is discussed. Then, the energy dissipation model of the VE-LLS device is established by simultaneously considering the viscoelastic and friction factors, and the comparison result indicates that the established energy dissipation model can accurately describe the energy dissipation capacity of the VE-LLS device under different ambient temperature, exaction amplitude and frequency. Finally, to further promote the stability of energy dissipation capacity of the VE-LLS device at different temperature and frequency, an energy dissipation compensation strategy is proposed by increasing the energy dissipation of the LLS joint friction to compensate for the energy dissipation attenuation of the VE damper caused by high temperature and low frequency, and the results shows that the compensation strategy expresses excellent effect for the energy dissipation stability of the VE-LLS device. [ABSTRACT FROM AUTHOR]

Viscoelastic dampers are conventional passive vibration control devices with excellent energy dissipation performance. The fractional derivative has a simple form and high accuracy in the modelling of viscoelastic materials/dampers. The internal variables reflect the internal state evolution of materials, and are often used to analyze the deformation and thermal process of materials. In the present work, the mechanical properties of a plate-shear-type viscoelastic damper at room temperature are tested under sinusoidal displacement excitations. The impacts of frequency and displacement amplitude on the dynamic properties of the viscoelastic damper in a wide frequency domain (0.1–25 Hz) are investigated. The higher-order fractional derivative model and the temperature–frequency equivalent principle are employed to characterize the frequency and temperature influence, and the internal variable theory considering the internal/microscale structure evolutions is introduced to capture the displacement affection. The higher-order fractional derivative model modified with the internal variable theory and temperature–frequency equivalent principle (ITHF) is accurate enough in describing the dynamic behaviors of viscoelastic dampers with varying frequencies and displacement amplitudes. [ABSTRACT FROM AUTHOR]

• An advanced frame structure system retrofitted by adding haunch viscoelastic damping braces is presented. • The seismic behavior and rebar strain at key locations of CFs and VFs are discussed. • A comparative study on the damage evolution about two types of frames at the material scale is carried out. • The addition of HVEDB guarantees the seismic design requirements of "strong nodes and weak components. To upgrade the existing RC frame structure system with insufficient seismic design and improve the seismic design of the RC frame structures, a novel and advanced frame structure system retrofitted by adding haunch viscoelastic damping braces (HVEDB) is presented in this study based on the good energy dissipation performance, the low-cost and non-invasive addition of viscoelastic dampers. For a comprehensive and systematic research of this new structure system, the seismic behavior of ten RC frames and another ten RC frames added by HVEDB with the axial load ratio (ALR) of 0.1–1.0 are carried out under horizontal sinusoidal steady-state excitation loading, including the hysteretic behavior, load-bearing capacity, stiffness degradation, energy dissipation capacity, additional damping ratio and rebar strain at key locations. On this basis, four reasonable damage indicators at the material scale are proposed, and a comparative study on the damage evolution about two types of frames at the material scale in the whole process is carried out. The study results show that the addition of HVEDB can greatly improve the seismic performance such as load-bearing capacity, lateral stiffness, deformation capability and energy dissipation, and it changes the failure mode of the RC frames. The HVEDB can provide the effective protection for the beam-column joints by transferring the damage region from the beam-column joint to the frame beam successfully, which guarantee the seismic design requirements of "strong nodes and weak components" avoiding the brittle failure mode of frame structure under high ALR. [ABSTRACT FROM AUTHOR]

Evaluating the performance degradation of the earthquake-damaged structure and optimizing the placement of dampers is important for retrofitting post-earthquake structures. In this study, a damage evolution model is developed to evaluate the degradation of strength, stiffness, and energy dissipation capacity for earthquake-damaged structures. The proposed damage model is validated using previous experimental results based on the nonlinear finite element analysis. Then, research on the optimal design of damper parameters and quantity is carried out. Considering the optimization range of earthquake-damaged structures, a genetic algorithm with multi-objective functions is developed to determine the optimal placement of viscoelastic dampers in damaged structures. The results demonstrate that the proposed damage model can effectively describe the performance degradation of damaged structures. The control effects of the acceleration response increase exhibited a maximum enhancement of 3.38 times after accounting for the optimization range of earthquake-damaged structures. The optimization results of the multi-objective function with the optimization range are better aligned with the objectives of designers. • A damage model is developed to evaluate the degradation of strength, stiffness, and energy dissipation for structures. • Understanding of the beneficial effect of the viscoelastic damper on the seismic response for earthquake-damaged structures. • A genetic algorithm with multi-objective functions is developed to optimize the design and placement of VE dampers. • The control effects of the acceleration response increase exhibited a maximum enhancement of 3.38 times. • The optimization results of the proposed method are better aligned with the objectives of designers. [ABSTRACT FROM AUTHOR]

The harmful vibration of the building structure usually can lead to huge casualties and property losses, it is necessary to reduce and eliminate the detrimental effect through effective vibration control device. In this paper, the viscoelastic damping limb-like-structure (VE-LLS) device is proposed by combing the viscoelastic (VE) damper and the limb-like-structure (LLS) together, which possesses coupling nonlinear characteristic that is benefit for improving the vibration control performance for building structure. Firstly, the property experiment is carried out to study mechanical performance of the proposed VE-LLS device, and the results show that the proposed device has better energy dissipation capacity and stability, the final failure mode of the device usually is caused by destruction of the VE damper. Next, the hysteretic curves of experimental results are plotted and discussed, and equivalent stiffness K e and equivalent damping C e are calculated to study the nonlinear influence of geometrical parameters on mechanical properties of the proposed device. Then, the mechanical model of the proposed device is established by considering the viscoelastic force and the friction force together. Lastly, the experimental and numerical results are compared and discussed together, and the results indicate that the established mechanical model has excellent accuracy and can precisely describe mechanical property of the proposed device. • The viscoelastic damping limb-like-structure device with coupling nonlinear characteristic is proposed by combing the viscoelastic damper and limb-like-structure firstly. • The property experiment of the proposed device is performed. The test results show that the proposed device has good energy dissipation capacity and stability;. • The mathematical model of the proposed device is established, which has excellent accuracy to describe the mechanical property of proposed device. [ABSTRACT FROM AUTHOR]