As constitutive models are too complicated and existing mechanical models lack universality, these models are beyond satisfaction for magnetorheological elastomer (MRE) devices. In this article, a novel universal method is proposed to build concise mechanical models. Constitutive model and electromagnetic analysis were applied in this method to ensure universality, while a series of derivations and simplifications were carried out to obtain a concise formulation. To illustrate the proposed modeling method, a conical MRE isolator was introduced. Its basic mechanical equations were built based on equilibrium, deformation compatibility, constitutive equations and electromagnetic analysis. An iteration model and a highly efficient differential equation editor based model were then derived to solve the basic mechanical equations. The final simplified mechanical equations were obtained by re-fitting the simulations with a novel optimal algorithm. In the end, verification test of the isolator has proved the accuracy of the derived mechanical model and the modeling method.

With the rapidly increasing number of long span bridges being built all over the world, the wind-induced vibrations of their constructing high bridge towers are becoming a serious issue. These vibrations will discomfort workers, affect construction accuracy, lead to construction period delay, and sometimes even cause accidents. Tuned mass dampers (TMDs) are well accepted to have a good performance in wind-induced vibration control under the condition that their natural frequencies are tuned to the natural frequencies of the main structures. However, as the natural frequencies of the bridge towers keep varying during its construction, their wind-induced vibrations can hardly be controlled by conventional TMDs. To improve the control efficiency, a novel magnetorheological elastomer variable stiffness tuned mass damper (MRE VSTMD) was proposed to retune the system. To verify the efficiency of the proposed system, a constructing bridge tower was modeled analytically and the corresponding MRE VSTMD was designed. Simulations were carried out and evaluations were made among the uncontrolled, passive controlled and semi-active controlled structures. It is proved that the proposed MRE VSTMD can improve the performance of passive TMDs by up to 40%. It is also observed that the softening behavior can double the stiffness variable range of MRE layers, indicating MRE VSTMD’s potential to further improve its performance with time varying excitation powers.

In order to extract more wind energy, the wind turbine rotor becomes larger and the tower becomes taller. With more flexibility and smaller damping, wind turbine tower is prone to vibrate in winds. Meanwhile, the tower suffers the periodic loadings caused by the rotor rotation in the operational condition. The excessive vibrations could not only significantly affect the power generation but shorten the structural life due to the fatigue as well. It is challenging to reduce the vibration caused by the rotor rotation using the passive tuned mass damper (TMD) and traditional LQR controller due to the limited effective bandwidth. Therefore, an active tuned mass damper (ATMD) using a virtual TMD algorithm is proposed to mitigate the along-wind vibration of the tower under parked and operational conditions. The virtual TMD algorithm exhibits wide effective bandwidth and only requires the acceleration information on the top of the tower or the relative displacement of the active TMD. Firstly, the aerodynamic-structure-servo coupling (ASSC) model of the wind turbine is established which considers the interaction among the aerodynamic load, structure, and servo system. Secondly, the accuracy of the ASSC model is then verified using the onshore 5 MW wind turbine by the National Renewable Energy Laboratory (NREL). Thirdly, the ATMD feedback control force is designed by the virtual TMD algorithm. Finally, the reduction effect on the along-wind vibration by the proposed controller is evaluated at both of operational and parked conditions using the ASSC model. The TMD and LQR controller are utilized for comparison. The numerical results demonstrate that tuned mass damper (TMD) system with fixed parameters becomes detuned and may loses its effectiveness at different wind speeds. In contrast, active control can suppress the vibration of wind turbines at different wind speeds. Compared to the LQR controller, the proposed controller can enhance the reduction effect of wind turbine response with smaller stroke and control force at operational conditions.

To quantify design wind load of photovoltaic panel array mounted on flat roof, wind tunnel tests were conducted in this study. Results show that the first and the last two rows on the roof are the most unfavorable ones regarding to the wind load. Influences of array spacing, panels’ tilt angle and parapet height on wind load of the panels are studied. Most unfavorable lift force of panels decreases with increase of array spacing for middle located panels. The aerodynamics are similar to flow over repeated hills. Middle located unit got greater turbulence, which leading to unfavorable C _{fp_min}. While the changing amplitude of most unfavorable wind pressure is small increase with array spacing. C _{fp_max} and C _{fp_min} of panel units shows quite strong dependence on tilt angle. There is significant pressure equalization for small tilt angle cases. The local flow separation is responsible for C _{fp_min} of larger tilt angle cases. Parapet height of 2 h (h is the panel height projected on the vertical plane) is the critical height for C _{fp_max} and C _{fp_min}. Increasing parapet height can significantly reduce the wind load of panel units. Design pressure coefficient of the basic working condition with different area sizes at different location are proposed.