Experimental Study on Influence of Temperature to Control Performance for Viscoelastic Materials Pounding Tuned Mass Damper

The pounding tuned mass damper (PTMD) is a novel passive damper that absorbs and dissipates energy by an auxiliary tuned spring-mass system. Viscoelastic materials are attached to the interface of the limitation collar in the PTMD so that the energy dissipation capacity can be enhanced. Previous studies have successfully demonstrated the effectiveness of PTMD at room temperature. However, in practice, the PTMD may face a broad temperature range, which can affect the mechanical properties of the viscoelastic materials. Thus, the study of vibration control effectiveness of PTMD at different temperatures is of great significance for its practical engineering application. In this paper, a series of experiments were conducted to investigate the performance of a PTMD in a temperature-controlled environment. A PTMD device was designed to suppress the vibration of a portal frame structure and tested across environmental temperatures ranging from –20°C to 45°C. The displacement reduction ratios demonstrated the temperature robustness of the PTMD. Additionally, the numerical results validated the accuracy of the pounding force model and the performance of PTMD.

Using passive control by a pendulum in a portal frame platform with piezoelectric energy harvesting

This work presents a passive control strategy using a pendulum on a simple portal frame structure, with two-to-one internal resonance, with a piezoelectric material coupling as a means of energy harvesting. In addition, the system is externally base-excited by an electro-dynamical shaker with harmonic output. Due to internal resonance the system may present the phenomenon of saturation, which provides some nonlinear dynamical behavior to the system. A pendulum is coupled to control nonlinear behaviors, leading to a periodic orbit, which is necessary to maintain energy harvesting. The results show that the system presents, most of the time, as being quasiperiodic. However, it does not present as being chaotic. With the pendulum, it was possible to control most of these quasiperiodic behaviors, leading to a periodic orbit. Moreover, it is possible to eliminate the need for an active or semi-active control, which are usually more complex. In addition, the control provides a way to detune the energy captured to the desired operating frequency.

OPTIMUM RELIABILITY OF A STEEL TAPERED PORTAL FRAME STRUCTURE EXPOSED TO FIRE

In this study, the optimum reliability of a tapered steel portal frame structure is presented for several cases. The aim of the research is to define target reliability indices for fire design situation since some research works (Balogh and Vigh, 2015a; 2015b) pointed that the achievable reliability (with using the prescriptive rules of Eurocode standards) is lower in extreme and seismic design situations than the suggested target value in (EN0, 2002). It seems that the target reliability indices of (JCSS, 2000) are preferable in these cases. In this paper, the optimum reliability is investigated as described in (Holickỳ, 2011), but total cost function is formulated with two decisive variables with respect to the amount of active and passive safety measures. The structural reliability is obtained with the help of a complex FORM (First Order Reliability Method) algorithm. The results of this investigation can help also to answer the question, whether active or passive safety measures are more effective tools to achieve optimal solutions in case of fire design of steel portal frames.

Potential Application in Energy Harvesting of Intermodal Energy Exchange in a Frame: FEM Analysis

This paper presents a Finite Element Analysis (FEA) of modal energy exchange and harvesting in a simple portal frame structure. We consider both horizontal and vertical support excitations resonant first with the first mode (sway mode) and latter with the second mode (the first symmetrical mode). As 2:1 internal resonance is present between these two modes, the phenomena of mode saturation and energy exchange (modal coupling) may occur. Thus, energy pumped into the system through one of the modes, is partially transferred to the other mode, not directly excited. An evaluation of the energy available for harvesting in each of the considered mode is computed.

Mode Saturation, Mode Coupling and Energy Harvesting From Ambient Vibration in a Portal Frame Structure

There has been much recent interest in the concepts of electro-mechanical systems that are able to scavenge, or harvest energy from their operating environment. Here, we present the extraction of energy from a simple portal frame structure excited via its second (first symmetric) mode. As 2:1 internal resonance is present between that mode and the first (sway) mode, the phenomenon of mode saturation and energy exchange (modal coupling) occurs. Energy pumped into the system through the second (vertical) mode is partially transferred to the horizontal (sway) mode. This paper presents results of numerical simulations of these phenomena and energy harvesting using a nonlinear piezoelectric material as a means of energy transduction. An evaluation of the energy available for harvesting in each of the considered modes is computed.

Research of the Influence of Snow Load Distribution Factor on Mechanical Performance of Portal Frame

The dissertation studies the force and deformation features of the portal frame structure under the snow load and load combination. The double cross gable portal frame model was established by 3d3s software in the paper, and analyzed under snow loading according to the regulations of China, Europe and the United States respectively. And some suggestions were put forward on the design of light-weight steel structure in China according to the comparison and analysis.