Hybrid Passive Control Strategies for Reducing the Displacements at the Base of Seismic Isolated Structures

In this paper, the use of hybrid passive control strategies to mitigate the seismic response of a base-isolated structure is examined. The control performance of three different types of devices used for reducing base displacements of isolated buildings is investigated. Specifically, the Tuned Mass Damper (TMD), the New Tuned Mass Damper (New TMD) and the Tuned Liquid Column Damper (TLCD), each one associated to a Base Isolated structure (BI), have been considered. The seismic induced vibration control of base-isolated structures equipped with the TMD, New TMD or the TLCD is examined and compared with that of the base-isolated system without devices, using real recorded seismic signals as external input. Data show that the New TMD is the most effective in controlling the response of base-isolated structures so that it can be considered as a practical and appealing means to mitigate the dynamic response of base-isolated structures

Efficient estimation of tuned liquid column damper inerter (TLCDI) parameters for seismic control of base-isolated structures

This paper presents an enhanced base-isolation (BI) system equipped with a novel passive control device composed of a tuned liquid damper and an inerter (TLCDI). With the aim of reducing the seismic response of BI systems, this contribution focuses on the design of the TLCDI providing analytical solutions for the optimal TLCDI parameters, easily implementable in the design phase. The effectiveness of the proposed approach in terms of seismic response reduction and computational gain is validated by comparison with classical numerical optimization techniques. The control performance of two different base-isolated TLCDI-controlled structures is assessed by employing real-ground motion records, and relevant comparisons with both uncontrolled base-isolated structures and equipped with a conventional TLCD are presented

Assessment of the tuned mass damper inerter for seismic response control of base-isolated structures

In this paper, the hybrid control of structures subjected to seismic excitation by means of tuned mass damper inerter (TMDI) and base-isolation subsystems is studied with the aim of improving the dynamic performance of base-isolated structures by reducing the displacement demand of the isolation subsystem. The seismic performance of TMDI hybrid controlled structures is investigated in a comparative study, considering simple isolated systems and systems equipped with other absorber devices such as the tuned mass damper (TMD) and the tuned liquid column damper (TLCD). The TMDI has been optimized by performing a simplified approach based on minimizing the base-isolation subsystem displacement variance, which provides simple analytical formulae for a quick definition of the TMDI parameters. The reliability of this approach is demonstrated by a comparison with a more accurate and computationally complex numerical optimization procedure. The control performance of three types of hybrid controlled structures exposed to a set of 44 recorded ground motions is investigated. Numerical results show that the TMDI can more efficiently control the structural response of low-damped isolated structures, even compared to the TMD and the TLCD

A novel identification procedure from ambient vibration data

Ambient vibration modal identification, also known as Operational Modal Analysis, aims to identify the modal properties of a structure based on vibration data collected when the structure is under its operating conditions, i.e., no initial excitation or known artificial excitation. This procedure for testing and/or monitoring historic buildings, is particularly attractive for civil engineers concerned with the safety of complex historic structures.However, since the external force is not recorded, the identification methods have to be more sophisticated and based on stochastic mechanics. In this context, this contribution will introduce an innovative ambient identification method based on applying the Hilbert Transform, to obtain the analytical representation of the system response in terms of the correlation function. In particular, it is worth stressing that the analytical signal is a complex representation of a time domain signal: the real part is the time domain signal itself, while the imaginary part is its Hilbert transform. A 3DOF numerical example will be presented to show the accuracy of the proposed procedure, and comparisons with data from other methods assess the reliability of the approach. Finally, the identification method will be extended to the real case study of the Chiaramonte Palace, a historic building located in Palermo and known as “Steri”

War and dissociation : the case of futurist aesthetics

Thanks to their deliberate engagement in state propaganda Italian Futurists deserved a prominent spot in the history of military aesthetics in the 20th century. However, under what looked like an unequivocal expression of support for war, lied a deep philosophical disagreement concerning its existential and epistemological value. The bone of contention concerned the effects of warfare on perception and, consequently, the means of its depiction. The author analyses this intellectual disagreement within the group and focuses, in particular, on its philosophical implications

Shedding a new light on Huntington's disease: how blood can both propagate and ameliorate disease pathology

Huntington's disease (HD) is a monogenic neurodegenerative disorder resulting from a mutation in the huntingtin gene. This leads to the expression of the mutant huntingtin protein (mHTT) which provokes pathological changes in both the central nervous system (CNS) and periphery. Accumulating evidence suggests that mHTT can spread between cells of the CNS but here, we explored the possibility that mHTT could also propagate and cause pathology via the bloodstream. For this, we used a parabiosis approach to join the circulatory systems of wild-type (WT) and zQ175 mice. After surgery, we observed mHTT in the plasma and circulating blood cells of WT mice and post-mortem analyses revealed the presence of mHTT aggregates in several organs including the liver, kidney, muscle and brain. The presence of mHTT in the brain was accompanied by vascular abnormalities, such as a reduction of Collagen IV signal intensity and altered vessel diameter in the striatum, and changes in expression of Glutamic acid decarboxylase 65/67 (GAD65-67) in the cortex. Conversely, we measured reduced pathology in zQ175 mice by decreased mitochondrial impairments in peripheral organs, restored vessel diameter in the cortex and improved expression of Dopamine- and cAMP-regulated phosphoprotein 32 (DARPP32) in striatal neurons. Collectively, these results demonstrate that circulating mHTT can disseminate disease, but importantly, that healthy blood can dilute pathology. These findings have significant implications for the development of therapies in HD

Optimal control of base-isolated systems with sliding TLCD under stochastic process

In this study, an innovative hybrid passive vibration control strategy, combining a base-isolated (BI) structure with a novel sliding version of a Tuned Liquid Column Damper (STLCD) to enhance the dynamic performance of BI structures, is explored from both theoretical and experimental perspectives. In contrast to conventional fixed TLCDs, the proposed STLCD consists of a U-shaped tank partially filled with water, mounted on a roller support, and linked to the BI subsystem through a spring-dashpot system. This configuration results in a more versatile tuning procedure utilizing the spring for tuning and obtaining supplementary damping through the dashpot. The optimal design of the STLCD device is discussed assuming a Gaussian white noise process as base excitation and the credibility of the presented mathematical formulation is assessed through a shaking table testing campaign, carried out at the Laboratory of Experimental Dynamics at the University of Palermo (Italy). For the experimentation, a reduced-scale model of a BI structure with the integrated STLCD is constructed, and its effectiveness is experimentally evaluated. Finally, comparisons to traditional TLCDs and TMDs are presented, emphasizing control efficiency and the reduction of base displacement in the BI syste

Optimal design of inerter-based absorbers with amplified inertance: from the improved tuned liquid column damper inerter (ITLCDI) to the improved tuned mass damper inerter (ITMDI) and improved tuned inerter damper (ITID)

This paper presents the optimal design of improved inerter-based absorbers to effectively mitigate vibrations in structural systems. The improvement of the inerter is achieved by integrating it within a rhombus truss, composed of rigid rods interconnected by hinges. This arrangement exploits the geometrical amplification effect to enhance inertial properties, thus leading to superior control performance. Specifically, both ends of the inerter are anchored to opposite points along one diagonal of the rhombus, while along the other diagonal, one end is grounded, and the other is linked to the structural system itself or other mechanical systems. The motion of these systems triggers the activation of the inerter, contributing to vibration dissipation. Previous studies have combined this improved inerter with a spring-dashpot unit proposing the so-called Improved Tuned Inerter Damper (ITID). Extending prior research, this study integrates the improved inerter with common passive control devices, such as the Tuned Liquid Column Damper (TLCD) and Tuned Mass Damper (TMD), resulting in the development of the novel Improved Tuned Liquid Column Damper Inerters (ITLCDI) and Improved Tuned Mass Damper Inerter (ITMDI). The optimal calibration for the ITLCDI through an analytical approach is presented, assuming stochastic processes for modeling seismic actions. Furthermore, it discusses how the ITLCDI configuration can be adapted to yield the ITMDI and ITID configurations, providing closed-form solutions for all three absorbers. Validation of the proposed method is performed through numerical simulations, with a thorough analysis conducted to assess the effectiveness of the ITLCDI relative to the ITMDI and ITID configurations

Optimal design of short-period structures equipped with sliding tuned liquid column damper and numerical and experimental control performance evaluation

In this paper, the structural vibration control of short-period systems by a sliding model of a tuned liquid column damper (herein referred to as STLCD) is investigated from both theoretical and experimental points of view. The proposed STLCD is essentially composed of a U-tube container with liquid inside, which can slide on a linear guide rail and is connected to the structure by a spring-dashpot system. Unlike traditional fixed TLCDs, this type of arrangement allows the proposed STLCD to be tuned to short-period structural systems since the spring can be used for tuning while the dashpot provides additional damping. Details on the selection of the optimal design parameters of the STLCD are provided, and the validity of the introduced mathematical model is verified both in time and frequency domains through experimental tests conducted at the Laboratory of Experimental Dynamics at the University of Palermo, Italy. For the experimental tests, a scale model of an STLCD-controlled structure is considered, focusing on the reduction of the roof accelerations. Finally, for comparison purposes, the control performance of the proposed control strategy for the vibration suppression of stiff structures is evaluated by analyzing its structural responses in contrast with the corresponding uncontrolled structure under harmonic excitations