High-performance control systems (HPCSs) are sophisticated vibration mitigation strategies that include active, semi-active and hybrid systems. They generally outperform passive supplemental damping systems by relying on a feedback mechanism enabling adaptability, resulting in better control reachability over a wide excitation frequency bandwidth. HPCSs are therefore ideal for multi-hazard mitigation. However, the performance of these systems is highly dependent on the controller design, which requires appropriate tuning based on assumptions or on knowledge of dynamic parameters, long-term performance of sensors, excitations, etc. The quantification of performance based on possible uncertainties on such assumptions and/or knowledge could be a powerful tool in financially or technically justifying the use of an HPCS, or simply to benchmark the long-term performance of a given control algorithm. This paper investigates a methodology to assess the performance of control algorithms under various sources of uncertainties. To reduce the computational demand of the uncertainty quantification process, surrogate models are employed to map the nonlinear relationship between structural response and controller configurations. Long-term performance is quantified using life-cycle cost analysis. The investigation is conducted on a 39-story building, located in Boston (MA), and equipped with a set of semi-active friction devices. Results demonstrate that the proposed framework can be used to assess the performance of a given control algorithm considering various sources of uncertainties.
A novel semi-active damping device termed Variable Friction Cladding Connection (VFCC) has been previously proposed to leverage cladding systems for the mitigation of natural and man-made hazards. The VFCC is a semi-active friction damper that connects cladding elements to the structural system. The friction force is generated by sliding plates and varied using an actuator through a system of adjustable toggles. The dynamics of the device has been previously characterized in a laboratory environment. In this paper, the performance of the VFCC at mitigating non-simultaneous multi-hazard excitations that includes wind and seismic loads is investigated on a simulated benchmark building. Simulations consider the robustness with respect to some uncertainties, including the wear of the friction surfaces and sensor failure. The performance of the VFCC is compared against other connection strategies including traditional stiffness, passive viscous, and passive friction elements. Results show that the VFCC is robust and capable of outperforming passive systems for the mitigation of multiple hazards.
High-rate systems operating in the 10 μs to 10 ms timescale are likely to experience damaging effects due to rapid environmental changes (e.g., turbulence, ballistic impact). Some of these systems could benefit from real-time state estimation to enable their full potential. Examples of such systems include blast mitigation strategies, automotive airbag technologies, and hypersonic vehicles. Particular challenges in high-rate state estimation include: 1) complex time varying nonlinearities of system (e.g. noise, uncertainty, and disturbance); 2) rapid environmental changes; 3) requirement of high convergence rate. Here, we propose using a Variable Input Observer (VIO) concept to vary the input space as the event unfolds. When systems experience high-rate dynamics, rapid changes in the system occur. To investigate the VIO’s potential, a VIO-based neuro-observer is constructed and studied using experimental data collected from a laboratory impact test. Results demonstrate that the input space is unique to different impact conditions, and that adjusting the input space throughout the dynamic event produces better estimations than using a traditional fixed input space strategy.
A structural system consists of gravity and lateral load resisting components. Structural walls in the gravity system are
typically designed to resist vertical loads only, and are assumed to be inactive to mitigate lateral loads. In this paper, we
propose a novel multifunctional wall system, which is embedded with multiple-capillaries containing free-flowing fluids
and can act as both a load carrying member and a Tuned Liquid Wall Damper (TLWD). Functioning similarly to a
Tuned Liquid Column Damper (TLCD), the damping force of the proposed wall system is provided by the head loss of
the fluid between each capillary. An analytical model is derived first to describe the dynamic behavior of the TLWD.
The accuracy of the analytical model is verified using Computational Fluid Dynamics (CFD) simulations. The model is
further used to compute the reduced response of an assumed primary structure attached with a TLWD to demonstrate the
damping capability. Results show that TLWDs can effectively dissipate energy while occupying much less space in
buildings compared to TLCDs.
KEYWORDS: Control systems, Probability theory, Numerical simulations, Buildings, Systems modeling, Magnesium, Hazard analysis, Magnetic resonance imaging, Computer simulations, Seaborgium, Turbulence
High performance control systems (HPCS) are advanced damping systems capable of high damping performance over a
wide frequency bandwidth, ideal for mitigation of multi-hazards. They include active, semi-active, and hybrid damping
systems. However, HPCS are more expensive than typical passive mitigation systems, rely on power and hardware (e.g.,
sensors, actuators) to operate, and require maintenance. In this paper, a life cycle cost analysis (LCA) approach is proposed
to estimate the economic benefit these systems over the entire life of the structure. The novelty resides in the life cycle
cost analysis in the performance based design (PBD) tailored to multi-level wind hazards. This yields a probabilistic
performance-based design approach for HPCS. Numerical simulations are conducted on a building located in Boston,
MA. LCA are conducted for passive control systems and HPCS, and the concept of controller robustness is demonstrated.
Results highlight the promise of the proposed performance-based design procedure.
KEYWORDS: Lawrencium, Sensors, Control systems design, Control systems, Probability theory, Hazard analysis, Systems modeling, Signal processing, Process control, Adaptive control, Lithium, Computer simulations, Data modeling, Information theory
Semi-active and active structural control systems are advanced mechanical devices and systems capable of high damping performance, ideal for mitigation of multi-hazards. The implementation of these devices within structural systems is still in its infancy, because of the complexity in designing a robust closed-loop control system that can ensure reliable and high mitigation performance. Particular challenges in designing a controller for multi-hazard mitigation include: 1) very large uncertainties on dynamic parameters and unknown excitations; 2) limited measurements with probabilities of sensor failure; 3) immediate performance requirements; and 4) unavailable sets of input-output during design. To facilitate the implementation of structural control systems, a new type of controllers with high adaptive capabilities is proposed. It is based on real-time identification of an embedding that represents the essential dynamics found in the input space, or in the sensors measurements. This type of controller is termed input-space dependent controllers (ISDC). In this paper, the principle of ISDC is presented, their stability and performance derived analytically for the case of harmonic inputs, and their performance demonstrated in the case of different types of hazards. Results show the promise of this new type of controller at mitigating multi-hazards by 1) relying on local and limited sensors only; 2) not requiring prior evaluation or training; and 3) adapting to systems non-stationarities.
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