Abstract
Semi-active isolation systems with controllable stiffness have been widely developed in the field of seismic mitigation. Most systems with controllable stiffness perform more robustly and effectively for far-field earthquakes than for near-fault earthquakes. Consequently, a comprehensive system that provides comparable reductions in seismic responses to both near-fault and far-field excitations is required. In this regard, a new algorithm called Feed-Forward Predictive Earthquake Energy Analysis (FPEEA) is proposed to identify the ground motion characteristics of and reduce the structural responses to earthquakes. The energy distribution of the seismic velocity spectrum is considered, and the balance between the kinetic energy and potential energy is optimized to reduce the seismic energy. To demonstrate the performance of the FPEEA algorithm, a two-degree-of-freedom structure was used as the benchmark in the numerical simulation. The peak structural responses under two near-fault and far-field earthquakes of different earthquake intensities were simulated. The isolation layer displacement was suppressed most by the FPEEA, which outperformed the other three control methods. Moreover, superior control on superstructure acceleration was also supported by the FPEEA. Experimental verification was then conducted with shaking table test, and the satisfactory performance of the FPEEA on both isolation layer displacement and superstructure acceleration was demonstrated again. In summary, the proposed FPEEA has potential for practical application to unexpected near-fault and far-field earthquakes.
Highlights
Continual improvements in earthquake engineering have allowed many structures to meet seismic design requirements for reducing earthquake-induced damage or collapse that exceeds the allowable range of construction
The results indicate that the Forward Predictive Earthquake Energy Analysis (FPEEA) control performed favorably in terms of structural response under the excitations of Whittier Narrows-01
A FPEEA algorithm is proposed in this paper to reduce the structural responses to earthquakes, namely the isolation layer displacement and superstructure acceleration
Summary
Continual improvements in earthquake engineering have allowed many structures to meet seismic design requirements for reducing earthquake-induced damage or collapse that exceeds the allowable range of construction. Structural strength is utilized to dissipate energy, which causes a considerable amount of plastic deformation in the frame. Robust control systems are crucial for reducing seismic energy and structural responses in terms of displacement and acceleration [1]. Kobori et al [2] were the first to investigate earthquake isolation systems according to the concept of variable stiffness, theoretically and experimentally demonstrating its feasibility [3]. In the case of variable stiffness controllable isolation systems, optimum variable stiffness will make the structure in controllable under the earthquake excitations without further increase of acceleration. Narasimhan et al [4] proposed a semi-active variable-stiffness control system mainly composed of four springs arranged in a diamond shape and an actuator requiring minimal electrical power for changing the spring angle
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