Enhanced passive control of dual‐mode systems under extreme seismic loading: An optimal control approach

Abstract

Devastating economic losses can arise from damage to mission-critical facilities, structures, and systems supporting vital equipment (systems in general). One of the sources of damages to such systems is displacements in excess of the displacement capacity. The increase in displacement demand is more pronounced in systems located on soft soils 1-3 or when they are exposed to long-period seismic loadings or near-fault excitations with large pulse duration. 4,5 Exceeding the displacement capacity results in the pounding between adjacent structures or the impact in system's components. [6][7][8] Pounding/impact produces harmful undesired transmitted acceleration to the system, [9][10][11][12] which is detrimental for acceleration sensitive components.The most straightforward solution to mitigate impact is to increase the displacement capacity. However, it is not always possible to increase the displacement capacity because of environmental limitations or cost prohibitions, in both new construction and retrofit of an existing structure. 8,9 In the literature, different solutions for pounding mitigation have been proposed and assessed. One method is to connect adjacent structures at some specific locations. These connections enforce the adjacent structures to have in-phase motions with one another. [13][14][15] For instance, the use of hard rubber bumpers or stiff linking between the segments of a bridge can improve the bridge behavior during severe earthquakes 13 or inserting a shock-absorbing material such as rubber for pounding mitigation in buildings. 8 Alternatively, a pair of pressurized fluid-viscous dissipaters was used for pounding mitigation between a church structure and its bell tower. 7 Applying a similar concept, a share tuned mass damper between two adjacent tall buildings can reduce both structural responses and the probability of pounding. 14 Others have shown that using links such as springs, dashpots, or viscoelastic elements between two adjacent three-story buildings can significantly reduce the gap size and prevent pounding. 15 Another solution to this problem is to reduce the displacement demand via some energy dissipative mechanisms, which has been studied extensively. For instance, increasing the damping in an isolation system reduces the isolator displacement and base shear. [16][17][18] Approaches based on semi-active control have also been developed to decrease structural displacement. 19 Recently, inerters have been shown to be effective for response reduction as well. 20,21 Although the above-mentioned solutions have shown to be effective, there are some drawbacks with these approaches, and several studies showed that devastating damage to systems has been observed under high-amplitude seismic loadings, even with the presence of some energy dissipative mechanisms. 4,7,17 One of the disadvantages of connecting adjacent structures is the impairing of the dynamics of each individual structures. In addition, reducing the displacement demand comes at the expense of increasing the total transfer...

Characterization and real‐time hybrid simulation testing of rolling pendulum isolation bearings with different surface treatments

“…Moreover, the “impacts” produce spikes in the sustained acceleration, as seen in Figure 26(right). Therefore, an improved impact mechanism 33 should be explored to prevent the quick reversals of motion and resulting high accelerations.…”

“…To simulate impact in the FIS, 33,34 an elastic Hertz-type impact model 35 was incorporated. At a displacement of ±127 mm, an elastic spring force engaged, providing a (numerical) restoring force that was superimposed on the measured restoring force in the Simulink model.…”

Analysis and optimization of a nonlinear dual‐mode floor isolation system subjected to earthquake excitations

“…Figure 1(B) presents the phased force–displacement relationship. This model can represent either a harsh impact with a restraining wall (i.e., = seismic gap [ 48 ] ) or a gap at which a supplemental device is activated (e.g., dual‐mode system, [ 49 ] such as a gap damper [ 28 ] ).…”