No abstract

During the lifetime of a structural system, many severe events such as earthquakes and strong winds may impact the system and result in potential damage. To mitigate the structural vibration and damage during these extreme events, control devices such as active and semi‐active devices have received considerable attention because of their attractive characteristics. Active control devices are adaptable to any change and semi‐active devices have the capability of offering the reliability of passive devices and the versatility and adaptability of active devices. In this research, a direct‐adaptive‐control method is used to control the behavior of an undamaged and a damaged structure using semi‐active and active devices. In the adaptive control method, the controlled system is forced to behave like the model system which exhibits the desired behavior. The model of the adaptive control method is defined in a way to optimize the response of the controlled structure. The controller developed using this method can deal with changes that occur in the characteristics of the structure because it can modify its parameters during the control process. A magnetorheological (MR) damper is used as the semi‐active device in this study, whereas a hydraulic actuator is utilized as the active device to control the behavior of the structure. The performance of a three‐story building from the SAC project for the third generation of the control benchmark problem is studied by performing time–history analyses. The structure is subjected to different earthquakes and controlled by the direct adaptive control method. In the analysis of the structure, some stiffness reduction is assumed as a result of potential damage in the first story of the building. Also, the direct adaptive control strategy is used to optimize the response of the undamaged structure and to mitigate the damage impact on the performance of the controlled structure in the presence of noise for output measurements. The results of adaptive control method are compared with those of other control strategies. It is shown that the performance of the three‐story building is improved using the adaptive control method. By assessing the results of different control approaches, it is found that the adaptive control method works more effectively than other methods and semi‐active devices can provide reliable results.

The use of semi-active devices for natural hazard mitigation is particularly attractive as they do not destabilize the structure and have the ability of adapting to varying usage patterns and loading conditions. However, even in the presence of supplemental control devices, extreme earthquake, wind loads, and deterioration caused by corrosion or fatigue may result in structural damage. Adaptive control approaches are attractive methods to control the structural performance of the structure as it can deal with these changes. In this study, first, the behavior of a 3-story building is controlled by a direct adaptive control approach using active devices, and then, magnetorheological (MR) dampers are controlled by the direct adaptive method. This control approach is used to reduce the impact of damage in the 3-story building. In the analysis of the structure, some stiffness reduction is assumed as a result of potential damage in different stories of the building. The controlled damaged structure responses under different ground motions are presented and compared with the uncontrolled damaged structure behavior. The goal of the adaptive control method in this research is to force the damaged structure to behave like an undamaged structure which performs acceptably. The effectiveness of this method in controlling the MR dampers is then verified.

SUMMARYThis paper describes a proposed methodology, referred to as probabilistic seismic control analysis, for the development of probabilistic seismic demand curves for structures with supplemental control devices. The resulting curves may be used to determine the probability that any response measure, whether for a structure or control device, exceeds a pre-determined allowable limit. This procedure couples conventional probabilistic seismic hazard analysis with non-linear dynamic structural analyses to provide system speciÿc information. This method is performed by evaluating the performance of speciÿc controlled systems under seismic excitations using the SAC Phase II structures for the Los Angeles region, and three di erent control-systems: (i) base isolation; (ii) linear viscous brace dampers; (iii) and active tendon braces. The use of a probabilistic format allows for consideration of structural response over a range of seismic hazards. The resulting annual hazard curves provide a basis for comparison between the di erent control strategies. Results for these curves indicate that no single control strategy is the most e ective at all hazard levels. For example, at low return periods the viscous system has the lowest drift demands. However, at higher return periods, the isolation system becomes the most e ective strategy.

A main goal of supplemental control devices is to manage the energy dissipation in the system. Resettable devices have emerged as a promising control device for application to civil structures as they are effective energy dissipators. This paper presents an investigation of the ability of semi-active control methods utilizing resettable devices to mitigate structural response in the presence of hysteretic, geometric and yielding nonlinearities under various intensity level seismic hazard suites to define control efficacy and seismic hazard statistics. A major component of this research is to assess the effect of device placement on control benefit. Results show that resettable devices limited to realistic peak force/dissipation levels of $13% building weight are effective at limiting permanent deflections and indicate the importance of zero tracking for nonlinear systems. However, floor accelerations rise significantly as displacement is limited, and the performance improvement is not the same for all ground motions. Owing to predominantly firstmode response of the case study structure, peak and permanent drifts saw larger reductions as more device authority was placed at the base of the structure, although the best overall results distributed device authority roughly proportional to the structural storey shears.As the sign of the velocity values at time steps before and after the stationary point will be different, a simple sign comparison will effectively detect the stationary point. The control law