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Summary Stay cables used in cable‐stayed bridges are prone to vibration due to their low‐inherent damping characteristics. Many methods have been implemented in practice to mitigate such vibration. Recently, negative stiffness dampers have gained attention because of their promising energy dissipation ability. The viscous inertial mass damper (VIMD) has been shown to have properties similar to negative stiffness dampers. This paper examines the potential of the VIMD to enhance the damping, and mitigate the vibration, of stay cables. First, a control‐oriented model of the cable is employed to formulate a system level model of the cable–VIMD system for small in‐plane motion. After carefully classifying and labeling the mode order, the modal characteristics of the system are analyzed, and the optimal damper parameters for the several lower frequency modes are determined numerically. The results show that the achievable modal damping ratio can be up to nearly an order of magnitude larger than that of the traditional linear viscous damper; note that the optimal parameters of the VIMD are distinct for each mode of interest. These results are further validated through analysis of the cable responses due to the distributed sinusoidal excitation. Finally, a case study is conducted for a cable with a length of 307 m, including the design of practical damper parameters, modal‐damping enhancement, and vibration mitigation under wind loads. The results show that the VIMD is a promising practical passive damper that possesses greater energy dissipation capacity than the traditional viscous damper for such cable–damper systems.

Summary Outriggers are usually added in structural systems of tall buildings to collaborate central shear walls with peripheral columns. With outriggers, the structural overturning moment can be balanced, and the inter‐story drift can be controlled under horizontal loads. Therefore, the optimal location of outriggers plays a very important role in controlling the behavior of the whole building. Existing research has focused on the optimal position of outriggers on the base of the structural roof deflection. In the engineering practice, however, inter‐story drift is the most important target to control the design of tall building structures. This paper investigates the theoretical method of inter‐story drift‐based optimal location of outriggers. A Matlab program is written to perform the parameter analysis of optimal location of outriggers. Take a 240‐m tall building for a target building, the optimal location of one to three sets of outriggers under wind and earthquakes is obtained and can be utilized for the structural preliminary design of tall buildings. Copyright © 2015 John Wiley & Sons, Ltd.

A tuned mass damper (TMD) is one of the most used structural control devices. However, a traditional TMD has the disadvantage of high sensitivity to frequency deviation and difficulty adjusting the frequency. The optimal frequency for a TMD is dependent on the structural dominant frequency and the TMD mass ratio. Nevertheless, the actual structural modal mass is difficult to obtain, and the presence of a TMD may interfere with identification of the natural structural frequency. Aiming to control wind-induced vibration, an adaptive-passive retuning device is developed for a pendulum TMD called an adaptive-passive variable pendulum TMD (APVP-TMD). When it is time to adjust the pendulum, the mass will first be locked, and the structural frequency in this case is identified through wavelet transformation by an acceleration sensor and a microcontroller. It is found that this is actually the optimal frequency for the TMD. Then, a stepper motor will adjust the length of the pendulum under the guidance of the microcontroller. The effectiveness of APVP-TMD is verified through both discrete and continuous models. For the discrete model, a single-degree-offreedom primary structure coupled with an APVP-TMD is presented as an experiment with analysis comparison, and a five-degree-of-freedom primary structure coupled with an APVP-TMD is proposed as a numerical simulation. For the continuous model, a wind-sensitive concrete chimney is controlled by an APVP-TMD as a case study. The results all show that the APVP-TMD can identify the optimal frequency and retune itself effectively, and the retuned TMD has better vibration control than the mistuned one.

The increasing need to reduce damage and downtime in modern buildings has led to the development of a low-damage design philosophy, where the earthquake loads can be resisted with damage confined to easily replaceable components. Post-tensioned (PT) concrete walls have emerged as a popular lowdamage structural system that have been implemented in a range of buildings. In order to provide essential evidence to support the development of lowdamage concrete structures, a system-level shake-table test was conducted on a two-storey low-damage concrete wall building implementing state-of-art design concepts. The test building included PT rocking walls that provide the primary lateral-load resistance in both directions, a frame that utilized slotted beam connections, and a range of alternative energy dissipation devices that were installed at wall base or/and beam-column joints. The building was subjected to 39 tests with a range of intensity ground motions, incorporating both unidirectional and bidirectional ground motions on the structure with different combinations of wall strength and energy dissipating devices. The building performed exceptionally well during the intense series of tests, confirming the suitability of both the design methods and the connection detailing implemented. The building achieved an immediate occupancy performance objective even when subjected to maximum considered earthquake hazard shaking. The building exhibited only minor damage at the conclusion of testing, with distributed cracking in the floors and cosmetic spalling in the wall toes that did not compromise structural capacity or integrity and could be easily repaired with minimal disruption.The test has provided a rich dataset that is available for further analysis of the building response and validation of design methods and numerical models.

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A novel damping outrigger system is proposed for tall buildings by replacing the diagonal members with buckling restrained bracings. To investigate the conceptual design of the system, a simplified mechanical model for the outrigger system is first put forward in this paper. Four configurations of outriggers, which are commonly used in practical engineering, are compared from the aspects of stiffness, strength, and energy-dissipating capacity. The damping outriggers of the best configuration with buckling restrained braces acting as diagonal web members of outriggers are then proposed. The effect of the system on the whole structure is demonstrated through a 632-m-tall building. The results indicate that the damping outrigger can serve as stiffness member under the frequently occurred earthquakes and energy dissipating member under the rarely occurred earthquakes to protect the main structure from severe damages.

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