Seismic performance of high-rise segmented rocking truss steel frame with multiple tuned mass dampers

High-rise buildings in seismically active regions face a critical engineering challenge: traditional seismic design approaches often struggle to control complex vibration patterns that can lead to catastrophic damage during major earthquakes. But the traditional rocking truss mainly controls the damage distribution of the structure according to the first-order vibration mode, which has limited applicability to high-rise structures.

A research team led by Professor Zhi-Qian Dong at Dalian University of Technology has proposed a solution: a steel frame-segmented rocking truss-MTMD damping system. The system divides rocking structures into multi-segment trusses along the vertical direction, allowing deformation along multiple mode shapes while arranging MTMDs based on system vibration characteristics without increasing frame lateral stiffness.

The research focused on a 35-story steel frame structure with a total height of 140 meters, analyzing single-segment, double-segment, and triple-segment rocking truss configurations under severe earthquake conditions. The team investigated critical parameters including segmentation number and position, lateral stiffness ratios between the frame and rocking truss, MTMD mass ratios and placement locations, and the effects of velocity-dependent dampers and self-centering energy-dissipative braces.

The findings reveal that the segmented rocking truss system offers several distinct advantages over conventional designs. The segmentation effectively reduces the maximum bending moment in the middle of the rocking truss. By introducing hinged joints between segments, the system allows each rocking truss segment to deform along multiple mode shapes, significantly reducing internal forces while maintaining structural integrity.

The integration of multiple tuned mass dampers arranged according to the system's vibration mode represents another innovation which can reduce the structure's maximum inter-story drift ratio by 7% to 29%. The researchers found that placing MTMDs at the top of the structure—where deformation of the first three vibration modes is largest—proves more effective than locating them at segment joints. With a mass ratio of just 1%, the MTMDs achieved an 8.5% reduction in maximum inter-story drift under certain ground motions, while a 4% mass ratio delivered average vibration reduction rates of 19.5% at the top.

Additional energy dissipation is provided by velocity-dependent dampers, which the study found particularly effective. "Compared with self-centering energy dissipation braces, velocity-dependent dampers provide no additional stiffness and can dissipate seismic energy effectively," the researchers reported. Installation of these dampers reduced maximum inter-story drift ratios by 53% to 59% and decreased roof displacements by 24% to 37% under various earthquake scenarios.

The research also explored variable stiffness designs for segmented rocking trusses, demonstrating that upper segments can use smaller cross-sections than lower segments without compromising seismic performance. This approach significantly reduces overall structural weight and steel consumption while maintaining effective lateral deformation control. The system's self-centering energy-dissipative braces, installed at each rocking truss segment base, further reduce residual structural deformation after earthquakes, facilitating faster post-earthquake recovery. This system is particularly well-suited for high-rise structures where higher-order modes play a significant role. Through incremental dynamic analysis (IDA) and vulnerability analysis, the results show the seismic performance of controlled structures is significantly better than that of uncontrolled structures.

The segmented structural design effectively minimizes the impact of higher-order modes on internal forces and stress concentrations in the sway wall structure. Each sway wall segment can be designed and constructed independently based on its specific location and structural characteristics, making maintenance more convenient and flexible compared to a monolithic sway wall.

The research team expects this innovative system to provide a practical and efficient solution for high-rise building seismic design, particularly in regions with high seismic risk. Future work will focus on optimizing the integration of these various damping mechanisms and further refining the vulnerability analysis of relevant influencing factors. The ultimate goal is to develop standardized design methodologies that can be readily implemented in engineering practice, making tall buildings more resilient against earthquakes while maintaining economic feasibility.

Other contributors to this research include Hao Wu, Yi-Zhang Chai, Qing-Tao Meng from Dalian University of Technology, Hui-Dong Liu from China Construction Third Engineering Bureau Group, and Yi Zhao from Guangxi University and Rice University.

This research was supported by the Open Project Program of Guangdong Provincial Key Laboratory of Intelligent Disaster Prevention and Emergency Technologies for Urban Lifeline Engineering, and the Opening Funds of State Key Laboratory of Building Safety and Built Environment & National Engineering Research Center of Building Technology.