Comparison and analysis of seismic isolation, energy dissipation structure and traditional seismic structure

This paper uses SAP2000 finite element software to perform nonlinear time history analysis of nine structural systems, and compares the period, total floor displacement, base shear force, vertex displacement, and top acceleration of the structure under the action of an 8-degree rare earthquake. The research results show that seismic isolation and damping technology can effectively reduce the impact of earthquakes on structures.

Rare Earthquake Swarm Strikes Puerto Rico

Puerto Rico hasn’t seen this many strong quakes in a single sequence since seismic monitoring began 46 years ago. The last earthquake to damage the island this badly occurred in 1918.

Dynamic Nonlinear Analysis of an Irregular Office Building

The common analysis methods of structural building include the response spectrum, static nonlinear analysis (pushover) and dynamic nonlinear analysis method. Meanwhile, for the analysis of irregular structures, dynamic nonlinear analysis method could accurately simulate the seismic response of structure under rare earthquake. In this paper, the dynamic nonlinear analysis was carried out to evaluate the seismic performance of an office building with irregular in plan and in elevation. The simulation results show that the maximum inter story-drift angle can satisfy the requirement in the nation code. Few shear walls exceeded the concrete yield compressive stress and most of the shear walls remained in the elastic stage. Most frame columns were within the component acceptance criterion of IO. By the above analysis results, it can be judged that the seismic capacity of the building structure can reach the seismic performance objectives in the code.

Retrofit Existing Frame Structures to Increase Their Economy and Sustainability in High Seismic Hazard Regions

The study proposes a retrofitting method with an optimum design of viscous dampers in order to improve the structural resistant capacity to earthquakes. The retrofitting method firstly uses a 2D frame model and places the viscous dampers in the structure to satisfy the performance requirements under code-specific design earthquake intensities and then performs an optimum design to increase the structural collapse-resistant capacity. The failure pattern analysis and fragility analysis show that the optimum design leads to better performance than the original frame structure. For regular structures, it is demonstrated that the optimum pattern of viscous damper placement obtained from a 2D frame model can be directly used in the retrofitting of the 3D frame model. The economic loss and repair time analyses are conducted for the retrofitted frame structure under different earthquake intensities, including the frequent earthquake, the occasional earthquake, and the rare earthquake. Although the proposed method is based on time-history analyses, it seems that the computational cost is acceptable because the 2D frame model is adopted to determine the optimum pattern of viscous damper placement; meanwhile, the owner can clearly know the economic benefits of the retrofitting under different earthquake intensities. The retrofitting also causes the frame to have reduced environmental problems (such as carbon emission) compared to the original frame in the repair process after a rare earthquake happens.

SHAKING TABLE TESTS ON HAUNCH RETROFITTED REINFORCED CONCRETE FRAMES

Shaking table tests were performed on five one-third reduced scale two storey reinforced concrete (RC) moment resisting frames having construction defects (using low strength concrete without confining ties in beam-column joints, larger tie spacing, and reduced longitudinal and transverse reinforcements). The deficient frames were observed to have severe joint damageability, resulting in joint panel cover spalling and core concrete crushing. Haunch retrofitting technique was adopted to upgrade the seismic behaviour of deficient RC frames. Additional four deficient RC frames were built and retrofitted with steel haunch; both axially stiffer and deformable with energy dissipation, fixed to the beam-column connections to reduce shear demand on joint panels. The as-built and retrofitted frame seismic response modification factor (R) was calculated and compared to evaluate the viability of the haunch retrofitting technique. The haunch retrofitting technique increased the lateral stiffness and strength of the structure, resulting in the increase of structure overstrength. The retrofitting increased R factor by sixty percent to one hundred percent. The presented results indicate that the technique can significantly enhance the seismic performance of deficient RC frames, particularly against the frequent and rare earthquake events.

Seismic Performance of the Pre-Fabricated Steel Frame Infilled with AAC Wall Panels and their Joint Connection: Full-Scale Shaking Table Test

A series of shaking table tests were performed to investigate the seismic behavior of the pre-fabricated steel frame structure infilled with autoclaved aerated concrete (AAC) external wall panels. The reliability of a new type of joint connections adopted in the structure between the steel frame and the wall panels was particularly validated during the test. Dynamic tests were carried out on a two-story full-scaled steel frame, considering seismic loading of three earthquake waves with different imposed peak accelerations in the range of 70[Formula: see text]cm/s2 to 400[Formula: see text]cm/s2. The experimental analyses encompassed cracking patterns, failure mechanisms, dynamic property and seismic response of the structure. The results show that the structural components, including the joint connections between the steel frame and the walls, behaved well even under the rare earthquake at 8∘. The structural stiffness of the steel frame infilled with wall panels was increased by 56%, compared with the steel frame infilled without wall panels. The damping ratio of the undamaged steel frame installed with wall panels was 7.25%.

Seismic Response Reduction of Megaframe with Vibration Control Substructure

Megaframe with vibration control substructure (MFVCS) is a tuned mass damper system, which converts the substructures into the tuned mass. In this study, a kind of MFVCS using both lead-rubber bearings and viscous dampers to connect the vibration control substructure with the megaframe was proposed. Then, based on a validated finite element model, a parametric analysis was conducted to study the effect of two parameters, the tuning frequency (i.e., the frequency of the substructure) and the damping provided by the lead-rubber bearings and viscous dampers on the seismic response reduction of the MFVCS under both frequent and rare earthquakes (i.e., probability of exceedance of 63% and 2% in 50 years, resp.). Furthermore, the optimized values of these two parameters were achieved. The results indicated that (1) the proposed MFVCS could provide a considerable seismic response reduction under frequent earthquake and showed a strong robustness; (2) the optimized values of the frequency ratio (ratio of tuning frequency to the megaframe’s natural frequency) and damping scale factor (ratio between the investigated damping and a standard value) were 0.96 and 1.0, respectively; and (3) the seismic response reduction of the MFVCS under rare earthquake was lower than that under frequent earthquake.