Earthquake Engineering & Structural Dynamics最新文献

Viscoelastic (VE) dampers, known to be highly sensitive to temperature and excitation frequency, are widely used to mitigate structural vibrations of high-rise buildings induced by long-duration wind loading as well as long-period earthquakes. Recently, building employment of full-scale multilayered VE dampers is increasing as such devices can be made relatively easy due to the advancement of manufacturing technology. Despite this, there are few studies focused on such devices. To address this matter, the authors herein present their benchmark study on a full-scale VE damper subjected to long-duration excitation. Deformation-controlled dynamic tests were first carried out using random waveforms. The corresponding equivalent sinusoidal waveforms (determined using the previously proposed technique of the coauthors) of the random damper deformations were also used, and equivalence was experimentally verified. Numerical investigation was then carried out using the equivalent sinusoidal waveform and adopting a previously proposed method of combining static analysis and three-dimensional heat transfer analysis. By doing so, the behavior of the full-scale VE damper subjected to long-duration wind loading was better understood. In particular, the important role of heat transfer (i.e., heat conduction and heat convection) was discussed. Additionally, the authors address the lack of guidelines on conducting reduced-scale VE damper tests by proposing similarity rules. Based on the numerical investigations, the first-of-its-kind similarity rules produce precisely scaled behavior of VE dampers subjected to long-duration harmonic loading.

Due to the rocking effect, the majority of existing three-dimensional (3D) seismic isolators are applied to low-rise structures, and there are few studies conducted to investigate the seismic response of 3D base isolation structures (3D-BISs) featuring large aspect ratios. This study proposed a novel multi-dimensional earthquake isolation and mitigation device (denoted MEIMD), which was composed of a viscoelastic (VE) bearing, disc spring-damper elements (DSDEs), and rocking suppression elements (RSEs). Dynamic tests were conducted to reveal the mechanical property of the MEIMD under different excitation frequencies and displacement amplitudes. Then, to explore the seismic performance of the MEIMD and the rocking effect of the 3D-BIS, full-scale shaking table tests were implemented on a four-story frame structure under one-dimensional (1D) and 3D ground motion excitations. The results demonstrate that, compared to the fixed-base structure, employing the MEIMD significantly reduced the horizontal accelerations, and this isolation effect primarily stemmed from a coupled horizontal-rocking motion mode. The MEIMD ensured a nearly vertical translational motion mode for the superstructure, thereby effectively mitigating the out-of-plane vibrations of floor slabs. Compared to that under 1D excitations, the overall isolation effect of the MEIMD was weakened under 3D excitations, which was ascribed to the aggravated coupling between horizontal and vertical motions of the seismic isolation interface. Finally, a simplified analytical model is established for the 3D-BIS, and good agreement is found between analytical solutions and test results.

This study revisits the damage and collapse of Daikai station during the 1995 Kobe earthquake using a coupled porodynamic peridynamic approach. By integrating the strengths of non-ordinary state-based peridynamics (PD) for modeling structural localized discontinuities and the finite element method (FEM) for field-scale soil layers and fluid flow, this approach provides an integrated framework for simulating both the damage and collapse of the station and the liquefaction of surrounding soils. An elastic-brittle model is used for the station, while the liquefiable sand is modeled with a plasticity model named CycLiq. A staggered solution scheme is proposed to enhance computational efficiency. The model is validated through the simulation of three numerical examples: a one-dimensional (1D) dynamic consolidation problem, a centrifuge shaking table test involving liquefaction, and the Kalthoff–Winkler test for dynamic fracture. The application of the coupled porodynamic peridynamic approach in simulating the seismic response of Daikai station reveals that liquefaction played a critical role in triggering horizontal displacements and structural failure. The drift ratio of the center column increased significantly after 3 s of seismic shaking, leading to complete collapse when it exceeded 1.0%. Initial cracks appeared in the side walls and ceiling slab, while severe damage to the center column caused the overall collapse. Two significant diagonal cracks in the center column, located at approximately 1/6 and 5/6 of its height, indicate structural collapse. Roof cracks were primarily tensile, while side wall cracks exhibited mixed tensile-shear behavior. The center column failed in a compression-shear mode under large bending moments and pressure from the overlying soil.

In nuclear power plant (NPP) structures, equipment and pipelines are all anchored to shear walls using embedded parts. The shear walls with embedded parts may suffer cracks and potential structural damage under earthquakes due to stress concentrations. The individual mechanics of the embedded part or the shear wall had been investigated worldwide; however, comprehensive research on their coupled interaction has never been found. To address this deficiency, this study investigates the impact of suspended equipment on shear walls by integrating embedded parts and applying predetermined stresses. A novel quasi-static loading system and experimental procedure with out-of-plane localized loading are proposed to meet the experimental requirements. The system integrates multi-actuator coordinated control and a follow-up device that ensures real-time alignment of prestress direction, effectively addressing the challenges posed by combined in-plane and out-of-plane loading. A three-phase loading protocol is developed to simulate the dynamic interaction between the shear wall and anchored equipment during earthquakes. Experimental investigations of distribution analysis are conducted on five squat reinforced concrete (RC) shear walls with embedded parts, focusing on the combined effects of loading forms, position, and prestress of embedded parts on seismic performance. The results reveal that the placement of embedded parts exacerbates crack distribution and disrupts the hysteresis symmetry. As Embedded Part's Prestress (EPP) increases, the stiffness and strength of the shear walls decrease, leading to significant stress concentrations around the embedded parts and reinforcement yielding. Furthermore, wall damage significantly influences the performance of the embedded parts, and load-displacement analysis was conducted to quantitatively assess this damage. Additionally, shear stress application significantly influences reinforcement strain evolution, and appropriate embedded reinforcement stress can effectively modify the shear transfer mechanism. This study provides valuable insights into the design and regulation of NPP structures.

Museum artefacts experience significant rocking and may overturn and collapse under moderate-to-large magnitude earthquakes. Use of base isolation (BI) is a viable strategy to enhance the resilience of such artefacts. However, experimental studies aimed at further investigating the effects of ground motion parameters on the response of statues/busts with BI are still scarce. This study illustrates comprehensive shake table tests to demonstrate the efficiency and robustness of double concave curved surface slider isolators (DCCSSs) as viable means to protect museum artistic contents. Different geometries and weights of typical bust-pedestal systems were considered during the tests. Uni- and bi-axial records with varying amplitudes and frequency contents were considered as inputs. Using DCCSS significantly reduces peak accelerations on the isolated platform. Bidirectional input has a weak influence on the response of artefacts with BI. Typical seismological integral parameters were utilized as engineering demand parameters (EDPs) to quantify the seismic response of the BI system. The ratio of integral parameters for isolated platform and shake table is an effective measure to quantify the response of DCCSS. Dynamic modification factors (DMFs) and component amplification factors (CAFs) were also selected as response parameters for isolated and non-isolated components, respectively. For solid systems it was found that values of DMFs are lower than CAFs, which, in turn, are higher typically than 1.5. Ratios of CAF/DMF for hollow systems are higher than solid counterparts. Further numerical investigations are required to validate the reliability of the multiple response parameter analysis illustrated in this study, namely, peak quantities and integral parameters.