Earthquake Engineering & Structural Dynamics最新文献

This work evaluates how the dynamic response of the tuned mass damper (TMD) systems changes following the insertion of suitable displacement limiters. The systems, pounding tuned mass damper (PTMD), use the tuned mass to absorb the kinetic energy from the main system and dissipate it through the TMD damper and the impacts with the bumpers. Through numerical analyses, an optimal bumper design procedure is introduced; the effectiveness of the PTMD systems subjected to harmonic excitations at the base is evaluated, both for conventional and unconventional mass ratios; it is evaluated under which conditions the PTMD systems are more effective than the TMD systems; finally, the robustness of these systems to both TMD and bumpers parameters is investigated. The main results obtained have shown that (i) inserting bumpers to an optimally designed TMD does not lead to a more effective mitigation system; (ii) in those cases where optimally realizing a TMD can be complicated, or there are design constraints, the insertion of bumpers can bring significant increases in effectiveness; (iii) all the systems analyzed have shown an increase in effectiveness as the mass ratio of the TMD increases, up to a critical mass ratio after which losses in effectiveness are recorded; (iv) the analyses on the robustness of the PTMD systems have shown that such systems have good robustness both to TMD and bumpers parameters, highlighting how the parameter to which such systems are most sensitive are the distance between the auxiliary mass of the TMD and the bumpers.

Prior studies have demonstrated that walls implementing unbonded post-tensioned (PT) tendons can provide an effective solution to achieve a low-damage design objective. The wall-to-floor connection is crucial for the floor to achieve the low-damage performance requirements, and wall-to-floor interaction can also alter the lateral load transfer and overstrength actions that develop in the system. To validate low-damage concepts and connection detailing, a two-storey PT concrete wall building with both flexible and isolated wall-to-floor connection designs was recently subjected to shake-table tests. The design of the flexible connections aimed to transfer lateral loads while accommodating wall uplift with a link slab or composite floor. The isolated connections were designed to decouple the floor from the uplift and rotation of the wall to minimise the damage to the floor while transferring forces in the horizontal direction. The behaviour of these wall-to-floor connections was investigated in this paper with consideration of several performance criteria. Key objectives of this investigation of the two wall-to-floor connections included: (1) summarise the observed performance and damage states; (2) quantify the deformation responses; and (3) investigate the force transfer and acceleration responses. Test results confirmed that both the flexible and isolated connections effectively addressed deformation compatibility in the system. The flexible connection primarily accommodated wall uplift by developing narrow cracks that were distributed within the floor. The isolated connection allowed lateral load transfer without imposing deformations on the floor. The acceleration responses of the two connections exhibited different trends. The integral design of the flexible connection ensured that forces were fully transferred from the wall to the floor with consistent acceleration responses, while the isolated connection partially released the transfer mechanism, with only horizontal and vertical accelerations with low-frequency components transmitted through the connection.

This study demonstrates that seismically isolated buildings incorporating a quasi-zero stiffness device and tuned inerter damper (SQT) system mitigate displacement and acceleration responses, confirming the feasibility and robustness of this passive seismic control strategy. We propose design equations for the tuned inerter damper in an SQT system. To gain fundamental insights, we model the SQT system as a two-degree-of-freedom system and examine it from both theoretical and experimental perspectives. A theoretical solution for sinusoidal excitation is derived to provide a general understanding. A shaking table test validates the theoretical solution and confirms the SQT system's effectiveness in damping the earthquake response. Close agreement between the numerical and experimental results indicates that the theoretical model accurately predicts amplitude-frequency curves. The test results show that the SQT system limits the displacement response to be within the criterion and reduces the acceleration response to levels comparable to conventional seismic isolation under sinusoidal and earthquake excitations.

The hybrid testing based on restart loading technology (HT-RLT) was developed in recent years, which enables the refined model calculation of the numerical substructure possible for the real-time hybrid testing (RTHT). However, for multiple experimental substructures in the RTHT, the HT-RLT still encounters high requirement of multiple loading equipment and the technical challenges of synchronization among loading equipment. For solving this problem, a hybrid testing based on multi-task overall restart loading technology (HT-MORLT) is proposed in this paper. This method achieves the loading of multiple experimental substructures one by one by means of multiple rounds of overall restart technology on a single agent specimen. Furthermore, for solving the experimental duration problem, a hybrid testing based on multi-task partial restart loading technology (HT-MPRLT) is proposed. This method achieves the loading of multiple experimental substructures one by one by means of multiple rounds of partial restart technology on a single agent specimen. The accuracy and effectiveness of the proposed HT-MORLT and HT-MPRLT are verified through numerical simulations and experiments on one three-story steel frame structure equipped with three viscous dampers. The numerical and experimental results show that both the HT-MORLT and the HT-MPRLT can achieve high-precision loading and reset-waiting operations for multiple experimental substructures. The correlation coefficients under all working conditions are above 96%, indicating that the two methods have high experimental accuracy. Moreover, the results also show that the HT-MPRLT can effectively improve the experimental efficiency by 50% compared to the HT-MORLT.

Rubber-based devices have been widely employed in base isolation systems to safeguard essential facilities, demonstrating exceptional effectiveness under extreme lateral demands. Elastomeric isolators are designed to achieve a high vertical-to-horizontal stiffness ratio while maintaining stability at significant lateral displacements. However, isolating lightweight structures with these devices poses challenges, as they require relatively high vertical pressures to sufficiently shift the fundamental vibration period while ensuring stability under large deformations. Moreover, rubber degradation over time necessitates periodic, labor-intensive maintenance, leading to elevated long-term costs associated with bearing replacements when aging impairs performance. This paper introduces a novel elastomeric base isolation concept: the Multi-Stage Fiber-Reinforced Bearing (MS-FRB) system. In this innovative approach, multiple Fiber-Reinforced Bearings (FRBs) operate in series under shear loads, enabling substantial deformation capacity through the sequential engagement of slender rubber-based isolators. This configuration allows precise tuning of the isolation layer's vertical and horizontal stiffnesses to accommodate varying seismic hazard levels, effectively adapting the response of rubber-based bearings to multiple earthquake intensities. A comprehensive parametric three-dimensional finite element analysis is conducted on bearings with diverse geometric and mechanical parameters, evaluating MS-FRB performance under different vertical pressures, bearing shapes, and both uni- and bi-directional shear loading. The system's efficacy is further assessed under realistic earthquake conditions via full 3D finite element models of two case-study structures: low-rise, lightweight reinforced concrete frames with and without masonry infill. Results are compared to fixed-base configurations and those isolated with stable unbonded FRBs, highlighting the MS-FRB's superior ability to protect structures that are typically challenging for conventional rubber-based isolation. This work advances the application of rubber-based devices for seismic protection, particularly in lightweight or heavyweight essential facilities, and provides a proof-of-concept for the design and behavior of MS-FRBs under combined axial and shear loads.