Earthquake Engineering & Structural Dynamics最新文献

Real-time hybrid simulation (RTHS) inherently functions as a feedback system with intrinsic time delays, which can be accurately modeled using a delay differential equation (DDE). The presence of time delays introduces infinite-dimensional dynamics, complicating the analysis of associated errors. While time delay represents a key experimental imperfection, its quantitative influence on structural vibration remains insufficiently understood. To address this gap, we propose a spectral decomposition framework for linear RTHS systems. This method decomposes the delay system into a finite set of single-degree-of-freedom (SDOF) systems, enabling systematic analysis of delay-induced effects, including frequency shifts, spurious mode generation, and energy redistribution. We establish explicit relationships linking time delay to substructural partitioning and excitation characteristics. Based on these insights, we propose three error mitigation strategies: (1) minimizing actuator delay, (2) reducing the experimental substructure ratio, and (3) optimizing spectral alignment between external excitation and system response. Additionally, we introduce two energy-based evaluation metrics—with corresponding tolerances—to quantify the influence of time delay on total energy input and the modal concentration of input energy. The effectiveness of the proposed approach is validated through numerical simulations and physical experiments, offering novel insights into RTHS error mechanisms from modal and energetic perspectives.

Summary

Reducing residual deformation or earthquake loads on the frame structure can enhance its seismic performance during ground motions. This study explores a novel system that uses a self-centering brace (SCB) to provide the re-centering capability of the frame and a sliding slab to reduce the system's acceleration. The floors are allowed to slide with respect to the re-centering steel frame by adding low-friction Teflon sheets, while various horizontal energy dissipating devices are used to enhance the seismic response of the frame. A self-centering disc-spring device is added to re-center the slab after sliding in Phase 1. In addition to the spring device, a friction device in Phase 2 or a steel-only sandwiched buckling-restrained brace in Phase 3 is incorporated. The floor is “rigidly” connected to the frame in Phase 4, simulating a typical frame construction. Four phases, comprising 32 shaking table tests, were conducted on the specimen. A near-fault motion record from the 2022 Guanshan and Chihshang earthquake was used. Phase 1 tests demonstrated that the SCB and horizontal disc-spring device could fully re-center both the frame and sliding slab at the maximum-considered earthquake (MCE) level. In Phases 2 and 3, the addition of horizontal energy dissipating devices to the frame reduced slab movement but resulted in higher floor acceleration compared to Phase 1 tests. Compared to Phase 4, the effect of the sliding slab caused a roof drift reduction of 23% and 18%, and a base shear reduction of 15% and 5%, in Phases 2 and 3, respectively.

Summary

Pipeline vibrations are a major contributor to structural fatigue and leakage incidents, resulting in significant economic losses and environmental hazards. Particle dampers have demonstrated strong effectiveness in suppressing pipeline vibrations. However, existing research on pipeline vibration control has largely overlooked the impact of the placement of particle dampers, limiting their practical engineering applications. To address this challenge, the multi-cavity particle damper (MPD) with high damping effect is taken as the research object. A mechanical model of an MPD-controlled pipeline incorporating placement effects was first developed, alongside an innovative simulation methodology. Subsequently, horizontal vibration control tests were conducted to validate the accuracy of the mechanical model. The effects of MPD parameters and placement on the damping performance were then investigated, and the optimal parameters and placement were obtained. Finally, an optimization design process was proposed for MPD-controlled pipelines under multi-modal broadband excitation. The results indicate that MPDs exhibit a significant damping effect under resonant excitation, achieving a damping rate of up to 97.31%. Additionally, adjusting the placement of MPDs can effectively enhance damping performance under non-resonant excitation. By optimizing MPD parameters and placement under low-order modal broadband excitation, the performance of MPDs under multi-modal broadband excitation can be significantly improved. The proposed optimization design process provides a scientific basis for designing MPD-based vibration control solutions for pipelines operating under complex conditions.

Summary

Resonance in actuator dynamics poses critical instability and control challenges, particularly in real-time hybrid simulations (RTHSs). During rapid control, unintended resonance can induce instability, thereby compromising the accuracy of the experimental outcomes. Servo-hydraulic actuators—implemented in RTHS for their robust actuation capabilities—are inherently prone to oscillations resulting from the oil-column compressions, leading to contamination in the measurements with resonant frequencies. Traditionally, mitigating this issue required extensive tuning of control parameters, which demanded significant time and effort. To resolve the above-mentioned control challenges, a novel design method for a minimum phase finite impulse response notch (MPFN) filter is proposed. The performance of the MPFN filter in resonance suppression is thoroughly validated through numerical simulations, RTHS using an electromagnetic linear actuator, and experimental applications with servo-hydraulic actuators. The results demonstrate that the proposed MPFN filter not only eliminates the need for exhaustive control parameter tuning but also enhances experimental performance across all tested conditions, ensuring improved stability and accuracy in a wide range of experimental settings.

Summary

Real-time hybrid testing (RTHT) is an effective approach for obtaining the dynamic response of large and complex structures, but achieving real-time performance is highly challenging. In recent years, an offline RTHT method has been proposed, where the loading of the experimental substructure and the computation of the numerical substructure are performed independently. Compared to conventional online RTHT, offline RTHT demonstrates significant advantages in terms of accuracy, stability, and cost. In the scenarios involving multiple experimental substructures, it can further reduce the cost of the testing system. However, the existing offline RTHT methods are primarily employed in single experimental substructure scenarios and have difficulties being applied in multiple experimental substructure scenarios. In this study, a Time History Iteration (THI) method and an Accelerated Time History Iteration (ATHI) method are proposed for application in offline RTHT involving multiple experimental substructures. System identification and virtual iteration are performed to accelerate the iteration process. The proposed methods are validated through offline RTHTs for a dual-TMD wind resistance problem. The test results demonstrate that the proposed THI method enables the reuse of the same testing equipment and specimen in offline RTHT. Meanwhile, the proposed ATHI method significantly accelerates the convergence process while ensuring stability and accuracy.

Summary