Earthquake Engineering & Structural Dynamics最新文献

Repairs were carried out on a full-scale, single-story specimen of a traditional Ottoman-period Greek structure, comprising a stone masonry wall with timber ties and three timber-framed ones with fired clay brick infill, which had been subjected to biaxial shaking table tests. The connection between the walls was enhanced, as was the roof-level diaphragm. The timber-framed walls were clad with plywood panels and the cracks in the stone wall were repaired. The repaired specimen was then subjected to biaxial seismic tests, while its dynamic characteristics before and after seismic testing were determined with sine sweep tests. The repaired specimen safely withstood 22% increased base acceleration (0.44 g compared to 0.36 g for the As-built one), with damages concentrating in the stone wall, while the rocking mechanism of the timber-framed ones changed.

To study the seismic behavior of horizontal-hole interlocking concrete block-confined masonry walls with openings, in-plane cyclic loading tests were conducted on specimens with no openings, a window opening, and a door opening. The results indicated that the specimens with no openings and window openings exhibited typical diagonal shear failures of the entire wall. However, the structure and bearing mode were changed by including a door opening. The door-opening specimen could no longer be analyzed as an entire confined masonry wall owing to its lateral resistance and failure modes. The tie columns on both sides and the adjacent masonry formed wall columns, and the lintel beam and masonry above the opening formed a wall beam. Under a horizontal force, localized shear failure occurred in the wall beam, which resembled the shear failure of the coupling beam of double-limb shear walls and was an expected failure mode. Finally, this study proposes a new method for analyzing the lateral resistance of confined masonry walls with openings, called the force transmission path method, with a maximum calculated difference of 8.51%. This reflected the lateral resistance contribution of the reinforced concrete lintel beams.

Free rocking isolation systems (FRIS), characterized by negative post-uplift stiffness, have demonstrated favorable seismic performance such as resonance avoidance and gravity-driven self-centering (SC); however, a key design challenge lies in simultaneously ensuring sufficient deformability of the rocking isolation story while effectively mitigating the seismic demand on the superstructure. To address this challenge, this study investigates controlled rocking isolation systems (CRIS) with flag-shaped (FS) hysteretic devices. An analytical model is developed for elastic single-degree-of-freedom (SDOF) oscillators (representing elastic low-to-medium rise frames) fixed on CRIS with FS hysteresis. A practical application using NiTi shape-memory alloy (SMA)-based rocking columns is proposed to realize the intended FS behavior. The analytical model is validated through comparisons with a newly developed finite element model in OpenSees. Dimensional analysis is employed to reduce the number of governing variables in the equations of motion, thereby facilitating the identification of fundamental similarities in seismic responses across different structural scales and loading conditions. Both case-to-case and statistical comparisons confirm the accuracy of the proposed model. Based on the validated model, parametric studies are performed to examine the effects of varying FS hysteretic parameters and seismic input characteristics on the structural seismic performance. The results further confirm that CRIS exhibit enhanced dynamic stability relative to FRIS. Furthermore, it is possible to achieve a balance between controlled rocking and minimized superstructure demand for CRIS with FS hysteresis.

Due to the structural parameters diversity, material attributes nonlinearity, and ground motions uncertainty, predicting the elastic-plastic seismic response of columns is challenging and crucial, particularly in near-fault areas where significant damage can occur. Traditional machine learning (ML) models have demonstrated powerful capabilities for predicting structural seismic demand. However, their difficulty in accurately capturing latent system nonlinearity and the challenges associated with quantifying the impact of pulse effects on structural seismic demand complicate their application in practical engineering. This study proposes an efficient, high-precision, and highly interpretable physic-law-integrated neural network (PLNN) method. It introduces a novel physic-law model (PLM), which establishes the relationship between the normalized period (pulse to structural fundamental period ratio) and seismic demand. In addition, this research examines and quantifies the effects of column properties and pulse attributes on the characteristic coefficients of the PLM using an artificial neural network model (ANN). This method provides a PLNN model for estimating seismic demand based on the structural parameters, material attributes, and seismic characteristics by integrating the ANN model with the PLM. The ability and stability of the PLNN are evaluated by comparing its prediction performance with that of a traditional ML model. The results indicated that the proposed PLNN model maintains high prediction accuracy and significantly enhances computational efficiency. The PLNN model in this research requires 10 neurons to achieve optimal fitting goodness, one-third of the number required by the corresponding ANN model. In addition, the accuracy of the PLNN model is twice that of the ANN model in small sample settings, indicating the stability of the PLNN.

As one of the most widely implemented passive control systems in structural engineering, Tuned Mass Dampers (TMDs) require precise parameter tuning to maintain optimal performance. However, the incorporation of motion-limiting stoppers introduces nonlinear effects that alter the system's inherent frequency and damping characteristics, ultimately leading to detuning and compromised control effectiveness. To address this issue, a TMD with piecewise stiffness-damping (PSDTMD) is proposed to optimize the TMDs with limiting stoppers. Numerical simulation results indicate that the classical linear method fails to design the PSDTMD parameters. Considering the nonlinearity of the PSDTMD, the decoupled motion equation for the PSDTMD is first obtained, and then its frequency response equation is analytically derived using the averaging method. By determining the frequency that maximizes the displacement of the PSDTMD, the analytical optimal frequency ratio is derived from the frequency response equation, and the optimal damping is discussed through comparisons with the classical linear design. Furthermore, the effectiveness of the PSDTMD using the novel design method is investigated using a single-degree-of-freedom (SDOF) structure and a nine-story benchmark structure. The control performance of the PSDTMD designed by the novel method is compared to that designed by the classical linear method. Results show that the control performance of the PSDTMD designed by the novel method is greatly improved. Besides, results show that the PSDTMD can significantly reduce the tuned mass stroke compared to the conventional TMD. In conclusion, the novel design method can consider the adverse effects of the viscoelastic motion-limiting stoppers and improve the control performance of TMDs, which is meaningful for the engineering application of TMDs.

Step-back buildings, characterized by a stilted story with columns of varying lengths, are prevalent in mountainous regions. These different vertical components often result in uneven structural stiffness, both vertically and laterally, which affects the seismic performance of these structures. This study investigates the seismic performance of step-back reinforced concrete (RC) frame structures through experimental tests and numerical simulations. Shaking table tests were conducted on two 1/8-scale models: one representing a step-back RC frame and the other a conventional structure. The comparison focused on failure patterns, dynamic properties, and structural responses, including acceleration, deformation, torsional effects, and story shear. The results show that the superstructure of the step-back structure model suffers more severe damage with a partial column hinge failure mechanism. The damage to columns in the stilted story and the first story of the superstructure is uneven. In particular, the torsional response of the stilted story is particularly significant. The shear force in the stilted story increases significantly, indicating an apparent redistribution of internal forces. Moreover, a 3D numerical simulation model of the tested step-back structure was established and validated. The influence of lateral stiffness in the stilted story on the seismic response was investigated. The results show that the reduced lateral stiffness in the stilted story leads to a reduced internal force redistribution of columns in the stilted story, with seismic damage being shifted downwards and concentrated in the shortest column. The torsional effect tends to increase, which may be due to the reduced torsional stiffness of the stilted story. More research is needed on the effect of torsional stiffness or related indicators on the torsional effect of step-back structures.