Bulletin of Earthquake Engineering最新文献

This study presents an integrated approach for the seismic assessment of the 13th-century San Michele Arcangelo Cathedral Bell Tower in Caserta Vecchia, Italy, utilizing a detailed photogrammetric survey and Finite Element (FE) modelling. The analysis focuses on the structural vulnerability and seismic response of the historical masonry tower to assess its response against earthquake-induced damage. By employing Ambient Vibration Tests (AVTs) present in literature and calibrating the FE model accordingly, the research identifies the principal vibrational modes and natural frequencies of the tower, enhancing the model's accuracy. Various earthquake intensities were inputted to the structural model to evaluate the bell tower's structural performance and potential collapse mechanisms. The findings reveal a significant susceptibility of damage under severe seismic conditions, emphasizing the critical need for tailored conservation strategies to preserve such irreplaceable cultural heritage. The study underscores the importance of integrating historical documentation, structural analysis, and modern engineering techniques to safeguard historical architecture in seismically active areas.

Our study focuses on predicting topographic amplification of ground motion in the near-source region, where seismic rays reach the free-surface at varying incidence angles. We rely on data from previous 3D numerical simulations conducted on a topographic relief with a homogeneous medium. First, using neural networks, we identify which key parameters, describing the geometric characteristics of the relief relative to the seismic source position, control ground motion amplification. Then, we determine the functional form that relates these parameters to the simulated amplifications. Subsequently, we conduct a regression study to develop a model of topographic amplification, referred to as the i-FSC proxy (Illuminated Frequency-Scaled Curvature). Our estimator depends on the frequency-scaled (1) curvature, a parameter that accounts for the occurrence of amplifications over convex topographies and de-amplification over concave ones; (2) normalized illumination angle, a newly defined parameter that quantifies the slope exposure to the incoming wavefield, accounting for high amplification on slopes oriented opposite to the seismic source. The illumination parameter reduces the uncertainties of the proxy by a factor of 2 compared to estimators that rely solely on curvature. The proxy does not require high computational resources. It uses a digital elevation map and a seismic source position to predict amplification factors (without lithological effects) for an S-wave at any site on the surface topography. It allows exploration of variations in topographic amplification near seismic sources, representing a significant breakthrough as areas closest to the fault typically sustain the highest damages. A MATLAB script performing the i-FSC calculations is provided.

Well foundations are one of the most widely used deep foundations for bridges. As in case of other foundations, these foundations are also subjected to combined vertical force V, horizontal force H, and moment, M. In this research study, the geotechnical capacity of well foundation in frictional soil is determined under gravity and seismic loading condition, using 3D finite element limit analyses (FELA). Applicability of modelling of the well foundation as a rigid body, and effect of shape of bottom plug of the well, on the foundation capacity is also studied. Failure patterns at salient points along the capacity surface are identified and their characteristics are explained. Specifically, the location and shift in the position of point of rotation, for different combinations of H-M loading, are discussed in detail. A parametric study is also performed to identify the effect of vertical load, embedment depth ratio of foundation, soil strength parameters and seismic loading on foundation capacity. The capacity of the well foundation obtained using design methodology of Indian bridge design standards is also compared with the numerical results and a modification is proposed in the existing design methodology. The proposed methodology enables the designer to determine reasonably good estimate of the foundation V-H-M capacity.

The September 19, 2017 earthquake (Mw = 7.1) struck México between the states of Puebla and Morelos. The ground motion damaged buildings near the epicenter and in Mexico City, with 44 collapsed buildings and many more experiencing some level of damage. The study gathers and statistically analyzes all available information, identifying characteristics in the plan and elevation of the damaged structures. The analysis identified structural issues typically associated with damage, such as buildings with soft or flexible ground floors and corner buildings supported by reinforced concrete frames. Corner buildings often have infill walls on two sides adjacent to neighboring properties, which, when connected to columns, cause significant torsional effects. The corner effect, combined with other structural pathologies such as soft-story, irregular building shapes, and seismic amplification effects in some city regions, significantly contributed to the damage and building collapses presented during the earthquake. The results, in addition to showing damage statistics for buildings located in a corner with infill walls, showed that the facade walls in the corner provide very little lateral stiffness comparatively to the stiffness of the perimeter walls situated on the other two sides of the building, which causes significant torsion in the building. The study also revealed that corner buildings with infill walls next to low-rise buildings were significantly more at risk than those surrounded by buildings of similar heights. A non-linear analysis of a case study showed that the observed earthquake damages in corner buildings were indeed expected, given the building’s seismic demands obtained with the numerical model.

Change in the fundamental period of a structure during strong earthquakes (the change from the linear to nonlinear period) can be a good indicator of the damage level of the structure. Given that the incremental dynamic analysis (IDA) has played an effective role in investigating the nonlinear behavior of engineering structures, in this article, we try to use the nonlinear (fundamental) period of the structure as a damage criterion in IDA curves for multi-degree-of-freedom (MDOF) systems, which was previously introduced for single-degree-of-freedom (SDOF) systems. In this regard, the nonlinear period at different seismic intensity levels and the collapse threshold period of steel moment-resisting frame (SMRF) structures are studied by considering the spectral shape indicators of earthquake records, and the strength and stiffness deterioration parameter. For this purpose, three regular SMRF buildings with 3, 10, and 20 stories as representatives of low-, medium-, and high-rise buildings are investigated. Fast Fourier transform (FFT) is used to calculate the nonlinear period of the structures, and the eigenvalue analysis method by using the instantaneous characteristics (stiffness) of the structure is implemented to confirm it. To perform the time history analysis, the bilinear modified Ibarra-Medina-Krawinkler (IMK) model is used in modeling the structural hysteretic behavior. One of the important applications of the nonlinear period of structures is in the process of scaling records for time history analysis. This study intends to evaluate the scaling period range by computing the nonlinear period based on the records scaled to the design spectrum. The results demonstrate that the spectral shape parameters and the structural deterioration affect the nonlinear period of the case study structures in a regular manner, while the effect of the mentioned spectral parameters on the collapse threshold period does not follow a clear trend. Also, it is shown that the upper bound period (1.5(:{text{T}}_{text{1}}) or 2(:{text{T}}_{text{1}})) mode period for scaling ground motions is too conservative for structures with a special SMRF load-resisting system having a low deterioration.

In the performance-based earthquake engineering, the ground motion (GM) records are generally selected for performing nonlinear time history analysis to evaluate the performance of the structure. However, due to the limited GM database, it is difficult to select GM sequences with high intensity by amplitude-scaled method for condition mean spectrum (CMS) to reasonably evaluate the performance of the structure. To solve the problem, an efficient method for constructing GM sequences is proposed as a supplement to traditional CMS. To construct GM sequences that meets the specific response spectrum sequence, a target response spectrum (conditional spectrum) sequence with physical meaning is simulated firstly based on the CMS and Latin hypercube sampling. Then, the time domain spectral matching (TDSM) method is introduced to generate GM sequences matching the target response spectrum sequences constructed above by adding adjustment wavelet functions so that available ground acceleration time history with high intensity and long period can be obtained from the limited GM database. However, in the previous studies, the coefficient used to constrain the adjustment wavelet functions usually is taken as an empirical constant value, which makes the efficiency of the iterative calculation unable to be guaranteed by the TDSM method. The particle swarm optimization method is introduced to optimize the TDSM method to find the best coefficient used to constrain the adjustment wavelet functions to improve the calculation efficiency and accuracy. To verify the effectiveness of the proposed method, the GM sequences selected by amplitude-scaled and proposed method are input into single-degree-of-freedom and multi-degree-of-freedom systems. The result shows that the proposed method for constructing GM sequences can be used as a supplement for the traditional CMS.

The partitioning of masonry buildings in Structural Units (SUs), or aggregate of Structural Units, is a useful tool to simplify the analysis of the buildings and the study of static and seismic vulnerability. However, this allocation is affected by uncertainties, simplification, and sometimes unavoidable miscalculation due to the directionality of this subdivision. This procedure exposes the results to discrepancies due to the way the building is divided. The Castle of Rosignano is emblematic. In this paper, the dependence of the results on how the Structural Units are considered is analyzed, as well as the role of structural in plan and elevation irregularities on various SUs and their combination. Non-linear static analysis corresponding to different distributions of the building in Structural Units, the uncertainties about material properties, and different directions of the seismic action are analyzed, and the respective results are discussed here. A simplified approach, for the study of aggregate buildings on an urban scale, is based on the so-called “tabular method”. Several Authors proposed and improved similar methods applied to different urban contexts. A comparison of simplified methodologies with the results of the detailed FEM analysis is also discussed and presented here. Finally, a simplified approach is proposed based on the regularity parameter of the building in aggregate. Taking the evidence from FEM analysis as a physical-mechanical base, the authors propose the quantitative definition of irregularity parameters and the use of them to determine the building vulnerabilities. The proposed procedure aimed to be a practical tool to determine, in an expeditious manner, the seismic capacity of a masonry building in aggregate. The model proposed in this paper, applied to the case of the study of Rosignano Marittimo (a typical situation of aggregate building in a historical context in Tuscany, Italy) shows emblematic results that can be extended to analogous configuration.