Seismic Reconnaissance and Observed Damage after the Mw 6.8, 24 August 2016 Chauk (Central Myanmar) Earthquake

On 24 August 2016, Mw 6.8 earthquake occurred near Chauk, Central Myanmar. This earthquake caused a significant amount of damage over a very large number of historical monuments. After providing a general summary of the regional tectonic settings and seismicity, the observed ground motion has been discussed, and performance of structures in the epicentral area is addressed, focusing on the damage observed in both historical and recent constructions. The observed damage patterns and their extent are analyzed and interpreted in light of observed damage that was found. Lastly, seismic fragility curves of local buildings have been derived.     

Seismic Hazard Analysis Using Discrete Faults in Northwestern Pakistan: Part I – Methodology and Evaluation

This article is the first of two companion articles that evaluate the seismic hazard in northwestern Pakistan. The area, located at the western edge of the Himalayas, has numerous active faults including the Main Boundary Thrust (MBT) and Main Mantle Thrust (MMT). This article describes the methodology used to perform regional deterministic and probabilistic seismic hazard analyses. Here, seismic sources were defined from 32 identified faults while prior studies have been based on diffuse seismicity and areal source zones. Fault parameters were selected using available data and empirical correlations for faults elsewhere. Recurrence relations were constructed for all discrete faults based on both historical and instrumented seismicity in addition to geologic evidence. Due to lack of region specific attenuation relationships, four plate boundary attenuation relations from the Next Generation Attenuation of Ground Motions Project [Abrahamson et al., 2008 Abrahamson, N., Atkinson, G., Boore, D., Bozorgnia, Y., Campbell, K., Chiou, B., Idriss, I. M., Silva, W. and Youngs, R. 2008. Comparisons of the NGA ground-motion relations. Earthquake Spectra, 24(1): 45–66. [Crossref], [Web of Science ®] , [Google Scholar]] were employed to predict ground motions. Predicted ground motion parameters are compared to measurements from the recent 2005 Kashmir earthquake. In the companion article, the methodology developed and evaluated here is used to conduct deterministic and probabilistic seismic hazard analyses for the entire study region.     

关于建立国内馆藏文物防震应急管理体系的探讨

我国地处环太平洋地震带和欧亚地震带间,因地震导致的馆藏文物损毁现象时有发生。近年来,我国馆藏文物防震技术研究取得了不少成果,并在部分博物馆成功进行了一体化防震示范应用。但总体而言,馆藏文物防震风险预防和应急管理水平仍相对滞后,部分博物馆存在防震措施不合理、日常管理匮乏、应急能力不足等现象,亟待健全馆藏文物防震应急管理体系,其中应急预案的编制尤为重要。通过建立完善的应急管理体系,博物馆能够全面提高防震意识和应急处置能力,合理利用各类防震措施降低潜在风险,更好地保护馆藏文物。     

Variability in Wood-Frame Building Damage using Broad-Band Synthetic Ground Motions: A Comparative Numerical Study with Recorded Motions

Earthquake damage to light-frame wood buildings is a major concern for North America because of the volume of this construction type. In order to estimate wood building damage using synthetic ground motions, we need to verify the ability of synthetically generated ground motions to simulate realistic damage for this structure type. Through a calibrated damage potential indicator, four different synthetic ground motion models are compared with the historically recorded ground motions at corresponding sites. We conclude that damage for sites farther from the fault (>20 km) is under-predicted on average and damage at closer sites is sometimes over-predicted.     

THE SHADOW-ZONE OF LARGE ITALIAN EARTHQUAKES. EARLY JOURNALISTIC SOURCES AND THEIR PERCEPTION OF 17TH-18TH CENTURIES SEISMICITY

From their earliest beginnings in the 16th century, journalists never failed to find earth-quakes interesting. As a result, early journalistic sources offer a huge hoard of original earthquake data, mostly untapped to this day for seismological purposes [Camassi and Castelli, 2003]. In the aftermath of large earthquakes, the journalists of the 17th and 18th centuries tended to react in two ways. Either their interest for seismic news would increase, leading them to hunt for more news of the same kind, or it would focus exclusively on the “big one” to the detriment of lesser contemporary earthquakes. In the first case, it was possible that more earthquakes than usual would be given coverage; but in the second case more earthquakes than usual were likely to be overlooked and shadowed by the larger event. Through a comprehensive cross-check of Italian early journalistic sources, this paper attempts to highlight the “shadow-zones” of some major 17th–18th centuries Italian earthquakes.     

Energy-Based Similitude for Shake Table Testing of Scale Woodframe Structures

The development and refinement of performance seismic design is underway, thus understanding the dynamic behavior of woodframe structures has become critical. Although several full scale shake table tests have been performed, many details associated with load transfer/path and behavior of varying systems remains to be investigated. This short technical communication presents the results of a study whose objective was to scale a woodframe structure to one-half scale using similitude theory, something that has eluded researchers to date. It is widely felt that woodframe structures cannot be scaled because there is no way to scale a naturally occurring fibrous material with non isotropic properties. However, because the dynamic response of wood shearwalls (and thus woodframe structures) is dominated by the behavior of the sheathing-to-framing connectors, an energy-based similitude was developed at the connector/fastener (nail) level. Shake table tests were performed for both the full-scale prototype and half-scale model. Peak displacements at roof level for the prototype and model were found to be very close, i.e., within 2%, for the largest simulated ground motion and only within 30% for the smallest simulated ground motions. While the displacement time series scaled very well, the resulting damage did not scale.     

Neural Network-Based Damage Detection from Transfer Function Changes

This article puts forth the work on a neural network-based approach to determine the degree of damaged floors of the building considering changes in the transfer function. The transfer function is considered for that part of forced vibration in which system vibrates linearly after the structure has been damaged considering the building is instrumented during the earthquake. The results showed that accuracy of degree of damage detected increased with the increase in the number of combination of damages. The instrumentation of the first floor is expected to give best results for damage detection based on the transfer function-based approach.     

Seismic Performance Assessment of Steel Frames with Shape Memory Alloy Connections,Part II – Probabilistic Seismic Demand Assessment

This article is the second of two companion articles that evaluate the seismic performance of steel moment-resisting frames with innovative beam-to-column connections that incorporate shape memory alloy (SMA) elements to enhance the energy dissipation characteristics of such frames. Building upon the finite element models of the three- and nine-story frames that were developed in the first article, the seismic demands on partially restrained frames with and without SMA elements are evaluated within a probabilistic framework. The results of this evaluation, expressed in the form of demand hazard curves, depict the effectiveness of the SMA connections in enhancing building performance over a range of demand levels. Martensitic SMA connections are most effective in controlling deformation demands on the frame from high levels of seismic intensity. In contrast, the recentering capability of superelastic SMA connections make them most suitable for reducing residual deformations in the structure, a reduction that is achieved at the expense of increased deformation demands during strong excitation. However, neither connection is uniformly beneficial at all hazard levels, suggesting that SMA systems must be tailored to the specific performance objectives for the building structural system.     

Macro-Scale Analysis of Damage to Churches after Earthquake in Abruzzo (Italy) on April 6, 2009

This article focuses on the effects of the earthquake which struck the Abruzzo region (Central Italy) on April 6, 2009, causing considerable damage to many ancient buildings, particularly churches. During the emergency after the earthquake, many churches and other historical monuments (towers, city walls, large town houses, etc.) were surveyed, according to first-level damage survey forms for Cultural Heritage buildings, by multidisciplinary working groups composed of experts from several Italian institutions (Universities, Ministry for Cultural Heritage, Fire Brigade, etc.). This article presents a statistical study on the information collected by the University of Padova during the surveys, which was later inserted and organized in a database, and illustrates data on damage assessment of the buildings in question. It also presents an intuitive overview of the seismic effects on several churches, allowing not only better understanding of the response of these structures to this particular earthquake, but also correlating data on it with its effects on the churches.     

Development of Probabilistic Framework for Performance-Based Seismic Assessment of Structures Considering Residual Deformations

Recently, the importance of considering residual (permanent) deformations in the performance assessment of structures has been recognized. Advanced structural systems with re-centering properties as those based on unbonded post-tensioning tendons are capable of controlling or completely eliminating residual deformations. However, for more traditional systems, which count for the vast majority of buildings, residual deformations are currently considered an unavoidable result of structural inelastic response under severe seismic shaking.

In this article, a probabilistic framework for a performance-based seismic assessment of structures considering residual deformations is proposed. The development of a probabilistic formulation of a combined three-dimensional performance matrix, where maximum and residual deformations are combined to define the performance level corresponding to various damage states for a given seismic intensity levels, is first presented. Combined fragility curves expressing the probability of exceedence of performance levels defined by pairs of maximum-residual deformations are then derived using bivariate probability distributions. The significance of evaluating and accounting for residual deformations within a Performance-based Earthquake Engineering (PBEE) approach is further confirmed via numerical examples on the response of Single Degree of Freedom (SDOF) systems, with different hysteretic behavior, under a selected suite of earthquake records. Joined fragility curves corresponding to various performance levels, defined as a combination of maximum and residual response parameters, are derived while investigating the effects of hysteretic systems and strength ratios. It is observed that stiffness degrading Takeda systems result in lower residual deformations than elasto-plastic systems and show lower probability of exceeding a jointed maximum-residual performance level. For a chosen performance level, Takeda systems with higher strength ratios show better performance, particularly with lower intensity of excitations.