Influence of Collapse Definition and Near-Field Effects on Collapse Capacity Spectra

In the present article, the impact of both near fault ground motions and a finite ductility threshold on the collapse capacity is studied. Single-degree-of-freedom systems with non-deteriorating bilinear hysteretic behavior, vulnerable to P-delta effects, are considered. Defining collapse as excessive ductility is investigated, and the difference to collapse associated with instability is elaborated. Medians of individual record dependent collapse capacities are presented as function of the initial structural period for characteristic structural and ground motion parameters. Analytical expressions for influence coefficients, which account for a differing ground motion set, and finite ductility thresholds, respectively, are derived via non-linear regression analysis.     

Simplified Mechanical Model to Estimate the Seismic Vulnerability of Heritage Unreinforced Masonry Buildings

Traditional or historic masonry structures occur in large populations throughout the world, particularly in preserved historical city clusters. Being non-engineered and aging these structures are in urgent need of assessment and seismic repair/rehabilitation. However, traditional masonry presents important challenges to computational modeling, owing to complexity of structural system, material inhomogeneity, and contact interactions that collectively can only be addressed through detailed 3D nonlinear representation. In this article, a simple performance assessment model is developed in order to address the need for preliminary assessment tools for this class of structures. The objective is to be able to rapidly identify buildings that are at higher risk in the event of a significant earthquake, potentially justifying a second round of more detailed evaluation. The proposed model defines the characteristics of a Single Degree of Freedom representation of the building, formulating consistent 3D shape functions to approximate its fundamental mode of vibration considering both in-plane and out-plane wall bending as a result of insufficient diaphragm action. Parametric expressions for the dynamic properties are derived in terms of the important geometric, material, and system characteristics, and are used to express local demand from global estimates. Acceptance criteria are established both in terms of deformation and strength indices to guide retrofit. An application example of the proposed assessment methodology is included to demonstrate the ability of the model to reproduce the essential features of traditional masonry buildings under seismic action.     

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.     

Empirical Fragility Curves for Non-Residential Buildings from the 2010–2011 Canterbury Earthquake Sequence

This study develops a motion-damage database (the Canterbury Earthquake Building Assessment, CEBA database) using surveyed information obtained from the Canterbury earthquake sequence. The database is then applied to derive fragility curves for non-residential buildings in New Zealand. The results indicate that unreinforced masonry buildings are the most vulnerable to damage, while the concrete shear wall buildings were found to be the most resilient. Discrepancies were found when comparing equivalent structures in New Zealand and the United States. Inherent difference of building characteristics between the two countries, significant ground failure, and accumulated damage from multiple events might explain the difference.     

Review of Different Pushover Analysis Methods Applied to Masonry Buildings and Comparison with Nonlinear Dynamic Analysis

This article presents the comparison among different nonlinear seismic analysis methods applied to masonry buildings, i.e., pushover analyses with invariant lateral force distributions, adaptive pushover analysis and nonlinear dynamic analysis. The study focuses on the influence of lateral force distribution on the results of the pushover analysis. Two simple benchmark case studies are considered for the purpose of the research, i.e., a four-wall masonry building prototype without floor rigid diaphragms and a two-wall system with a cross-vault. The comparative study offers a useful review of pushover analysis methods for masonry structures and shows advantages and possible limitations of each approach.     

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.