Probabilistic performance-based seismic assessment of an existing masonry building (original) (raw)
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Loss Assessment of Unreinforced Masonry Buildings
2016
Seismic risk is defined as the potential of negative consequences of hazardous events that may occur in a specific area unit and period of time. In particular, the outcome of a seismic risk analysis is the mean annual rate of specific consequences, for example economic loss, which is obtained by the probabilistic convolution of the three components: hazard, vulnerability and exposure. These types of analyses are increasingly directed to the evaluation of the socioeconomic consequences of the earthquake, which represent a critical aspect that requires more research than others components of risk, since in the past most of attention has been addressed to the hazard and vulnerability. For this reason, the paper provides a contribution for the assessment of economic losses in masonry buildings, that implies the definition of a methodology on how to pass from structural seismic response to a response in terms of losses, following a component-based approach from which the direct loss is c...
Performance assessment for unreinforced masonry buildings in low seismic hazard areas
… of the 13th World …, 2004
Most of housings in the Eixample district of Barcelona are unreinforced masonry buildings, which have been constructed without any seismic resistant consideration. Furthermore, they show some particular features, typical of the constructive techniques at that time, which have been identified as additional potential damage sources. In order to evaluate the expected seismic performance of these buildings, a typical six-story unreinforced masonry building was modeled. The dynamic behavior was studied by means of a structural analysis procedure, which uses macro elements to model the masonry panels. Monte Carlo simulation has been used to take into account the uncertainties in the mechanical properties of the materials. In this way, the mean seismic capacity curves of the building and their corresponding standard deviations have been obtained. The seismic demand has been considered by using response spectra proposed by the Cartographic Institute of Catalonia (ICC). The results here obtained for the seismic performance of this type of building; make clear their high vulnerability and, therefore, it is advisable retrofitting them in order to improve their seismic behavior. Finally, a sensitive analysis shows than the methods used to evaluate the seismic performance are sensible to the uncertainties of the structural parameters.
Performance-Based Approach for the Seismic Assessment of Masonry Historical Buildings
2014
The high vulnerability shown by historical masonry buildings (such as churches, towers, palaces) after past and recent earthquakes confirmed the need of proper procedures for the protection of cultural heritage in seismic prone areas. The wide variability and complexity of such classes of monuments, as well as the fact they were not based on an engineered design, make difficult to propose wellestablished approaches, as those adopted in codes for the case of ordinary newer buildings. In fact, as a function of various historical architectonic assets and the different seismic behaviors they may be exhibit (e.g. with a prevailing in-plane or out-of-plane response), different modeling strategies and approaches may constitute the optimal choice for a reliable seismic assessment. This issue has been recently faced in PERPETUATE project (Lagomarsino et al. 2010), specifically addressed to the earthquake protection of cultural heritage. Within this context, in the paper the basic principles ...
Simplified procedure for the seismic risk assessment of unreinforced masonry buildings
2004
The scope of the paper is to present the development and application of a new procedure for the seismic risk assessment at urban or territorial scale of unreinforced masonry buildings (URMB). The procedure, named MeBaSe, is based on four main features: the formulation of the structural capacity and response in terms of mechanics concepts, the representation of seismic demand and structural capacity by means of displacement, the inclusion of the most commonly acknowledged sources of uncertainty and the consideration of in-plane and out-of-plane failure mechanisms. The procedure aims to the evaluation of seismic risk of classes of buildings and is intended as a tool that could in perspective solve most of the drawbacks associated with existing procedures. The uncertainty originating in the material properties and the structural response is treated separately from that coming from the statistics of the population of buildings. The former is directly included in the computation of probability of failure of a class of buildings, whilst the latter is considered in a second stage. The demand, represented by a displacement response spectrum, can be obtained from regional probabilistic seismic hazard studies, and is defined by the median, for each spectral period, and by the corresponding scatter. Concerning the limit states, appropriate median values corresponding to each given drift limit state are used, depending on the type and quality of masonry. For the out-of-plane mechanism, the procedure is restricted so far to simple oneway bending mechanisms. A case study for the validation of the procedure has been carried out in the city of Benevento, Italy, and some preliminary results are presented in the paper, showing the feasibility of the new methodology. Drawing from the above discussion, the features of an "ideal" methodology could be summarized as follows: • To use a continuous rather than a discrete measure of the earthquake demand, and to use a more complete representation of the demand in the form of response spectra, rather than single parameters such as PGA.
Assessment of the seismic vulnerability of unreinforced masonry buildings
A methodology for seismic vulnerability analysis of URM buildings is presented. It includes the estimation of capacity curves for typical building classes, as well as vulnerability (fragility) curves in terms of peak ground acceleration (PGA). The methodology for developing vulnerability curves is based on a hybrid approach, combining statistical data with appropriately processed results fiom nonlinear static analyses that permit extrapolation of statistical data to intensities for which no data are available. The data used are statistical, derived fxom Greek earthquakes, the Thessaloniki 1978 and the Aegion 1995 events, with some additional data from the Pyrgos 1993 earthquake used for comparison purposes. The databases of the first two earthquakes are briefly presented and processed using a filtering technique. The resulting hybrid vulnerability curves correlate PGA to the probability that a building type exceeds a particular damage state.
Simulation-Based Fragility Relationships for Unreinforced Masonry Buildings
Journal of Structural Engineering, 2013
Unreinforced masonry (URM) structures represent a significant portion of the residential building stock of the Central and Eastern United States (CEUSA), accounting for 15% of homes in the 8-state region impacted by the New-Madrid Seismic Zone and an even greater portion of the building stock in most other regions of the world. In addition to significant population, the brittle nature of URM buildings further supports a thorough consideration of seismic response given the susceptibility to severe failure modes. Currently, there is a pressing need for analytically based fragility curves for URM buildings. In order to improve the estimation of damage state probabilities through the development of simulation-based masonry fragilities, an extensive literature survey is conducted on pushover analysis of URM structures. Using this data, capacity diagrams are generated, from which damage exceedance limit states are defined.
Journal of Earthquake Engineering, 2015
Traditional or historic masonry structures occur in large populations throughout the world, particularly in preserved historical city clusters. Being non-engineered and ageing these structures are in urgent need of assessment and seismic repair/rehabilitation. But 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 paper, 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 Loss Estimation for an Old Masonry Building in Italy
2019
The last seismic events in Central Italy (L’Aquila 2009, Amatrice 2016) have demonstrated that the economic loss from physical damage strongly influence the community’s recovery capability, especially when a relevant portion of the building stock is represented by unreinforced masonry (URM) constructions. As a matter of fact, URMs are recognized as the most vulnerable structures with respect to seismic forces. Furthermore, damage on masonry usually involves expensive and time-consuming repairing activities that can be carried out only by expert builders. Although these considerations are widely known among the Italian technical-scientific community, nowadays the social and political awareness about the problem is still quite low. One of the key aspects for an effective seismic risk mitigation is the analytical quantification of decision variables (e.g. monetary loss) to be shared with different stakeholders such as building owners, policy makers, insurance companies, etc. In respons...
2017
The concept of performance-based earthquake engineering has gained significant attentions in both the research and engineering communities. The development of a performance-based seismic loss assessment framework, known as the FEMA P-58 method, allows one to estimate the potential financial losses of a building using performance-based engineering method. This research employs a seismic loss estimation framework derived using the P-58 method to estimate the monetary loss of a mid-rise wood-frame hotel building which is assumed to be located in Napa Valley, California. A 3D structural model representative of the dynamic behavior of the wood-frame hotel was created and subjected to Incremental dynamic analysis (IDA). The structural demands (peak inter-story drifts, peak floor accelerations etc.) obtained from the IDA were utilized in the developed loss estimation framework to assess losses of structural and non-structural components as well as content damages. Preliminary results such ...
ANALYTICAL PROCEDURE FOR SEISMIC ASSESSMENT OF MASONRY BUILDINGS WITH HISTORICAL VALUE
Today, about 60 years after the proliferation of reinforced concrete in urban construction , structures that are classified as heritage buildings carrying a significant value from the past belong mostly to the class of unreinforced load-bearing masonry construction (URM), dating back to the 19th and early 20th Century. Extending current practices for seismic assessment to these buildings is not straightforward, as, in contrast with conventional frame structures, they are characterised by distributed stiffness and mass and poor diaphragm action. Interventions are often restricted by international treaties for non-invasiveness and re-versibility of the intervention-given the practical requirements for the buildings' intended reuse. Poor understanding of the mechanics of masonry and the inherent brittleness of the material further compounds the uncertainties in analytical methods used for assessment and rehabilitation. Simplified procedures that produce dependable results for estimating seismic demand for this class of structures are a primary objective of this paper. In a displacement-based context, requirements are determined from the spectral acceleration and displacement at the end of the constant acceleration range, T c , in light of the fact that these structures seldom exceed two storeys in height above ground. Displacement demand at the reference point is then distributed through the structure following a simplified estimate of the fundamental mode of vibration; this is calculated in each of the two principal directions of the building in plan, by applying a lateral load distribution analogous to its mass distribution. The intensity of local demand and likelihood of damage are estimated as relative drift ratios, in plan and in height, of the masonry piers of the structure. A case study of two neoclassical buildings damaged in the 1978 earthquake in Thessaloniki are used as a point of reference for illustration of concepts-results are correlated based on their ability to reproduce the patterns of damage observed during post-earthquake reconnaissance evaluations of the building.