Seismic Vulnerability Assessment of Slender Masonry Structures

Seismic Vulnerability Assessment of Slender Masonry Structures

Manjip Shakya (University of Aveiro, Portugal), Humberto Varum (University of Porto, CONSTRUCT, Portugal), Romeu Vicente (University of Aveiro, RISCO, Portugal) and Aníbal Costa (University of Aveiro, RISCO, Portugal)
DOI: 10.4018/978-1-4666-8286-3.ch010
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Existing slender masonry structures, such as Pagoda temples, towers, minarets and chimneys, exist all over the world and constitute a relevant part of the architectural and cultural heritage of humanity. Their protection against earthquakes is a topic of great concern among the earthquake engineering research community. This concern mainly arises from the strong damage or complete loss suffered by these types of structures when subjected to earthquake and also from the need and interest to preserve them. This chapter firstly presents a methodology for assessing the seismic vulnerability of slender masonry structures based on vulnerability index evaluation method. Secondly, presents the correlation between vulnerability index and Macroseismic method to estimate the physical damage in relationship with seismic intensity. Finally, presents implementation of the methodology to construct vulnerability curves, fragility curves and estimate losses.
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Slender masonry structures are featured by their notable slenderness and also represent one of the main differences from most of the historic structures or ordinary buildings (see Figure 1). These structures are able to resist gravitational actions, but as they were not explicitly designed to withstand seismic loading, show particularly weakness with regard to horizontal loadings induced by a strong motion (Pineda et al., 2011). The limited ductility of the masonry combined the slenderness of theses tower, that behave as a vertical cantilever fixed at the base, generally provides a rather brittle structural behaviour (Abruzzese et al., 2009). Therefore these constructions are particularly vulnerable with respect to seismic action (D’Ambrisi et al., 2012).

Figure 1.

Slender masonry structures: (a) towers; (b) minarets; (c) chimney; (d) Pagoda temples

The historical slender masonry construction, have demonstrated during the past to be susceptible to damage, and prone to partial or total collapse, under earthquake actions, sometimes due to inadequate retrofit or lack of it (Russo et al., 2010). In Italy, the sudden collapse of the Pavia civic tower, in 1989, motivated the development of many investigations concerning these types of structures (Gentile & Saisi, 2007). At present, a number of studies are available in the technical literature dealing with numerical and experimental analyses of slender masonry structures. However, there is no sufficient research work carried out on developing the relevant seismic vulnerability assessment tools for such structures. It is fact, seismic vulnerability assessment of these types of historical constructions is a difficult task due to the complexity of several factors involved, including the heterogeneity and uncertainty typical of the constituent materials, the intricate geometry configurations, often modified by previous structural or architectural interventions, and the cultural and artistic importance of this type of structure.

This chapter presents a methodology for assessing the seismic vulnerability of slender masonry structures based on vulnerability index evaluation method. This methodology evaluate of the seismic vulnerability index for the structure. Here, qualitative as well as quantitative parameters are defined to evaluate the vulnerability index. Finally, the evaluated vulnerability index, in relationship with seismic intensity can be used to estimate the physical damage, construct vulnerability and fragility curves and estimate losses.



In general terms, vulnerability measures the amount of damage caused by an earthquake of given intensity over a structure (Orduña et al., 2008). However, amount of damage and seismic intensity are concepts without a clear and rigorous numerical definition. According to Sandi (1986), seismic vulnerability is an intrinsic property of the structure, a characteristic of its own behaviour due to the action of an earthquake described trough a law of cause-effect, where the cause is the seismic action and the effect is the damage. However, the amount of damage identified in the seismic vulnerability assessment of buildings depends on many factors such as intensity of the seismic action, soil conditions, constructive materials, structural elements and conservation state.

Corsanego & Petrini (1990) classified methodologies for the evaluation of structural vulnerability in four groups:

Key Terms in this Chapter

Vulnerability Index: The empirical method used to identify the potential seismic deficiencies of a structure by means of evaluating significant component of the structure.

Seismic Vulnerability Assessment: The evaluation of potential damage to the structure as a consequence caused by the seismic events.

Mean Damage Grade: The quantitative as well as physical interpretation of the consequence caused by the seismic events.

Macroseismic Method: The method makes reference to the EMS-98 Macroseismic scale and defines a damage model for different structural vulnerability classes (A to F).

Slender Structure: The structure featured by its notable slenderness ratio, such as tower, minaret, chimney and Pagoda temples.

Probability Distribution Function: A statistical function that describes all the possible values and likelihoods that a random variable can take within a given range.

Fragility Curve: The curve plotted between earthquake intensity and damage grade in terms of the conditional cumulative probability of reaching a certain damage state.

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