An Applied Method for General Regional Seismic Loss Assessment—With A Case Study in Los Angeles County

We describe the formulation and application of an integrated general regional seismic loss assessment (RSLA) method for buildings in seismic regions. An efficient method for RSLA is valuable for engineers involved in city planning, risk management, and insurance dealings. In contrast to previously reported methods, the framework presented herein is hazard-based and utilizes a regional rapid seismic hazard deaggregation tool that allows regional assessment to be conducted more efficiently. The proposed technique is implemented as an example to assess general regional seismic loss in Los Angeles County for a ground motion hazard with 10% probability of exceedance in 50 years.     

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.     

Sustainability of Highway Bridge Networks Under Seismic Hazard

In order to evaluate the seismic risk of transportation networks, it is necessary to develop a methodology that integrates the probabilities of occurrence of seismic events in a region, the vulnerability of the civil infrastructure, and the consequences of the seismic hazard to the society, environment, and economy. In this article, a framework for the time-variant seismic sustainability and risk assessment of highway bridge networks is presented. The sustainability of the network is quantified in terms of its social, environmental, and economic metrics. These include the expected downtime, expected energy waste and carbon dioxide emissions, and the expected loss. The methodology considers the probability of occurrence of a set of seismic scenarios that reflect the seismic activity of the region. The performance of network links is quantified based on individual bridge performance evaluated through fragility analyses. The sustainability and risk depend on the damage states of both the links and the bridges within the network following an earthquake scenario. The time-variation of the sustainability metrics and risk due to structural deterioration is identified. The approach is illustrated on a transportation network located in Alameda County, California.     

FRAGILITY OF STANDARD INDUSTRIAL STRUCTURES BY A RESPONSE SURFACE BASED METHOD

National and international regulatory standards require industrial risk assessment, taking into account natural hazards including earthquakes, in the framework of Quantitative Risk Analysis (QRA). Seismic fragility analysis of industrial components may be carried out similarly as what has been done for buildings, even though some peculiar aspects require the development of specific tools. In the present paper a contribution to the definition of a rational procedure for seismic vulnerability assessment of standardised industrial constructions in a probabilistic framework is given. The method covers a range of components of the same structural type. Seismic reliability formulation for structures is used. Both seismic capacity and demand are considered probabilistic with the latter assessed by dynamic analyses. The application example refers to shell elephant foot buckling of unanchored sliding tanks. A regression-based method is applied to relate fragility curves to parameters varying in the domain of variables for structural design.     

Knowledge-Based Performance Assessment of Existing RC Buildings

One of the most challenging aspects of the seismic assessment of existing buildings is the characterization of structural modeling uncertainties. Recent codes, such as Eurocode 8, seem to synthesize the effect of structural modeling uncertainties in the so-called confidence factors that are applied to mean material property estimates. The confidence factors are classified and tabulated as a function of discrete knowledge levels acquired based on the results of specific in-situ tests and inspections. In this approach, the effect of the application of the confidence factors on structural assessment is not explicitly stated. This work presents probabilistic performance-based proposals for seismic assessments of RC buildings based on the knowledge levels. These proposals take advantage of the Bayesian framework for updating the probability distributions for structural modeling parameters based on the results of tests and inspections. As structural modeling parameters, both the mechanical material properties and also the structural detailing parameters are considered. These proposals can be categorized based both on the amount of structural analysis effort required and on the type of structural analysis performed. An efficient Bayesian method is presented which relies on simplified assumptions and employs a small sample of structural model realizations and ground motion records in order to provide an estimate of structural reliability. As an alternative proposal suitable for code implementation, the simplified approach implemented in the SAC-FEMA guidelines is adapted to existing structures by employing the efficient Bayesian method. This method takes into account the effect of both ground motion uncertainty and the structural modeling uncertainties on the global performance of the structure, in a closed-form analytical safety-checking format. These alternative proposals are demonstrated for the case study structure which is an existing RC frame. In particular, it is shown how the parameters for the safety-checking format can be estimated and tabulated as a function of knowledge level, outcome of tests, and the type of structural analysis adopted.     

Comparing expeditious procedures for the seismic vulnerability assessment on the European territorial context: reliability,feasibility, cost,and time consumption

ABSTRACT

The definition of strategies for the preservation and protection of cultural heritage is a topical issue, especially in view of the increasing relevance of the theme of seismic risk mitigation and reduction.

The prediction of the impact an earthquake could have on existing buildings requires the knowledge of their dynamic behaviour. The procedure to be adopted for this purpose is quite complex and onerous in terms of costs, time, and implementation, especially when the study concerns territorial areas rather than single buildings. The definition of methodologies aimed at respecting the principles of economic sustainability and preserving human life and architectural heritage is of paramount importance to assess seismic vulnerability using available resources. Rapid methods for the seismic vulnerability assessment, aimed at defining buildings vulnerability and intervention priority lists, must be implemented to guarantee the preservation of historical centers.

This article describes the application to some case studies of different methods aimed at creating fragility curves for the vulnerability assessment on the European territorial context. The comparison between a deterministic approach and a new probabilistic one is performed for all case studies, to define the most suitable methodology in terms of reliability and savings in cost and time.     

Critical Issues in Earthquake Scenario Loss Modeling

The assessment of human or economic losses due to single events (scenario) may effectively support decision makers in the development of important risk mitigation actions. The study presented herein sheds light on several problems and limitations in the current practice of scenario loss modeling, such as: the number of simulations required to achieve convergence; epistemic and aleatory uncertainty in the ground motion prediction and vulnerability models; and consideration of the earthquake rupture geometry. These issues are investigated using the Metropolitan Area of Lisbon (Portugal), and it has been observed that distinct assumptions in the loss modeling can lead to considerably different results. The findings of this study are also pertinent for probabilistic seismic risk analyses in which a large number of stochastically generated events are employed to assess probabilistic losses.     

Use of Cumulative Ductility Spectra Within a Deformation-Control Format for Seismic Design of Ductile Structures Subjected to Long Duration Motions

Due to the large economical losses derived from recent seismic events, design methodologies that are based in the explicit control of the dynamic response of structures have been formulated. This article introduces, within the framework of performance-based design, a numerical methodology for the seismic design of structures that are expected to undergo severe cumulative plastic demands. The methodology explicitly considers and integrates: (1) the structural and non-structural performance of the building; (2) the life safety limit state; and (3) the prevention of low cycle fatigue.     

Mine blast vibration response spectrum for structural vulnerability assessment: case study of heritage masonry buildings

Ground-borne vibrations induced by mine blasting are typically of low amplitudes, which are not considered a major concern for modern engineered structures. However, historic structures are often considered more vulnerable due to inadequate knowledge regarding the state of construction materials and structural response. Specifically, the construction materials used might be fragile or have deteriorated to a stage that could be vulnerable to such vibrations. Simplistic rule based on peak ground motion parameter has been adopted worldwide for safety assessment, while the frequency characteristics of vibrations are not taken into account. Further, there is very limited study on response of heritage structures to near-field blasting. This article presents a practical structural vulnerability assessment method for mine blast-induced vibrations. In particular, a design response spectrum model is proposed based on close range measurements of nearby mine blasting, which is compared with an existing design spectrum model for far-field mine blasts and a typical design spectrum model for earthquake actions. The method is illustrated through a case study of heritage masonry buildings in Australia. The unique blast data presented and the generalized methodology would be useful to both structural engineers and blast engineers in considering potential effects of blasting on heritage structures.     

METHODOLOGY FOR THE PROBABILISTIC ASSESSMENT OF q FACTORS. A DAMAGE INDEX APPROACH

The objective of the present work is to present a methodology for the identification of relevant limit states, namely ultimate limit states leading to structural collapse, and for the assessment of design q factors (or force reduction factors) for reinforced concrete structures under seismic loading. It follows a probabilistic approach based on damage indices. The utilised nonlinear models, as well as the damage indices, which are those proposed by Miner and by Park and Ang, are.described. The methodology of analysis is presented emphasising its probabilistic characteristics. Some parametric studies are carried out, including the analysis of one regular plane frame reinforced concrete structure, designed for three different ductility classes (those proposed by Eurocode 8) and assuming different q factors in design. Results show how the chosen damage indices can be used as parameters to characterise the structural response and how the proposed methodology can be used to assess the design q factors. It is also shown that, for moderate seismic input, the three ductility classes are essentially equivalent in terms of maximum damage indices, but that for higher seismic levels the differences are evident, justifying the use of different q factors.     

Prologue to a contextual archaeology

The thesis of this essay is that a gap presently exists between the research interests of modern scientific archaeology and the research methodology which structures archaeological investigation. It is argued that this is a function of the traditional objectives of archaeology, and that a methodology justified by a distinctive set of goals is necessary to produce studies more closely related to present archaeological concerns. The traditional goals of archaeology are here characterized as the historical result of prior interests, reinforced by the character of formal programmes of graduate study. The set of distinctive goals identified in the essay derives from assessment of the significance of methodologies appropriate to the investigation of palaeoenvironments in modelling prehistoric cultural systems and subsystems.The proposed methodology is substantively, as well as substantially, different from methodologies in present use. I have called it Contextual Archaeology in recognition of its debt to the statement of an archaeologically-significant method Butzer (1978) has advanced under the name Contextual Approach. It is argued here that contextual archaeology, despite practical problems, is both a productive and an implementable alternative.     

Linking Agricultural Policies with Decision-Making: A Spatial Approach

Abstract

The loss of agricultural land and its implications have been of great concern in the last decade. By undertaking a spatial analysis of the appropriation of agricultural land for urban use with an overlay of population and urban data, a focus on the consequences of certain regulations on the dynamics of land-use change is explored. This is achieved by integration of data inventories of agricultural land use for Portugal, and linking this information with CORINE Land Cover data as to assess change in the Algarve. An integrated assessment of agricultural land loss follows, undermined by the consequences of urban sprawl. In this sense, this paper expands on the currently existing decrees which provide support to sustainable development in the region while providing a qualitative assessment of future roles based on ethical values and economic efficiency and offering a feasible framework for policy-makers regarding the trends of urban/agricultural dichotomy in a planning and decision-making context.     

Critical Issues on Probabilistic Earthquake Loss Assessment

Probabilistic loss modeling can be used to develop risk reduction measures, such as the identification of regions more prone to human and economic losses, or to develop financial mechanisms to transfer the earthquake risk from local governments to the private sector. This study addresses several critical issues in probabilistic loss modeling, and provides recommendations depending on the intended final use of the risk results. Modeling issues related to convergence in probabilistic event-based analysis; consideration of epistemic uncertainties within a logic tree; generation of different types of loss exceedance curves; and derivation of risk maps are thoroughly investigated. The Metropolitan Area of Lisbon is used to explore these issues, and it is demonstrated that different assumptions in the loss modeling process can lead to considerably different risk results. Furthermore, the findings and recommendations of this study are also relevant for institutions that promote the assessment of earthquake hazard and risk, such as the Global Earthquake Model Foundation.     

THE BAYESIAN APPROACH TO THE INTERPRETATION OF ARCHAEOLOGICAL DATA

Archaeologists are increasingly becoming aware of an approach to data investigation known as Bayesian statistics. In this paper we outline both the philosophical and statistical background to the approach. We show that it provides a logical and coherent framework in which to make inferences on the basis of both data and a priori expert knowledge. We note that adoption of the Bayesian framework is particularly timely since there have been recent dramatic developments in numerical methods which mean that a number of previous implementation problems have now been solved. As a result, many questions of archaeological interest, which require the use of complex statistical models, are being investigated using this methodology. We use a variety of recently published examples from a range of archaeological areas to illustrate the type of questions that can be answered and the nature of the methodologies used, and we make comparisons with the results obtained using more traditional statistical techniques.     

A Framework for Assessing the Vulnerability of Archaeological Sites to Climate Change: Theory,Development, and Application

Abstract

The predicted impacts of climate change on cultural heritage are likely to be dynamic and complex. Understanding the potential risks at site level is vital to ensure that appropriate adaptation and mitigation measures are put in place. There is, however, a dearth of tools and methodologies suitable for use by heritage managers. In this paper the potential of vulnerability analysis for site-based assessment is explored. A six-step vulnerability framework, adapted for cultural heritage, is illustrated utilizing material from two case-study sites (Brú na Bóinne and Skellig Michael). The implementation of each step in the proposed framework is demonstrated to aid those wishing to apply the method in practice. The ‘values based’ approach taken is suitable for a wide range of cultural heritage including landscapes, monuments, and buried archaeology. The six-step framework and the utilization of indicators provide a method that allows comparison between sites and yet is sufficiently flexible to account for localized concerns. The framework will aid decision makers with planning and prioritization.     

Indigenous Methodologies: Suggestions for Junior Researchers

Indigenous methodologies in geography have recently been developed to decolonise Western dominated paradigms. It has been argued that research which does not benefit Indigenous communities should not be conducted. However, Indigenous methodologies are not taught in many post-secondary institutions. Therefore, when they pursue Indigenous topics, many junior researchers are self-taught in these methodologies. However, these methodologies cannot be defined simply and they are too diverse to be learnt in a short period. In Japan, Indigenous peoples are not widely recognised and research on contemporary Indigenous issues is limited. The concept of Indigenous methodologies is rarely discussed. Because of this, Japanese researchers rarely identify their research as adopting an Indigenous methodology. Indigenous researchers are thereby discouraged from pursuing Indigenous methodologies. Furthermore, a methodology or a thesis statement used by researchers to reflect Indigenous perspectives often gets little support from Indigenous peoples. My master's research on the Ainu mirrored this situation. While Indigenous methodologies remain difficult to learn, junior researchers should not be discouraged from this form of engagement. Practical suggestions are therefore necessary to encourage their use and application. Based on my experience, I suggest that researchers approach Indigenous communities from a learning perspective. This would encourage open-mindedness and sensitivity. Researchers should also be prepared and willing to refine their research questions and to continue their literature searches after their fieldwork is completed. These strategies could limit misinterpretation and exploitation of Indigenous knowledges and peoples.     

Technical Note: Practical Challenges Facing the Selection of Conditional Spectrum-Compatible Accelerograms

There are various possibilities for the selection and scaling of ground motions for advanced seismic assessment of buildings using nonlinear response-history analyses. As part of an on-going project looking at building-specific loss assessment in Italy, this article highlights a number of challenges currently facing the use of conditional spectra for ground motion selection in practice, essentially related to the limited amount of seismic hazard information that is publicly available. To illustrate the points being made, the challenges faced when trying to develop conditional spectra and select spectrum-compatible accelerograms for a rock site in Napoli, Italy, are described and the seismic assessment results obtained for a number of reinforced concrete wall structures are presented. Aside from providing practitioners with an appreciation of the potential difficulty associated with using conditional spectra for record selection, this technical note should also motivate national authorities to provide more background information on national seismic hazard data and detailed guidance for record selection.     

Regional polycentricity: an indicator framework for assessing cohesion impacts of railway infrastructures

Territorial cohesion has become one of the main objectives in transport planning. This has fostered the development of assessment methodologies to quantitatively estimate the territorial impact of major transport infrastructures, which are particularly scarce at the intra-regional level. Linked to cohesion, polycentricity has been defined as the best spatial configuration to achieve balanced regions where population and opportunities are distributed among several entities linked by functional relationships. This paper aims to present a methodology to estimate these impacts based on the use of a new regional composite polycentricity indicator. The proposed indicator is tested by comparing the effects of conventional and high-speed railway (HSR) alternatives in the territorial system of a northern region of Spain. This quantitative assessment is a ranking tool for prioritizing rail network alternatives in terms of achieving the most balanced territory, which is especially relevant in countries where HSR networks follow cohesion goals. Our results show that new HSR links should only be complementary to regional railway services, and that the suppression of secondary lines should be avoided if a reduction in polarization is to be achieved.