Displacement demand for nonlinear static analyses of masonry structures: Critical review and improved formulations

This paper discusses different formulations for calculating earthquake‐induced displacement demands to be associated with nonlinear static analysis procedures for the assessment of masonry structures. Focus is placed on systems with fundamental periods between 0.1 and 0.5 s, for which the inelastic displacement amplification is usually more pronounced. The accuracy of the predictive equations is assessed based on the results from nonlinear time‐history analyses, carried out on single‐degree‐of‐freedom oscillators with hysteretic force–displacement relationships representative of masonry structures. First, the study demonstrates some limitations of two established approaches based on the equivalent linearization concept: the capacity spectrum method of the Dutch guidelines NPR 9998‐18, and its version outlined in FEMA 440, both of which overpredict maximum displacements. Two codified formulations relying on inelastic displacement spectra are also evaluated, namely the N2 method of Eurocode 8 and the displacement coefficient method of ASCE 41‐17: the former proves to be significantly unconservative, while the latter is affected by excessive dispersion. A non‐iterative procedure, using an equivalent linear system with calibrated optimal stiffness and equivalent viscous damping, is then proposed to overcome some of the problems identified earlier. A recently developed modified N2 formulation is shown to improve accuracy while limiting the dispersion of the predictions

Effects of vertical ground motions on the dynamic response of URM structures: Comparative shake-table tests

This paper discusses the results of an experimental study aimed at evaluating the influence of the vertical ground motion component on the seismic performance of unreinforced brick-masonry buildings. The research was motivated by post-earthquake observations of significant structural damage in the vicinity of the fault, where horizontal and vertical ground motions are often strong and synchronized. Vertical accelerations can fluctuate gravity loads, which control the in-plane lateral load capacity of masonry piers and affect the out-of-plane overturning stability of thin walls. Such phenomena seem not to be sufficiently explained in existing literature, while experimental evidence is undoubtedly missing. Here, the damage potential of vertical accelerations was investigated through a series of multidirectional shake-table tests on full-scale structures under simulated near-source ground motions of increasing intensity. The experiments comprised three nominally identical building specimens subjected to the principal horizontal component alone, the horizontal component combined with the vertical one, and the full three-component ground motion. The buildings included structural/nonstructural elements (e.g., gables, chimneys, and parapets) sensitive to gravity load variations due to their low axial loads. Two different sets of three-component earthquake records were employed to assess the effects of both tectonic and induced seismicity scenarios. Overall, the vertical earthquake motion did not cause appreciable differences in the behavior of the buildings. Any influence on the strength and peak response of structural/nonstructural walls was marginal and non-systematic. Data and observations from these experiments add substantially to our understanding of the vertical acceleration effects on masonry structures

The efficiency of tourism sector in eu mediterranean coastal regions: The effects of seasonality and spatiality of demand

The present paper studies the effects of seasonality and spatiality of tourist flows on the regional performance of tourism sector. The empirical analysis is conducted for 36 coastal North Mediterranean EU NUTS II regions, for the period 2010-2016. Performance is estimated under the concept of efficiency under a Data Envelopment Analysis methodology and the relationship of efficiency with seasonality, spatiality, and some other contextual factors is estimated with a double bootstrap method. The empirical analysis demonstrates that a typical linear function seems to be inappropriate to describe the relationships of these tourism features, as an N-shaped relationship between performance and seasonality and a U-shaped relationship for performance and spatiality were found. © 2021 by the authors. Licensee: REGION

Spatial variations of employment change in Greece over the early-crisis period (2008-2011)

Towards conceptualizing and understanding the spatial impact of the contemporary economic crisis, the paper scrutinizes the spatial variations of employment change in Greece. To this end, the paper employs a trade-adjusted shift-share analysis; a shift-share formulation accounting for employment changes resulting from changes in exports, imports and domestic demand. Trade-adjusted shift-share analysis is employed against the backdrop of the world economy, on the basis of employment data that refer to NACE Rev. 2 aggregation sectoral levels and to NUTS II spatial level, and covers the early-crisis period (2008-2011). The results obtained highlight the negative national effect component as an outcome of the shocks and the upsets that the Greek economy has suffered. The industry mix component and the competitive shift component are positive only for specific regions and sectors. Particularly, for the industry mix component it comes that all Greek regions specialize in sectors that, at the national level, are export-declining and import-declining and experience labor productivity losses. © 2016, Hellenic Association of Regional Scientists. All rights reserved

Understanding the regional engagement of universities from a stakeholders’ perspective: The case of the university of Thessaly, Greece

International literature pays vast attention to the role and the regional engagement of universities as a facilitator of sustainable regional development. Most papers use top-down approaches by looking at how well conceptual models of a university’s role fit any case study considered or by measuring predefined dimensions of university engagement. The present paper prioritizes the stakeholder views and provides a framework for revealing the critical dimensions of the university’s regional engagement from a bottom-up perspective. The region of Thessaly is selected as a case study, and the university’s engagement is conceptualized by a four-dimensional framework that considers the university’s contributions, student roles, beneficiaries, and barriers. Then, through a survey, relevant items are provided to stakeholders to formulate any potential engagement factors. The factors are extracted using the principal component analysis, and then the consensus of different stakeholders on their response patterns is then also evaluated with relevant statistical tests. In practical terms, the analysis shows that a capable number of factors could be formulated under each dimension of the framework and that there are not many significant differences in stakeholder per-ceptions, regardless of their institutional role. In theoretical terms, the identified factors may act as a baseline for any future relevant evaluation. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

COVID-19 pandemic and lockdown fine optimality

The first stream of economic studies on public policy responses during the COVID-19 pandemic focused on the stringency, the effectiveness, and the impact of the countries’ interventions and paid rather little attention to the corresponding means used to support them. The present paper scrutinizes the lockdown measures and, particularly, examines the optimality of the lockdown fines imposed by countries worldwide towards ensuring citizens’ compliance. Initially, a triad of fine stringency indicators are compiled, and the stringency of fines is evaluated in a comparative context, among the countries considered. Consequently, the fine stringency is incorporated into a regression analysis with various epidemiological, socioeconomic, and policy factors to reveal any drivers of fine variability. Finally, theoretical approaches behind fine optimality are capitalized and real data are used towards estimating the optimal fine for each country considered. The objectives of the paper are, first, to check for any drivers of fine stringency around the world and, second, to develop and test a formula that could be used in order to assist policy makers to formulate evidence-based fines for confronting the pandemic. The findings of the paper highlight that fines do not seem to have been imposed with any sound economic reasoning and the majority of countries considered imposed larger real fines, compared to the optimal ones, to support the lockdowns. The paper stresses the need for the imposition of science-based fines that reflect the social cost of non-compliance with the lockdown measures. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Collapse shake-table testing of a clay-URM building with chimneys

This paper discusses the results of a unidirectional shake-table test carried out on a full-scale unreinforced clay-brick masonry building with chimneys. The specimen embodied construction details representative of old detached single-storey houses of the Groningen province in the Netherlands, without any specific seismic-resistant detailing. The house featured a typical Dutch gambrel roof that allowed for living space above the attic floor, with high gables that were vulnerable to out-of-plane excitation. The floor consisted of timber joists and planks, resulting in a flexible diaphragm. Two clay-brick chimneys were included to investigate the performance of falling non-structural masonry elements in earthquakes. A cumulative incremental dynamic test was performed up to collapse conditions, using input ground motions compatible with induced seismicity scenarios for the examined region. The paper summarises the key characteristics of the specimen and the observations from the shake-table tests, illustrating the evolution of the structural and non-structural damage, and the dynamic response of the building. The attainment of significant damage limit states is correlated with experimentally defined engineering demand parameters and ground-motion intensity measures for the performance-based seismic assessment of unreinforced masonry buildings. All data from the tests are available upon request on www.eucentre.it/nam-project