Simulation of Shake Table Tests on Out-of-Plane Masonry Buildings. Part (VI): Discrete Element Approach

ABSTRACT

Although many experimental tests and numerical models are available in the literature, the numerical simulation of the seismic response of existing masonry buildings is still a challenging problem. While the nonlinear behavior of masonry structures is reasonably predictable when the out-of-plane behavior can be considered inhibited, when the in-plane and out-of-plane responses coexist and interact, simplified models seem unable to provide reliable numerical predictions. In this article, taking advantage of the experimental tests carried out in a shaking table on two masonry prototypes at LNEC, a macro-element approach is applied for the numerical simulations of their nonlinear response. The adopted approach allows simulating the nonlinear behavior of masonry structures considering the in-plane and out-of-plane responses. Since it is based on a simple mechanical scheme, explicitly oriented to representing the main failure mechanisms of masonry, its computational cost is greatly reduced with respect to rigorous solutions, namely nonlinear FEM approaches. Two modeling strategies are adopted, namely a regular mesh independent from the real texture of the prototypes and a detailed one coherent with the units disposal. The numerical results are discussed and the correlation between the nonlinear static analyses and the dynamic response is provided.     

A Review of the Environmental Policy Literature from 2014 to 2017 with a Closer Look at the Energy Justice Field

This review article documents and analyzes trends within the environmental policy literature published between 2014 and 2017. We find that environmental policy scholarship has recently shifted its focus from more traditional topics, such as watershed and ecosystem management, to other modern issues, such as climate change and energy. The environmental policy literature has increased in complexity and become more interdisciplinary in nature, which we illustrate with a discussion of the energy justice literature. The methodological approaches used by environmental policy scholars have also become increasingly diverse, with a notable uptick in statistical and modeling approaches. We find that some topics, such as policy failure, gender issues, and energy welfare policies are under‐explored, and certain regions within the world, such as developing countries, are less frequently studied. We encourage scholars to consider these gaps in the literature when developing future research.     

The Role of Pilot Projects in Urban Climate Change Policy Innovation

Cities are taking a leadership role in addressing global climate change and reducing greenhouse gas (GHG) emissions, but policy innovations are needed to help cities move from goals to outcomes. Pilot projects are one means by which cities are experimenting with new ways of governing and financing climate change mitigation. In this paper, we develop a framework for understanding the role of pilot projects in urban policy innovation: their emergence and rationale, and the means by which they ultimately scale up and out to reduce GHG emissions. We use this framework to evaluate a pilot project for retrofitting social housing buildings in Toronto. We find the initial pilot project helped address the challenges of pursuing deep retrofits of social housing. Scaling these lessons up to the city level required overcoming challenges to financing and coordinating a larger project; scaling out to the provincial level revealed institutional and political obstacles to pursuing the co-benefits of deep building retrofits in social housing. Bridging agents play an important role in both scaling processes. The analysis reveals the additive nature of urban policy innovation and the dynamic interplay of change agents and institutional and political context in innovation processes.     

A Micro Model of Problem Definition and Policy Choice: Issue Image,Issue Association,and Policy Support of Power Plants

Past research on problem definition and public policy primarily focuses on the macro-system level. In this study, we propose a micro model of problem definition and policy choice at the individual level. We argue that while individual citizens' problem definitions and policy preferences are rooted in and filtered through their predisposition characteristics (such as socioeconomic status, political orientation, and informational base), their policy choices also strongly depend on how they define public issues, particularly how they perceive the image of an issue at hand and how they associate the issue with other public issues. Our empirical analyses, based on data from a national public survey on energy and power plant issues, support the key propositions derived from our theoretical model. Key contributions to and implications for policy studies are discussed in conclusion.     

Earthquake Protection of Colonial Bell Towers in Colima,Mexico with Externally Prestressed FRPs

A methodology for the seismic vulnerability reduction of old masonry towers with external prestressing is presented. It is applied at the Colonial bell-towers of the Cathedral of Colima, Mexico, characterized for being a high seismic area (M>7.5). The 3D FE models are calibrated with experimental data and assessed through nonlinear static approaches including the seismic demand and an accurate validated masonry model. Based on an extensive parametric study on different configurations of old masonry towers, it is selected an optimal prestressing force and device. The Colonial towers are retrofitted with four prestressing devices of FRPs to convert them into a high energy-dissipative reinforced masonry. The external vertical prestressing is included at key points identified in the seismic vulnerability assessment. This technique is in compliance with the demand for architectural conservation and may be located without drilling and unbounded in order to be fully removable. The seismic performance is enhanced by increasing force, displacement, and internal confinement. It is observed an upgrading of 35% and 20% of displacement capacity. With these results it is corroborated that external vertical prestressing allows a substantial increment of ductility for seismic energy dissipation purposes.     

Are Ukraine’s reforms breaking its state capture? An agenda for genuine change

Abstract

Ukraine is one of a handful of post-communist countries that has a lower Gross Domestic Product today than in 1990, according to the World Bank. The problem is that it has seen too little reform. The country has experienced three serious periods of reform, but none has been as important as the reforms of 2015. The big question is whether Ukraine has finally broken out of persistent state capture. This paper by long-lasting Ukraine-watcher Anders Åslund suggests that Ukraine has carried out greater economic reforms than ever before with the unification of energy prices, large budget cuts, floating exchange rates, halved payroll tax, and a major bank purge. Yet, the question remains whether Ukraine has really broken out of state capture and whether it will be able to turn to a steady course of high economic growth of 5–7% a year.     

A HISTORY OF THE SPECIES?1

By rejecting the old divide between prehistory and history, the group of scholars behind Deep History opens a new window on the problem of the unity and diversity of human experience over the very long run. Their use of kinship metaphors suggests not only a link between modern society and the deep past, but also perhaps a way to imagine the common legacy of the human species. But what emerges from Deep History is hardly a sunny story about the distant origins of social justice and ecological harmony. The other central metaphor of the book—the fractal—uncovers the slow prelude to the Anthropocene. Rather than seeing a sharp break in the Industrial Revolution from an “organic” to a fossil fuel‐burning economy, these scholars stress the history of environmental destruction that has accompanied human expansion. My critical reading presents an alternative understanding of deep history as an arena for a new politics of species. Here a cornucopian understanding of human adaptation clashes with a new pessimism about the climatic fragility of Neolithic civilization.     

The Impact of Energy,Transport, and Trade on Air Pollution in China

A team of U.S.- and China-based geographers examines the relationship between China's economic development and its environment by modeling the effects of energy, transport, and trade on local air pollution emissions (sulfur dioxide and soot particulates) using the Environmental Kuznets model. Specifically, the latter model is investigated using spatial econometrics that take into account potential regional spillover effects from high-polluting neighbors. The analysis finds an inverted-U relationship for sulfur dioxide but a U-shaped curve for soot particulates. This suggests that soot particulates such as black carbon may pose a more serious environmental problem in China than sulfur dioxide. Journal of Economic Literature, Classification Numbers: C50, F10, Q43, R40. 4 figures, 3 tables, 47 references.     

The stress regime of the Western Canadian Sedimentary Basin

All available information relevant to in situ stress orientations and magnitudes in the Western Canadian Sedimentary Basin (WCSB) were examined to provide a better understanding of how regional stress fields may affect geothermal development. The smallest principal stress is horizontal over most of the Western Canadian Sedimentary Basin, and it varies in magnitude across the region. Horizontal stress trajectories show that S_Hmax axes are generally aligned SW–NE. A total of 1643 measurements of microfracture and minifracture closure pressures, leak‐off pressures and fracture breakdown pressures have been harnessed to map S_Hmin gradients across the basin at depths of 156–500, 500–1000, 1000–4185 and 2000–4185 m. Vertical stress magnitudes, calculated in 91 wells, showed that at constant depth, S_V increases towards the Canadian Rocky Mountains. Resultant regional stress maps show consistent trends in orientation of stress axes. As a result, predictions can be made that propagation axes of subsurface hydraulic fractures will be dominantly SW–NE, except over the Peace River Arch area, where they will trend more towards SSW–NNE. Engineered geothermal systems in the WCSB can be optimised by drilling horizontal wells parallel to S_Hmin.     

INELASTIC SEISMIC RESPONSE ANALYSIS BASED ON ENERGY DENSITY SPECTRA

Energy balance is used to characterise the seismic energy in inelastic structures where energy input to the structure is decomposed into strain energy, kinetic energy, damping energy, and plastic energy. The exact quantification of plastic energy is derived based on force analogy method for moment-resisting frames. A method of generating energy density spectra is then proposed based on yield displacement of a single degree of freedom system. The effects of different structural vibration characteristics are then studied on energy density spectra. These effects include variations of yield displacement level, earth-quake scaling factor, and damping ratio, which proves to be useful in improving the basic understanding of energy characteristics in structural dynamic response. Finally, the use of energy density spectra is demonstrated on a multi-degree of freedom structure to show the practical applications of these spectra.