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.     

FRICTION DAMPED STEEL MOMENT-RESISTING FRAMES SUBJECTED TO LONG-DISTANCE EARTHQUAKES: INFLUENCE OF WELD FRACTURES

It has been generally accepted that steel moment-resisting frames behave in a ductile manner under seismic excitations. However, during the 1994 Northridge earthquake in California, weld fractures at the beam-to-column connections occurred in many steel buildings. Such brittle failures obviously precluded the traditional ductile-behaviour assumption and had a significant effect on the responses of steel moment-resisting frames. In this paper, the performance of a friction damping system for retrofitting steel moment-resisting frames was investigated under long-distance earthquakes. For this purpose, the 1985 Mexico City (SCT), the 1995 Bangkok, or the 1977 Romania ground motions, all scaled to a peak ground acceleration of 0.17 g, were considered in this study. Responses of the building under the 1940 El Centro N-S component were also included for comparison. The results of the study show that a friction damping system can reduce the seismic responses significantly. The devices can also prevent the total collapse and joint failures of the building equipped with friction dampers, while the one without dampers would collapse, even under a peak ground acceleration of only 0.17 g.     

STRENGTH REDUCTION FACTORS FOR DUCTILE STRUCTURES WITH PASSIVE ENERGY DISSIPATING DEVICES

In recent years, current seismic codes started contemplating the design of structures with passive energy dissipating devices. One important issue for the rational seismic design of these devices and the structure that contains them is the formulation of numerical methods to estimate their design seismic forces. From the study of the dynamic response of single-degree-of-freedom systems subjected to accelerograms recorded in Mexico during the last two decades, expressions to estimate the strength reduction factor that should be used to reduce the elastic design strength spectra for 5 percent damping, to establish the design seismic forces for structures having different combinations of plastic and viscous energy dissipating capacities, are formulated.     

Energy Intensity in Light of China's Economic Transition

Two economic geographers examine the impacts of economic transition on the efficiency of energy use in China, the second-largest energy consumer in the world. Following a brief review of reform and deregulation in China's energy sector, they proceed to systematically test the relationship between economic transition (conceptualized as a triple process of marketization, decentralization, and globalization) and energy intensity using a panel data set. The statistical units of analysis are China's 30 provincial-level administrative regions, facilitating the investigation of spatial variations in energy intensity. Journal of Economic Literature, Classification Numbers: O53, P20, Q40, Q43. 9 figures, 5 tables, 62 references.     

The Clean Energy Dilemma in Asia: Observations on Russia and China

Two American economic geographers and prominent specialists, respectively, in the energy industries and resources of Russia and related economic developments in China, evaluate and supplement the material presented in the preceding paper on the clean energy dilemma in Asia (Wilbanks, 2008). The paper covers changes in the relationship between energy consumption and economic growth globally as well as in Russia and China, Russian oil and gas exports to Asia (more specifically to China), the development of energy resources and production in China, and energy intensities in both countries.