INTEGRATED PASSIVE-ACTIVE SYSTEM FOR SEISMIC PROTECTION OF A CABLE-STAYED BRIDGE

This paper presents an integrated passive-active (i.e. hybrid) system for seismic response control of a cable-stayed bridge. Since multiple control devices are operating, a hybrid control system could alleviate some of the restrictions and limitations that exist when each system is acting alone. Lead rubber bearings are used as passive control devices to reduce the earthquake-induced forces in the bridge and hydraulic actuators are used as active control devices to further reduce the bridge responses, especially deck displacements. In the proposed hybrid control system, a linear quadratic Gaussian control algorithm is adopted as a primary controller. In addition, a secondary bang-bang type (i.e. on-off type) controller according to the responses of lead rubber bearings is considered to increase the controller robustness. Numerical simulation results show that control performances of the integrated passive-active control system are superior to those of the passive control system and are slightly better than those of the fully active control system. Furthermore, it is verified that the hybrid control system with a bang-bang type controller is more robust for stiffness perturbation than the active controller with a μ-synthesis method, and there are no signs of instability in the over-all system whereas the active control system with linear quadratic Gaussian algorithm shows instabilities in the perturbed system. Therefore, the proposed hybrid protective system could effectively be used for seismically excited cable-stayed bridges.     

ON ISOTOPES AND OLD BONES*

This review charts the developments and progress made in the application of stable light isotope tools to palaeodietary adaptations from the 1970s onwards. It begins with an outline of the main principles governing the distribution of stable light isotopes in foodwebs and the quality control issues specific to the calcified tissues used in these analyses, and then proceeds to describe the historical landmark studies that have marked major progress, either in their archaeological applications or in enhancing our understanding of the tools. They include the adoption of maize agriculture, marine‐focused diets amongst coastal hunter–gatherers, trophic level amongst Glacial‐period modern humans and Neanderthals, and the use of savannah resources by early hominins in Africa. Particular attention is given to the progress made in addressing the challenges that have arisen out of these studies, including issues related to the routing of dietary nutrients. I conclude with some firm, and some more speculative, pointers about where the field may be heading in the next decade or so.     

EVALUATION OF DEFORMATION CAPACITY FOR RC T-SHAPED CANTILEVER WALLS

If RC structural walls are properly designed and proportioned, these walls can behave in a ductile manner. To achieve this goal, the designer should provide adequate strength and deformation capacity of structural walls corresponding to each performance level (e.g. immediate occupancy, life safety and collapse prevention). This study investigates the drift and ductility capacities of T-shaped structural walls on the basis of results from experimental tests and sectional analyses. To determine proper deformation capacities for T-shaped structural walls, structural performances of T-shaped walls were evaluated with several parameters such as longitudinal reinforcement ratio, distribution of longi-tudinal reinforcement, lateral confinement ratio, and axial load ratio. Based on these results, the level of deformation capacity specified in current design provisions (ICBO, UBC 1997), which were expressed as both strain-based damage limit and interstorey drift ratio, were evaluated.     

GENERATION OF ARTIFICIAL EARTHQUAKE MOTION RECORDS USING WAVELETS AND PRINCIPAL COMPONENT ANALYSIS

In the last century alone two to three million people died in earthquakes; More than 240 000 perish in Tangshan earthquake in China, 20 000 in the Izmit [Ikeya, 2004] 50 000 in India Bhuj earthquake, 100000 in Sumatra and 90000 in Pakistan earthquakes. Earthquake engineering has progressed to the stage where it is now computationally practical and desirable to perform a dynamic analysis of most civil engineering structures. Such an analysis requires the engineer to create an accurate analytical model of the structures as well as prescribe an earthquake input excitation. The design earthquake input excitation for the site under consideration is usually prescribed in the form of response spectra or in the form of an ensemble of artificial earthquake acceleration time histories. There is every need for generating artificial accelerograms since recorded accelerograms are very limited at site. This paper proposes five neural network based models for the generation of artificial earthquake and response spectra using wavelet transforms (WT) and principal component analysis (PCA) where the recorded accelerograms are limited at site of interest. The proposed model is compared with Lee and Han's model. The data for 25 earthquakes are taken for training and 4 for testing. Just like response spectra, this is also a convenient way of obtaining the design solution to a structural dynamics problem and is certainly an important tool.     

EVALUATION OF CAPACITY SPECTRUM METHOD FOR ESTIMATING THE PEAK INELASTIC RESPONSES

The accuracy of the capacity spectrum method (CSM) depends on the precise estimation of equivalent period and damping ratio as well as the modification of the demand spectrum. In this paper, the CSM provided in ATC-40 for estimating the peak inelastic responses is evaluated. First, the effect of equivalent period and damping ratio estimation on the accuracy of the CSM is assessed. Analyses results indicate that the difference between estimation methods is large when the structural nonlinearity is large, but becomes negligible as the hardening ratio increases. Next, the reduction factors provided in ATC-40 and Eurocode are evaluated. It is found that the acceleration responses obtained using the factor of Eurocode is closer to the actual ones than those obtained using the factors of ATC-40. Finally, the demand spectrum is constructed using the peak absolute acceleration and pseudo-acceleration. The results obtained using the peak absolute acceleration is found to be generally larger than those obtained using the pseudo-ones. Since the original CSM generally underestimates the response, the use of peak absolute acceleration in the construction of demand spectrum produces the response relatively closer to the exact one. However, the use of peak absolute acceleration overestimates the response more when the original CSM overestimates the response.     

At the end of the journey: the risks of Cold War thinking in a new era1

This article examines the justification for the existence of nuclear weapons. For many they were the saviour that brought an implacable foe to its knees in 1945 and held another at bay for nearly a half‐century. The belief that superior technology brought strategic advantage, that greater numbers meant strong security, and that the end of containment justified whatever means were necessary to achieve them prevailed. The author was an adherent to this point of view for several years. But these beliefs, Lee Butler contents, have proved dangerous. They account for the most severe risks and most extravagant costs of the US–Soviet confrontation; they intensified and prolonged an already acute ideological animosity; and they continue to entail enormous costs and expose humankind to unconscionable dangers. The author discusses how his convictions have evolved, and concludes that we have no greater responsibility than to bring the nuclear era to a close.     

Managing the interlocking climate and resource challenges

Energy security, climate change and food and water concerns are posing serious challenges to the management of international relations in an already turbulent world. These new developments—and the corresponding risk management strategies—will change the calculus of interests, powers and strategies for all actors, with significant impacts on the global political economy. Climate change action (such as targets for emissions reductions) will challenge the existing power structures, with the transition to a low-carbon economy creating new winners and losers in the global economy. Today, there is a fresh appreciation about the consequences of bad policy choices. Comparisons have been drawn between the fallout in the global financial system and the kind of risks that unmitigated climate change may bring. Even though the pressure on some resources may have eased since the onset of the global economic downturn in 2008, it is unlikely that the longer term trajectory has been reversed. This calls for renewed understanding and appreciation of the magnitude of risks foreseen. Multiple public goods need to be generated from the same production systems or sectors. In the context of climate change, international cooperation offers the only option that can best serve even narrowly defined national interests. Ensuring human security and peaceful relations among states in the decades to come will require short-term common action within the framework of long-term strategizing and visionary leadership as well as concerted efforts to deal head-on with worst case scenarios in our forecasting and policy planning.     

Louis de La Vallée Poussin, Theodore Stcherbatsky, and Tibetan Tradition on the Place of the Absolute in Yogācāra Buddhism

This paper examines the contrasting approaches to the study of Buddhism of two great early twentieth-century Buddhologists, Louis de La Vallée Poussin and Theodore Stcherbatsky. La Vallée Poussin understood Buddhism primarily as 'religion' and saw philosophic methods as subsumed in the religious experience of salvation; Stcherbatsky, coming from the Russian school, which had direct contact with Tibetan Buddhist scholasticism, saw Buddhism primarily as 'philosophy' and emphasised critical enquiry and logical consistency. The paper explores how this influenced their understanding of the place of the absolute in Buddhism generally and in Yogācāra Buddhism in particular. It compares their disagreement to differences at the heart of Tibetan scholasticism evident in the writings of Dolpopa (1292–1361) and Tsongkhapa (1357–1419) over the proper interpretation of Yogācāra. The paper also explores implications of the legacy of these two scholars for recent Western scholarship and for the understanding of Yogācāra.     

西汉张安世墓葬M1墓室内的大气环境调查

了解待发掘封闭墓葬内的大气环境,可为考古发掘和文物保存环境研究提供科学依据。西汉张安世墓园中的M1墓葬是一座未被盗扰的墓室,本研究在墓室开启前,有针对性地监测了墓室内的微气候参数和大气污染物。结果显示,相对于外界大气,密闭的墓室内低温、高湿、缺氧,且酸性气态污染物浓度较低。因此,在考古发掘及后续保存文物时,应针对不同文物材料采取密闭容器、保湿、避光等措施,避免由于环境骤变导致文物的风化损坏。本研究建立的待发掘墓葬大气环境测试体系及基础数据,可为相关考古和文保工作提供有益的借鉴。