Stay cables, the primary load carrying components of cable-stayed bridges (CSBs), are characterised by high flexi-bility which increases with the span of the bridge. This makes stay cables vulnerable to local vibratio...Stay cables, the primary load carrying components of cable-stayed bridges (CSBs), are characterised by high flexi-bility which increases with the span of the bridge. This makes stay cables vulnerable to local vibrations which may have significant effects on the dynamic responses of long-span CSBs. Hence, it is essential to account for these effects in the assessment of the dynamics CSBs. In this paper, the dynamic responses of CSBs under vehicular loads are studied using the finite element method (FEM), while the local vibration of stay cables is analyzed using the substructure method. A case study of a cable-stayed steel bridge with a center span of 448 m demonstrates that stay cables undergo large displacements in the primary mode of the whole bridge although, in general, a cable’s local vibrations are not obvious. The road surface roughness has significant effects on the interaction force between the deck and vehicle but little effect on the global response of the bridge. Load impact factors of the main girder and tower are small, and the impact factors of the tension of cables are larger than those of the displacements of girders and towers.展开更多
Several research efforts have focused primarily on policy implementation and improving innovative actions to address disaster risks. Discussions are ongoing on how to measure the effectiveness of policy implementation...Several research efforts have focused primarily on policy implementation and improving innovative actions to address disaster risks. Discussions are ongoing on how to measure the effectiveness of policy implementation at the local level. But there is no definitive theory of effective policy implementation, and very few frameworks have been found acceptable as the basis of an analysis of the effectiveness of policy implementation, especially on droughts. Based on the 2009–2010 extreme drought in Yunnan, China, this article presents a modified framework to assess the effectiveness of policy implementation by defining policy, practice, and performance, as well as a feedback loop by which to share the lessons learned. Water conservancy projects in Luliang County and the agricultural diversity program in Longyang County in Yunnan Province were analyzed from a farmers' perspective. It was found that farmers are highly dependent on government policies and projects, and the effectiveness of policies is measured by short-term, immediate, and tangible benefits rather than long-term adaptation strategies. The results highlight the urgent need to reduce risks by developing better awareness about climate change and drought and its impacts, increased understanding of drought hazards, and implementation of appropriate measures for long-term adaptation.展开更多
基金Project(No.20100481432)supported by the China Postdoctoral Science Foundation
文摘Stay cables, the primary load carrying components of cable-stayed bridges (CSBs), are characterised by high flexi-bility which increases with the span of the bridge. This makes stay cables vulnerable to local vibrations which may have significant effects on the dynamic responses of long-span CSBs. Hence, it is essential to account for these effects in the assessment of the dynamics CSBs. In this paper, the dynamic responses of CSBs under vehicular loads are studied using the finite element method (FEM), while the local vibration of stay cables is analyzed using the substructure method. A case study of a cable-stayed steel bridge with a center span of 448 m demonstrates that stay cables undergo large displacements in the primary mode of the whole bridge although, in general, a cable’s local vibrations are not obvious. The road surface roughness has significant effects on the interaction force between the deck and vehicle but little effect on the global response of the bridge. Load impact factors of the main girder and tower are small, and the impact factors of the tension of cables are larger than those of the displacements of girders and towers.
基金supported by the University of Chinese Academy of Sciences(UCAS)/Kunming Institute of Botany(KIB)the Himalayan Climate Change Adaptation Programme(HICAP) funded by the governments of Norway and Sweden+2 种基金core funds of the International Centre for Integrated MountainDevelopment(ICIMOD)supported the Summer Institute for Disaster and Risk Research implemented by Beijing Normal University (BNU)funded by the State Administration of Foreign Experts Affairs, Ministry of Education, and BNU
文摘Several research efforts have focused primarily on policy implementation and improving innovative actions to address disaster risks. Discussions are ongoing on how to measure the effectiveness of policy implementation at the local level. But there is no definitive theory of effective policy implementation, and very few frameworks have been found acceptable as the basis of an analysis of the effectiveness of policy implementation, especially on droughts. Based on the 2009–2010 extreme drought in Yunnan, China, this article presents a modified framework to assess the effectiveness of policy implementation by defining policy, practice, and performance, as well as a feedback loop by which to share the lessons learned. Water conservancy projects in Luliang County and the agricultural diversity program in Longyang County in Yunnan Province were analyzed from a farmers' perspective. It was found that farmers are highly dependent on government policies and projects, and the effectiveness of policies is measured by short-term, immediate, and tangible benefits rather than long-term adaptation strategies. The results highlight the urgent need to reduce risks by developing better awareness about climate change and drought and its impacts, increased understanding of drought hazards, and implementation of appropriate measures for long-term adaptation.
