Climate change-induced hazards and local adaptations in agriculture: a study from Koshi River Basin,Nepal

Natural Hazards - Changes in climate, associated hazards, local adaptations in agriculture, and socioeconomic factors affecting adaptation were investigated using data from a large survey of 2310...     

Cyclic behavior of laterally loaded concrete piles embedded into cohesive soil

Modern seismic design codes stipulate that the response analysis should be conducted by considering the complete structural system including superstructure, foundation, and ground. However, for the development of seismic response analysis method for a complete structural system, it is first imperative to clarify the behavior of the soil and piles during earthquakes. In this study, full‐scale monotonic and reversed cyclic lateral loading tests were carried out on concrete piles embedded into the ground. The test piles were hollow, precast, prestressed concrete piles with an outer diameter of 300 mm and a thickness of 60 mm. The test piles were 26 m long. Three‐dimensional (3D) finite element analysis was then performed to study the behavior of the experimental specimens analytically. The study revealed that the lateral load‐carrying capacity of the piles degrades when subjected to cyclic loading compared with monotonic loading. The effect of the use of an interface element between the soil and pile surface in the analysis was also investigated. With proper consideration of the constitutive models of soil and pile, an interface element between the pile surface and the soil, and the degradation of soil stiffness under cyclic loading, a 3D analysis was found to simulate well the actual behavior of pile and soil. Copyright © 2007 John Wiley & Sons, Ltd.     

Visualising the spatial extent of predicted coastal zone inundation due to sea level rise in south-west Western Australia

Visualising coastal zone inundation is crucial for both a quick assessment of coastal vulnerability and a full understanding of possible implications to population, infrastructure and environment. This study presents a simple but effective method of assessing the spatial extent of coastal zone inundation due to predicted sea level rise using commonly available elevation and image data as well as GIS software. The method is based on the geometrical principle of matching the raised sea level with the corresponding elevation contour line on land. Results for a test area along the south-west coast of Western Australia (∼200 km of coast line) show that a sea level rise of less than 0.5 m over the 21st century will have only minor impact but will become important when added to an extreme sea level event (e.g. storm surge). Both century-scale (∼0.5 m) based on tide gauge records and larger (>few metres) longer-term sea level rise predictions based on the melt of ice covered areas show essentially the same areas that are most vulnerable. Furthermore, the effectiveness of the method is demonstrated by the detection of areas that can be protected by relatively small flood protective structures at river and estuary entrances, thus providing valuable information for policy makers and local councils.     

Seismic microzonation of the greater Bangkok area using microtremor observations

Bangkok, the capital city of Thailand, is located at a remote distance from seismic sources. However, it has a substantial risk from these distant earthquakes due to the ability of the underlying soft clay to amplify ground motions. It is therefore imperative to conduct a detailed seismic hazard assessment of the area. Seismic microzonation of big cities, like Bangkok, provides a basis for site‐specific hazard analysis, which can assist in systematic earthquake mitigation programs. In this study, a seismic microzonation map for the greater Bangkok area is constructed using microtremor observations. Microtremor observations were carried out at more than 150 sites in the greater Bangkok area. The predominant periods of the ground were determined from the horizontal‐to‐vertical (H/V) spectral ratio technique. A microzonation map was then developed for the greater Bangkok area based on the observations. Moreover, the transfer functions were calculated for the soil profile at eight sites, using the computer program SHAKE91, to validate the results from the microtremor analysis. The areas near the Gulf of Thailand, underlaid by a thick soft clay layer, were found to have long natural periods ranging from 0.8s to 1.2s. However, the areas outside the lower central plain have shorter predominant periods of less than 0.4s. The study shows that there is a great possibility of long‐period ground vibration in Bangkok, especially in the areas near the Gulf of Thailand. This may have severe effects on long‐period structures, such as high‐rise buildings and long‐span bridges. Copyright © 2003 John Wiley & Sons, Ltd.