Seismic performance of buildings with structural and foundation rocking in centrifuge testing

Rocking motion, established in either the superstructure in the form of a 2‐point stepping mechanism (structural rocking) or resulting from rotational motion of the foundation on the soil (foundation rocking), is considered an effective, low‐cost base isolation technique. This paper unifies for the first time the 2 types of rocking motion under a common experimental campaign, so that on the one hand, structural rocking can be examined under the influence of soil and on the other, foundation rocking can be examined under the influence of a linear elastic superstructure. Two building models, designed to rock above or below their foundation level so that they can reproduce structural and foundation rocking respectively, were tested side by side in a centrifuge. The models were placed on a dry sandbed and subjected to a sequence of earthquake motions. The range of rocking amplitude that is required for base isolation was quantified. Overall, it is shown that the relative density of sand does not influence structural rocking, while for foundation rocking, the change from dense to loose sand can affect the time‐frequency response significantly and lead to a more predictable behaviour.     

Geographically distributed hybrid testing & collaboration between geotechnical centrifuge and structures laboratories

Distributed Hybrid Testing (DHT) is an experimental technique designed to capitalise on advances in modern networking infrastructure to overcome traditional laboratory capacity limitations. By coupling the heterogeneous test apparatus and computational resources of geographically distributed laboratories, DHT provides the means to take on complex, multi-disciplinary challenges with new forms of communication and collaboration. To introduce the opportunity and practicability afforded by DHT, here an exemplar multi-site test is addressed in which a dedicated fibre network and suite of custom software is used to connect the geotechnical centrifuge at the University of Cambridge with a variety of structural dynamics loading apparatus at the University of Oxford and the University of Bristol. While centrifuge time-scaling prevents real-time rates of loading in this test, such experiments may be used to gain valuable insights into physical phenomena, test procedure and accuracy. These and other related experiments have led to the development of the real-time DHT technique and the creation of a flexible framework that aims to facilitate future distributed tests within the UK and beyond. As a further example, a real-time DHT experiment between structural labs using this framework for testing across the Internet is also presented.     

Determinants of agricultural commercialization and mechanization in the hinterland of a city in Nepal

In view of the significance of agricultural commercialization for rural development, this study analyzed factors determining agricultural commercialization and mechanization in the hinterland of an urban centre in Morang district, Nepal. Information needed for the study was collected through a questionnaire survey, covering 120 farm households, and group discussion and key informant interviews. The regression analysis of determinants of agricultural commercialization revealed four significant variables, namely, the amount of inorganic fertilizer used, area under tractor-ploughing, area under pump-set irrigation and landholding size. The predicted R value of 0.87, R square of 0.75, and adjusted R square of 0.75 indicate the high explanatory power of the model as a whole. The regression model related to the area under pump-set irrigation predicted the degree of agricultural commercialization and the distance from the city as significantly influencing factors, with a predicted R value of 0.79, R square of 0.63, and adjusted R square of 0.62. The analysis of determinants of the area under tractor-ploughing found only the degree of commercialization as a significantly influencing factor, with a predicted R value of 0.77, R square of 0.59, and adjusted R square of 0.58. In both instances of farm mechanization, the degree of commercialization is the most influential factor, indicating the significant role of mechanization in agricultural commercialization. The major policy implications of the findings of the study are outlined.     

Future of wetlands in tropical and subtropical Asia, especially in the face of climate change

Tropical and subtropical Asia differs from other tropical regions in its monsoonal climate and the dominant influence of the Hindukush and Himalayan mountain ranges which result in extremes of spatial and temporal variability in precipitation. However, several major rivers and their tributaries arise in the Himalayan ranges and are fed by thousands of glaciers. Huge sediment loads carried by these rivers result in important deltas at their mouths. The climatic and physiographic diversity have endowed the region with many kinds of wetlands. Of these, the peatswamps of southeast Asia constitute about 56% of the world’s tropical peatlands, and more than 42% of the world’s mangroves occur in South and southeast Asia. Among other wetlands, riverine swamps are rather restricted whereas the seasonal marshes are a dominant feature. Another characteristic feature of tropical Asia are the innumerable human-made and intensively managed wetlands of which the paddy fields and aquaculture ponds are the most extensive. Throughout tropical Asia, wetlands have been a part of the socio-cultural ethos of the people and many communities have lived in wetlands. However, the pressures of high population and the economic development have extensively impacted upon wetlands which have been transformed for paddy cultivation and aquaculture, drained and converted to other land uses for economic gains (e.g., conversion to oil palm), and degraded by discharge of domestic and industrial wastes. Invasive plant and animal species have also played a significant role. The climate change is already being felt in the rapid retreat of Himalayan glaciers, increased temperature and variability in precipitation as well as the frequency of extreme events. Sea level rise is seen as a major threat to the coastal wetlands, particularly the mangroves. Increasing droughts have caused frequent fires in Indonesian peat swamps that have further feedback impacts on regional climate. However, the actual threat to wetlands in this region arises from the extensive hydrological alterations being caused by storage, abstraction and diversion of river flows for agriculture, industry and hydropower. Currently, the state of our understanding wetlands in general, and the efforts and infrastructure for research and training in wetlands are very poor. Although a few wetlands have been designated as Ramsar sites, the policies aimed at wetland conservation are either non-existent or very weak. Human responses to greater uncertainty and variability in the available water resources in different parts of Asia will be crucial to the conservation of wetlands in the future.     

Comparative analysis of some geomechanics problems using finite and infinite element methods

Four classical geomechanics problems involving semi-infinite linear elastic media have been solved numerically using recently developed mapped infinite elements coupled to finite elements.The effect of the remoteness of the truncated boundary and the location of infinite element coupling on solution accuracy has been studied. The results of conventional analyses using finite elements over a relatively large but restricted region are compared to the coupled analyses. Comparison of the results shows that for the same number of degrees of freedom the performance of the coupled solutions is superior to the conventional approach with respect to accuracy of solution and computational efficiency. Finally, some general guidelines are proposed for the efficient numerical solution of these types of problems using the coupled finite/infinite element approach.     

Modelling Solitary Waves and Its Impact on Coastal Houses with SPH Method

The interaction between solid structures and free-surface flows is investigated in this study. A Smoothed Particle Hydrodynamics (SPH) model is used in the investigation and is verified against analytical solutions and experimental observations. The main aim is to examine the effectiveness of a tsunami-resistant house design by predicting the wave loads on it. To achieve this, the solitary wave generation and run-up are studied first. The solitary wave is generated by allowing a heavily weighted block to penetrate into a tank of water at one end, and the near-shore seabed is modelled by an inclined section with a constant slope. Then, the SPH model is applied to simulate the three-dimensional flows around different types of houses under the action of a solitary wave. It has been found that the tsunami-resistant house design reduces the impact force by a factor of three.     

The Distribution Patterns of Timberline and Its Response to Climate Change in the Himalayas

Himalayan region represents the highest and most diverse treeline over the world. As one of the most conspicuous boundaries between montane forests and alpine vegetation, the alpine timberline attracted the interest of researchers for many decades. However, timberline in the Himalayas is understudied compared with European counterparts due to remoteness. Here we review the distribution pattern of timberline and its climatic condition, the carbon and nutrient supply mechanism for treeline formation, and treeline shift and treeline tree recruitment under climate change scenarios. Growth limitation, rather than carbon source limitation is the physiological cause of timberline under the low temperature condition. Nutrient limitation and water stress are not the direct cause of timberline formation. However, more clear local limitation factors are need to integrate in order to enable us to predict the potential impacts and changes caused by human activity and related global change in this sensitive region.     

Ten best practices to strengthen stewardship and sharing of water science data in Canada

Water science data are a valuable asset that both underpins the original research project and bolsters new research questions, particularly in view of the increasingly complex water issues facing Canada and the world. Whilst there is general support for making data more broadly accessible, and a number of water science journals and funding agencies have adopted policies that require researchers to share data in accordance with the findable, accessible, interoperable, reusable (FAIR) principles, there are still questions about effective management of data to protect their usefulness over time. Incorporating data management practices and standards at the outset of a water science research project will enable researchers to efficiently locate, analyse and use data throughout the project lifecycle, and will ensure the data maintain their value after the project has ended. Here, some common misconceptions about data management are highlighted, along with insights and practical advice to assist established and early career water science researchers as they integrate data management best practices and tools into their research. Freely available tools and training opportunities made available in Canada through Global Water Futures, The Gordon Foundation DataStream, the Digital Research Alliance of Canada Portage Network, Compute Canada, and university libraries, among others are compiled. These include webinars, training videos, and individual support for the water science community that together enable researchers to protect their data assets and meet the expectations of journals and funders. The perspectives shared here have been developed as part of the Global Water Futures programme's efforts to improve data management and promote the use of common data practices and standards in the context of water science in Canada. Ten best practices are proposed that may be broadly applicable to other disciplines in the natural sciences and can be adopted and adapted globally.     

Soil and water conservation measures improve soil carbon sequestration and soil quality under cashews

Land degradation is becoming a serious problem in the west coast region of India where one of the world's eight biodiversity hotspots,the‘Western Ghats’,is present.Poor land management practices and high rainfall have led to increasing problems associated with land degradation.A long-term(13-year)experiment was done to evaluate the impact of soil and water conservation measures on soil carbon sequestration and soil quality at three different depths under cashew nut cultivation on a 19%slope.Five soil and water conservation measures-continuous contour trenches,staggered contour trenches,halfmoon terraces,semi-elliptical trenches,and graded trenches all with vegetative barriers of Stylosanthes scabra and Vetiveria zizanoides and control were evaluated for their influence on soil properties,carbon sequestration,and soil quality under cashews.The soil and water conservation measures improved significantly the soil organic carbon,soil organic carbon stock,carbon sequestration rate and microbial activity compared to the control condition(without any measures).Among the measures tested,continuous contour trenches with vegetative barriers outperformed the others with respect to soil organic carbon stock,sequestration rate,and microbial activity.The lower metabolic quotient with the measures compared to the control indicated alleviation of environmental stress on microbes.Using principal component analysis and a correlation matrix,a minimum dataset was identified as the soil available nitrogen,bulk density,basal soil respiration,soil pH,acid phosphatase activity,and soil available boron and these were the most important soil properties controlling the soil quality.Four soil quality indices using two summation methods(additive and weighted)and two scoring methods(linear and non-linear)were developed using the minimum dataset.A linear weighted soil quality index was able to statistically differentiate the effect of soil and water conservation measures from that of the control.The highest value of the soil quality index of 0.98 was achieved with continuous contour trenches with a vegetative barrier.The results of the study indicate that soil and water conservation measures for cashews are a potential strategy to improve the soil carbon sequestration and soil quality along with improving crop productivity and reducing the erosion losses.