Dam Engineering — Earthquake Analysis

The performance of dams subjected to earthquakes is addressed with particular emphasis of recent earthquakes. Analysis of dams stability during earthquakes by experimental and mathematical models is referred. Foundation studies for soil and rock materials are described and assessment of liquefaction potential is discussed. Selection of design earthquakes by deterministic and probabilistic criteria is presented. Also neotectonics and attenuation relations are described. Monitoring and dam safety during construction and operation are addressed. Reservoir induced seismicity and prototype dynamic tests are treated. Ageing effects and rehabilitation of dams are discussed. Benefits and concerns of dams are referred. Risk analysis is addressed. Some final considerations and topics for discussions are presented

Entrepreneurial Strategies in a Declining Industry

This study explores the strategies of small firms in the North Carolina furniture supply industry, an industry that has suffered significant job loss due to foreign competition. In case studies of 17 firms, managers identified the strategies that they believed would be most effective in confronting the threats of global competition and imports. Entrepreneurial strategies involving development of new products and entry into new markets ranked highest, but most of the firms were employing strategies that emphasized efficiency and focused on existing products and markets. Firms that employed more entrepreneurial strategies reported superior financial performance in terms of revenue growth, suggesting that entrepreneurial strategies were in fact more effective in this declining industry. This research identifies the impediments that prevented firms from employing entrepreneurial strategies, as well as the types of resources the managers believed would be required for successful implementation of entrepreneurial strategies

A Community-Focused Health & Work Service (HWS)

We recommend establishment of a community-focused Health & Work Service (HWS) dedicated to responding rapidly to new health-related work absence among working people due to potentially disabling conditions. The first few days and weeks after onset are an especially critical period during which the likelihood of a good long-term outcome is being influenced, either favorably or unfavorably, by some simple things that either do or do not happen during that interval. It is the optimal window of opportunity to improve outcomes by simultaneously attending to the worker’s basic needs and concerns as well as coordinating the medical, functional restoration, and occupational aspects of the situation in a coordinated fashion

Representation Of Dam-Breach Geometry Using Quadtree Local Mesh Refinement

Advances in two-dimensional numerical modeling have allodam break floods to be simulated with larger domains than ever before. These types of simulations are important to meet the needs of inundation mapping, consequence analysis, and emergency planning for the large number of significant and high-hazard dams in the United States. Globally refining the mesh to the small cell sizes necessary to resolve small features such as dam breach geometry result in significant computational burden for these types of simulations. This manuscript details the research done to facilitate the implementation of quadtree local mesh refinement to represent dam breach geometry in an existing two-dimensional flood model and to test the model\u27s results and performance with several test cases. Results using local refinement agree with the results of global refinement with a significant reduction in computational burden

Additional crossing of the Clarence River at Grafton: flood impact, levee upgrade, and structural considerations

The Clarence River catchment, on the far north coast of New South Wales (NSW), is one of the largest catchments on the east coast of Australia, with an area of approximately 20,000km2. The lower Clarence River floodplain spans 500km2, within which lie the towns of Grafton and Maclean. These towns are home to over 20,000 residents collectively and serve as a rural centre for the surrounding agricultural lands. Both Grafton and Maclean are protected by levee systems which have been developed over time as a response to previous floods in the region. Roads and Maritime Services (RMS) is currently investigating options for an additional crossing of the Clarence River at Grafton to address short-term and long-term transport needs. All upgrade options for an additional crossing of the Clarence River will increase flood levels. RMS intends to maintain the current level of immunity and mitigate any adverse impact from piers and structures within the Clarence River by raising current levees. This paper draws upon and consolidates some of the findings from the options analysis to investigate considerations associated with spanning a 600m section of the Clarence River, mitigation of flood impacts, and modifications proposed to the existing levee systems

Understanding Seismic Embankment Dam Behavior Through Case Histories

From the lessons learned from past earthquakes, it is noticed that modern embankment dams withstand the design earthquake without significant damages. In spite of this scenario it is important to prevent the occurrence of incidents and accidents of embankment dams during the earthquakes and so a deep understanding of the triggering factors is important. Well documents case histories from many parts of the world related embankment dams behaviour during recent earthquakes were carefully selected and are discussed. Based in the governed factors attention is given to the requirements for materials characterization, modelling, analysis, monitoring and safety evaluation. Ageing effects and rehabilitation of dams are analysed. The risks associated with dam projects are discussed. The benefits and concerns of dams are presented. It is important to develop new ways of thinking and strategies to address the future challenges

Behavior of Two Big Rockfill Dams, and Design Aims

The case histories of two major compacted embankment dams are analysed with regard to the problem most amenable to reasonings and computations of statistics of averages, the problem of deformations, discussed regarding specific laboratory testing compared with use of generalized correlations. Improved mental models for predictions are proposed. In the earthcore-compacted rockfill section the problem of crest cracking suggests the interest in a significant change of zoned section in the topmost stretch. For the concrete-face rockfill dam it is suggested that one needs a significant revision of instrumentation and monitoring orientation. Both dams behaved extraordinarily well on questions of consequence and served to show that unfavourable observations, if too indirect, lead to no benefit, but may sometimes prove the inexistence of the consequential misbehavior to be guarded against

Reliability-based Assessment of Concrete Dam Stability

Risk management is increasingly used in dam safety and includes risk analysis, risk evaluation and risk reduction. Structural Reliability Analysis (SRA) is a probabilistic methodology that may be used in the risk assessment process. SRA has been frequently used for calibration of partial factors in limit state design codes for structures (not dams). In a reliability analysis a mathematical description of the failure mode, a limit state function, is defined. All parameters describing the limit state function should be random variables and are described by stochastic distributions (or, where appropriate, a deterministic value). The safety index (or probability of failure) may be determined by e.g. First Order Reliability Method and the result is compared to a target safety index to determine if the structure is safe enough. Several difficulties exists in the use of SRA for concrete dams, mainly due to the fact that only a few examples of such analysis for dams exist. One difficulty is how to define the failure modes. In this thesis a complete system of failure modes is identified, where failure is considered as a series system of “failure in the concrete part”, “failure in the concrete-rock interface” and “failure in the rock mass”. Failure in the concrete-rock interface may occur due to sliding or overturning. Sliding is the joint occurrence of sliding with a partially bonded contact (fails at very small displacement) and sliding with broken contact (fails at larger displacement) and both have to occur for sliding to occur, hence they are treated as a parallel system. Adjusted overturning is a combination of overturning and crushing of the concrete or crushing of the rock. A substantial part of the work has been to define the necessary input data. - Cohesion in the interface is very important. Due to the expected brittle failure in a partly intact interface, treatment of the shear resistance as a brittle parallel system is proposed. - Description of the headwater results in a series system; either failure occurs for water levels at retention water level (rwl) or for water levels above rwl, the latter described by an exponential distribution. - Uplift is one of the most important loads. A geostatistical simulation procedure is presented, where the hydraulic conductivity field of the foundation is described by a variogram and uplift is simulated by a FE-analysis. This methodology is demonstrated to be very useful and gives estimates of the statistical distribution of uplift. Three papers on this subject are included; the first is a description of the methodology, the second presents a sensitivity analysis performed for a large number of different combinations of input data and the last is an application to a Brazilian dam, where water pressure tests and monitoring results are available. In two papers SRA is applied to concrete dams and the system reliability is determined. In the first paper a spillway section where information of e.g. cohesion, friction angles etc. were available is analysed. In the last paper an idealized dam and a power intake structure are analysed. The conclusions are that SRA may be used for assessment of concrete dam stability and that it is well fitted for the dam safety risk management process. Every dam is a unique prototype and SRA enables specific behaviour and properties of a certain structure to be taken to consideration. The system reliability analysis is a very valuable tool in understanding the relationship between failure modes and enables the safety for the whole structure to be determined. In a reliability analysis the most important parameters may be identified and thus safety measures can be focused where it gives the best possible output. A general safety consideration is that development of the safety concept for concrete dams, from deterministic to probabilistic or semi-probabilistic, will give a known and more uniform level of safety