Pier scour in coarse bed and cohesive materials Research Paper

Pier scour in coarse bed and cohesive materials - Research Paper Example This results to approximately 60 percent of all bridge failures. The societal repercussions that are associated with failures and the costs that are linked to repair are amplified in Alaska, alternate routes of ground transportation between several cities are not in existence. Bridge culvert damages cost a lot to the economy, for example, in 2002 the damage in Kenai Peninsula was estimated at about 19 million dollars. This led to bridge site examination for scour. This paper therefore seeks to discuss the background of scour, its description, the pier scour, and its equation. Scour Scour is a hole that remains behind when sand and rocks, sediments are washed away from the river bottom. Even though scour often occur at any particular time, the scour action is strong especially during flood season. This is because swiftly flowing water has much energy than slowly flowing calm water to lift and wash away sediments from the river bottom. Scour is of a great concern to bridges. This is be cause if rocks or sediment on which bridge is supported or rest is scoured by the river, it is most probably that the bridge could be very unsafe for travel purposes. For example, in 1987 when the Interstate Highway bridge over Schoharie Creek in the state of New York collapsed following a flood, the Federal Highway Administration demanded that each state to specify bridges on the highway over water that are likely to experience problems of scour and to have the bridges with severe scour identified. This knowledge of bridge sites in which there are potential scour problems will enable the States to improve and monitor the bridge conditions ahead of time before they pose danger to travelers. Types of scour There are three main types of scour that affect bridges. The following are the major types of scour that may pose danger to highway bridges over water: Local scour: this occurs when sediments are swept away from around bridge piers and/ or abutments. Piers in this particular case a re the pillars that support bridges, while abutments are the ones supporting the end of the bridge. Flowing water past abutment or pier may scoop holes out in the sediment resulting into scour holes. Contraction scour: this type of scour occurs the sediments are swept away from the sides and bottom of the river. Contraction scour is majorly caused by an increased speed in water flow as it flows through an opening of a bridge which is narrower than the natural channel of the river. Degradation scour: this is a general removal of sand and rocks, sediments from the bottom of the river by the flow of the river. This is often a natural process of sediment removal that lowers the bottom of the river resultantly. In most cases, the process removes large quantities of sediment with time. Pier scour Piers scour is the removal of sediments around the pier. This occurs when rocks and sand in which the bridge rests are removed by flowing water. This is very dangerous to travelers and may cause high magnitude accidents. Adequate definition of potential pier scour at piers is very essential to a proper construction, design, and maintenance of bridges. Designing cost effective and safe bridge depends on accurate estimate of the depth of scour. Thus, underestimating the depth of the scour can place both human life and structures at risk. On the other hand, consistent

Business Model Part 3 Essay Example | Topics and Well Written Essays - 1500 words

Business Model Part 3 - Essay Example It makes use of decision centre, decision frame, horizon, period, and so on which is described below for an EBE of ResearchArchive. GRAI grid helps to achieve good control and management of activities. The GRAI grid is a two dimensional structure containing horizontal functional blocks with decision centers. â€Å"A decision centre is an organization unit which is the locus of a decision making process.† (Vernadat, F, 1996, p.296) A decision center represents an entity that gives decisions which can be persons or automated machines or computer programs as well. The flow of decision marks the dependencies between various activities. Diagrammatically it is represented by a double arrow. The information flow is the amount of data that is exchanged, referred or shared by different functional units amongst themselves for efficient functioning. For example, the recruitment process will need the information from various units; about costing plans, about vacancies, roles that need responsibility, etc. In that case the flow of information is marked accordingly to show linkages between units. This information flow is diagrammatically represented by single arrow. Different levels in the grid signify occurrence of activities at that level. Precisely, grid makes it simpler to understand the frequency of repetition of certain activities over other activities with respect to priorities and duration of execution. The nature of task is also of prime importance while locating the task in grid. The company functions by first making available and organizing the e-material that is to be traded. Hence it needs to locate sources for its own benefit. Next important step is to acquire and manage human as well as non human resources to carry out company tasks. Managing funds, cash inflow and out flow is crucial for company growth and its survival in competitive market. It