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Fracture Critical Bridge
A fracture critical bridge is a bridge or similar span that is vulnerable to collapse of one or more spans as a result of the failure in tension of a single element. While a fracture critical design is not considered unsafe, it is subject to special inspection requirements that focus on the tension elements of its structure. Definition For a bridge to be defined as fracture critical: * It must possess structural members that are subject to tensile stresses from bending or axial forces. * The members must be non-redundant, lacking alternate load paths or means of safely redistributing forces in the event of a tensile failure. While members subject to compressive stress may also fail catastrophically, they typically do not fail from crack initiation. Examples of bridge designs that would typically be considered fracture critical are: * Most truss bridges with two main load-bearing assemblies * Two-beam girder bridges (three-beam bridges in California) * Two-cell steel box girder ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bridge
A bridge is a structure built to Span (engineering), span a physical obstacle (such as a body of water, valley, road, or railway) without blocking the path underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually something that is otherwise difficult or impossible to cross. There are many different designs of bridges, each serving a particular purpose and applicable to different situations. Designs of bridges vary depending on factors such as the function of the bridge, the nature of the terrain where the bridge is constructed and anchored, the material used to make it, and the funds available to build it. The earliest bridges were likely made with fallen trees and stepping stones. The Neolithic people built boardwalk bridges across marshland. The Arkadiko Bridge, dating from the 13th century BC, in the Peloponnese is one of the oldest arch bridges in existence and use. Etymology The ''Oxford English Dictionary'' traces the origin of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pontoon Bridge
A pontoon bridge (or ponton bridge), also known as a floating bridge, is a bridge that uses float (nautical), floats or shallow-draft (hull), draft boats to support a continuous deck for pedestrian and vehicle travel. The buoyancy of the supports limits the maximum load that they can carry. Most pontoon bridges are temporary and used in wartime and civil emergencies. There are permanent pontoon bridges in civilian use that can carry highway traffic; generally, the relatively high potential for collapse and sinking (e.g. due to waves and collisions) and high continuous maintenance costs makes pontoons unattractive for most civilian construction. Permanent floating bridges are useful for sheltered water crossings if it is not considered economically feasible to suspend a bridge from anchored Pier (architecture), piers (such as in deep water). Such bridges can require a section that is elevated or can be raised or removed to allow waterborne traffic to pass. Notable permanent pontoo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single Point Of Failure
A single point of failure (SPOF) is a part of a system that would Cascading failure, stop the entire system from working if it were to fail. The term single point of failure implies that there is not a backup or redundant option that would enable the system to continue to function without it. SPOFs are undesirable in any system with a goal of high availability or Reliability engineering, reliability, be it a business practice, software application, or other industrial system. If there is a SPOF present in a system, it produces a potential interruption to the system that is substantially more disruptive than an error would elsewhere in the system. Overview Systems can be made robust by adding Redundancy (engineering), redundancy in all potential SPOFs. Redundancy can be achieved at various levels. The assessment of a potential SPOF involves identifying the critical components of a complex system that would provoke a total systems failure in case of wikt:malfunction, malfunction. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fracture Mechanics
Fracture mechanics is the field of mechanics concerned with the study of the propagation of cracks in materials. It uses methods of analytical solid mechanics to calculate the driving force on a crack and those of experimental solid mechanics to characterize the material's resistance to fracture. Theoretically, the stress ahead of a sharp crack tip becomes infinite and cannot be used to describe the state around a crack. Fracture mechanics is used to characterise the loads on a crack, typically using a single parameter to describe the complete loading state at the crack tip. A number of different parameters have been developed. When the plastic zone at the tip of the crack is small relative to the crack length the stress state at the crack tip is the result of elastic forces within the material and is termed linear elastic fracture mechanics (LEFM) and can be characterised using the stress intensity factor K. Although the load on a crack can be arbitrary, in 1957 G. Irwin foun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Bridge Inventory
The National Bridge Inventory (NBI) is a database, compiled by the Federal Highway Administration, with information on all bridges and tunnels in the United States that have roads passing above or below them. That is similar to the grade-crossing identifier number database, compiled by the Federal Railroad Administration, which identifies all railroad crossings. The bridge information includes the design of the bridge and the dimensions of the usable portion. The data is often used to analyze bridges and to judge their condition. The inventory is developed for the purpose of having a unified database for bridges to ensure the safety of the traveling public, as required by the Federal Aid Highway Act of 1968. It includes identification information, bridge types and specifications, operational conditions, bridge data including geometric data and functional description, and inspection data. Any bridge more than 20 ft (6 m) long used for vehicular traffic is included. Descripti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ohio River
The Ohio River () is a river in the United States. It is located at the boundary of the Midwestern and Southern United States, flowing in a southwesterly direction from Pittsburgh, Pennsylvania, to its river mouth, mouth on the Mississippi River in Cairo, Illinois, Cairo, Illinois. It is the third largest river by discharge volume in the United States and the largest tributary by volume of the Mississippi River. It is also the sixth oldest river on the North American continent. The river flows through or along the border of six U.S. state, states, and its drainage basin includes parts of 14 states. Through its largest tributary, the Tennessee River, the basin includes several states of the southeastern United States. It is the source of drinking water for five million people. The river became a primary transportation route for pioneers during the westward expansion of the early U.S. The lower Ohio River just below Louisville was obstructed by rapids known as the Falls of the Oh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Point Pleasant, West Virginia
Point Pleasant is a city in and the county seat of Mason County, West Virginia, United States, at the confluence of the Ohio River, Ohio and Kanawha River, Kanawha Rivers. The population was 4,101 at the 2020 United States Census, 2020 census. It is the principal city of the Point Pleasant micropolitan area extending into Ohio. The town is best known for the Mothman, a purported humanoid creature reportedly sighted in the area that has become a part of Folklore of the United States, West Virginia folklore, and more broadly part of Culture of the United States, American popular culture. History A Shawnee village known as Upper Shawneetown was established in this area before 1749, which the Shawnees called "Chinoudaista" or "Chinodahichetha." The Céloron Expedition (1749) In the second half of 1749, the France, French explorer Pierre Joseph Céloron de Blainville (1693-1759) claimed French sovereignty over the Ohio Valley, burying a lead plaque at the meeting point of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silver Bridge
The Silver Bridge was an eyebar-chain suspension bridge built in 1928 which carried U.S. Route 35 over the Ohio River, connecting Point Pleasant, West Virginia, and Gallipolis, Ohio. Officially named the Point Pleasant Bridge, it was popularly known as the Silver Bridge for the color of its aluminum paint. On December 15, 1967, the Silver Bridge collapsed amid heavy rush-hour traffic, resulting in the deaths of 46 people, two of whom were never found. Investigation of the wreckage soon pointed to the failure of a single eyebar in one of the suspension chains as the primary cause — a finding noted in a preliminary report released within 10 months of the collapse. However, to explain why that eyebar failed — a failure triggered by a flaw just deep, which led to a fracture — required significantly more time and effort to uncover, with the final accident report taking three years to complete. The collapse led to significant changes in the way bridges in the U.S. are insp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eyebar
In structural engineering and construction, an eyebar is a straight bar, usually of metal, with a hole ("eye") at each end for fixing to other components. Eyebars are used in structures such as bridges, in settings in which only tension (physics), tension, and never compression (physical), compression, is applied. Also referred to as "pin- and eyebar construction" in instances where pins are being used. Structure A closed eyebar will typically have a rectangle, rectangular cross section of constant thickness throughout its length and a constant width for all but the ends. The ends will transition to a wider part that is terminated by a rounded end. In the center of this end will be a hole which will receive a cylinder (geometry), cylindrical pin, which may have provision to accept one or more nut (hardware), nuts or Screw, bolts. If of round cross section the bar will typically be end-forged to create a head, which is then flatted by additional forging. The head may then be mac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bent (structural)
A bent in American English is a transverse rigid frame (or similar structures such as three-hinged arches). Historically, bents were a common way of making a timber frame; they are still often used for such, and are also seen in small steel-frame buildings, where the term portal frame is more commonly used. The term is also used for the cross-ways support structures in a trestle. In British English this assembly is called a "cross frame". The term ''bent'' is probably an archaic past tense of the verb ''to bind'', referring to the way the timbers of a bent are joined together. The Dutch word is ''bint'' (past participle ''gebint''), the West Frisian is , and the German is . Compare this with the term bend for a class of knots. Bents are the building blocks that define the overall shape and character of a structure. They do not have any sort of pre-defined configuration in the way that a Pratt truss does. Rather, bents are simply cross-sectional templates of structural member ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tension (physics)
Tension is the pulling or stretching force transmitted axially along an object such as a string, rope, chain, rod, truss member, or other object, so as to stretch or pull apart the object. In terms of force, it is the opposite of ''compression''. Tension might also be described as the action-reaction pair of forces acting at each end of an object. At the atomic level, when atoms or molecules are pulled apart from each other and gain potential energy with a restoring force still existing, the restoring force might create what is also called tension. Each end of a string or rod under such tension could pull on the object it is attached to, in order to restore the string/rod to its relaxed length. Tension (as a transmitted force, as an action-reaction pair of forces, or as a restoring force) is measured in newtons in the International System of Units (or pounds-force in Imperial units). The ends of a string or other object transmitting tension will exert forces on the objects ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pin And Hanger Assembly
A pin and hanger assembly is used to connect two plate girders of a bridge. These assemblies are used to provide an expansion joint in the bridge. One beam (the ''anchor span'') is set on a pier with a short section cantilevered out toward the next pier. The other (the ''suspended span'') begins underneath the anchor span, and has its far end resting on the next pier. The beams have holes directly above each other. The two holes are connected using ''hangers'', a pair of connecting plates sandwiching the bridge girders. A pair of large steel pins through the plates and girder webbing provide the hinges, holding up the suspended span while allowing it to move longitudinally. Large washers are bolted to each end of the pin to retain the hangers. Exceptionally long spans may have two sets of girders cantilevered from opposite bridge piers with a third set of girders suspended by pin and hanger assemblies from both cantilevers. Safety concerns Pin and hanger assemblies are co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
