Bridges - Steelconstruction. From Steelconstruction. Steel is widely used around the world for the construction of bridges from the very large to the very small. Types of Bridges and How They Work Beam Bridge Plank/bridge is supported by two bases. Under load, the top portion of the bridge compresses while the bottom. 2.2 BEAM SUPERSTRUCTURES Longitudinal beam superstructures are the simplest and most common timber bridge type (in bridge design, the longitudinal direction is meas Timber beam bridges, in the form of fallen tree trunks across streams. The most spectacular example of timber beam bridge construction is the long timber. It is a versatile and effective material that provides efficient and sustainable solutions. Steel has long been recognised as the economic option for a range of bridges. It dominates the markets for long span bridges, railway bridges, footbridges, and medium span highway bridges. It is now increasingly the choice for shorter span highway structures as well. Society gains in many ways from the benefits delivered by steel bridge solutions. Landmark steel bridges embody good design, they are fast to build, and have stimulated the regeneration of many former industrial, dock and canalside areas. Few man- made structures combine the technical with the aesthetics in such an evocative way. Look closely at the next . Steel also scores well on all the sustainability measures, and offers a broad range of benefits addressing the economic, environmental, and social priorities of the . Introduction of Speaker B. Bridge Construction Methods i. Precasting Techniques D. Presented by: Antonio Ledesma, PE When is balanced cantilever bridge construction a more feasible option? Design and Construction of the I-95/I-295 and. The Beam Bridge - Bridges support tremendous weight, span huge distances and all the while withstand the greatest forces of nature. Find out about these engineering. Bridge Design Engineers. Steel Bridge Design Handbook November 2012 U.S. Department of Transportation Federal High way Administration Structural Steel Bridge Shop. Minimum self- weight is also an important factor in the cost of transporting and handling components. Use of steel facilitates shallow construction depths, which overcomes problems with headroom and flood clearances, and minimises the length and cost of approach embankments. When a steel bridge reaches the end of its useful life, the girders can be cut into manageable sizes to facilitate demolition, and returned to steelworks for recycling. Some 9. 9% of structural steel either finds its way back into the steelmaking process where it is used to create new steel products or is reused. There is no degradation in the performance of recycled steel. Alternatively, component parts of steel bridges can be reused in other structures; entire bridges have been relocated and bridges can be designed with ease of future relocation in mind. Steel bridges can be made to look light or reassuringly solid, and can be sculptured to any shape or form. The high surface quality of steel creates clean sharp lines and allows attention to detail. Modern fabrication methods can easily provide curvature in plan and elevation. Beam Bridge Construction Pdf SoftwareThe painting of steelwork introduces colour and contrast, and repainting can change or refresh the appearance of the bridge. Structural steelwork is used in the superstructures of bridges from the smallest to the greatest. There is a wide variety of structural forms available to the designer but each essentially falls into one of four groups; beam bridges, arch bridges, cable- stayed bridges and suspension bridges. There are two principal forms of this beam and slab construction; multi- girder construction and ladder deck construction. Beam Bridge Construction Pdf EditorBetween them, they account for the majority of medium span highway bridges currently being built in the UK, and are suitable for spans ranging from 1. The choice between the two forms depends on economic considerations and site- specific factors such as form of intermediate supports and access for construction. This eliminates the need for expansion joints and bearings, which minimises future maintenance requirements. In these circumstances, . In beam and slab bridges, box girders are an alternative to plate girders at the upper end of the span range, where they offer a lower steel weight, although this has to be balanced against increased fabrication costs. Such composite box girder decks may take the form of multiple closed steel boxes, with the deck slab over the top, or an open top trapezoidal box, closed by the deck slab. For such long spans and for bridges such as lifting bridges, where minimising structural weight is very important, an all- steel orthotropic deck may be used instead of a reinforced concrete slab. Above about 2. 00m, box girders are likely to be part of a cable- stayed bridge or a suspension bridge, where they are specially shaped for optimum aerodynamic performance. Trusses have been used in a similar way to beams in composite decks (Oresund Approach Spans), as arches (Sydney Harbour Bridge), as cantilevers (Forth Rail Bridge) or as stiffening girders to suspension bridges (Forth Road Bridge). However, for through or half- through forms, truss bridges do offer a very stiff, lightweight solutions with minimum structural depth. Hence, they are widely used in the UK for footbridges, demountable bridges (Bailey bridges), gantries and longer span railway bridges (over 5. The arch springs from the foundations and exerts horizontal thrusts on them. The arch elements act primarily in compression. The deck may either be supported on struts, resting on arch below, or it may be suspended on hangers from the arch above. The horizontal thrusts from the arching action are resisted by tension members between the arch springings. Effectively the deck acts as a tension tie, and is supported by hangers from the arch above. This form is suited to the soft soils of riverbanks, where the ground cannot withstand the large horizontal thrusts from arching action. Arches are sometimes skew to the line of the deck and sometimes the arch planes are inclined for dramatic visual effect. There may be either a single plane of stays down the centre of the bridge, or two planes; one on each side of the bridge. The towers act in compression and can have a variety of forms (A- frame, H- frame or columns). The deck girders sustain compression forces as well as bending forces. The visual appearance of stayed structures can be very effective, even dramatic. They are frequently considered appealing or eye- catching. On a more modest scale, cable- stayed construction is sometimes used for footbridges, to give support and stiffness to an otherwise very light structure. The cables and hangers are in simple tension and the deck spans transversely and longitudinally between the hangers. In most cases the cables are anchored at ground level, either side of the main towers; often the side spans are hung from these portions of the cables. The stiffening girder spreads concentrated loads and provides stiffness against oscillation; such stiffness is needed against both bending and twisting actions. The graceful curve of the suspension cable combined with the strong line of the deck and stiffening girder generally give a very pleasing appearance. The combination of grace and grandeur in such situations leads to the acknowledged view that many of the world’s most exciting bridges are suspension bridges. Prefabrication of steelwork in controlled factory conditions leads to high quality work at minimum cost. The excellent quality control is achieved through a thorough testing regime at the steel mills and during the fabrication processes of cutting and drilling, assembly, welding, and protective treatment. The quality assurance that is attained should give confidence to all clients and engineers who specify steel for their bridge project. For structural use in bridges these products are inevitably cut (to size and shape) and welded, one component to another. In the structure, the material is subject to tensile and compressive forces. Structural steel generally responds in a linear elastic manner, up to the . All these aspects of steel material are utilised by the designer of a steel bridge. The yield strength is probably the most significant property that the designer will need to use or specify. The achievement of a suitable yield strength whilst maintaining other properties has been the driving force behind the development of modern steel making and rolling processes. S2. 75 steel is often used on railway bridges, where stiffness rather than strength governs the design, or where fatigue is the critical design case. However, the use of such steels confers no benefits in applications where fatigue, stiffness or the instability of very slender members is the overriding design consideration. These steels are also less readily available in the UK. In exposed conditions they need to be protected by a coating system. There are no special requirements of the steel material for ordinary coating systems, including both aluminium and zinc metal spray. However, if the steel is to be galvanized, then there is a need to control the alloy content (notably the Silicon content). The corrosion rate is so low that bridges fabricated from unpainted weathering steel can achieve a 1. This extends from initial concept design, through detailed design verification and on to appropriate specification. There may be little detailed calculation at this stage but there should be consultation with steelwork contractors and main contractors. Most bridge construction in the UK currently takes place under collaborative arrangements and thus access to steelwork contractors and main contractors should be readily available to the designer. In the absence of a collaborative arrangement, designers should at least discuss the options with a steelwork contractor at an early stage. So, as well as aiming for a structurally efficient solution, designers should consider how the steelwork will be fabricated and erected, how the deck will be completed (i. The chosen bridge erection scheme will clearly have a big influence on the type and location of any connections. However, for steel composite highway bridges, preliminary design charts and an associated software tool are available to facilitate far more accurate initial girder sizes. Detailed design is effectively design verification to the Eurocodes, which is more of a checking process than original creative design. Modelling and analysis is carried out for the selected structural arrangement for the various loading conditions (including fatigue) taking full account of any curvature and skew. Details such as shear connection, stiffener sizes and bracing member sizes, etc, are chosen at this stage to suit the global actions of the main members.
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