Rehabilitation of Steel Truss Bridges in Ontario
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Bridge (graph theory)
Truss bridge
Decision process
AAR Bridge Program No. 2, thoroughly updated, calculates maximum bar forces and support reactions of general railway truss bridges under stationary or moving loads. Trusses may be simple supported, continuous over several supports, internally indeterminate or contain counter diagonals. Maximum span length cannot exceed 620 ft for a Standard Cooper E loading, of 1000 ft for other types of moving loads. Truss can have no more than 25 panels and number of panels with counter diagonals cannot exceed 10. There are restrictions on trusses containing counter diagonals. Input required is truss geometry, cross sectional areas, dead loads, live loads. Output includes dead load, live load, AREA impact and total forces in each member and truss reactions.
Truss bridge
Statically indeterminate
Bridge (graph theory)
Structural load
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The main bridge of Tongling Changjiang River Rail-cum-Road Bridge is a five-span continuous steel truss girder cable-stayed bridge with span arrangement(90+240+630+240+ 90)m.The main girder of the bridge is comprised of 3N-shape main trusses and the trusses are all of the two-panel all-welded truss unit structures.A two-panel truss unit is 30mlong,2.85m wide,18mhigh and the heaviest unit weighs 360t.The truss unit is formed by welding the upper,lower chords and web members.For the manufacturing of the main girder,the techniques of manufacturing the two-panel all-welded truss units and the upper and lower deck plates in blocks in integrity are used.To ensure the manufacturing accuracy of a truss unit,the technique of the 2+1 match manufacturing is used.After a upper chord,lower chord,vertical web member and inclined web member of the unit are manufactured,the unit is then generally assembled.3allwelded truss units are manufactured on one jig stand.When the previous two units are manufactured and moved out of the jig stand,the last unit is moved to the front and is used as the parent girder,the successive truss units are continuously match assembled until all units are assembled. Presently,the erection of the truss girder of the bridge has been completed and the manufacturing accuracy of the truss girder can meet the relevant requirements in the codes.
Chord (peer-to-peer)
Truss bridge
Bridge (graph theory)
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Most statics courses begin with a considerable amount of abstract discussion of forces and vectors. Since the mechanical engineering technology department's goal is to focus on practical, concrete instruction methods, the faculty has been working to expose students to more exercises that involve the practical application of statics to daily life. For the statics curriculum, a laboratory was developed that investigates the use of trusses in the surrounding community. Each truss is examined to determine its primary purpose, its type and any unique design features. Small groups discuss each example qualitatively (quantitative analysis of the forces in the truss is not performed) and then the whole class meets to compare the results. The trusses include the following: • Sherman Minton Bridge - Double arch truss. • K&I Railroad Bridge - Parker and Warren through trusses with a swing section and a cantilevered road deck parallel with the tracks. • Pedestrian Bridge - Pratt truss. • Pennsylvania Railroad Bridge - Combination of Parker through trusses over shipping lanes with Warren deck trusses. • Clark Memorial Bridge - Cantilever truss. Since each truss serves a similar transportation purpose, each truss is compared to the others to determine why its particular design was chosen. This paper describes each example and the effects the exercise had on student learning. This includes discussion of: increased interest by relating statics to daily experiences, experience with reverse engineering, practice identifying members in tension and compression, comparison of a standard truss with a cantilever truss bridge and recognition of changing design practices as technology changes over the years. Lastly is a description of the assessment, evaluation and planned improvements to the truss laboratory.
Statics
Truss bridge
Bridge (graph theory)
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The erection of a new steel truss bridge in Charleston, South Carolina is described. Bid competetively with a concrete cable-stayed design, the 1,600-ft through truss span of the Cooper River Bridge employs a parallel-chord Warren truss, with no vertical members or sway bracing. It is noted that because there are no stress-relieving joints in the truss deck, reduced maintenance costs will result. The bridge is 3.1 miles, inlcuding the 800-ft main span, 400-ft flanking truss spans, and long viaducts over tidal marshes and lowlands. The main span will have 155 ft vertical clearance, and 700 ft horizontal clearance over the Cooper River navigation channel. Load factor design was used to obtain the size of all elements of the truss span, while development of high strength steels made possible fabrication of slim, low profile truss elements. Details of the design, truss erection, and the paint system are summarized.
Truss bridge
Bracing
Chord (peer-to-peer)
Bridge (graph theory)
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An eastbound train transporting a 100 ton wrecking crane was travelling over an 894 ft long bridge crossing the St. Maurice River when the boom of the crane broke loose and hit the side of one of the 132 ft truss spans. The boom of the crane then swung towards the caboose, striking it and derailing both the crane and the leading truck of the caboose, resulting in further damage to the truss. Extensive damage resulted to a considerable number of main truss members, including an end post that was sheared by 60% of its cross-section on one side of the truss and on the other side shearing and twisting of up to 80% of the end post, diagonal, vertical, hanger and a large number of secondary members. This paper describes the design, analysis and unusual methodology used in replacing the damaged truss members in record time without the use of any type of shoring.
Truss bridge
Bridge (graph theory)
Hammer
Shoring
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Bridges will always be an important project on human beings’ development. The society is in continuous decelopment, and the construction never stop, thus, the demand for bridges has been increasing for thousands of years. The bridge which can take more loads whilst using less materials will replace old one. And then the truss structure and truss bridges gradually come into public’s view. For the special triangle structure applied on them, the truss structure and truss bridges become of vital important in engineering, using the truss structure on the bridges which have long span can save a lot of money, and because of its special triangle structure, truss bridges can get the same or even more intensity than other bridges in different material. And the development of the truss can be tracked back to the simple wood structure, whilst the current truss bridges use some new materials such as shape memory alloys and modified reinforced concrete. The current study gives an overview on the development history about truss bridges in all ages from China to the world, and will discuss the alternative from material to the structure.
Truss bridge
Bridge (graph theory)
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In a recent article, Adeli and Balasubramanyam [2] presented a heuristic approach for analysis of bridge trusses subjected to American Association of State Highway and Transportation Officials (AASHTO) moving loads. This procedure is based on the recognition of patterns of influence line diagrams (ILDs) for various members of a bridge truss. The procedure was applied to Pratt trusses. This arricle extends and generalizes the previous work of the authors by applying it to other classes of trusses, i.e., the statically determinate K‐trusses and the statically indeterminate Parker trusses. This approach is significantly more efficient than the bruteforce method of generating the nodal load vectors due to the moving loads positioned at numerous locations along the span and performing numerous structural analyses. Thus, it is particularly suitable for microcomputers. The heuristic approach presented in this article can be easily extended to other classes of bridge trusses.
Statically indeterminate
Bridge (graph theory)
Truss bridge
Influence line
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In steel truss bridges, some truss members are exposed to solar radiation, while others are shaded by steel decks, which may result in large temperature gradients between truss members and further induce significant horizontal rotation angles (HRAs) at beam ends of steel truss bridges. Therefore, using the long-term monitoring data from a railway steel truss bridge with a 2-layer deck, the effect of temperature gradients on HRA was studied. Several analytic methods related to this topic are proposed, including a method for identifying large temperature gradients in steel truss bridges, a method for identifying whether the thermal load is the dominant load affecting HRA, and a method for identifying what kinds of temperature gradients have significant impacts on HRA. The results show that there are significant vertical temperature gradients between the top and bottom truss members in the side trusses and significant transverse temperature gradients between the bottom truss members, the thermal load is the dominant load affecting HRA compared with the other dynamic loads, and the temperature gradient between the bottom truss members in the side trusses has the greatest effect on HRA.
Truss bridge
Temperature Gradient
Beam bridge
Bridge (graph theory)
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In 1829 Stephen Harriman Long built a wood truss with details well suited to the mechanical behavior of wood. The truss was statically indeterminate, prestressed by wedges and required no tensile connections for the diagonals. In 1840 William Howe and Amasa Stone improved Long's design by using threaded vertical iron rods for prestressing. In 1839 Long patented a truss with diagonals that were pretensioned by using wedges on the vertical members. Long's method of prestressing the diagonals in tension was improved by Thomas and Caleb Pratt, who prestressed by tightening threaded iron diagonals. However, their design was not immediately successful for bridges with wood chords because prestressing often caused local crushing of the wood. Therefore, the dominant American truss at mid-century was the Howe truss, wonderfully adapted to the properties of wood, statically indeterminate, prestressed, easily adjusted and maintained, and with precompressed diagonals bearing on joint castings without positive connections to the chords and verticals. All these features were destined to be abandoned by American engineers over the next 20 years.
Truss bridge
Statically indeterminate
Bridge (graph theory)
Prestressed concrete
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Analogous cantilevered truss method developed which embraces principles of internal and external work as produced by 1-lb load applied at end of structure after all reactions are removed and truss is cantilevered from wall support; analysis only requires one stress analysis of analogous cantilevered truss; procedure illustrated on example of Mississippi River bridge at Dubuque, Ia.
Truss bridge
Bridge (graph theory)
Internal forces
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