A truss is an assembly of members such as beams , connected by nodes , that creates a rigid structure.
79-773: The University Heights Bridge is a steel-truss revolving swing bridge across the Harlem River in New York City . It connects West 207th Street in the Inwood neighborhood of Manhattan with West Fordham Road in the University Heights neighborhood of the Bronx . The bridge is operated and maintained by the New York City Department of Transportation . The bridge carries two lanes of traffic in each direction, along with
158-444: A cruck frame or a couple of rafters. One engineering definition is: "A truss is a single plane framework of individual structural member [sic] connected at their ends of forms a series of triangle [sic] to span a large distance". A truss consists of typically (but not necessarily) straight members connected at joints, traditionally termed panel points . Trusses are typically (but not necessarily ) composed of triangles because of
237-412: A lattice . The Vierendeel truss is a structure where the members are not triangulated but form rectangular openings, and is a frame with fixed joints that are capable of transferring and resisting bending moments . As such, it does not fit the strict definition of a truss (since it contains non-two-force members): regular trusses comprise members that are commonly assumed to have pinned joints, with
316-558: A swing bridge over the Harlem River , connects West 207th Street in Inwood, Manhattan , with West Fordham Road in University Heights, Bronx . The movable central span pivots around a small masonry island in the middle of the river. The movable section is designed as a metal truss bridge composed of numerous Howe trusses and Warren trusses . The University Heights Bridge carries the Bx12 local and Select Bus Service bus routes operated by MTA New York City Transit . Between 2000 and 2014,
395-476: A ceiling joist , and in other mechanical structures such as bicycles and aircraft. Because of the stability of this shape and the methods of analysis used to calculate the forces within it, a truss composed entirely of triangles is known as a simple truss. However, a simple truss is often defined more restrictively by demanding that it can be constructed through successive addition of pairs of members, each connected to two existing joints and to each other to form
474-403: A larger cross section than on a previous iteration requires giving other members a larger cross section as well, to hold the greater weight of the first member—one needs to go through another iteration to find exactly how much greater the other members need to be. Sometimes the designer goes through several iterations of the design process to converge on the "right" cross section for each member. On
553-402: A matrix method such as the direct stiffness method , the flexibility method , or the finite element method. Illustrated is a simple, statically determinate flat truss with 9 joints and (2 x 9) − 3 = 15 members. External loads are concentrated in the outer joints. Since this is a symmetrical truss with symmetrical vertical loads, the reactive forces at A and B are vertical, equal, and half
632-404: A new joint, and this definition does not require a simple truss to comprise only triangles. The traditional diamond-shape bicycle frame, which utilizes two conjoined triangles, is an example of a simple truss. A planar truss lies in a single plane . Planar trusses are typically used in parallel to form roofs and bridges. The depth of a truss, or the height between the upper and lower chords,
711-665: A result of the River and Harbor Act, passed by the United States Congress in 1890, bridges on the Harlem River with low vertical clearance were to be replaced with those with at least 24 feet (7.3 m) of clearance during mean high water springs . Drawbridges and swing spans were determined to be most suitable for this purpose. In 1891, a wooden pedestrian drawbridge was constructed between 207th Street in Manhattan and Fordham Road in
790-644: A roadway-bridge having sidewalks is very much enhanced, and at a very small cost." Birdsall appears to have been given ex officio credit, by virtue of his position as Public Works chief engineer. From 1895 to 1905, the bridge structure was situated on the Harlem River Ship Canal further north, during which time it was known as the Harlem Ship Canal Bridge. It carried Broadway between the Inwood and Marble Hill neighborhoods of Manhattan. Prior to
869-493: A sidewalk on its southern side. The bridge has three masonry piers supporting the steel approach spans. The sidewalk features four shelters with cast-iron supports while the bridge deck has decorative iron railings and two stone pavilions. The bridge structure was originally installed further to the north, carrying Broadway across the Harlem River Ship Canal . It opened in 1895 as the Harlem Ship Canal Bridge and
SECTION 10
#1732852843097948-412: A sidewalk on the southern side for pedestrians. The deck previously had two sidewalks, each 5.67 feet (2 m) wide. The northern sidewalk was eliminated during the 1989–1992 renovation and the southern sidewalk widened to 8 feet (2.4 m). The swing span is variously cited as being 264 feet (80 m) or 270 feet (82 m) long. The swing span's trusswork consists of concave chords running along
1027-406: A similar upright support, but stand on a round base; in many contexts columns may also be called piers. In buildings with a sequence of bays between piers, each opening (window or door) between two piers is considered a single bay. Single-span bridges have abutments at each end that support the weight of the bridge and serve as retaining walls to resist lateral movement of the earthen fill of
1106-428: A single point to fracture floating pieces of ice striking the pier. In cold climates, the starling is typically sloped at an angle of about 45° so current pushing against the ice tends to lift the downstream edge of the ice translating horizontal force of the current to vertical force against a thinner cross-section of ice until unsupported weight of ice fractures the piece of ice allowing it to pass on either side of
1185-501: A structure or superstructure such as an arch or bridge . Sections of structural walls between openings (bays) can function as piers. External or free-standing walls may have piers at the ends or on corners. The simplest cross section of the pier is square , or rectangular , but other shapes are also common. In medieval architecture , massive circular supports called drum piers, cruciform (cross-shaped) piers, and compound piers are common architectural elements. Columns are
1264-405: A total width of 50 feet (15 m), with a roadway of 33.5 feet (10.2 m) and two sidewalks of 8.25 feet (2.51 m). The bridge weighed 1,200 short tons (1,100 long tons; 1,100 t), with the machinery comprising one-sixth of the weight. The University Heights Bridge is composed of five sections. The easternmost section and the two westernmost sections are fixed-deck Warren trusses, while
1343-560: A truss are called 'top chords' and are typically in compression , the bottom beams are called 'bottom chords', and are typically in tension . The interior beams are called webs , and the areas inside the webs are called panels , or from graphic statics (see Cremona diagram ) 'polygons'. Truss derives from the Old French word trousse , from around 1200 AD, which means "collection of things bound together". The term truss has often been used to describe any assembly of members such as
1422-538: Is a 393 meter (1,291 foot) long truss bridge built in 1912. The structure is composed of nine Pratt truss spans of varying lengths. The bridge is still in use today. The Wright Flyer used a Pratt truss in its wing construction, as the minimization of compression member lengths allowed for lower aerodynamic drag . Named for their shape, bowstring trusses were first used for arched truss bridges , often confused with tied-arch bridges . Thousands of bowstring trusses were used during World War II for holding up
1501-422: Is a roof or floor truss whose wood members are connected with metal connector plates . Truss members form a series of equilateral triangles, alternating up and down. Truss members are made up of all equivalent equilateral triangles. The minimum composition is two regular tetrahedrons along with an octahedron. They fill up three dimensional space in a variety of configurations. [REDACTED] The Pratt truss
1580-496: Is preferable to a braced-frame system, which would leave some areas obstructed by the diagonal braces. A truss that is assumed to comprise members that are connected by means of pin joints, and which is supported at both ends by means of hinged joints and rollers, is described as being statically determinate . Newton's Laws apply to the structure as a whole, as well as to each node or joint. In order for any node that may be subject to an external load or force to remain static in space,
1659-457: Is similar to a king post truss in that the outer supports are angled towards the centre of the structure. The primary difference is the horizontal extension at the centre which relies on beam action to provide mechanical stability. This truss style is only suitable for relatively short spans. Lenticular trusses, patented in 1878 by William Douglas (although the Gaunless Bridge of 1823 was
SECTION 20
#17328528430971738-422: Is the force in the member, γ is a safety factor (typically 1.5 but depending on building codes ) and σ y is the yield tensile strength of the steel used. The members under compression also have to be designed to be safe against buckling. The weight of a truss member depends directly on its cross section—that weight partially determines how strong the other members of the truss need to be. Giving one member
1817-405: Is the simplest space truss, consisting of six members that meet at four joints. Large planar structures may be composed from tetrahedrons with common edges, and they are also employed in the base structures of large free-standing power line pylons. There are two basic types of truss: A combination of the two is a truncated truss, used in hip roof construction. A metal plate-connected wood truss
1896-465: Is what makes it an efficient structural form. A solid girder or beam of equal strength would have substantial weight and material cost as compared to a truss. For a given span , a deeper truss will require less material in the chords and greater material in the verticals and diagonals. An optimum depth of the truss will maximize the efficiency. A space frame truss is a three-dimensional framework of members pinned at their ends. A tetrahedron shape
1975-554: The East and Harlem rivers, in 1971. The proposal failed in 1977 after the United States Congress moved to ban tolls on these bridges. The city and state were planning to restore or replace the bridge by the 1980s. A $ 1.25 billion bond issue, proposed in 1983, had provided $ 15 million for the bridge's rehabilitation. The Landmarks Preservation Commission held a hearing to designate the crossing as an official city landmark, which would mandate that any bridge replacement would have to conform with
2054-429: The Bronx to 210th Street in Manhattan. However, that span was reduced to 1,250 feet (380 m) long and 50 feet (15 m) wide to save money. The city suggested that the Harlem Ship Canal Bridge could be relocated for that purpose. Ultimately, the city made an agreement with the three railroads to relocate the first span down the Harlem River, only ten years after it had been constructed. The Board of Estimate authorized
2133-584: The Bronx to Manhattan when the bridge was announced. By late 1908, after the opening of the bridge, the Union Railway applied for permission for a Manhattan extension. After the permission was granted, streetcar service across the bridge began in November 1910. The bridge was designated as part of U.S. Route 9X in December 1934, which was redesignated as New York State Route 9X shortly afterward. The highway designation
2212-417: The Bronx. To the north, the New York City Department of Public Works was commissioned in 1892 to build the Harlem Ship Canal Bridge between Inwood and Marble Hill, carrying Broadway over the new canal. This bridge was designed by Burr, Boller, and Birdsall, and constructed by A. McMullen & Co. The bridge opened on January 1, 1895. At the time, it was one of several swing bridges that had been built on
2291-574: The Commissioner of Bridges to repurchase the bridge from the IRT. Accordingly, the spans of the old Harlem Ship Canal Bridge were replaced with the new double-decker spans in three phases. After the old spans were disconnected from their old location and moved aside, the corresponding sections of the new Broadway Bridge were floated into place. The southern approach at Broadway was replaced in October 1905, followed by
2370-516: The Harlem River's eastern bank. The railroad wished to avoid a grade crossing with the Metropolitan Street Railway 's streetcar tracks on the replacement Broadway Bridge. In 1903, bridge engineer Gustav Lindenthal suggested constructing a bridge from University Heights in the Bronx to Inwood in Manhattan. An early proposal called for a 2,600-foot-long (790 m), 80-foot-wide (24 m) bridge from 184th Street (now Fordham Road) in
2449-730: The Harlem River, and it was the second oldest major bridge in New York City behind the Brooklyn Bridge . By the first decade of the 20th century, the city sold the Harlem Ship Canal Bridge to the Interborough Rapid Transit Company (IRT), which was constructing the New York City Subway 's first line . A branch of the line was to cross the Harlem Ship Canal above Broadway, which involved modifying or replacing
University Heights Bridge - Misplaced Pages Continue
2528-484: The Macombs Dam and University Heights Bridges were "highly creditable works, in an artistic as well as in a scientific sense." The University Heights Bridge was also described by Engineering Magazine in 1909 as "probably the prettiest of the swing bridges". Notes Sources Truss In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so that
2607-610: The University Heights Bridge's western approach. The following month, the swing span was towed from its Broadway location and lifted onto the new pivot pier at 207th Street. In November 1907, the old northern approach was towed to Fordham Road and reinstalled as the University Heights Bridge's eastern approach. The relocation was conducted under the supervision of chief engineer Othniel F. Nichols. The bridge reopened to traffic on January 8, 1908. The Union Railway Company planned to extend their Fordham Road streetcar line from
2686-620: The University Heights station and the I-87 exit and entrance ramps. On June 12, 2008, the New York City Bridge Centennial Commission organized a parade to mark the centennial of the bridge. The event was attended by Bronx Borough President Adolfo Carrión, Jr. and Manhattan Borough President Scott Stringer . The celebration was the commission's first such event. Architectural critic Montgomery Schuyler stated that
2765-512: The assemblage as a whole behaves as a single object". A "two-force member" is a structural component where force is applied to only two points. Although this rigorous definition allows the members to have any shape connected in any stable configuration, trusses typically comprise five or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes . In this typical context, external forces and reactions to those forces are considered to act only at
2844-449: The bridge approach. Multi-span bridges require piers to support the ends of spans between these abutments. In cold climates, the upstream edge of a pier may include a starkwater to prevent accumulation of broken ice during peak snowmelt flows. The starkwater has a sharpened upstream edge sometimes called a cutwater . The cutwater edge may be of concrete or masonry, but is often capped with a steel angle to resist abrasion and focus force at
2923-435: The bridge opened for vessels 114 times. The bridge was designed by consulting engineer William Hubert Burr , who later became consulting engineer at several other bridge and tunnel projects, mostly in the New York City area. Burr was posthumously described as "one of the engineers who helped to raise the level of American building technology to the status of exact science". Burr also gave credit to Alfred Pancoast Boller , who
3002-483: The bridge, and wheelchair-accessible buses were swapped with lighter, non-accessible buses. By 1988, the deck contained several holes and was supported by corroded steel beams. The NYCDOT estimated that it would cost $ 24 million to fix the corroded approach viaduct, and the New York State Department of Transportation received a $ 34.3 million low bid for the bridge's reconstruction that year. The replacement of
3081-468: The center of the river and one on each bank; these piers are made of concrete and faced with ashlar . At either end of the bridge's approach spans are concrete ramps with walls made of granite ashlar. The western end of the bridge is at 207th Street's intersection with Ninth Avenue . At the eastern end of the bridge, an overpass crosses the Metro-North Railroad 's Hudson Line , and an entrance to
3160-448: The central sections comprise the swing span above the Harlem River. The westernmost approach span was made for the 207th Street location, while the other spans were carried over from their original Broadway location. According to the New York City Department of Transportation (NYCDOT), which maintains the bridge, its total length is 1,566 feet (477 m), including its approach spans. The bridge carries four lanes for vehicular traffic and
3239-407: The connections may also be required to transfer bending moment. Wood posts enable the fabrication of strong, direct, yet inexpensive connections between large trusses and walls. Exact details for post-to-truss connections vary from designer to designer, and may be influenced by post type. Solid-sawn timber and glulam posts are generally notched to form a truss bearing surface. The truss is rested on
University Heights Bridge - Misplaced Pages Continue
3318-683: The construction of the Harlem River Ship Canal, Marble Hill was part of Manhattan Island, and the Spuyten Duyvil Creek made a tight curve around the northern shore of Marble Hill, connecting the Hudson River on the west shore of Manhattan Island with Harlem River on the east shore. Marble Hill was separated from Manhattan Island when the canal opened in 1895. The Harlem Ship Canal Bridge measured 551 feet (168 m) from end to end, or 483 feet (147 m) excluding stone abutments. It
3397-527: The curved roofs of aircraft hangars and other military buildings. Many variations exist in the arrangements of the members connecting the nodes of the upper arc with those of the lower, straight sequence of members, from nearly isosceles triangles to a variant of the Pratt truss. One of the simplest truss styles to implement, the king post consists of two angled supports leaning into a common vertical support. The queen post truss, sometimes queenpost or queenspost ,
3476-452: The design decisions beyond mere matters of economics. Modern materials such as prestressed concrete and fabrication methods, such as automated welding , have significantly influenced the design of modern bridges . Once the force on each member is known, the next step is to determine the cross section of the individual truss members. For members under tension the cross-sectional area A can be found using A = F × γ / σ y , where F
3555-410: The deteriorated structure was a high priority for residents of University Heights. The bridge was entirely reconstructed starting in 1989, with a budgeted cost of $ 35 million. Because of the bridge's landmark status, the replacement latticework had to be built in the same design as in the old span. Mechanical and electrical equipment was also replaced, and the northern sidewalk was removed. Reconstruction
3634-403: The equilibrium condition described. Because the forces in each of its two main girders are essentially planar, a truss is usually modeled as a two-dimensional plane frame. However if there are significant out-of-plane forces, the structure must be modeled as a three-dimensional space. The analysis of trusses often assumes that loads are applied to joints only and not at intermediate points along
3713-414: The exact arrangement of forces is depending on the type of truss and again on the direction of bending. In the truss shown above right, the vertical members are in tension, and the diagonals are in compression. In addition to carrying the static forces, the members serve additional functions of stabilizing each other, preventing buckling . In the adjacent picture, the top chord is prevented from buckling by
3792-576: The existing bridge. Ultimately, the IRT determined the existing structure could not support the elevated subway line, choosing instead to build the double-decker Broadway Bridge . The need to replace the bridge was further emphasized when, in 1903, the New York State Legislature passed legislation allowing the realignment of the New York Central Railroad 's Spuyten Duyvil Line (now the Metro-North Railroad 's Hudson Line ) along
3871-461: The first of the type), have the top and bottom chords of the truss arched, forming a lens shape. A lenticular pony truss bridge is a bridge design that involves a lenticular truss extending above and below the roadbed. American architect Ithiel Town designed Town's Lattice Truss as an alternative to heavy-timber bridges. His design, patented in 1820 and 1835, uses easy-to-handle planks arranged diagonally with short spaces in between them, to form
3950-417: The following conditions must hold: the sums of all (horizontal and vertical) forces, as well as all moments acting about the node equal zero. Analysis of these conditions at each node yields the magnitude of the compression or tension forces. Trusses that are supported at more than two positions are said to be statically indeterminate , and the application of Newton's Laws alone is not sufficient to determine
4029-504: The implication that no moments exist at the jointed ends. This style of structure was named after the Belgian engineer Arthur Vierendeel , who developed the design in 1896. Its use for bridges is rare due to higher costs compared to a triangulated truss. The utility of this type of structure in buildings is that a large amount of the exterior envelope remains unobstructed and can be used for windows and door openings. In some applications this
SECTION 50
#17328528430974108-466: The line's University Heights station leads from the sidewalk. The overpass continues as Fordham Road, which intersects with the on- and off-ramps of Interstate 87 (I-87), the Major Deegan Expressway. On either bank of the river is an iron, copper, and stone shelter house with a red tile roof. The shelter house on the east bank is north of the roadway, while that on the west bank is south of
4187-501: The member forces. In order for a truss with pin-connected members to be stable, it does not need to be entirely composed of triangles. In mathematical terms, the following necessary condition for stability of a simple truss exists: where m is the total number of truss members, j is the total number of joints and r is the number of reactions (equal to 3 generally) in a 2-dimensional structure. When m = 2 j − 3 {\displaystyle m=2j-3} ,
4266-558: The members means that longer diagonal members are only in tension for gravity load effects. This allows these members to be used more efficiently, as slenderness effects related to buckling under compression loads (which are compounded by the length of the member) will typically not control the design. Therefore, for given planar truss with a fixed depth, the Pratt configuration is usually the most efficient under static, vertical loading. The Southern Pacific Railroad bridge in Tempe , Arizona
4345-446: The members. Component connections are critical to the structural integrity of a framing system. In buildings with large, clearspan wood trusses, the most critical connections are those between the truss and its supports. In addition to gravity-induced forces (a.k.a. bearing loads), these connections must resist shear forces acting perpendicular to the plane of the truss and uplift forces due to wind. Depending upon overall building design,
4424-431: The members. The weight of the members is often insignificant compared to the applied loads and so is often omitted; alternatively, half of the weight of each member may be applied to its two end joints. Provided that the members are long and slender, the moments transmitted through the joints are negligible, and the junctions can be treated as " hinges " or "pin-joints". Under these simplifying assumptions, every member of
4503-427: The minimum cross section of the members, the last step in the design of a truss would be detailing of the bolted joints , e.g., involving shear stress of the bolt connections used in the joints. Based on the needs of the project, truss internal connections (joints) can be designed as rigid, semi rigid, or hinged. Rigid connections can allow transfer of bending moments leading to development of secondary bending moments in
4582-477: The nodes and result in forces in the members that are either tensile or compressive . For straight members, moments ( torques ) are explicitly excluded because, and only because, all the joints in a truss are treated as revolutes , as is necessary for the links to be two-force members. A planar truss is one where all members and nodes lie within a two-dimensional plane, while a space frame has members and nodes that extend into three dimensions . The top beams in
4661-588: The northern approach in November. At 207th Street, the Foundation and Contracting Company started constructing the pier at the center of the river in November 1903, completing it ten months later. The relocated bridge, initially slated to be known as the Fordham Heights Bridge, was formally renamed the University Heights Bridge in May 1904. The Snare & Triest Company was hired in 1905 to perform additional work on
4740-409: The notches and bolted into place. A special plate/bracket may be added to increase connection load transfer capabilities. With mechanically-laminated posts, the truss may rest on a shortened outer-ply or on a shortened inner-ply. The later scenario places the bolts in double shear and is a very effective connection. Pier (architecture) A pier , in architecture , is an upright support for
4819-423: The original design. Manhattan Community Board 12 voted against the landmark designation and the city and state governments advised against designating the bridge as a landmark. Despite the opposition, on September 11, 1984, the bridge was designated a city landmark. The bridge's condition continued to deteriorate; in late 1987, vehicles weighing over 15 short tons (13 long tons; 14 t) were banned from crossing
SECTION 60
#17328528430974898-438: The other hand, reducing the size of one member from the previous iteration merely makes the other members have a larger (and more expensive) safety factor than is technically necessary, but doesn't require another iteration to find a buildable truss. The effect of the weight of the individual truss members in a large truss, such as a bridge, is usually insignificant compared to the force of the external loads. After determining
4977-523: The pier. In the Arc de Triomphe , Paris ( illustration, right ) the central arch and side arches are raised on four massive planar piers . Donato Bramante 's original plan for St Peter's Basilica in Rome has richly articulated piers. Four piers support the weight of the dome at the central crossing. These piers were found to be too small to support the weight and were changed later by Michelangelo to account for
5056-425: The presence of bracing and by the stiffness of the web members. The inclusion of the elements shown is largely an engineering decision based upon economics, being a balance between the costs of raw materials, off-site fabrication, component transportation, on-site erection, the availability of machinery and the cost of labor. In other cases the appearance of the structure may take on greater importance and so influence
5135-406: The relation (a) is necessary, it is not sufficient for stability, which also depends on the truss geometry, support conditions and the load carrying capacity of the members. Some structures are built with more than this minimum number of truss members. Those structures may survive even when some of the members fail. Their member forces depend on the relative stiffness of the members, in addition to
5214-456: The relocated bridge's approaches, as well as construct an additional span for the western approach. The same year, the Department of Bridges issued $ 821,215 in capital stock to fund the relocation. The existing spans underwent major modifications before being installed at 207th Street. The Harlem Ship Canal Bridge's southern approach was towed by barges to 207th Street in May 1906 and reinstalled as
5293-416: The roadway. There are drawbridge gates near these end piers, blocking off access to the swing span when it is open for maritime traffic. Many of the original railings have been replaced. The bridge's sidewalk contains four pergolas or shelters, two on each bank of the river. The pergolas each consist of six cast-iron columns with elliptical wrought-iron arches, as well as hip roofs with copper shingles. As
5372-400: The same function as the flanges of an I-beam . Which chord carries tension and which carries compression depends on the overall direction of bending . In the truss pictured above right, the bottom chord is in tension, and the top chord in compression. The diagonal and vertical members form the truss web , and carry the shear stress . Individually, they are also in tension and compression,
5451-404: The structural stability of that shape and design. A triangle is the simplest geometric figure that will not change shape when the lengths of the sides are fixed. In comparison, both the angles and the lengths of a four-sided figure must be fixed for it to retain its shape. The simplest form of a truss is one single triangle. This type of truss is seen in a framed roof consisting of rafters and
5530-405: The top. The chords taper up toward a square section in the center of the span, which is topped by four finials . The swing span can be rotated around a tower below the center of the deck, which in turn is on the small masonry island. The rotating tower is about 50 feet (15 m) in diameter and is anchored into the bedrock beneath the Harlem River. The swing span is supported by three piers, one in
5609-421: The total load. The internal forces in the members of the truss can be calculated in a variety of ways, including graphical methods: A truss can be thought of as a beam where the web consists of a series of separate members instead of a continuous plate. In the truss, the lower horizontal member (the bottom chord ) and the upper horizontal member (the top chord ) carry tension and compression , fulfilling
5688-415: The truss is said to be statically determinate , because the ( m +3) internal member forces and support reactions can then be completely determined by 2 j equilibrium equations, once we know the external loads and the geometry of the truss. Given a certain number of joints, this is the minimum number of members, in the sense that if any member is taken out (or fails), then the truss as a whole fails. While
5767-519: The truss is then subjected to pure compression or pure tension forces – shear, bending moment, and other more-complex stresses are all practically zero. Trusses are physically stronger than other ways of arranging structural elements, because nearly every material can resist a much larger load in tension or compression than in shear, bending, torsion, or other kinds of force. These simplifications make trusses easier to analyze. Structural analysis of trusses of any type can readily be carried out using
5846-461: Was constructed with four sections supported by three masonry piers . The two central sections comprised the swing span, which pivoted around a small masonry island in the middle of the canal. On either side of the masonry island were navigable openings that measured 104 feet 1 inch (31.72 m) wide at mean high water. The swing span was approached by two 100-foot-long (30 m) approach structures, as well as stone abutments. The bridge had
5925-533: Was deleted in the 1940s. The Fordham Road streetcar service was replaced with the Bx19 bus, later the Bx12 bus, in 1948. The next year, the deck was replaced and the streetcar tracks were removed. A freestanding gantry for the streetcar's electric wires remained on the swing span's eastern end through the 1980s. Mayor John Lindsay proposed enacting tolls along the University Heights Bridge, as well as all other free bridges across
6004-415: Was patented in 1844 by two Boston railway engineers, Caleb Pratt and his son Thomas Willis Pratt . The design uses vertical members for compression and diagonal members to respond to tension . The Pratt truss design remained popular as bridge designers switched from wood to iron, and from iron to steel. This continued popularity of the Pratt truss is probably due to the fact that the configuration of
6083-439: Was performed in three phases: the southern portions of the approach viaducts were renovated first, followed by the swing span and the northern portions of the approaches. The bridge reopened on February 18, 1992. The Fordham Road overpass was renovated starting the same year. The work was supposed to be finished in 1995 but was delayed by two years because of a lack of coordination with other government agencies, which were renovating
6162-402: Was relocated southward to University Heights in 1908. Over the following decades, the University Heights Bridge carried streetcar and bus service. By the late 20th century it was in disrepair. The New York City Landmarks Preservation Commission designated the University Heights Bridge as a city landmark in 1984, and it was completely rebuilt between 1989 and 1992. The University Heights Bridge,
6241-576: Was responsible for the bridge's aesthetics, and George W. Birdsall, chief engineer of the Department of Public Works. Boller had been involved in the design of several other Harlem River bridges, including the Madison Avenue Bridge and the Macombs Dam Bridge , and was also a consulting engineer or designer for numerous other bridges across the world. He had stated in 1877 that, by including ornamental detail in bridge designs, "the appearance of
#96903