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Monthly Archives: February 2014

We’ve been on a steel kick lately, sharing the top steel bridges, top steel skyscrapers…  But how about the best steel…  Well, “things,” in the world?  Not just one category, but the best new steel structures, period?  The Building Design and Construction website covered just this subject very recently, with a list of their 2013 award winners in the subject, so it’s time to share their choices for the best new in 2013 steel structures!

NASCAR Hall of Fame

 

Building Team
Owner/Developer: City of Charlotte; NASCAR Hall of Fame, Charlotte, N.C.
Owner’s Representative: NASCAR, Charlotte, N.C.
Architect: Pei Cobb Freed & Partners LLP, New York
Architect: Little Diversified Architectural Consulting, Charlotte, N.C.
Structural Engineer: Leslie E. Robertson Associates, RLLP, New York
General Contractor: BE&K Building Group, Charlotte, N.C.
Steel Fabricator: SteelFab, Inc., Charlotte, N.C.
Steel Detailer: Hutchins & Associates, Clemmons, N.C.
Steel Erector: Williams Erection Company, Smyrna, Ga.
Bender/Roller: SteelFab, Inc., Charlotte, N.C.
Design-Build Contractor for Ribbon: Zahner, Kansas City, Mo.
Consultant: Ralph Appelbaum Associates, Inc., New York
Consultant: Jaros Baum & Bolles, New York
Photograph: Paul Warchol Photography Inc.

In approaching the challenge of designing a Hall of Fame for NASCAR, the project’s design team sought to capture the essential spirit of NASCAR and its sport in architectural form. In exploring the possibilities for expressing speed and spectacle, the team was drawn to the arena of action, the racecourse, where fans and race teams come together each race week for the spectacle of race day.
Curving, sloped forms are evocative not only of the dynamic and changing sinuous shape of the racetrack but also of the perception of speed, which is at the heart of the NASCAR spectacle.

The expression of these forms could only have been achieved through the use of steel, as cladding and as structure, encompassing several long-span elements, architecturally exposed structural steel (AESS) elements, and employing innovative approaches to connections, steel detailing, and the interface of structural steel with stone, glass, and steel as a finish material.

The Hall of Fame consists of four basic elements:
• A large glazed oval shape forming a Great Hall serves as the symbolic core of the Hall of Fame.
• A rectangular volume houses visitor services, including entry and exhibit space on upper floors.
• An expressed Hall of Honor is situated as an iconic element within the Great Hall.
• A broadcast studio enlivens the Hall of Fame Plaza, the sweeping forecourt that welcomes visitors.

The results of the teams’ explorations of speed and spectacle evolved into an architectural element — the Ribbon – 5,000 stainless steel panels that envelope the full-block building in a form that speaks to the imagery and spirit of NASCAR. Made of stainless steel in a lustrous angel-hair finish that softly reflects light and accentuates its dynamic aspect, the Ribbon is a sculpted form that changes as it wraps around the building.

Within the Great Hall, a signature element of a curved banked ramp leads the visitor from the main floor to exhibit levels above. The ramp contains a display of race cars frozen in a moment from a race, capturing in another way the speed and spectacle that is the essence of the sport.

Steel trusses are used to achieve significant spans in the project: • A set of trusses spanning 175 feet achieve a grand column-free ballroom • A 100-foot-long, bi-level footbridge, supported by a pair of one-story-deep trusses, links the ballroom with the existing Charlotte
Convention Center. • Two- and three-story-high trusses cantilever 30 feet over the broadcast studio.

Among the AESS elements in the project is the Vierendeel frame supporting the glass façade of the Great Hall. The lateral-load-resisting system at this façade also functions as the braced frame that supports the Ribbon.

The project’s structural bid set was issued six months before the 100% CD set. The steel tender was divided into multiple packages to enable steel detailing and fabrication of portions of the project to proceed before the full design was complete. A 3D model was used in the steel detailing to identify and resolve potential conflicts in the field. These efforts and effective team communication allowed the long scheduled public opening to occur on time.

 

Barclays_Center_Exterior_1

 

Building Team
Owner/Developer: Forest City Ratner Companies, Brooklyn, N.Y.
Architect: AECOM, Kansas City, Mo.
Architect: SHoP Architects, New York, N.Y.
Structural Engineer: Thornton Tomasetti, New York
General Contractor: Hunt-Bovis joint venture, Indianapolis
Steel Fabricator: Banker Steel Company, Lynchburg, Va.
Steel Detailer: WSP Mountain Enterprises, Inc., Sharpsburg, Md.
Photographer: Bess Adler

The Barclays Center arena is the 675,000-sf home to the NBA’s Brooklyn Nets. The design-build project features 18,103 seats, an 85-foot open canopy that spans the entrance, and an ice floor for hockey and other events. The arena will host more than 200 sporting and cultural events annually with seating capacity increases to 19,000 for concerts and family shows. It features 95 luxury suites, four party suites, two conference suites, four bars/lounges, four clubs, a restaurant and several street-level retail stores. The project was designed to achieve LEED Silver certification.

The iconic feature of the of the arena is the weathered Cor-ten steel lattice that wraps around the structure. Rows of steel panels envelop the exterior including an entrance canopy that cantilevers 85 feet over the plaza. The façade design with 12,000 pre-weathered steel panels and the canopy were added a month after the GMP package was released and two months before the first steel mill order was due. This required the team to incorporate the developing façade design while keeping pace with the original schedule. Nearly 1,000 tons of steel was added to support the façade, which also became a prominent design feature.

The distinctive arched roof spans more than 380 ft and is supported by a pair of 350-ft tied arch trusses spanning the long direction of the arena. The roof system geometry is complex, further complicated by the additional loads imposed by the outer façade system. The building lateral system and diaphragms were designed to resist thrust forces from the roof arches, which were minimized by use of the tension tie.
The arena’s location in a tight urban setting near a subway station and train terminal presented a multitude of challenges for the foundation system. To facilitate truck turnaround, a pair of truck elevators were designed to feed a below-grade loading dock with a large truck turntable. Building columns in this area were transferred using large plate girders spanning over the dock.

The project’s structural engineer provide structural models, connection samples, and full connection design, which allowed the team to produce models quickly, store large quantities of information and coordinate with the entire team. From its initial design, the project constantly pushed the limits of building information modeling (BIM). The complex geometry of the façade and the shortened schedule meant that the team needed to coordinate in a 3D environment and provide the information to the contractor in this format as well.

The schedule was adjusted frequently and changed even from hour to hour at the peak of construction. The design team consisted of staff members across multiple offices and practice areas. Managing the team’s efforts on such a large, fast moving project made coordination critical to the project’s success. Teams in Kansas City and New York designed the roof and bowl after which the two components were integrated. Construction support services teams worked on the structural models, model delivery and connection design. Erection engineering was performed in Chicago. Achieving integration of these services in a way that is seamless to the client required extensive communication, intense collaboration and careful management. Design staff was maintained on site full-time to accommodate changes and oversee work. Weekly coordination meetings helped identify issues early on and develop solutions proactively.

 

National Geospatial-Intelligence Agency_0

 

Building Team
Owner/Developer: National Geospatial-Intelligence Agency, Springfield, Va.
Owner’s Representative: U.S. Army Corps of Engineers-Baltimore District, Fort Belvoir, Va.
Architect: RTKL/KlingStubbins joint venture, Baltimore
Structural Engineer: RTKL/ KlingStubbins joint venture, Baltimore
General Contractor: Clark/Balfour Beatty joint venture, Bethesda, Md.
Steel Fabricator: SteelFab Inc., Charlotte, N.C.
Steel Detailer: SteelFab Inc., Charlotte, N.C.
Consultant: Hinman Consulting Engineers, San Francisco
Photo: Paul Warchol

Situated on the outskirts of the Capital Beltway adjacent to the Accotink Creek stands the National Geospatial-Intelligence Agency’s (NGA) 2.4 million-sf campus known as New Campus East (NCE), which has not only been designed to enhance the agency’s capabilities as one of the leading intelligence organizations in the world but also to achieve a unifying, cultural transformation. This effort to foster a unified culture is expressed in the design of the nine-story Main Office Building.

Composed of two curved 900-foot long overlapping bars around a 500-foot long central atrium and elliptical auditorium, the building’s overall form is in the shape of a lens — a fitting metaphor for NGA which serves as the nation’s eyes as the primary source of geospatial intelligence (GEOINT) for the purposes of U.S. national security, defense and disaster relief.

This defining architectural expression was accomplished primarily due to the benefits of structural steel. Steel facilitated the large bay size needed for program flexibility of the typical office, reinforced the architectural concept and imagery expressed in the transparent atrium roof, west end wall and exterior V columns, and accommodated the constraints of highly complex technical anti-terrorism/force protection (ATFP) criteria and a demanding schedule.

Managed by the U.S. Army Corps of Engineers (USACE) Baltimore District, the project has its origins in the 2005 Base Realignment and Closure Act (BRAC). RTKL Associates Inc. and KlingStubbins formed a joint venture to provide design services, including master planning and full architecture, engineering, interiors, site/civil, landscape and technology design.

At 2.2 million sf, the nine-story Main Office Building is the second largest single occupancy building in the world (after the Pentagon) and the largest federal building in the world to achieve LEED Gold certification from the U.S. Green Building Council (USGBC).

To fill the central atrium and interior of the building with light, the west end wall of the atrium was glazed with a curtain-wall system and the roof of the atrium was covered with a transparent fabric membrane. The west end atrium wall consists of a 135 foot tall by 140 foot wide curtain wall backed by a round hollow structural section (HSS) tube steel frame. Architecturally exposed structural steel (AESS) requirements were incorporated into the design, fabrication and erection of the space frame structure which served several functions. In addition to supporting the gravity loads of the curtain-wall, it supports atrium roof gravity and wind loads, and meets all mandated ATFP criteria. It also acts as a pedestrian bridge at several levels providing access and circulation between the towers.

The central atrium also serves as the main area of pedestrian circulation with a central elevator core linked by multiple bridges to each tower. Structural steel minimized the visual obstruction of these elements within the atrium and enabled them to be constructed after the towers.
The atrium roof is over 500 feet long and 45,000 sf, and consists of AESS arched steel tube members supporting an air-filled ethylene tetrafluoroethylene (ETFE) fabric roof. Although it appears clear, the custom silkscreen pattern and air filled ETFE system provides significant daylight while minimizing solar gain. Being extremely lightweight minimized ATFP-related effects, and aided in reducing the tube structure size and tonnage.

The two 900 foot wings are configured to focus on the central atrium. These dramatic spaces, as well as, the atrium’s light filled amenities create a main street for the office building community. The west end atrium wall and the atrium roof structure enhance this effect.
The unique exterior design of the main office building was achieved using signature “V” columns spaced at 40 foot on center and featured along the first and second floor perimeter, providing a separation between the visually solid base and the triangulated precast façade of the upper six floors, while also continuing the diagonals of the upper façade. In addition to providing a strong aesthetic statement, the “V” columns participate in the lateral load resisting system and accommodate alternate load path/progressive collapse design.

As with every project, the main office building had its complexities with the most obvious being its size. Using innovative Early Contractor Involvement (ECI), the USACE Baltimore District awarded the construction contract early in the design process, at about 35% design, enabling the contractor to provide valuable input to the design process and facilitate fast-tracking and value engineering. In addition, the design team delivered phased procurement packages including steel mill-order and fabrication. A committed long-term partnering process between owner, designer and contractor began early in the design process, built trust and fostered a one-team environment. That collaborative effort fostered flexible and creative, attitudes by all parties, and was a key factor leading to the project being completed on budget and six months ahead of original schedule.

 

City Creek Center Retractable Roof

 

Building Team
Owner: City Creek Reserve, Salt Lake City
Architect: Hobbs + Black Architects, Ann Arbor, Mich.
Structural Engineer: Magnusson Klemencic Associates, Seattle
General Contractor: Jacobsen Construction, Salt Lake City
Steel Fabricator: Ducworks, Inc., Logan, Utah
Steel Detailer: Uni-Systems, Minneapolis
Steel Erector: Uni-Systems, Minneapolis
Mechanization Consultant: Uni-Systems, Minneapolis
Photograph: Magnusson Klemencic Associates

City Creek Center is the result of a plan by the Church of Jesus Christ of Latter‐day Saints to transform two Salt Lake City mega‐blocks just south of Temple Square into a 5.5 million-sf, mixed‐use development featuring retail, residential, office, and parking space. Developers wanted an urban, open‐air setting, but also needed the assurance that retail businesses would be protected during inclement weather. After studying many skylight possibilities, the project’s structural engineer produced a retractable roof concept that fully met the developer’s needs.
The resulting retractable, barrel‐vaulted roof is configured in two sections, each spanning one city block. Each section is 240 ft. long and 58 ft wide, with an S‐shape that echoes the curve of the signature City Creek. The precision‐sculpted steel and glass transparently shields patrons when closed, and disappears from sight when open; connecting nature with the areas below.

For each block, the retractable roof is comprised of three pairs of glass‐covered, arching panels that cantilever 33 ft from the adjacent structures over the retail concourse. When closed, all six panels seal together and create an air and water‐tight barrier. To open, the panels part in the middle and retract onto the building structure as the panels bow down out of sight from below.

Key to the bowing action are innovative whalebone‐shaped ribs that support the glass roof. Each roof panel is comprised of three parallel whalebones made of curved and tapered welded steel box girders that run from the tip of each panel’s arch to the end of its back span.
The glazed portion of the three whalebone arches are joined by four purlins made of 8‐in. XX‐strong A106 Grade B pipe and one purlin of hollow structural section (HSS) 10‐3/4 x 1⁄2 in. ASTM A500 Grade B tube. The purlins are designed with concealed connections that are invisible from below. The three whalebone back spans are connected with rectangular HSS ASTM A500 Grade B tubing in a K‐brace configuration to provide shear stiffness between whalebones. In order to meet special finish and detailing requirements, the side and bottom whalebone girder walls were ground and filled to produce perfectly flat plane surfaces.

The whalebones were built in two sections using custom‐ designed fixtures and joined with a plate‐welded connection to accommodate the unique geometry. The preassembled rail girders and whalebones were hoisted onto the roof, and the panels were assembled in place, stick framing whalebones, purlins, and K‐braces.

Each 10.5‐ton whalebone is supported by a 27‐in. double‐flanged steel wheel located at the bottom of the arch and two guide rollers located at the end of the back span. The wheel follows one geometric path on top of the rail girder, and the guide rollers ride an inclined track along the bottom of the rail girder. As the guide rollers travel up the incline, the roof’s cantilevered front edge dips down, causing the roof to bow down, with the wheel as the vertical rotation point.

An industrial computer located in a remote control room operates the retractable roof, which travels up to 8 ft per minute and opens or closes in approximately 6 minutes. Each panel has a unique operating sequence to prevent the panels from interfering with one another as the seals engage and disengage. The roof’s curvature, along with its complex seals and intersecting panels, made the control system the most complicated ever developed by the mechanization engineer.

 

HL23

 

Building Team
Owner: 23 High Line, LLC, New York
Architect: Neil M. Denari Architects, Los Angeles
Structural Engineer: DeSimone Consulting Engineers, New York
General Contractor: TF Nickel & Associates, Ronkonkoma, N.Y.
Photograph: Rinze van Brug Photography

Located in Manhattan’s West Chelsea District, HL23 creates a new 14-story, 42,395-sf ultra-luxury residential building. In total, the project creates 11 condominium units, 3,585 sf of ground floor gallery space and an elevated terrace/garden area. The floor plate of the building, which is smaller at the base than at the top, owes its uniqueness to the existing elevated exposed Highline Railway – retrofitted into a city park facility – located at the eastern portion of the building lot.

Clad with a mega-panel glass and stainless steel curtain wall system, the project’s distinct form comes from the dramatic sloping of the south and east facades, creating a dynamic and undulating three-dimensional composition.

The building’s dual-lateral support system is the most intriguing element of the structure. A steel plate shear wall (SPSW) system – unique in New York City — provided the project with the benefits of increased stiffness and smaller dimension – both tremendous benefits for this site. The SPSW system is located at the elevator and stairs in combination with a full-building perimeter braced frame system. As a true sign of synergy between form and function, the architect incorporated the perimeter lateral pipe braces into the final interior aesthetic of the residences. This required special care during the design of the exposed connections of the perimeter steel diagonal braces to perimeter steel beams. It was achieved by replacing the traditional use of multiple bolts gusset plates with end plates hidden in the concrete metal deck slab for intermediate diagonal braces and with pin-end connections for end braces.

Architectural requirements played a large part in the final structural layout, and the use of structural steel was driven by three primary factors: • Minimizing the overall weight of the structure for the capacity of the raft foundation • Minimizing the amount of interior columns • Providing the perimeter diagonal architectural expression.

In New York, most residential buildings are designed using a cast-in-place reinforced concrete flat plate system to maximize floor-to-floor height. However, due to the unique geometry of the building, the sprawling architectural layouts, the quality of the soil, and the hybrid gravity and lateral load system on the perimeter of the building, steel was the more economical and efficient material of choice.

Floor beams are composite with the concrete slab-on-deck; however, all of the intermediate steel beams were removed to increase headroom in the living areas. This was achieved by using shored construction in many areas with a slab thickness between 6 in. and 7 in. and varying metal deck properties throughout the floor. At the upper floors, the maximum beam/girder span was nearly 30’-0”.

Due to the building’s modest height, a SPSW system was considered both-structurally effective and visually attractive. The east-west dimension of the building is very tight, and any reduction in dimension of structure was beneficial to the floor layouts. Using 3/8-in. thick plates, instead of wide-flange brace members, freed up an extra foot of usable floor area between the columns for each wall of the system. This two foot savings was an enormous achievement in a building that is 38 feet wide.

To help speed erection, the structural engineer worked with the general contractor and the fabricator to develop a system where the perimeter of the plate was continuously welded, with three of the four sides shop welded. Prefabricated shear wall panels, with integral columns and beams, were shipped to the site and spliced in the field. This process ultimately saved a considerable amount of time in erecting the SPSW system.

The second part of the dual lateral system is comprised of perimeter brace frames on each of the elevations. In addition to lateral loads, the perimeter braced frames in many locations are part of the gravity system as well. The braced exoskeleton members are 8” diameter double-extra strong pipes at the North, South and part of the East façade; HSS 10×5 tubes on the West facade and 6×4 back-to-back angles on the remainder of the East facade. All of the pipe elements are primary architectural features and exposed on the façade and in the residences. Therefore, the detailing of these elements was heavily scrutinized. In addition to standard Architecturally Exposed Structural Steel (AESS) specifications, the nodes of the system have been designed with an exposed single 11⁄2-in. diameter pin connection. The final building aesthetic merges the strength and beauty of steel into a composite whole.

 

See the remaining 8 choices in the full article RIGHT HERE!

A few weeks ago, we shared a list of the most impressive steel bridges, and while they certainly are extremely impressive, let’s be honest, the first thing you think of when you think of impressive steel buildings are skyscrapers!  Construction Week, through Arabian Business, published a list a few years ago of what they felt were the ten most impressive “modern” steel skyscrapers, meaning steel skyscrapers that use Fazlur Khan’s tubular structural engineering designs.  It’s especially interesting since it looks at it from a non-American perspective.  Not-surprisingly, Chicago and New York dominate the list, and all ten buildings are in the USA or China.  Remember, since it’s from 2010, new buildings like One World Trade Center aren’t on the list.  Let’s take a look!

Sears_Tower

Willis Tower (formerly the Sears Tower)

America’s building boom tailed off during the 1970s, but not before the monolithic Sears Tower was erected in Chicago. Using Khan’s Bundled Tube structural engineering principles, the building takes its strength from the combination of nine main structures arranged in a three by three grid that make up the impressive complex.

It’s a clever arrangement. All towers rise to 50-storeys, where the northeast and southwest buildings stop. The remaining seven towers continue to the 66th floor where the northeast and southwest structures end, and at 90-storeys, the north, south and east floors top out. The two remaining towers, the west and central towers, then stretch to 110 floors, the building’s top. A similar system of bundled towers was used by SOM to construct the Burj Khalifa.

Work started on construction of the Sears Tower in 1970 and the building was finished three years later. It has received numerous design and structural awards since its 1973 inauguration, and remains a defining development for mega structures which have followed since.

The Sears naming rights ran out in 2003 and in 2009, London-based insurance broker Willis Group Holdings agreed to lease a portion of the building and take over the naming rights.

The building’s owners last year commissioned SOM to install 10ft square and four foot deep glass viewing balconies on the Skydeck at the 103rd floor that offer staggering five-sided views from the tower – at a height of 1353ft. The boxes are mounted within a steel frame and can be retracted back in to the building for cleaning.

Statistics

Location: Chicago, USA 
Height: 442m 
Year completed: 1973 
Number of storeys: 110 
Made of: steel 
Use: office

Empire_State_Building

Empire State Building

It goes without saying that The Empire State Building is the most iconic skyscraper ever built. Whether its legend was sealed with scenes of a giant ape battling bi-planes with one hand while cradling Fay Wray in the other, or by its enduring status as the tallest building in New York (post World Trade Centre), the Empire State Building is the one sight most visitors to the city have at the top their lists.

The art deco building set new benchmarks for construction when it was completed in 1931, and it held the title of world’s tallest building for over 40 years before being eclipsed by the World Trade Centre in 1972.

The building’s history is as interesting as the project itself. Financed by John J Raskob, a former DuPont (hired by Pierre Du Pont himself) and GM vice president (he engineered DuPont’s 43% ownership of GM), the building was designed by architects Shreve, Lamb and Harmon Associates. One version of the story is that Raskob stood a pencil on its end and asked William F Lamb, “Bill, how high can you make it so that it won’t fall down?”

As it turned out, that ended up being 381m. The steel-framed structure was built in record time (13 months), mainly fueled by the need to get the building up during the depression so that the developer could start renting out floorspace – and partly because the Empire State Building was in race with the Chrysler building to gain worldwide recognition as the tallest building. Contractors Starrett Brothers and Eken fast tracked the project through meticulous planning and it was opened by US president Herbert Hoover on May 1 1931.

Statistics

Location: New York, USA 
Height: 381m 
Year completed: 1931 
Made of: steel 
Use: office 

Aon

Aon Center

Originally commissioned by Standard Oil of Indiana, the building uses a tubular steel frame structure to support itself and provide the building with its weather and earthquake resistant properties.

Designed by the late Edward Durell Stone, the 88-storey skyscraper is the third tallest building in Chicago (behind the Sears and Trump towers) and third tallest all-steel building in the world. Built between 1970 and 1972 by Turner Construction (now a subsidiary of Hochtief), the building also held the record for the tallest marble clad tower.

Turner Construction is well known throughout the Middle East: the company acted as project managers on the Burj Khalifa and has also been involved in the Al Hamra Tower project in Kuwait City, Emirates Palace Hotel in Abu Dhabi and Al Faisaliyah Centre in Riyadh, Saudi Arabia.

Like the Willis Group which has naming rights on the tallest tower in Chicago, Aon is an insurance brokerage firm. The company specialises in risk management services, insurance and reinsurance brokerage. The Aon Center is the company’s global headquarters.

Statistics

Location: Chicago, USA 
Height: 346m 
Year completed: 1973 
Made of: steel 
Use: office

The_Center

The Center

Though it only stands as the fifth tallest tower development in Hong Kong, The Center is one of the very few buildings in the city that is constructed entirely out of steel.

Dennis Lau & Ng Chun Man Architects & Engineers (HK) Ltd designed the building, with structural engineering services provided by Maunsell AECOM Group. The structure was started in 1995 and finished three years later by main contractors Paul Y ITC Construction.

The building has 73 floors and is currently listed as the 22nd tallest building in the world, 14th tallest in Asia and 10th tallest in China. Site preparation required the demolition of several historical structures and the relocation of many shops in Cloth Alley.

Statistics

Location: Hong Kong 
Height: 346m 
Year completed: 1998 
Made of: steel 
Use: office

Hancock_tower

John Hancock Center

Chicago’s love for steel construction is apparent in the shape of its skyline. Most buildings that dominate the city’s ceiling use steel as their primary construction material, and of the five tallest steel buildings in the world, three of them are situated in the city.

Another Skidmore Ownings and Merrill designed project, the John Hancock Center is an example of Khan’s trussed tube design. The trusses are clearly visible on the exterior of the building and are an obviously hint at the way Khan turned traditional skyscraper construction on its head.

The building was constructed over a five year period from 1965 by Tishman Construction, which went on to complete the World Trade Center’s twin towers in 1972 and 1973.

Statistics

Location: Chicago, USA 
Height: 344m 
Year completed: 1969 
Made of: steel 
Use: residential/office

See the rest of the list, and the original article, HERE!

The uses of our favorite metal, steel, are diverse, to put it mildly.  You’ll find steel in everything from pieces of art to skyscrapers, tanks to video game consoles.  Most things made out of steel do their best to hide the fact that they are, though.  For instance, glass-covered skyscrapers don’t often give away the presence of their steel superstructures underneath, with the exception of buildings built specifically to show off steel, like One Liberty Plaza in New York, and the US Steel Tower in Pittsburgh.  One of the best places to see steel in action remains the beautiful, exposed metalwork of bridges.  Architectural Digest put together a top ten of their favorite steel bridges, and we wanted to share it, because these structures really are amazing examples of what our civilization has accomplished with steel.

item01.rendition.slideshowHorizontal.amazing-bridges-01-new-river-gorge-bridgeNew River Gorge Bridge in Fayetteville, West Virginia
Completed in October 1977 and extending 3,030 feet across the New River Gorge, the imposing steel structure was at one point the longest single-span arch bridge in the world. It has become a symbol of West Virginia, so much so that each year, on the third Saturday in October, Fayette County celebrates Bridge Day by closing the span to vehicular traffic. In addition to offering rappelling and BASE-jumping demonstrations, the festival marks the only day pedestrians are allowed to walk across the bridge.

item02.rendition.slideshowHorizontal.amazing-bridges-02-sundial-bridgeSundial Bridge in Redding, California
Spanish architect and engineer Santiago Calatrava designed this innovative 700-foot-long pedestrian link—his first bridge in the U.S. Opened in July 2004, the cantilevered, cable-stayed 1,600-ton structure, whose shape mimics that of a large sundial, gracefully arcs across the Sacramento River in Redding’s Turtle Bay Exploration Park. Calatrava’s first vehicular bridge in the U.S., the Margaret Hunt Hill Bridge in Dallas, is slated to open later this year.

item03.rendition.slideshowHorizontal.amazing-bridges-03-sachs-bridgeSachs Bridge in Gettysburg, Pennsylvania
Considered one of the covered-bridge capitals of the world, Pennsylvania was once home to nearly 1,500 covered bridges. But only a fraction remain intact today, including the 160-year-old Sachs Bridge, which was used by both the Union and Confederate armies during the Civil War (most notably during the Battle of Gettysburg). It was designated the state’s most historic bridge in 1938 and is listed on the National Register of Historic Places.

item04.rendition.slideshowHorizontal.amazing-bridges-04-bp-bridgeBP Bridge in Chicago
Pritzker Prize–winning architect Frank Gehry’s first and only bridge opened in downtown Chicago’s Millennium Park in July 2004. Named for the energy company BP, a major donor to the project, the stainless-steel footbridge—bearing Gehry’s signature biomorphic curves—winds its way across Columbus Drive from Millennium Park to Daley Bicentennial Plaza.

item05.rendition.slideshowHorizontal.amazing-bridges-05-bixby-creek-bridgeBixby Creek Bridge in Big Sur, California
As part of the legendary Highway 1 that stretches along the Pacific coast, the Bixby Creek Bridge is emblematic of one of the country’s most scenic drives. When the bridge was completed in 1932, it was the highest single-arch span in the world (measuring 280 feet high and 714 feet long) and provided a welcome alternative to the long detour previously necessary to cross Bixby Canyon.

Check out the rest of the list on the original article, HERE.