page_title: Suspension bridge
section_title: Construction sequence (wire strand cable type)
hierarchical_section_title: Suspension bridge / Construction sequence (wire strand cable type)
caption_attribution_description: English: Wide view of the New Little Belt Bridge in Denmark between Jutland mainland and Funen island Svenska: Lilla Bältbron (1970) Français&#160;: Vue panoramique du Lillebæltsbroen (pont de la petite ceinture) au Danemark entre la péninsule du Jutland et l'île de Fionie
context_page_description: A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. The first modern examples of this type of bridge were built in the early 1800s. Simple suspension bridges, which lack vertical suspenders, have a long history in many mountainous parts of the world.
  This type of bridge has cables suspended between towers, with vertical suspender cables that transfer the live and dead loads of the deck below, upon which traffic crosses. This arrangement allows the deck to be level or to arc upward for additional clearance. Like other suspension bridge types, this type often is constructed without falsework.
  The suspension cables must be anchored at each end of the bridge since any load applied to the bridge is transformed into a tension in these main cables. The main cables continue beyond the pillars to deck-level supports, and further continue to connections with anchors in the ground. The roadway is supported by vertical suspender cables or rods, called hangers.
context_section_description: Typical suspension bridges are constructed using a sequence generally described as follows. Depending on length and size, construction may take anywhere between a year and a half (construction on the original Tacoma Narrows Bridge took only 19 months) up to as long as a decade (the Akashi-Kaikyō Bridge's construction began in May 1986 and was opened in May 1998 – a total of twelve years).
  Where the towers are founded on underwater piers,  caissons are sunk and any soft bottom is excavated for a foundation. If the bedrock is too deep to be exposed by excavation or the sinking of a caisson, pilings are driven to the bedrock or into overlying hard soil, or a large concrete pad to distribute the weight over less resistant soil may be constructed, first preparing the surface with a bed of compacted gravel. (Such a pad footing can also accommodate the movements of an active fault, and this has been implemented on the foundations of the cable-stayed Rio-Antirio bridge.) The piers are then extended above water level, where they are capped with pedestal bases for the towers.
  Where the towers are founded on dry land, deep foundation excavation or pilings are used.
  From the tower foundation, towers of single or multiple columns are erected using high-strength reinforced concrete, stonework, or steel. Concrete is used most frequently in modern suspension bridge construction due to the high cost of steel.
  Large devices called saddles, which will carry the main suspension cables, are positioned atop the towers. Typically of cast steel, they can also be manufactured using riveted forms, and are equipped with rollers to allow the main cables to shift under construction and normal loads.
   Anchorages are constructed, usually in tandem with the towers, to resist the tension of the cables and form as the main anchor system for the entire structure. These are usually anchored in good quality rock but may consist of massive reinforced concrete deadweights within an excavation. The anchorage structure will have multiple protruding open eyebolts enclosed within a secure space.
  Temporary suspended walkways, called catwalks, are then erected using a set of guide wires hoisted into place via winches positioned atop the towers. These catwalks follow the curve set by bridge designers for the main cables, in a path mathematically described as a catenary arc. Typical catwalks are usually between eight and ten feet wide and are constructed using wire grate and wood slats.
  Gantries are placed upon the catwalks, which will support the main cable spinning reels. Then,  cables attached to winches are installed, and in turn, the main cable spinning devices are installed.
  High strength wire (typically 4 or 6 gauge galvanized steel wire), is pulled in a loop by pulleys on the traveler, with one end affixed at an anchorage. When the traveler reaches the opposite anchorage the loop is placed over an open anchor eyebar. Along the catwalk, workers also pull the cable wires to their desired tension. This continues until a bundle, called a "cable strand" is completed, and temporarily bundled using stainless steel wire. This process is repeated until the final cable strand is completed. Workers then remove the individual wraps on the cable strands (during the spinning process, the shape of the main cable closely resembles a hexagon), and then the entire cable is then compressed by a traveling hydraulic press into a closely packed cylinder and tightly wrapped with additional wire to form the final circular cross-section. The wire used in suspension bridge construction is a galvanized steel wire that has been coated with corrosion inhibitors.
  At specific points along the main cable (each being the exact distance horizontally in relation to the next) devices called "cable bands" are installed to carry steel wire ropes called Suspender cables. Each suspender cable is engineered and cut to precise lengths, and are looped over the cable bands. In some bridges, where the towers are close to or on the shore, the suspender cables may be applied only to the central span. Earl
caption: The Little Belt suspension bridge in Denmark was opened in 1970.
exif: {"Image Make": "EASTMAN KODAK COMPANY", "Image Model": "KODAK DX4330 DIGITAL CAMERA", "Image Orientation": "Horizontal (normal)", "Image XResolution": "230", "Image YResolution": "230", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "GIMP 2.10.20", "Image DateTime": "2020:11:03 09:13:34", "Image YCbCrPositioning": "Centered", "Image ExifOffset": "234", "Thumbnail ImageWidth": "256", "Thumbnail ImageLength": "110", "Thumbnail BitsPerSample": "[8, 8, 8]", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail PhotometricInterpretation": "6", "Thumbnail SamplesPerPixel": "3", "Thumbnail JPEGInterchangeFormat": "868", "Thumbnail JPEGInterchangeFormatLength": "4471", "EXIF ExposureTime": "1/500", "EXIF FNumber": "8", "EXIF ExposureProgram": "Program Normal", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2004:04:11 12:50:45", "EXIF DateTimeDigitized": "2004:04:11 12:50:45", "EXIF ComponentsConfiguration": "YCbCr", "EXIF ShutterSpeedValue": "9", "EXIF ApertureValue": "6", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "4", "EXIF MeteringMode": "Average", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash did not fire, auto mode", "EXIF FocalLength": "187/10", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "1350", "EXIF ExifImageLength": "581", "EXIF ExposureIndex": "120", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "0", "EXIF FocalLengthIn35mmFilm": "89", "EXIF SceneCaptureType": "Standard", "EXIF GainControl": "Low gain up", "EXIF Contrast": "Normal", "EXIF Saturation": "Normal", "EXIF Sharpness": "Normal", "EXIF SubjectDistanceRange": "0"}