Search by name or by what you are trying to do, or pick a family. Methods marked "in the game" are the ones Bridge Master lets you choose and judges by the same rules printed on their pages.
Site investigation and testing 15Ground improvement 11Shallow foundations, cofferdams and dewatering 10Driven piles 15Bored piles and deep foundations 12Caissons and marine foundations 12Piers, pylons and abutments 11Cast-in-place concrete decks 10Precast concrete decks 14Steel erection 8Cable-supported and arch bridges 14Heavy lift, moving and accelerated construction 12Finishing, articulation and maintenance 18
Site investigation and testing
Nothing in a bridge is decided before the ground is known. These are the methods that turn a site into numbers: what to drill, what to test, and how to prove a foundation before the bridge sits on it.
Ground improvement
When the ground is too soft, too loose or too wet for what the bridge and its approaches need, it is treated rather than replaced. These methods make soft clay consolidate faster, densify loose sand, mix cement into mud, or bypass the problem with light fill and piles.
Shallow foundations, cofferdams and dewatering
Where good ground is near the surface, a footing is cheaper than any pile. Getting to that ground dry, especially in a river, is the real work: cofferdams hold the water back, dewatering keeps the excavation workable, and a concrete seal stops the bottom from blowing.
Driven piles
A pile that is hammered, vibrated or pressed into the ground displaces the soil rather than removing it. Driven piles are fast, their quality is visible blow by blow, and the ground around them is densified; the price is noise, vibration, and refusal when they meet something hard.
Bored piles and deep foundations
When the ground is removed and replaced with concrete rather than displaced, the pile can be as large as the rig can drill and can be socketed into rock. Bored piles carry the heaviest bridge loads, tolerate boulders and city limits on noise, and demand the most from supervision because nobody sees the pile until it is tested.
Caissons and marine foundations
Deep water, deep scour, ships, ice and earthquakes call for foundations that are structures in their own right: wells sunk through the bed, boxes floated into place, single giant piles, and the platforms that let people work over water at all.
Open caisson (well foundation)A concrete or steel shell with a cutting edge, built up in lifts on the bed or on a sand island and sunk under its own weight while the soil inside is dredged out. It ends as a massive block founded far below scour depth: the traditional foundation of large river bridges in India, China and the Mississippi, still unmatched for deep scour and ship impact.
Pneumatic caissonAn open caisson with a sealed working chamber at the bottom kept dry by compressed air, so workers (now often remote-controlled excavators) dig in the dry through boulders and onto rock. Precise founding, no tilt surprises, and historically dangerous; modern Japanese practice uses unmanned excavation and pressures beyond 0.3 MPa with mixed-gas decompression.
Floating (box) caissonA concrete or steel box built in a dry dock, towed to the pier, ballasted down onto a prepared bed or a pile group, and filled. It moves the foundation work into a yard and leaves only the seating to the sea: the pylon foundation of choice for straits where dredging or piling in place is slow.
Steel pipe sheet pile (SPSP) well foundationInterlocking steel pipe piles are driven in a ring; the interlocks are grouted so the ring works as a rigid well, and a top slab ties it together. The ring is first the cofferdam and then the permanent foundation: a Japanese method that cut river and coastal pier construction time dramatically.
Large-diameter monopilesOne steel tube 3-6 m in diameter, driven or drilled to 40-70 m, carries a pier alone, borrowed from offshore wind. It removes the cap and the group: one pile, one pier, one lift. In bridge work it suits sea viaducts with many identical piers in sand.
Suction caissonsAn open-bottomed steel cylinder lowered onto the seabed and sucked in by pumping water out of the top, so the pressure difference drives it into clay or sand without a hammer. Quiet, reversible, and quick in the right soils; used for anchors, offshore jackets and increasingly for temporary and light bridge foundations.
Gravity base foundationsA large concrete base that resists sliding and overturning by its own weight, placed on a prepared gravel bed on rock or dense sand. For pylons in straits with good seabeds it is the simplest foundation there is, provided the bed can be prepared and the base delivered.
Jack-up platformsA barge with legs that are lowered to the seabed and then jack the hull above the waves, giving a steady drilling or piling deck in 5-40 m of water. Weather-independent once elevated, it is the platform behind most bored pile work at sea.
Temporary trestles and access bridgesA steel-piled bridge for cranes and trucks built out over shallow water alongside the alignment, so the permanent piers can be built with land plant. It costs a bridge of its own but removes barges, tides and weather from the pier works.
Floating barges and spud bargesA flat-top barge with a crane, held by spuds (vertical legs dropped into the bed) or anchors. The cheapest way to put a rig or crane over water, and the most weather-sensitive: it moves with the waves and the tide, so precision work waits for calm.Artificial islands for marine foundations (sand, rock-bund and cellular islands)An island of sand or rock is built in the water, held by slopes, rock bunds, sheet-pile cells or large steel cylinders, so that foundations can be built with land methods or a bridge can hand over to a tunnel. Temporary islands let caissons be sunk and piles be drilled in shallow rivers; permanent islands carry tunnel portals and can shield piers from ships.Steel jacket foundations on pilesA prefabricated tubular steel space frame (the jacket) is set on the seabed and fixed by steel piles driven through its legs or through sleeves at its base, then grouted. Borrowed from offshore oil and wind, it moves most of the work into a fabrication yard and gives a stiff, light foundation in deep or soft water, and it has been used for marine bridges and pile-supported airport structures.
Piers, pylons and abutments
Between foundation and deck stands the substructure. How a pier is formed decides how fast a viaduct rises, how a 200 m pylon stays plumb, and whether an abutment moves with the deck or fights it.
Cast-in-place piers with formwork liftsThe ordinary way to build a pier: steel or timber formwork panels are set on the footing, concrete is poured in lifts of 3-6 m, the panels are stripped and lifted to the next lift by crane. Cheap, flexible and slow when the pier is tall.
Climbing and jump formworkFormwork that lifts itself on the pier it has just cast, anchored into the previous lift, with working platforms attached. Crane-climbed systems move with a crane; self-climbing systems use hydraulic rams and free the crane entirely. The method for tall piers and every concrete pylon.
SlipformA short form (1-1.2 m) is raised continuously by jacks on climbing rods while concrete is poured around the clock; the pier grows 3-6 m per day with no lift joints. Fast for constant sections, unforgiving of stops.
Pier heads, hammerheads and pier capsThe widened top of a pier that carries the bearings. A hammerhead cantilevers out on both sides and is cast on brackets or a shored platform; a cap on a multi-column bent spans between columns on falsework. Post-tensioning is common in wide hammerheads.Precast segmental piers and capsPiers and caps cast in a yard as segments or complete units, stacked on site in hours and connected with grouted couplers, post-tensioning or grouted sleeves. Removes formwork, curing and scaffold from the site: the substructure half of accelerated bridge construction.in the game
Pylon construction: concrete, anchorage zones and geometryA pylon is a tall pier with a cable anchorage zone at the top: the concrete legs climb with jump forms, the cross beams are cast on brackets or lifted as steel, and the stay anchorages are steel boxes or corrugated pipes embedded in a congested, heavily post-tensioned zone. Geometry control is the whole game: the pylon must be where the cables expect it.
Steel and composite pylonsPylons fabricated as steel boxes in sections of 10-20 m, lifted by tower or floating cranes and bolted or welded, sometimes over a concrete lower part. Faster than concrete above the deck, lighter on the foundation, and dependent on lifting capacity and fabrication precision.
Seat-type and cantilever abutmentsA concrete wall with a bearing shelf, retaining the approach fill and carrying the end of the deck on bearings, with an expansion joint between deck and backwall. The conventional abutment; simple to build, and the place where most bridge maintenance happens (joints, bearings, approach slabs).MSE (reinforced soil) abutmentsThe approach fill itself is turned into a wall with layers of steel strips or geogrid behind precast facing panels, and the deck sits on a small seat on top or on piles through the fill. Cheaper and faster than a concrete wall, tolerant of settlement, and the standard in the game and in most highway practice for fills up to about 12-15 m.Integral and semi-integral abutmentsThe deck is cast into the abutment so there is no expansion joint and no bearing at the ends; the abutment moves with the deck on flexible piles or a sliding sleeper. No joint means no leak, no bearing replacement and lower whole-life cost: the game rewards it in the upkeep score.
Pier protection: fenders, dolphins and collision wallsA pier in a navigation route or beside a railway is protected from what can hit it: rubber fenders and floating fenders absorb ship energy, independent dolphins and artificial islands stop the ship before the pier, and a crash wall shields rail-side piers from derailed trains.
Cast-in-place concrete decks
Concrete poured where the bridge will stand: on falsework from the ground, in a travelling scaffold, from the piers outward as balanced cantilevers, or on a casting bed behind the abutment and pushed out. Each way trades formwork cost against span, height and access.
Precast concrete decks
Concrete cast in a yard under a roof, then carried to the bridge. Precasting trades site work for logistics: girders by the truckload, segments by the barge, whole spans by the carrier. It is fast, repeatable and quality-controlled, and it stands or falls on the erection equipment.
Crane erection of precast girdersPrecast I, U or bulb-T girders are lifted from the truck onto the pier caps by one or two mobile or crawler cranes standing beside the bridge, then a deck slab is cast on top. The most common bridge construction on earth for spans of 20-45 m wherever a crane can stand.in the gameLaunching girder (beam launcher) for precast girdersA steel truss spanning two piers ahead of the completed deck, with trolleys that pick each precast girder from the deck behind and place it on the next span. It erects girders where no crane can stand: over water, rail, roads and steep ground, at one span per one to three days.in the gameSpliced precast girders on temporary towersPrecast girder segments too long to transport in one piece (up to 60-90 m spans) are erected on temporary towers or a strongback, spliced with cast-in-place joints, and post-tensioned through the whole length. It stretches precast girders to spans that used to need cast-in-place boxes.in the gameSpan-by-span precast segmental with gantryAll the match-cast segments of one span (2.5-3.5 m each) are hung from an overhead or underslung gantry, glued with epoxy, and post-tensioned into a span in two to four days. The fastest viaduct method ever built and the standard for metros, expressways and long approach viaducts.in the gameBalanced cantilever with precast segmentsMatch-cast segments are lifted from barges or trucks by a deck-mounted lifting frame, a crane or a launching gantry, glued and stressed symmetrically from each pier, two to four segments a day per pier. The fast way to build 60-150 m spans in quantity.in the gameFull-span precast erection (high-speed rail type)Complete 25-40 m box spans of 600-900 t are cast in a yard, carried along the finished deck by a rubber-tyred carrier and set on the next pier pair by a launching gantry. One span per shift and kilometres per year: the viaduct method of Chinese, Taiwanese and Korean high-speed rail.in the gameSegment casting: short-line and long-line match castingPrecast segmental bridges are only as good as the yard. Match casting pours each segment against the previous one so the joints fit perfectly; short-line does it in a fixed cell with the previous segment moved into position, long-line casts a whole cantilever on a long bed. Geometry control in the yard decides the geometry of the bridge.Epoxy and dry joints, shear keys and temporary PTThe joint between match-cast segments: a thin epoxy layer squeezed by temporary bars until the permanent tendons take over, with multiple shear keys carrying the shear. Dry joints without epoxy were once used with external tendons but are now avoided in most codes for durability.Precast girder casting and prestressing bedsI, U and bulb-T girders are pretensioned on long beds: strands are stressed between abutments, concrete is cast around them, and when it reaches strength the strands are cut and the girder cambers up. The girder's quality, camber and durability are set here, not on site.
Deck slabs on girders: cast-in-place, precast panels and stay-in-place formsThe slab that turns a row of girders into a bridge. Cast in place on removable or stay-in-place forms, or laid as partial-depth precast panels with a topping, or as full-depth precast panels post-tensioned together for speed. The choice decides the site time after the girders are up.
Post-tensioning: tendons, stressing and groutingSteel strands in ducts tensioned after the concrete hardens, anchored at the ends and usually grouted for bond and protection. Internal tendons live inside the concrete; external tendons run inside the box and can be inspected and replaced. Grout quality decides whether the bridge lasts a century or corrodes in twenty years.Progressive placement of precast segmentsPrecast segments are placed in one direction from one abutment to the other, each span cantilevered from the last pier until it reaches the next, with temporary stays from a mast on the deck or temporary bents carrying the advancing cantilever. All the work comes from the deck already built, which suits curved alignments and sites where nothing but the permanent piers may touch the ground.Full-depth precast deck panels with UHPC or grouted jointsDeck slabs are made of precast panels the full slab thickness, set on the girders and joined either by grouted keyways with longitudinal post-tensioning or by field-cast UHPC joints, with pockets or channels grouted over the shear connectors. Most of the forming, reinforcement fixing and curing leaves the site, so a span can be decked in days or in overnight closures.Continuity over piers for precast girders: stitch pours, diaphragms and link slabsSimply supported precast girders are made continuous over the piers by a cast-in-place diaphragm poured with, or after, the deck over the support; alternatively a link slab ties only the deck slabs together while the girders stay simply supported. Either way the deck joints over the piers disappear, removing the main source of leakage onto bearings and pier caps.
Steel erection
Steel arrives finished from the shop and is assembled in the air. The methods are about carrying pieces to their place, joining them, and keeping the half-built frame stable until the last bolt is tight.
Cable-supported and arch bridges
The longest spans are built from the top down: the deck hangs from stays or a main cable, or pushes against an arch, and the structure only works once the last piece is in. These methods are as much about temporary conditions and geometry control as about erection.
Cable-stayed cantilever erectionThe deck of a cable-stayed bridge is built outward from each pylon as a cantilever, each new segment (cast in a traveller or lifted as steel or precast) supported by the stay installed right behind it. The stays are the falsework; the cantilever grows 8-15 m per week from each pylon until closure at midspan and at the side-span piers.in the gameStay cable installation and tensioningModern stays are bundles of 15.7 mm greased and sheathed strands inside an HDPE pipe, installed strand by strand with a small winch and stressed one at a time with a monostrand jack (isotensioning), then adjusted as a bundle. Older and some Japanese bridges use prefabricated parallel wire strands or locked coil ropes installed whole.Extradosed bridge constructionA balanced cantilever box girder with short pylons and stiff external stays that act as prestressing more than as suspension. Built exactly like a cast-in-place cantilever with the stays added in the cycle; spans of 100-275 m with pylons only a tenth of the span high, and stays that hardly fatigue.
Suspension bridge erection: cables, hangers and deckThe anchorages and towers are built first, a catwalk is hung, the main cables are formed (spun or prefabricated), then the hangers are installed and the deck is lifted in sections from barges below and joined from midspan outward. Every step changes the cable geometry; the sequence is engineered as carefully as the bridge.in the gameAerial spinning of main cablesA spinning wheel carries loops of 5 mm galvanised wire across the span between the anchorages, thousands of times, building the main cable wire by wire in strands of several hundred wires that are then compacted into a circular cable. The traditional method of American and European suspension bridges; today it competes with PPWS where cables are very large or strand reels are hard to deliver, while PPWS has built the longest spans (Akashi Kaikyo, 1915 Çanakkale).Prefabricated parallel wire strands (PPWS)Main cable strands of 61–127 parallel wires are made in a factory with sockets at both ends, reeled, and hauled across the span one at a time on the catwalk. Faster and less weather-dependent than spinning; developed in the United States (Newport Bridge, 1969) and refined in Japan, where it built Akashi Kaikyo, and used for most Asian suspension bridges since.
Cable wrapping and dehumidificationMain cables corrode from inside; the modern cure is to wrap them airtight and blow dry air through them at 40 % relative humidity. Applied on new bridges from the start and retrofitted on old ones, it has replaced red lead paste and re-wrapping as the way to keep a cable for a century.
Arch erection by cantilever with temporary staysEach half of an arch is built outward from the springing as a cantilever, held by temporary stay cables running over temporary towers to anchors behind the abutments, until the halves meet at the crown. Concrete arches use form travellers; steel arches lift segments with deck or floating cranes. The method for arches over gorges and rivers where the arch cannot be supported from below.in the game
Cable crane (cableway) erectionA carrying cable strung between towers on each side of a gorge with a trolley that lifts arch segments or truss members from the valley floor or the banks and delivers them anywhere along the span. The classic plant of arch bridges in mountains and the standard in Chinese arch construction.in the game
Float-in of complete arches and spansA tied arch or truss is assembled complete on a bank or on barges, floated to the piers and set down by ballasting the barges or by jacking. Site erection is replaced by yard assembly and one tidal window; it suits navigable rivers and harbours where the span must go in quickly.in the game
Network tied arch constructionA network tied arch (inclined hangers crossing twice or more) is light enough to be built whole on falsework or on the bank and moved in, because the arch and tie are slender. The hangers are installed and tensioned in a strict sequence so that none goes slack during the deck pour.Self-anchored suspension bridge erectionA suspension bridge whose main cables are anchored to the ends of the stiffening girder instead of to the ground, so the deck carries the cable pull as compression. Because the cable needs the deck to anchor it, the deck is built first on temporary supports, the cables are formed and the hangers fitted, and the load is then transferred from the falsework to the cables by jacking the hangers.Concrete-filled steel tube (CFST) arch constructionThe arch ribs are first erected as hollow steel tubes or tube trusses, light enough to place by cable crane or rotation, and are then pumped full of high-strength concrete, so the tubes confine the concrete and the concrete stabilises the tubes. Developed mainly in China since 1990, it now builds arches of 100–575 m, and the same steel skeleton, encased in concrete, forms the core of the longest concrete arches.Stress-ribbon bridge constructionA thin concrete deck hangs as a shallow catenary between abutments; it is built by sliding precast segments along bearing tendons anchored in massive abutments and then prestressing the whole band. It uses very little material but passes very large horizontal forces to the ground, so it suits footbridges and pipeline bridges where the abutments can be anchored in rock or on large piles.
Heavy lift, moving and accelerated construction
Sometimes the fastest way to build a bridge is to build it somewhere else and move it. Floating cranes, strand jacks, self-propelled transporters, slide tracks and rotation bearings put whole spans in place in hours; the engineering is in the temporary condition, the weather window and the closure.
Finishing, articulation and maintenance
A bridge is finished when the traffic can use it and it can be kept: bearings and joints let it move, waterproofing and surfacing keep water out, barriers keep vehicles on. Then it must be inspected, strengthened, repaired and one day taken down.
