Which erection method should you even be shortlisting? Set the span, length and site conditions — the tool scores FSM, MSS, ILM, PSM and FCM against span bands from industry references (VSL, BBR, ASBI) and site-driven rules, and explains every plus and minus. Planning-level screening; the final call also weighs cost, schedule, contractor equipment and local practice.
Which erection method should you even be shortlisting? Set the span, length and site conditions — the tool scores FSM, MSS, ILM, PSM and FCM against span bands from industry references (VSL, BBR, ASBI) and site-driven rules, and explains every plus and minus. Planning-level screening; the final call also weighs cost, schedule, contractor equipment and local practice.
| # | Method | Score | Verdict | Working for it | Working against it |
|---|
The 28 construction methods of the Bridge Game database scored with the game's own fit rules (db/methods.json, engine/rules.js) for the span, length and site set above. Superstructure assumed from the span unless you choose one:
Scores: 70 to start, rules add or subtract; 85+ textbook, 65+ acceptable, 40+ questionable, below 40 wrong tool; a method that breaks a hard rule is marked. Methods that do not apply to the chosen superstructure are listed last, greyed. Each card links to the method's guide page. The same rules pick the reference design in the Bridge Game; Bridge Design covers a subset of these methods with its own cost and programme models.
The scoring is a screen, not a verdict — two methods within a few points of each other are genuinely interchangeable and the tender will decide. Watch the constraint inputs more than the span: crossing water or traffic quietly eliminates methods that look cheapest on paper.
Inputs are saved on this device · reset to defaults
The erection method is usually decided before the detailed design because it drives the structural system, the segment weights, the prestressing layout and the programme. The five families the selector scores are below; under the table, every one of the 28 methods in the site's database is ranked for the same inputs with the rules of the Bridge Game.
| Method | Span band | Best when | Watch out for |
|---|---|---|---|
| FSM — falsework, cast in place | up to ~40 m | low height, ground accessible, few spans | settlement of falsework, traffic under the bridge |
| Precast girders | 20–50 m | straight or gently curved, crane access, many spans | transport of 40 m+ girders, deck joints |
| MSS — movable scaffolding | 35–60 m | long viaducts (10+ spans), tall piers, no ground access | machine cost, span uniformity, wind on the MSS |
| ILM — incremental launching | 30–60 m (constant depth) | straight or constant radius, valley or water crossings, environmental limits | every section sees the full moment range; launching nose and temporary piers for longer spans |
| Precast segmental span-by-span | 30–55 m | urban viaducts, fast programme, casting yard available | gantry logistics, segment match-casting, epoxy joints |
| FCM — balanced cantilever | 70–250 m | rivers, gorges, navigation clearances, no falsework possible | time per span, creep redistribution, unbalanced stages |
Each method has a span band from published ranges (VSL, BBR, ASBI, FIB bulletins); the site inputs — total length and number of spans, height above ground, obstacle (river, road, rail, environmental exclusion), curvature and width — add or subtract points with an explanation for each. The output is a shortlist, not a decision: the final choice also weighs local contractor experience, equipment availability, programme and the cost of temporary works, which the budget estimator brackets by type.
The superstructure is cast in segments (15–30 m) in a fixed formwork behind one abutment and pushed out over the piers with a launching nose about 0.6 × span long; it suits straight or constant-curvature bridges with constant depth and spans of 30–60 m, and needs no access to the ground under the bridge.
When is a movable scaffolding system (MSS) used?For long viaducts with many similar spans of 35–60 m: the self-launching formwork casts one span in 7–14 days and moves to the next, so the cost of the machine is spread over 10 or more spans.
Precast girders or cast-in-place?Precast I / U girders up to about 45–50 m are the cheapest solution wherever cranes can reach and the geometry is simple; cast-in-place boxes take curved, variable-width or aesthetically demanding alignments.
Which method is fastest?Per span: full-span precast with a gantry (a span a day on high-speed rail viaducts), then precast segmental span-by-span (2–3 days), MSS (1–2 weeks), ILM (1 segment per week), FCM (5–7 days per pair of segments, months per span).