Φ160 PVC Drain Pipes: Keeping Box Girders Dry from Top to Bottom

Bridge drainage systems move rainwater off the deck and away from the steel box girder. Below is data from an actual box girder bridge drainage detail.

Basic Specs

Drainage Path

Water flows through the system in three steps:

• Step 1: Deck to cross pipe — deck drains feed Φ160 PVC cross pipes under deck
• Step 2: Cross to downpipe — cross pipes slope to elbows, feed vertical HDPE downpipes
• Step 3: Downpipe to ground — vertical HDPE pipe runs down pier to ground

Components

The drainage system includes:

• Cross PVC pipe: Φ160, runs transversely under deck
• Longitudinal PVC: Φ160, runs along box girder
• HDPE downpipe: vertical pipe down the pier
• Scupper box: HDPE funnel welded to crossbeam plate
• Pipe clamps: Type A and B, fix pipes to structure
• Elbows and T-fittings: PVC bends at all direction changes

Advantages

1. HDPE + PVC light weight — plastic pipes weigh nothing on steel structure
2. Corrosion proof — PVC and HDPE don't rust like steel pipes
3. Flexible fittings — elbows and T-fittings route around structure easily
4. Scupper welded to plate — HDPE scupper fixed to crossbeam, no leak
5. Clamp-on installation — pipe clamps bolted, no welding on pipes

Disadvantages / Limitations

1. PVC can crack in cold — low-temperature PVC becomes brittle
2. Blocked by debris — leaves and dirt clog Φ160 pipes
3. UV exposure — exposed HDPE downpipes degrade in sunlight
4. Pipe clamps can loosen — vibration from traffic shakes clamps loose
5. Freeze risk — water in pipes freezes and bursts in winter

Typical Applications

1. Steel box girder bridges — drainage under deck of box girders
2. Urban road bridges — drainage to stormwater system
3. Highway overpasses — downpipes along piers
4. Pedestrian bridges — light drainage for footbridges
5. Curved bridges — drainage follows curve geometry

Installation Notes

• Φ160 PVC cross pipes sloped 1–2% toward downpipe
• HDPE scupper box welded to crossbeam steel plate
• Vertical HDPE downpipe fixed to pier with Type B clamps every 2 m
• All bends use PVC elbows, no sharp angles
• Pipe ends at 200 mm above ground or stormwater inlet

Box girder bridge drainage system — Φ160 PVC cross and longitudinal pipes, HDPE downpipes along piers, HDPE scupper boxes on crossbeams, PVC T-fittings and elbows, corrosion-proof plastic drainage for steel box bridges.

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