Steel H-piles

How bridges get built · Driven piles · Steel H-piles

Also called: HP section piles, bearing piles

Steel H-piles — concept diagram — Concept diagram (TheBridgeEng)

How it is done

Select section and grade (HP 200-400) for load and driving stress; specify cast-steel driving shoes for gravel, boulders or sloping rock.
Set the pile in the leads with the flanges oriented as designed (strong or weak axis) and check plumbness or batter.
Drive with a hydraulic or diesel hammer sized by wave equation; record blows per 250 mm and watch for sudden drops in resistance or rapid drift that point to a bent or damaged toe.
Splice with full-penetration butt welds or proprietary splicers and inspect before driving resumes.
Approach the expected rock level with reduced energy, seat the pile and stop at the refusal criterion; never keep driving onto sloping rock.
Verify capacity by dynamic testing on a sample of piles and restrike piles that rely on setup.
Cut off square, weld cap plates or shear studs as detailed and embed in the cap; for integral abutments use a single row with the orientation the agency specifies, often in pre-bored holes filled with loose sand at the top.

Key numbers

SectionsHP 200 to HP 400 (US HP 8 to HP 14 most common, e.g. HP 10x42, HP 12x53, HP 14x73).
Working loadabout 0.5-2.5 MN per pile.
Driving stress limit0.9 fy (AASHTO); practical refusal about 10 blows per 25 mm on rock.
Integral abutmentssingle row, top 2.5-3 m often pre-bored and filled with loose sand to reduce stiffness.
Corrosion in undisturbed natural soilabout 1.2 mm per 100 years per face (EN 1993-5); more in fills, at the ground-air interface and in the splash zone.

Where it fits

End-bearing on shallow rock, dense gravels, integral abutments, sites with hard driving where displacement piles would refuse early.

Where it does not

Deep soft soil with no bearing layer (little shaft resistance); highly corrosive fills.

Choosing it

Choose H-piles over displacement piles where the pile must pass dense gravel or reach rock: their small displacement lets them penetrate layers that stop pipe and concrete piles.
Prefer displacement piles (prestressed concrete or closed pipe) where capacity must come from shaft friction in sand or clay: H-piles develop less shaft resistance per tonne of steel.
For integral abutments, prefer H-piles over concrete and pipe piles: they accept cyclic thermal movement with less cracking at the pile head.
Prefer drilled shafts or rock sockets on steeply sloping or karstic rock, where H-pile toes skid and bend.

Plant, pace and money

PlantCrawler piling rig, hydraulic or diesel hammer 5-10 t.

Productivity8-20 piles per shift.

CostUSD 120-250 per metre for HP 360.

Risks and controls

What goes wrong

Tip damage and deflection on sloping rock, corrosion in the splash and ground-air zone.

Quality assurance

Driving points inspected, plumbness, PDA on rock bearing piles.

Origins

H bearing piles followed the rolled wide-flange sections introduced in the United States in the early 20th century; they became the usual end-bearing pile for US highway bridges and later the standard support for integral abutments.

Examples

Integral abutment bridges in the US and UK; many small river bridges in Canada.

Case studies

Happy Hollow Creek Bridge (State Route 50), TennesseeUSA · 1997A 358 m, nine-span jointless precast girder bridge, long the longest fully integral bridge in the US, with stub abutments on a single row of HP 10x42 piles; Tennessee orients the piles for strong-axis bending, whereas many agencies use the weak axis.