Construction methods · Cable-supported and arch bridges

Prefabricated parallel wire strands (PPWS)

Main cable strands of 91-127 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; the Japanese method that built Akashi Kaikyo and most Asian suspension bridges since.

How bridges get built · Cable-supported and arch bridges · Prefabricated parallel wire strands (PPWS)

Also called: PPWS method, prefabricated strand erection

How it is done

Fabricate strands with hexagonal packing and zinc-cast sockets; ship on reels.
Unreel each strand across the catwalk with a hauling system, seat the sockets in the anchorage frames, adjust sag.
Compact, band, wrap and dehumidify as for spun cables.

Where it fits

Suspension spans 500-2,000 m; sites where cable erection time is critical.

Where it does not

Spans so long that strand reels become unmanageable; sites without a strand fabricator.

Plant, pace and money

PlantReel unwinders, hauling ropes and winches, catwalk, socket seating jacks.

ProductivityA strand across the span in a few hours; a full cable of 100-300 strands in 2-4 months.

CostComparable to spinning at large scale, cheaper at medium scale.

Risks and controls

What goes wrong

Socket casting quality, strand twist during hauling, sag adjustment in temperature swings.

Quality assurance

Socket tests, sag survey at night at stable temperature, strand ordering plan.

Examples

Akashi Kaikyo, Yi Sun-sin, Ulsan, Runyang, Xihoumen, 1915 Canakkale.