BBR HiAm CONA™

Parallel Strand Stay Cable System

The BBR HiAm CONA™ is the parallel Strand Stay Cable System employed by the BBR Network. The term HiAm™ stands for the superior fatigue resistance, or High Amplitude Fatigue Resistance.

The BBR HiAm CONA cables are made up of a compacted bundle of a predetermined number of parallel seven-wire strands enclosed in a ultra-violet resistant high-density polyethylene (HDPE) sheath of circular cross-section. The individual strands have generally a diameter of 0.62’’ and are of low relaxation grade, with nominal cross-sectional area of 150 mm2 and a minimum guaranteed ultimate tensile stress of 1770 N/mm2 or 1860 N/mm2. The strands are galvanized, greased or waxed and individually sheathed with a continuous and wear resistant HDPE coating, providing each strand with an individual multilayer protection system. Alternatively, epoxy coated strands with a corresponding corrosion protection system, compacted strands with a cross section of 165 mm2, or 0.6 diameter strand with 140mm2 cross section may also be employed.

In the anchorage zone of the HiAm CONA cable system, the strand bundle is passing a deviator and spread out towards the compact BBR HiAm CONA socket, where each strand is individually guided, sealed leak tight and locked. Ring Nuts screwed on to the Anchor Heads transfer the cable loads by contact pressure to the supporting bearing plates. All anchorage components of the BBR HiAm CONA have been designed for a stress range greater 300 N/mm2 and to withstand the ultimate breaking load of the strand bundle with adequate safety.

In the socket of the anchorage, each strand is individually protected with a proprietary Bending Damper. Bending effects in cables may be introduced from excessive construction tolerances and cable vibrations. Supplemental Internal or alternatively external high Damping Devices protect the stay cable from vibrations. Another effective countermeasure against wind and rain-induced vibrations is the use of a helical rib on the outside of the cable surface.

The BBR HiAm CONA stay cable system is deemed approved and in compliance with the fib recommendation “Acceptance of stay cable systems using prestressing steels” as well as the corresponding PTI and SETRA recommendations.

The installation of the BBR HiAm CONA™ system is typically performed on site using the strand-by-strand installation method, which is comprised of 4 basic steps:

• Installation of the upper (pylon) and lower (deck) HiAm CONA anchorage.
• The preassembled stay cable sheath is hung between the two anchorages using two master strands. The stay cable sheath is now used as a guide and passage from anchorage to anchorage.
• The strand is position at deck level and pulled up through the stay pipe and the upper anchorage and inserted into the lower anchorage.
• Each strand is tensioned immediately after installation, using the BBR ISOSTRESS tensioning method, ensuring an equal stress distribution among the strands of an individual cable.

Alternatively to the single-strand installation method, fully or partially prefabricated cables can be installed and tensioned. The BBR HiAm CONA stay cable system is exclusively installed by teams of certified BBR PT Specialist Companies.

Each individual strand installed in the BBR HiAm CONA cable system can be re-stressed at any time during or after the installation, allowing not only for a re-stressing but also for the selective removal, inspection, replacement or add-on of individual strands.

Note:

The BBR HiAm CONA was introduced in 2005 and provides an enhanced fatigue resistance, compactness and leak-tightness according to the latest international provisions. The BBR HiAm CONA is a further development of the BBR CONA STAY cable system.