DYWIDAG bond socket stay cables for an outstanding bridge project

Cairo, Egypt: 6th October Stay Cable Bridge

The DYWIDAG bond socket stay cable system was chosen to be incorporated into the first stay cable bridge in Egypt. The latest development of this bonded anchorage system combines both superior fatigue behaviour and excellent corrosion protection.

The 6th October Stay Cable Bridge is part of a 10 km long bridge system that connects downtown Cairo to the outer-ring highway. About half of the overall project has been completed so far. The stay cable bridge is located in the congested Gahmra traffic and railway junction where one other bridge structure already exists. Only a stay cable bridge could provide enough clearance in this situation. The two lane highway bridge separates both traffic directions on different levels. Each superstructure is a single cell 1.6 m tall and a 10.1 m wide box girder with two main spans of 66.5 m, supported by two planes of stays. The parallel stays rise up to a central 50 m tall pylon consisting of two shafts. Each stay plane has 2 x 11 DYWIDAG stays with 8 to 19 x 0.62" (St 1570/1 770) strands, so that a total of 88 cables were installed.

The DYWIDAG bond socket system was selected using C12 and C19 type anchorages and a multiple corrosion protection system (galvanized strand, greased and individually sheathed in a HDPE pipe). The relatively short spans were best suited for prefabrication of the stays on the bridge deck as outlined in the following steps:

• Uncoiling, stripping and cleaning of the greased and sheathed strand over a predetermined length for the anchorage zone
• Fabrication of the strand bundle using an assembly table
• Pushing of the pipe over the bundle and welding the HDPE pipe segments
• Attaching the bond sockets and wedge plates with wedges
• Lifting the prefabricated cable in place using a sling and two cranes
• Inserting the ends through the deck and tower exit points and spinning on both ring nuts.