DYWIDAG Tendons for Stay Cable Bridge in Peru

Atumpampa Bridge in the department of San Martín in the North of Peru, built as part of an infrastructure project, is one of the country’s first vehicular stay cable bridges.

The bridge has a main span of 84m, and the width of the bridge deck measures 7.20m. The stay cables were anchored both at the two inclined, 27m high, double pylons and on the bridge deck itself. The superstructure consists of two massive double T steel beams with varying camber that were reinforced with cross girders to support the 16cm thick concrete deck.

The stay cable anchorages were installed on the exterior steel T girders of the bridge deck. Afterwards, the 12 stay cables were aligned in pairs and installed and tensioned at the anchorages.

The stay cables consist of Ø 32mm DYWIDAG Bar Tendons. Both of the slanted pylons were additionally tied back at the abutments using 6 stay cables aligned in pairs on each side.

In addition, 16 Ø 36mm DYWIDAG Bar Tendons were installed and tensioned to serve as reinforcement in the horizontal cross girders and as bracing of the pylons.

Furthermore, transverse Double T steel girders were installed at distances of 4m to reinforce the bridge deck. The anchorages were then precisely installed at the anchorage points of the cross girders.

After their installation, the stay cables were tensioned using four hydraulic jacks, working simultaneously at each side of each of the pylons in order to transfer loads evenly. All in all, 24 pairs of stay cables were post-tensioned to accommodate the loads of the bridge deck. Tensioning of the 6 stay cables which were aligned in pairs to transfer loads into the direction of the abutment took place simultaneously. Once tensioning of the shorter stay cables had been completed, the longer stay cables leading towards the middle of the bridge deck were tensioned.

In order to ensure an easy replacement of stay cables in the future, metal ducts leading towards the anchorages were concreted into the pylons. As an additional protection against vandalism and for corrosion protection, the stay cables were inserted in HDPE ducts and post-grouted. The installation of all of the 40 bar tendons was successfully completed by Peruvian employees in a record time of two weeks.

DSI licensee SAMAYCA Ingenieros S.A.C. supplied the tendons and carried out the post-tensioning and grouting of the stay cables. In addition, SAMAYCA provided the detailed design for post-tensioning the stay cables. The stay cables were post-tensioned in June 2009, and the bridge was opened to traffic in August 2009.