East Huntington Bridge

The bridge crosses the Ohio river between the States of Ohio and West Virginia with a main span of 274 m and one tower only. The structurally equivalent system with two towers would have a main span of about 466 m which would have been a record at the time of construction. The design for this concrete alternate was only assigned after the design for the steel alter-nate was completed and its main foundations already built. In order to design a concrete bridge for the foundations of the lighter steel alternate, steel cross girders, high-strength concrete B 56 for the precast beam and 42 for the tower were used. The concrete alternate was bid in 1981 for 29 % less than the steel alternate with an orthotropic deck.

Construction

Approach bridge

The approach bridge on the West Virginia side was built as a haunched girder by free cantilevering in order to carry part of the loads in the main span directly via bending in the beam to the approach bridge and not via cables and towers to the hold- down pier which would have been more expensive.

Tower construction

The stay cables were connected in the tower head by overlapping. In this way the tensile forces from main and side span are directly connected in compression. The geometry of the cable anchorages and the tower inspection ladders and platforms were controlled during the design phase with the help of a model. The reinforcement for the tower head was preassembled for each concreting step. In order to ensure the precise location of the steel pipes for the cable anchorages, the pipes were fixed on the ground to the reinforcement cages. (For later bridges the steel pipes were fixed to cages from steel sections, for example for the Helgeland Bridge). Today composite anchorages with an inner steel box are used, for example for the Normandy Bridge. The steel cages were connected to the already built tower in their precise location.

Beam fabrication and erection

For the free cantilevering of the beam with 250 t precast elements the tower was again temporarily stayed forward and backwards. During construction, a barge ran into the forward stay, but no serious damage was done. (For later bridges, however, the temporary forward stays were avoided, for example for the Posa- das-Encarnación Bridge). The cross-section for the East Huntington Bridge was simplified compared to that of the Pasco-Kennewick Bridge:

• Instead of the triangular outside boxes, solid main girders were used.
• The concrete cross girders were replaced by steel cross girders.
• Instead of the usual concrete B 35 „high-strength“ concrete B 56 was used – quite unusual for the USA.
• Instead of the steel dowels the front ends of the main girders were profiled for shear transfer.
• The precast elements were cast in a long line (all elements together) instead of a short line (one after the other). The precast elements were not lifted by a traveler on the beam but with a floating crane.

Cable Installation

At the beginning of the cable installation a tie rod was threaded into the inner thread of the lower anchor head. The upper anchor head was lifted with the tower crane to the tower head and pulled into the anchorage pipes with grip hoists. The tie rod at the lower cable anchor head was initially pulled into the steel pipe with two strands. Once the tie rod had reached the jack located on a jack chair underneath the beam, the anchor head was pulled into its final position and the washers were installed. The actual cable length at this stage was determined by the thickness of the washers.

Completed bridge

The A-tower forms a tent-like space in the driver’s view, which provides a certain feeling of security.

In the skew view from the water the advantage of an A-tower is apparent, in that the stay cables in a fan arrangement hardly intersect visually.

Excerpt from: Svensson, Holger; Cable-Stayed Bridges, Wilhelm Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH, Berlin (Germany), ISBN 343302992X; pp. 346-351. References to figures and literature were omitted.