Fact Sheets of the Week

Featured Company:

Home > Civil Tech. > Segmental Precast Floating Draw Span

Segmental Precast Floating Draw Span

The floating section of Admiral Clarey Bridge is being retracted under fixed bridge span.

Assembly of precast components of pontoon.

Pontoon under tow to Hawaii

The Need

In order to make the Ford Island as the site of new housing and administrative facilities for U.S. Navy's Pearl Harbor Naval Base Hawaii, the Navy preferred a low profile bridge to the island that would not obscure the setting of memorial and the experience of its many visitors, while at the same time providing a convenient vehicle crossing. Although the traffic of large ships is infrequent, only a few times a year, the bridge should provide a wide navigation channel that allows the large ships to travel around Ford Island.

The Technology

To meet the requirements, the Navy built a bridge which was named after a decorated World War II submarine commander, Admiral Bernard "Chick" Clarey. The prime designer of the bridge was Parsons Brinckerhoff Quade & Douglas, Inc. and the contractor was a joint venture Dillingham-Manson.

The Admiral Clarey Bridge, includes a 100 ft long causeway, a 400 ft long fixed trestle and a 1035 ft long moveable section that includes the transition and floating drawspan. The fixed spans include a low level section as well as a high level section to allow a small boat channel. As the small boat channel is the high point of the bridge, it is also the location of the control house for moveable span.

The moveable span is designed to be opened or closed within a 25-minute period. This is accomplished by stopping traffic with traffic lights and lowering traffic gates, backed up by traffic barrier gates. The two transition spans are then raised hydraulically and the drawspan is withdrawn or extended using hydraulically powered winches.

The pontoon moves through the water at a speed of 14 inches per second. When withdrawn, the pontoon slides under six of the fixed approach spans, and for those spans, straddle type pier bents with transversely post-tensioned caps are used.

The drawspan is made up of three 310 ft long floating concrete modules, bolted together to provide a 930 long unit. The pontoon modules were constructed using a mixture of precast and cast-in-place concrete. each module is divided into 21 watertight cells by longitudinal and transverse bulkheads. The pontoon walls and diaphragms are precast and the reminder of the pontoon is made of cast-in-place concrete. Pontoons were produced in Concrete Technology Corporation, Tacoma, Washington, and integrated at the site into one continuos floating bridge pontoon.

The Benefits

Status

The Admiral Clarey Bridge is one of the five floating bridges in the world. Concrete Technology Corporation, as the precast concrete manufacturer for pontoons in this bridge project, has been built several floating structures since 1976 and the structures have been used as barge loading docks, ferry terminals, break-waters, floating dolphins, boathouses, fuel floats, bridge and sinkable caisson. The construction of floats has been variously hollow or foam filled, cast in place or precast segmental, and post-tensioned or conventionally reinforced.

Barriers

For a busy navigation channel, the operation of floating drawspan could be uneconomic since the opening or closing time of this moveable span is considerably too long (25 minutes for 650 feet).

Points of Contact

Refrences

  1. 1999 Nova Award Nominations, The Nova Award, Construction Innovation Forum, Inc., October 1998
  2. Precast Prestressed Segmental Floating Drawspan for Admiral Clarey Bridge, PCI Journal, July/August 1998, Vol. 43, No. 4.

Disclaimer Statement

Neither the Construction Industry Institute nor Purdue University in any way endorses this technology or represents that the information presented can be relied upon without further investigation.

Comments

Add Comment

This site is operated and maintained by the Division of Construction Engineering & Management, Purdue University as a not-for-profit service to the construction industry