3 Bridges Project, Laos PRD

Gordon Belton - Design, Fabricate and Commission Launch Equipment

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3 steel girder bridges (continuous over 3 to 5 spans, with a maximum span of 53 m) across river valleys at Xe BangFai, Xe BangHiang and Xe BangNuan in Laos PDR.

John Holland required a cost effective method of erecting the steel girder bridges, with the ability to work during the rainy season when access from the rivers was not possible.

An incremental launching system was designed, including all launching equipment, launch nose and specialist jacks.

• The piled foundations and piers were constructed in the dry season. During the rainy season the strong river currents and large variation in water level prohibited river access.
• The bridges were pre-assembled on runway beams on the embankment behind an abutment, and then incrementally launched in a continuous operation to the next pier.
• The bridge was supported during launching on elastomeric bearings with a stainless steel sliding surface. PTFE pads were placed between the bearings and the underside of the steel plate girder to provide a low friction launch.
• The 1.8 m. deep steel girders deflected up to1.5 m. during launching. A steel launching girder attached to the front of the bridge and contained long-reach jacks to push the steel girders back up to pier level.
• Twin sliding bearings at each pier head were used to "step" over the bridge splice plates during launching.
• After launching, the bridge was lowered on to the permanent pot type bearings and an in-situ concrete deck was cast.

Sliding Bearings mounted on hydraulic jacks permit launching over piers. Twin bearings provide the ability to "step" over the girder splice plates.

Rollers provide lateral control during launching of bridge

The bridge was pre-assembled on runway beams and launched from the abutment.

Sliding was accomplished by placing PTFE pads between temporary stainless steel bearings and the underside of the girders.