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TENSIONED CORRUGATED BARRIER (TCB)

OPEN BOX BEAM (OBB)


This type of barrier is the most frequently seen on the UK highways.  It is a corrugated steel strip 310 mm wide and mounted 610 mm above ground on 'Z' shaped posts. 

TCB absorbs impact by deflecting as a whole and assists the vehicle to decelerate, whilst guiding it back towards the carriage-way in a gradual and controlled manner. 

This principle is best applied to long straight runs on motorways.  It should not normally be installed on a radius of less than 120 m. 

There is no maximum installation length for TCB, but the approach/departure ends must be anchored at ground level to heavy-duty end posts or to full height anchors (a departure from standard is required). 

The tensioner units consist of two M24 bolts installed in special steel brackets fitted into the rear corrugations of the main beam elements.  These tensioner units are located at 70 m intervals along the length of the barrier. 

 


Open Box Beam is also suitable for use at the road edge or in the central reservation of motorways or high speed roads. 

The strength of the barrier lies in the section of the rails, which are normally supplied in 4.8 m and 2.4 m lengths. These are connected together by fishplates which match the profile of the rail and sit inside bridging adjoining beams. 

There is no limitation on the length of run which can be installed, but both the approach and departure ends should be anchored at ground level to strong SHS posts, or to full height anchor frames (a departure from standard is required). 

Due to the rigid nature of OBB some allowance must be made for the effects of temperature change, therefore a special expansion assembly must be fitted every 100m. 

Heavier duty 'Z' section posts are used for mounting OBB in double height format (DROBB), where a potential hazard exists for vehicles with a higher centre of gravity and mass. 

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