Chalumna Bridge is situated 40km south-west of East London and at its time of construction was considered an engineering marvel in South Africa. The construction of this bridge saw the pre-stressing of concrete technique to be implemented.

Furthermore, the deck was fully externally pre-stressed and launched on a double curvature. According to specialists, this method of construction resulted in a bridge that should be more durable and requires less maintenance in future.

Chalumna Bridge Instrumentation consists of the following:

• Vibrating Wire Strain Gauge in the deck and sides, measuring concrete and re-enforcing strain.
• Vibrating Wire Rebar Strain meter in the base, measuring strain on the reinforcing inside the concrete.
• Vibrating Wire Surface Mounted Strain Gauges in the sides, measuring external concrete strain.
• Vibrating Wire Load Cell measuring the pre-stressed steel cables.

Instruments installed in Bridge are intended to monitor:

• Stresses and strain of the internal reinforcing and concrete;
• Stresses and strain of the external concrete;
• Total tension of the pre-stressed cables;
• Stresses and strain of the horizontal reinforcing.

Installed Instruments Specification:

Concrete Strain Gauge (Piers, deck installation)

• Geokon Vibrating Wire Model 4210

Rebar Strain Meter (Piers, deck installation)

• Geokon Vibrating Wire Model 4911

Load Cell (Prestressed steel cables)

• Geokon Load Cells (Vibrating Wire) Model 4900

Designers: N/A

Consulting Engineers: Steward Scott Incorporated (SSI)

Contractors: Group 5