Story Bridge spatial monitoring

Spatial support for sustainable development

As part of its efforts to improve connection throughout the inner city, Brisbane City Council is developing the Kangaroo Point 'Bridges for Brisbane' river crossing – a new pedestrian walkway spanning the Brisbane River between Kangaroo Point and the city’s Botanic Gardens.

With one of the new bridge’s underpasses being constructed through one of Brisbane’s most well-known river crossings and heritage icons – the Story Bridge (circa 1940) – Council called on RPS to undertake a long-term spatial monitoring program for the elder structure.

The aim? To ensure construction of the new underpass did not compromise the stability of the heritage bridge.

Laser monitoring of bridge columns

To ensure that any movement to the Story Bridge's supports was detected and monitored, RPS, with the help of Ultimate Positioning Group (UPG), designed a monitoring program that would detect any shifts in column position as construction work for the underpass was underway.

Using the latest Trimble LaserTilt90 sensor devices, our survey team was able to monitor multi-variable changes in 3D positioning, tilt and distance between columns. Temperature measurements were also recorded which would add context to any minor (millimetre) differences recorded due to expansion/contraction of the structure.

Each sensor was set to take multiple measurements every hour throughout the construction process, and a real time alert system was in place should any significant deviations be recorded.

Benefits of an automated laser monitoring approach

• Less requirement for surveyors to be physically on site - cost-effective and safe.
• Measurement frequency could be updated remotely (up to five times per minute if required) for additional assurance when high intensity work was taking place.
• Live data available for stakeholders as required.

Site layout captured via Trimble SX10

Extra assurance through manual measurement

To give extra confidence to Council and the Bridges for Brisbane construction team, each RPS laser monitoring unit had additional survey equipment attached to allow our geospatial team to take traditional manual survey measurements regularly. These measurements were compared against the automated Trimble LaserTilt readings.

While the recalibration of some baseline measurements (column to column) were needed to account for temporary bracing structures, no notable shifts in columns were detected over the twelve-month monitoring program.

By combining tilt sensor technology, the alert system and manual/traditional monitoring, RPS was able to provide assurance that the new bridge’s construction was not causing any unexpected geotechnical impacts to Brisbane’s much-loved Story Bridge.