A Program Management Approach: Building Monitoring

“The world is always in movement.”

- V.S. Naipaul

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Structural Health Monitoring (SHM) systems can be of use during construction and after completion.?As super talls continue to “venture into the theoretical” related to design possibilities and construction techniques, learning from our past is equally important to understanding the present.??

Monitoring During Construction

During construction, SHM systems serve for the verification of planned deformations and should be reviewed iteratively to ensure that the compensation for vertical elements is as predicted or if it needs to be updated.?Monitoring super tall construction actively can be achieved in a variety of ways, and it will serve to not only understand structural performance but also to refine and improve construction sequence and work plans going forward.

??Monitoring Post-Construction

Post-construction, the SHM system serves to monitor the building performance in terms of confirming that the anticipated structural displacement and acceleration is within predicted limits during design.?Specifically, motion due to wind and temperature, as well as time-dependent concrete movements in walls and columns, are essential to understand constantly. Concrete time-dependent deformations (creep and shrinkage) are of particular concern in super tall towers due to continued core deformations that can affect lift operations both vertically and eccentrically (from time-dependent potential curvature resulting from unbalanced live loading).

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Case Study, SHM at the Burj Khalifa

For the Burj Khalifa, long-term monitoring of the structural performance, building movement, temperature, humidity, and corrosion of the foundation was designed and embedded in the project.?In fact, there are three (3) rooms in the tower basement designated specifically for this purpose.

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Strain Gauges & Extensometers.?Strain gauges attached to the rebar were installed in the bored piles and raft foundation. As the tower structure progressed, strain gauges were attached to the vertical rebar and electronic extensometers in the concrete at selected locations throughout the height of the tower with the primary purpose of monitoring the structural load distributions resulting from construction sequencing, construction loading, creep, shrinkage, and elastic shortening. Related pairs of strain gauges and concrete extensometers were installed at the column mid-heights and core wall structural elements at twenty (20) floor increments, starting at Level 5, with additional sets added at column / wall elements directly below the upper-level structural steel column bores. At each monitoring level, there are 24 sets of strain gauges and extensometers located at 12 column and 12 core wall locations. Locations and sequences of the monitoring points were coordinated with construction phasing and floor-level setbacks.?Monitoring stations are also installed at grade and at twenty (20) floor increments up the tower, starting at Level 5 to measure the temperature, humidity, and wind speed.?

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Raft Foundation Monitoring.?The health of the tower raft foundation is also monitored. To protect the tower raft foundation against the severe and corrosive environment of the soil onsite (with chloride concentrations of up to 4.5% and sulfates of up to 0.6%), a robust cathodic protection system was installed in the raft foundation and piles to enhance the durability.??

All monitoring systems and data are hard-wired to the monitoring control rooms at the tower basement and are still in use today to understand, evaluate, and improve the structural health of the world’s tallest building.?