Monitoring Surveys

Conducting monitoring surveys offers numerous benefits for asset owners, managers, and stakeholders: 

• Early detection of structural issues: Monitoring surveys help to identify potential problems at an early stage before they escalate into severe damage or failure. This allows for timely interventions, such as repairs, reinforcements, or evacuation, minimising risks to public safety and property.

 

• Informed decision-making: The data obtained from monitoring surveys provides a sound basis for making informed decisions about the future of the structure. This may include decisions on maintenance priorities, retrofit strategies, or even demolition if the structure is deemed unsafe. 
• Compliance with regulations: In many cases, monitoring surveys are required by law or as part of the building code, particularly for critical infrastructure or high-risk structures. Conducting regular surveys demonstrates compliance with these regulations and helps to avoid legal liabilities. 
• Cost savings: By detecting and addressing structural issues early on, monitoring surveys can help avoid costly repairs or replacements down the line. This proactive approach can result in significant cost savings over the life cycle of the structure. 
• Peace of mind: Monitoring surveys provide reassurance to occupants, users, and the general public that the structure is being actively monitored and managed for safety and stability. This can help to build trust and confidence in the asset owner or manager. 

The frequency of monitoring surveys depends on several factors, including the nature of the structure, the level of risk involved, and the specific project requirements. In general: 

• For structures undergoing active construction or excavation nearby, daily or weekly monitoring may be necessary to ensure prompt detection of any movements. 
• For structures with known stability issues or in areas prone to geohazards, monthly or quarterly monitoring may be appropriate to track long-term trends and seasonal variations. 
• For stable structures or those with low risk, annual or biennial monitoring may suffice as a precautionary measure. The frequency of monitoring should be determined based on a thorough risk assessment and in consultation with structural engineers, geotechnical experts, and other stakeholders.

 

Monitoring surveys can achieve high-levels of accuracy, depending on the technology and methodology employed. For example: 

• Laser scanning can typically achieve an accuracy of a few millimetres over distances of several hundred meters. 
• Fixed position monitoring using total stations can measure positions with an accuracy of 1-2 millimetres. 
• Tilt sensors can detect angular changes as small as 0.01 degrees. 
• Crack gauges and monitoring studs can measure crack widths with a resolution of 0.1 millimetres. However, the actual accuracy achieved in a monitoring survey also depends on factors such as the quality of the equipment, the skill of the surveyors, and the environmental conditions at the site. 

There are several types of monitoring surveys, each employing different techniques and technologies to measure and track structural movement:

• Laser scanning: This method uses high-precision laser scanners to capture millions of data points on the structure’s surface, creating a detailed 3D model. By comparing scans taken at various times, any changes or deformations can be identified and quantified.
• Fixed position monitoring: This technique involves installing reflective targets or prisms at specific points on the structure and using a total station to measure their positions accurately. Repeated measurements over time can reveal any movements or shifts in the structure.
• Tilt sensor monitoring: Tilt sensors are devices that measure the angle of inclination or tilt of a structure. They are particularly useful for monitoring tall buildings, towers, or retaining walls, where any deviation from the vertical alignment can indicate potential instability.
• Crack monitoring: Crack gauges and monitoring studs are used to measure the width and propagation of cracks in a structure. By tracking changes in crack dimensions over time, the severity and rate of structural damage can be assessed.

Monitoring surveys becomes necessary when there is a risk of movement or instability in a structure. This risk can arise due to several factors, including: 

• Construction or excavation activities near the structure 
• Unstable ground conditions, such as subsidence, sinkholes, or soil erosion 
• Structural deterioration due to age, weathering, or poor maintenance 
• Exposure to natural hazards, such as earthquakes, landslides, or flooding 
• Changes in the structure’s load distribution or occupancy patterns In such cases, monitoring surveys help to assess the extent and rate of movement, providing valuable insights for decision-making and risk mitigation strategies. 

A monitoring survey is a process that involves measuring and tracking the movement, deformation, or changes in a structure or object over a period. This is achieved by collecting precise data at regular intervals using various techniques and technologies, such as laser scanning, fixed position monitoring, tilt sensors, and crack gauges.

The data obtained from these surveys helps to identify any potential issues or risks associated with the structure’s stability, enabling timely interventions and preventive measures.