What is monitoring?
Monitoring is the systematic observation of characteristic structure reactions such as deformation and bending or recording important factors that influence the static, such as traffic load and temperatures.
Why are bridges monitored?
The metrological recording of the structure behaviour pattern leads to a significant knowledge gain regarding the structural condition and the remaining useful life. Monitoring can be an important tool for recording the actual condition reliably, in particular, when the load paths and damage development are unclear.
How often are measurements made?
An important feature of a reliable monitoring system is that it is continuous, in other words the data is permanently recorded. This is the only way to ensure that the interpretation and analysis of the determined data are reliable. A periodic measurement – such as for example, spot measurements (once an hour or once a day) results in an increase in the noise band by the factor 10. Such measurement values cannot recognise structural changes of a bridge or other civil engineering structure.
How long do the lasers last?
Our patented measurement system is dimensioned for a useful life of 20 years. We keep all components in stock so that defective components can be promptly replaced.
How is the data evaluated?
The data are transmitted to our server in hourly packages and evaluated. Both the raw data and the results can be retrieved at any time.
Is there an automatic alarm?
Our measuring system automatically sends emails if limit values are exceeded. An individual alarm plan with pre-alarms and main alarms is created for each structure.
Does bridge monitoring make economic sense?
Every decision for or against monitoring always poses a certain risk certain financial risk. In addition to the Net Present Value Method and economic considerations, the economic efficiency can, however, be assessed using a simple risk assessment. This is the risk assessment formula applied:
Risk costs or expected costs =
likelihood of occurrence × subsequent costs
It is assumed that the immediate reinforcement of a structure requires an investment amounting to €1 million. However, through monitoring it could, become apparent that the condition of the structure is better than expected. The probability for this prospect of success amounts to 50% according to engineering firms and test engineers. The costs for the monitoring amount to approximately € 100,000.00 (estimated).
The result is two variants:
The reinforcement of the structure without monitoring is required with a probability of 100 %.
Risk costs Variant A:
100% × € 1.0 m = € 1.0 m
The reinforcement is only required with a probability of 50%. This incurs costs for monitoring.
Risk costs Variant B:
50% × € 1.0 m + € 0.1 m = € 0.6 m
The risk costs for Variant B are distinctly lower. So the costs for the monitoring measures would actually be a financially viable risk.
The risk costs of potential supplements to the construction contract, etc. can be similarly estimated. So knowing the subsequent costs (constructional or economic, compare Section 5.2 and 5.3) is an important component when evaluating the risk and also for proving the economic feasibility.
Source: Deutscher Beton- und Bautechnik-Verein e.V.
[German Concrete and Construction Engineering Association]
Bridge monitoring - Planning, tendering and realisation, version August 2018
Download the data sheet: https://www.baufachinformation.de/merkblatt-brueckenmonitoring/mb/250218