What is and how is the performance of a bridge determined?
The strategy for diagnosis and repair of bridges should be based on condition, performance (risk consideration) and compliance with regulatory or contractual requirements.
As shown in the graph above, performance must be determined based on regulatory requirements, along with other factors that pertain to each structure’s particular risks.
To achieve a certain level of safety, the prescriptive branch of the graph focuses on complying with different standards and quality controls already established in regulations and legal agreements.
The goal-oriented branch considers the particular condition and performance needs of the structures. In order to address this aspect, it is necessary to identify and analyse the risks associated with each case to assess whether any risks may affect compliance with the required conditions and performance. As a result, a risk analysis is carried out (see example of risk map in section 6.7 on risk-based inspections), identifying and taking into account the various design requirements that will enable the design performance to be achieved based on the performance and safety objectives.
It must be noted that the initial performance condition can differ from the design condition due to deviations during the construction phase (less concrete cover, more permeable concrete because of poorly executed curing, etc.). In some cases, the expected performance of new bridges is potentially not achieved if faults occur during execution, or the design and material choices are inadequate.
Therefore, it is recommended to conduct tests on the recently completed bridge – preferably before handing over the structure from the Contractor to the Owner. This will be used to prepare a series of reports and technical documents, which should be used to produce a “Birth Certificate” for the bridge, which will reflect the real characteristics and performance of the structure at the commencement of its useful life.
All these documents need to be incorporated into the structure’s documentation. Requirements for tests required during construction must be specifically stated in the tender material. In addition, this documentation must be accompanied by the “as built” project, which will provide information on how the project was actually carried out.
The execution of a diagnosis after a certain period, according to the level of aggressiveness or initial damage observed in a bridge, will allow to identify if the structure’s actual performance corresponds to the design performance, and if the expected service life can be obtained.
In this regard, diagnostics are essential to determine the current condition of bridges, support conservation and maintenance decisions, and determine the remaining useful life of the structure.
Condition assessments are essential for determining the correct time for renovation projects and decision making on the technical solution for repair works.
In the case of a reduction of performance, if no action is taken, the remaining service life may be drastically reduced; it may be necessary to carry out maintenance works, which can be partial, or exhaustive.
