SAMCO Final Report 2006 F09 Report on Bridge Management
3.4 Need for assessment
Assessment may be loosely defined as the estimation of the bridge conditions. It may be the result of visual observations with all the limits of this practice; in this case, no complex computations are required. Or else, it may be the result of periodic (on site local testing) or continuous monitoring. In this case, testing results are linked to the definition of alarm thresholds or limit values for the monitored parameters, which might require a deeper knowledge of the structural behaviour (displacements below an acceptable value) or of the characteristics of the bridge (acceptable chloride con- tent).
Finally bridge assessment may consist in determining the load carrying capacity in relation to specific loadings. It may be necessary or advisable:
When loads are modified from the original design loads;
When the geometry is changed (number of lanes or the deck is widened);
When a structure has been damaged;
When repairs or alterations have been carried out which modify the structural
In presence of exceptional loadings.
Need for monitoring
Within the general framework of bridge management, monitoring may be seen as the periodic or continuous observation and recording of information on the conditions or performance of bridges. Its main purpose is to detect and follow the initiation and progress of deterioration, should it occur.
Periodic observations are carried out at discrete intervals. Within this category fall both measurements and visual inspections.
Visual inspections, in particular, are widely used as a monitoring system, mainly due to their easiness of execution and low cost, even if their results are quite conserva- tive. They give a qualitative estimation of the conditions of bridges, by identifying the level and extent of deterioration. Their frequency varies in function of the level of damage ascertained (from a few months to a few years).
Measurements (both periodic or continuous), as part of an on-site investigation, pro- vide a necessary input for the subsequent assessment of the structural elements and the bridges conditions.
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