Civil structural health monitoring : strategies, methods and applications

Abstract: This thesis describes a Civil Structural Health Monitoring (CSHM) method for assessment of civil structures by using a combination of advanced monitoring equipment with probabilistic based assessment. The numbers of civil structures such as bridges, tunnels, retaining walls, dams, etc. have increased dramatically the last 30 years since an increase in construction were present in the fifties and sixties. In the last decades new strategies in maintenance, inspection and assessment of out infrastructures have been developed to make it possible to continue to use the structures longer than the designed service life. Also the demands of the structures are different now compared to when they were erected, for example the loads are higher, fewer disturbances in traffic are accepted and higher traffic flows are present. Therefore new technologies for inspection, assessment, maintenance, strengthening are needed. Civil Structural Health Monitoring is defined as method for in-situ monitoring and performance evaluation of civil structures. Without CSHM it will not be possible to assess old structures in an effective way and the cost for rebuilding will have enormous impact of the society. Therefore it is motivated to use and continue to develop CSHM methods in the future. CSHM is also a very useful tool to evaluate the performance of constructions built with new materials and constructions which are strengthened with novel strengthening systems. In this thesis a new strategy to combine probabilistic evaluation of the structural performance with monitoring is described. Ideas how a strategic thinking can be done regarding inspections, investigations, monitoring and evaluation are also described in the presented CSHM method. Five cases have been used to develop, apply and validate my suggested CSHM method. The cases are testing different aspects of the model. - The first case shows a model application where the model is analysed in a recent performed strengthening and assessment project - The second case shows that it is possible to use CFRP strengthening without or with minor traffic disturbance. This is a important part of CSHM since proposed actions to continue use the structure as intended is the last step in the CSHM model - The third case is analysing tests, modelling, and verification of a composite hybrid bridge. - The forth case is testing of a new developed sensor type used to test the longterm effect of a strengthening system. The outcome of this paper is that the temperature effect was of major importance. - In the fifth case inspection, assessment and monitoring is used in a strengthening project where the goal was to evaluate the stiffness change of a bridge after it being strengthened. - The last case is an example of damage detection where the outcome point out the difficulties in global damage detection. Especially the first case shows the advantages of using probabilistic based evaluation in combination with monitoring.