Structural monitoring and modal properties of a real time bridge and lab tests

For understanding the actual state of durability of concrete structures, it is important to know its response due to external loading. This response mainly depends on the actual structural and material properties of the structure, while loaded. Mechanical and chemical degradation are the main mechanisms that may affect these properties with time. Strain sensors can be used to measure elongations, deflections and accelerations, which monitor the combined effect of temperature, prestressing forces, loading forces and local strain variation, while vibration sensors can be used to measure the dynamic response of a structure. Natural frequencies and mode properties can be calculated from monitored data and show the critical dynamic response behaviour of structures. However, this response behaviour can also be calculated using structural finite element models. A full-scale sensor network is installed underneath the first span of a concrete bridge in The Netherlands. Natural frequencies and mode shapes are calculated using both monitored data and a structural finite element model. Calculation results from both methods show good agreement. Understanding the impact of chemical degradation on the mode shape properties is considered experimentally. A test-setup is currently under development in the Stevin II laboratory of Delft University of Technology and is capable of testing the response of a dynamically loaded fourpoint-bending beam with a chloride solution bath mounted on top of it. During dynamic excitation, the chlorides penetrate into the cracks and accelerate corrosion of the reinforcement. Strain, deflection, crackwidth, and corrosion rate will be measured during this test