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Active control in civil engineering

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Control sensors for safer bridges

Modern bridges present particular problems for engineers, in that they are faced with limited means to control cable vibration and deck oscillation through passive dampers. Newly devised test models at the University Libre de Bruxelles are showing some promising results in active vibration actuator controls.

Industrial Technologies

Cable bridges, and their better known counterparts, suspension bridges, provide particular engineering challenges in that design specifications are ever open to environmental and physical constraints. In the quest to make them progressively longer, structurally more efficient and thinner, bridges have become increasingly more sensitive to flutter instability, wind oscillation, and live load induced vibrations. Various technologies like tuned mass dampers, dashpot dampers and cable ties have been employed with some success. However, dashpot dampers for example, tend to suppress cable vibration only to a certain extent, where after, serious vibration may occur and prove detrimental to structural integrity. These passive types of dampers have only ever been tested in theoretical simulations, which may not cover all applications. The current technology offers to switch from passive to active dampers, based on a tendon that would mitigate vibration in both cable and structure. This tendon is supported by an actuator and a force sensor that would monitor vibration levels and instruct the actuator to respond accordingly. So far, experiments on small-scale laboratory mock-ups have proved effective and the study has also resulted in a linear theory which has assumed that cable dynamics can be ignored and that their interaction with the structure is restricted to the cable tension. Larger application of this technology by civil engineers, which includes technical and economic aspects, shows that the application of this active control system is highly efficient.

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