Active structure

An active structure (also known as a smart or adaptive structure) is a mechanical structure with the ability to alter its configuration, form or properties in response to changes in the environment.

The term active structure also refers to structures that, unlike traditional engineering structures (e.g., bridges, buildings), require constant motion and hence power input to remain stable. The advantage of active structures is that they can be far more massive than a traditional static structure: an example would be a space fountain, a building that reaches into orbit.

The result of the activity is a structure more suited for the type and magnitude of the load it is carrying. For example, an orientation change of a beam could reduce the maximum stress or strain level, while a shape change could render a structure less susceptible to dynamic vibrations. A good example of an adaptive structure is the human body where the skeleton carries a wide range of loads and the muscles change its configuration to do so. Consider carrying a backpack. If the upper body did not adjust the centre of mass of the whole system slightly by leaning forward, the person would fall on his or her back.

An active structure consists of three integral components besides the load carrying part. They are the sensors, the processor and the actuators. In the case of a human body, the sensory nerves are the sensors which gather information of the environment. The brain acts as the processor to evaluate the information and decide to act accordingly and therefore instructs the muscles, which act as actuators to respond. In heavy engineering, there is already an emerging trend to incorporate activation into bridges and domes to minimize vibrations under wind and earthquake loads.

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Wikipedia