The 6 most common questions about Active Mass Damper. And how ISAAC replies.
In this article we have collected and organized the answers to the main questions received from our interlocutors, with the aim of providing a clear and up-to-date tool for better understanding ISAAC solutions.
We will address the following topics:
1. Reliability (safety)
2. What happens if there is no power supply?
3. How does it interface with an existing slab?
4. How can the system be tested?
5. Can it be installed on any building?
6. What it takes to do a free feasibility study
1. Reliability and safety
The reliability of ISAAC system is based on redundancy principles and software control. Activation occurs only when at least 80% of the measurement nodes detect an acceleration greater than the default threshold. In the presence of a seismic event, the motors activate the mechanical axes generating stabilising forces calculated deterministically, automatically excluding nodes with inconsistent readings.
Structural accelerations are monitored by measuring nodes each equipped with three triaxial accelerometers. If one of these sensors provides inconsistent data, the system will ignore the signal and report the need for maintenance. If at least two of the three sensors are inconsistent, the whole node is disabled.
The system is managed by a PLC that controls different drives responsible for driving the electric motors of the inertial axes. The management software is divided into modules which communicate with each other through global variables. The control panel is locked, while access to the user interface is restricted by password.
Each mechanical axle is protected by two limiting systems: one software and one mechanical. The software limitation occurs when the moving mass is too close to the limit, triggering a safety brake. The mechanical limitation consists of a bumper that stops the travel of the mass. In case of contact with the bumper, the axle is deactivated immediately. The system can also operate in “reduced performance” mode if an axle has anomalies. Both restrictions are necessary for safety reasons. However, if precise and conscious design is carried out, they are never achieved.
Each actuator is tested both in the factory and in the field, to verify the correct delivery of the reference force. The system incorporates safety logics that monitor in real time the energy dissipation capacity and the correct functioning of the mechanical axes. All components are experimentally validated during field testing.
Finally, the software is designed to be fail-safe, ensuring that safety is maintained even in the event of failure. Extensive tests were carried out, including in-plant testing and dynamic tests on real structures subjected to simulated earthquakes, with positive results.
2. What happens if there is no power supply?
Each mechanical axis, with its sensors and control electronics, is powered by a battery pack. The batteries are kept constantly charged through the mains. In case of power failure, they are able to guarantee the operation of the system both during the main earthquake (main shock), and during any subsequent shocks, such as in the case of a seismic swarm.
3. How does it interface with an existing slab?
The mobile mass has a weight that varies between 200 and 1000/1100kg, the carter and the rest of the machine system makes the device reach a maximum of 1150/1250kg. The machine has a footprint of 70cm for 2.5/4m, and tends to be around 3.0m/ 3.5m for maximum masses. This means that the weight of the machine per linear metre is about 1250kg/3.5m=360kg/ml. Given that roofs normally have a load capacity of between 300 and 400 kg/m2, in most cases there is no need for reinforcement of the existing structure.
4. How can the system be tested?
The testing of the system is divided into two parts:
· Internal factory testing
· On site testing
The internal test allows you to check the entire electronic components, ensuring their proper functioning before the installation of electrical panels. On-site testing, on the other hand, confirms the overall effectiveness of the system directly on the structure. In addition, by using vibrodine, it is possible to measure the impact of the system in terms of vibration damping.
5. Can it be installed on any building?
The active control system can be installed almost on any building. The first basic technical requirement is a flat surface. The inertial axes must work on a horizontal surface to exert the control forces necessary to reduce the oscillations of the structure. They are usually placed on the roof (if it is flat), or in an attic floor.
For the application of the system to a masonry building, this shall be considered on a case-by-case basis. Indeed, in order to allow the correct operation of the axles and an adequate distribution of the control force, the structure must guarantee a scattering behaviour.
6. What does it take to do a free feasibility study?
The basic data of the structure is required for a feasibility study:
· Site details
· Construction material
· Size and number of floor of the structure
· Type of cover (or roof)
· Drawings of the structure
· Initial state estimate (IS-V) and target to be achieved
· Budget
These parameters are the minimum necessary for a rough estimate of the effectiveness of the control system. For a more accurate prefeasibility study, other information may be used if available:
· Modal analysis of the structure
· Initial vulnerability study
· Possible improvement/adaptation projects with traditional techniques
· Any finite element models
Contacts and information request
ISAAC technologies are a concrete and effective response to the growing need for seismic safety.
If you would like a personalized assessment or would like to learn more about a specific case, please contact us: we will be happy to support you.
