TO Tokyoin Japan, there is an important complex of buildings, with both residential and public functions, called Harumi Island Triton Square. In the district, the presence of three skyscrapers relatively not far from each other is evident, but connected to altitude from those that may seem “normal catwalks”. Actually, These elements are an essential part of a particular vibration control system which allows the buildings of counteract the oscillations caused by strong winds and limit the accelerations that may be transmitted to residents and users.
Harumi’s towers Island Triton Square and the catwalks for the wind
Made in 2001, respectively call X, Y, Z, le three towers of the complex are 195 m high, 175 m And 155 mabout each other 13 meters and clearly outline the local landscape. In plan, their extension is approximately 54 m2 And they are connected to each other by two real “bridges”, to a height from the ground of about 162.4 m (between X and Y) e 138.4 m (between Y and Z). Why is this connection need?
Although it may seem like a connection functional at high altitude between the towers, these catwalks act as dampening devices and therefore have a fundamental structural role. In fact, the buildings showed in the project phase A strong susceptibility to wind actions: that is, the same exhibited – according to the calculations – strong vibrations As a result of the important winds affecting the area. These vibrations, which also turned into annoying accelerations on the various plans of the buildings, made the housing comfort poor and in any case not respectful of the reference project standards. To overcome this problem, a Mutual connection system between buildingswhose mechanical characteristics were able to provide the structure with the adequate damping necessary to counter the annoying accelerations. It’s not new for Japan! In fact, buildings often integrate control devices to improve structural safety towards exceptional actions, especially for earthquake but also for simple wind actions. Nonetheless, the mutual connection system built among the buildings was pioneering for the time.
The “shared” active damping system
The implemented system control “active” vibrations in a “active” wayin the sense that its operation is assisted by electrical devices That the device response change depending on what is happening to the connected structures. This occurs through different measuring points and data processing, as seen from the following figure. In essence, the mechanical device that is activated is made up of two coaxial elements – connected to two towers respectively in the two extremes – which have the possibility of scrolling together in a relative way. The “free” sliding is allowed, for example, when there are strong earthquakes: in this case, in fact, the system does not perform any structural function and allows complete freedom of movement to the three buildings individually. In the case of strong winds that could compromise living comfort, the system activates and limits the relative movements between the buildings, dissipating part of the actions transmitted among them and thus reducing the vibrations of the buildings.
This type of system, said “shared” – that is, shared – has been studied and proposed, among the former, by Prof. Kunieda in 1976. The system implemented in these buildings was baptized with the name of Active-Damping Bridgeas the same emulates a bridge between the buildings, but in substance does not allow any functional connection Among the same! The project, and its subsequent realization, represented the first application to the world of Active control systems of vibrations by means of mutual connection of multiple buildings.
Some results of the measurements performed
Valley of the actual assembly of these devices, different measures and analysis were performed to test the effective ability of the system to dampen the expected vibrations and therefore improve living comfort in non -extreme weather conditions. The results of these studies, summarized here by the figure reported below, show the response of the structure through a graph that connects The width of the response peaks of the building with and without active control of the vibrations. Without going too far into technicalities, we can do the following observation: the covered curves (system without control of vibrations) show some peaks of amplitude of about 3. When the active control system of vibrations intervenes, continuous curves, These peaks go out of the way even to halve compared to the initial values. This important descent of the peak represents the damping introduced by the system and the graph immediately quantifies its effectiveness.
The benefits of the connection between buildings
The structural connection between buildings is a technique used all over the world, also and above all to maximize the use of the spaces available in the perspective of new buildings. The connection controlled It guarantees greater safety also towards seismic events: having buildings very close to each other and unrelated in a reasoned way can be deleteriousas for the effect of counter -phase oscillations, buildings can “hammer“each other and damage each other, even to collapse.
