Metallic Dampers

One of the most effective mechanisms available for the dissipation of input energy of a structure during an earthquake is through the inelastic deformation of metallic substances. The idea of utilizing separate metallic dampers in a structure to absorb a large portion of the seismic energy started with the conceptual and experimental work of Kelly et al.(1972) . Also, numerous different types of energy-absorbed devices have been proposed, such as the X-shaped and triangular plate dampers by Whittaker et al.(1991) and Tsai et al.(1993). From the promising theoretical results, researchers and practitioners turned their interest to possible applications of metallic dampers in real structures. The first structural implementation of metallic energy-dissipated devices took place in New Zealand , which obtained effective seismic response reduction of the building. Another example is that of the 6-story Cardiology Hospital complex constructed in Mexico City in the 1970s, which suffered from severe damage and the collapse of some part of the buildings during the 1985 Mexico Earthquake.

 After the event, the building was retrofitted with 18 external steel-trussed buttresses linked to the building floors through 90 ADAS devices. Nonlinear analytical results showed significant reductions in both inter-storey drift and base shear of the retrofitted building, resulting from the combined effect of stiffening and increased energy dissipation through the ADAS devices. The commonly used metallic dampers use the out-of-plane bending deformation of the metallic plate to provide damping for the structure in order to reduce its dynamic response to environmental loadings. Since the bending curvature is produced by a uniform force perpendicular to the metallic plates of the damper, the plate can inelastically deform without deflection concentration. However, the inelastic deformation of the damper may occur even when subjected to relatively small disturbances (wind or earthquake), since the out-of-plane stiffness of the metallic plates of the damper is very small. As a result, the dampers have to be replaced after the disturbance. An important issue when dealing with metallic dampers is finding new ways for improving their stiffness.

 

Metallic dampers are usually made from steel. They are designed to deform so much when the building vibrates during an earthquake that they cannot return to their original shape. This permanent deformation is called inelastic deformation, and it uses some of the earthquake energy which goes into building.

There are different types of metallic damper. In this paper, three types of metallic yielding energy dissipation devices were presented.

Round-Hole Metallic Damper (RHMD)

The photograph of single round-hole metallic damper is shown in Fig.1 (a). Typical hysteretic curve of the test is shown in Fig.1 (b). The experimental results indicated the single round-hole damper not only has good energy-dissipated capability, but also is of high initial stiffness. It is suitable to be as an effective energy dissipating device.

 

Double X-Shaped Metallic Damper (DXMD)

 A photograph of the DXMD and it hysteretic curve are illustrated in the figures below. Hysteretic loop curve shows that the DXMD has both large initial stiffness and energy dissipating capability.

 

 

Metallic Yielding-Friction Damper (MYFD)

 The construction of the MYFD turns the phased seismic design into reality easily. The seismic design philosophy for the MYFD here is that inputting energy is dissipated through friction behaviors under the small earthquake, and inputting energy is dissipated by overall MYFD inelastic behaviors under the large earthquake. It can be observed from the MYFD construction that the length of sliding way is the best dividing for these two phases. Figure 3(a) and Figure 3(b) shows the photograph of model and deformed MYFD.

 

 

Source: STUDY AND APPLICATION OF METALLIC YIELDING ENERGY DISSIPATION DEVICES IN BUILDINGS