Dual End Buckling Restrained Damper Braces

What are dual end buckling Restrained damper braces?

Mitsubishi Power's dual end buckling restrained damper brace ("damper brace," hereafter) is a response control device that incorporates energy-absorbing damper components at each end, with an elastic circular steel pipe in-between. The damper at each end is made up of a cruciform steel core and a rectangular tube to restrain it, producing a satisfactory seismic energy dissipation system where the cruciform core yields constantly without buckling.

Experimental testing has demonstrated that the system is able to dissipate seismic energy constantly, and has enough durability to withstand even a level-two earthquake*1.

The application of Mitsubishi Power' s damper brace to a brace member of a structure makes it possible to have a good enough seismic-resistance performance to resist strong earthquakes.

  1. A level-two earthquake refers to "the strongest seismic motion experienced in past earthquakes and the strongest seismic motion that would conceivably be experienced in a future earthquake."
Damper Brace 1
Figure 1: Damper Brace Unit
Damper Brace 2
Figure 2: Conceptual Diagram Showing Absorption of Seismic Energy by Cruciform Core

Features of Damper Braces

The base shear and response displacements of a frame equipped with the new damper braces can be decreased more effectively than in the case of conventional frames. The reduction of response can be explained by two factors: One is "an increase in damping effect resulting from plastic energy absorption" and the other is "elongation of the structural natural-period resulting from decrease in equivalent stiffness given by plastic deformation of the dampers."

Figure 3 shows the hysteresis properties of a frame provided with damper braces, and Figure 4 (a) and Figure 4 (b) indicate the acceleration response spectrum and displacement response spectrum, respectively.

Figure 4(a) indicates that acceleration response is significantly decreased by the dual effects of "increased damping" and "elongation of natural-period."

Figure 4(b) indicates that displacement response increases due to the "elongation of natural-period" factor. However, the decrease of response due to "increased damping" exceeds the response increment as a result of the "elongation of natural-period" factor. Thus, the displacement response also decreases.

Damper Brace3
Figure 3: Elasto-plastic Hysteresis
Damper Brace 4
Figure 4(a): Acceleration Response Spectrum
Damper Brace 5
Figure 4(b): Displacement Response Spectrum

Damper Brace 6
Figure 5: Example of Vertical Section Figure

Scope of Application

This product is used for braces for steel frame structures. Though the system can be applied to ordinary buildings, it is also suitable for plant structures which require bigger story height and longer braces. Typical buildings and structures are given below.

  • Main turbine buildings
  • Main boiler buildings
  • Boiler support steel frames
  • Gasification furnace support steel frames
  • Steel tower support type chimney stacks

In addition, for existing structures, partial modifications to vertical braces make it possible to install this system for reinforcement against earthquakes. This product provides an effective method to decrease seismic force with the other members remaining as they are without modification.

Effect of Damper Braces

The effect of damper braces depends on the structures to which the damper braces are applied. For instance, when the damper braces are applied to boiler support structures, a common steel structure in thermal power plants, it is possible to reduce 30 to 50% of shear forces in the structure. This reduction of shear forces results in the improvement of seismic performance of the structure as well as the reduction in construction volume of steel structure erection and foundation work.

Certified by the Authority

This product has received blanket certification for General Use*2 (renewed in Feb 2018, certification number: BCJ-Rating-ST0091-04). This eliminates the need for individual ratings of each application.
  1. A "general-use rating" from the Building Center of Japan or other designated authority includes evaluation of the performance of the structural systems, materials and parts for buildings and structures in accordance with the Building Standards Act and other technical standards.
Damper Brace 7BCJ-Rating--ST0091-04