Fiber reinforced concrete: The future of coupling beams

By Bryce Buckley

Having buildings that can withstand the massive forces of earthquakes is imperative to the safety of millions of lives, and the use of fiber reinforced concrete is an uncomplicated and economical way to accomplish this task. On Feb. 2, 2018, Gustavo Parra-Montesinos, a professor of civil and environmental engineering at the University of Wisconsin-Madison,presented his research on simplifying reinforcement of earthquake-resistant buildings through the use of high-performance fiber reinforced concrete.

During an earthquake, dissipating as much energy as possible is necessary in order to ensure building stability. This is achieved by coupling beams. In a simple sense, coupling beams are the horizontal concrete blocks that connect the concrete walls to one another. The deformation of these coupling beams allows the building to “sway” during an earthquake and thus dissipate energy. However, the current method used to ensure these beams have enough deformation capacity involves using diagonal bars in the concrete as reinforcement. Although effective, this is both difficult to construct and very costly due to increased labor time and materials.

The use of fiber reinforced concrete may be the solution to this problem. Fiber reinforced concrete is concrete with discontinuous steel fibers in its mix. When tested in lab conditions under loads similar to those experienced during earthquakes, fiber reinforced concrete had better strength and deformation capacity than traditional coupling beams.

These findings are very important to civil engineering and the design of earthquake resistant structures. They suggest that the use of diagonal bars in coupling beams can be completely eliminated in some cases, and significantly reduced in others. This has an impact on many aspects of building construction, including construction time, labor costs, and material needs. The challenge, however, is to convince designers that fiber reinforced concrete coupling beams really can perform just as well as traditional beams with reinforcement bars and that the construction process can save time and money. As Parra-Montesinos said at end his talk: “Nobody wants to be the first, but once somebody else does it, then other people will start taking up the idea.”