New design would make high-rise buildings better braced for quakes

February 28th, 2009 - 2:53 pm ICT by ANI  

Washington, Feb 28 (ANI): Researchers at the University of Michigan (U-M), US, have designed a new technique for high-rise concrete buildings, which has passed an earthquake simulation test.

Their technique passed the test, withstanding more movement than an earthquake would typically demand.

The engineers used steel fiber-reinforced concrete to develop a better kind of coupling beam that requires less reinforcement and is easier to construct.

Coupling beams connect the walls of high rises around openings such as those for doorways, windows, and elevator shafts. These necessary openings can weaken walls.

We simulated an earthquake that is beyond the range of the maximum credible earthquake and our test was very successful, said James Wight, the Frank E. Richart Jr. Collegiate Professor in the U-M Department of Civil and Environmental Engineering.

Our fiber-reinforced concrete beams behaved as well as we expected they would, which is better than the beams in use today, he added.

Today, coupling beams are difficult to install and require intricate reinforcing bar skeletons.

The U-M engineers created a simpler version made of a highly flowable, steel fiber-reinforced concrete.

We took quite a bit of the cumbersome reinforcement out of the design and replaced it with steel fibers that can be added to the concrete while it’’s being mixed, said Gustavo Parra-Montesinos, an associate professor in the Department of Civil and Environmental Engineering, U-M.

Builders could use this fiber-reinforced concrete to build coupling beams that dont require as much reinforcement, he added.

The engineers envision that their brand of beam would be cast off the construction site and then delivered.

The engineers performed their test in December on a 40-percent replica of a 4-story building wall that they built in the Structures Laboratory.

They applied a peak load of 300,000 pounds against the building, pushing and pulling it with hydraulic actuators.

To quantify the results, they measured the buildings drift, which is the motion at the top of the building compared with the motion at the base.

In a large earthquake, a building might sustain a drift of 1 to 2 percent. The U-M structure easily withstood a drift of 3 percent.

The new beams could provide an easier, cheaper, stronger way to brace buildings in earthquake-prone areas.

The researchers are now working with a structural design firm to install the beams in several high rises soon to be under construction on the west coast. (ANI)

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