Architecture

Limb-inspired bridges promise high earthquake resistance at low cost

Limb-inspired bridges promise ...
A limb-inspired bridge column undergoes testing at Texas A&M University
A limb-inspired bridge column undergoes testing at Texas A&M University
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A limb-inspired bridge column undergoes testing at Texas A&M University
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A limb-inspired bridge column undergoes testing at Texas A&M University
The hybrid sliding-rocking bridge design, which engineers at Texas A&M University have been investigating as a more earthquake-resistant alternative to conventional designs
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The hybrid sliding-rocking bridge design, which engineers at Texas A&M University have been investigating as a more earthquake-resistant alternative to conventional designs

Today’s bridge columns are typically formed by large monolithic concrete structures that afford them great strength, but do invite the possibility of cracking should an earthquake strike. There are other options, including constructing these load-bearing structures out of limb-inspired joints and sections, which a new study suggests could not only offer greater durability under seismic activity, but also be repaired on the cheap should cracks start to appear.

The novel bridge design examined in this research is known as a hybrid sliding-rocking bridge, which engineers at Texas A&M University have been investigating as a more earthquake-resistant alternative to conventional designs.

These columns offer the same support as typical concrete bridge columns but are able to absorb more energy from ground-shaking thanks to moving joints and segments inspired by human limbs. If an earthquake hits, the individual segments slide over one another instead of cracking, at least that’s the idea. But there is a lot to learn about how this would play out in the real world.

“Our bridge design is relatively new and so there is little scientific literature that we could refer to,” says study author Dr. Petros Sideris. “And so, we took an unconventional approach to fill our gap in knowledge by recruiting a panel of experts in bridge damage and repair.”

This team of experts ran a series of experiments in which hybrid sliding-rocking columns were subjected to motion that simulated seismic activity. This allowed them to observe the damage taking place and come up with techniques and cost estimates to repair it. Using this information they then repaired the columns before subjecting them to more of the same simulated seismic activity that had damaged them in the first place.

The hybrid sliding-rocking bridge design, which engineers at Texas A&M University have been investigating as a more earthquake-resistant alternative to conventional designs
The hybrid sliding-rocking bridge design, which engineers at Texas A&M University have been investigating as a more earthquake-resistant alternative to conventional designs

These repeated experiments enabled the team to compare the performance of the repaired columns to columns in their original state, along with columns built in the conventional way. The engineers found that the hybrid sliding-rocking columns experienced less damage than the conventional designs and very little damage overall, even when subjected to forces equivalent to once-in-a-few-thousand-years earthquakes. When they did become damaged, the engineers found they could be easily patched up with grout and carbon fibers.

“Fixing bridges is a slow process and costs a significant amount of money, which then indirectly affects the community,” says Sideris. “Novel bridge designs that may have a bigger initial cost for construction can be more beneficial in the long run because they are sturdier. The money saved can then be used for helping the community rather than repairing infrastructure.”

The research was published in the Journal of Structural Engineering, and Dr. Petros Sideris provides an overview of hybrid sliding-rocking bridges in the video below.

Hybrid Sliding Rocking Bridges

Source: Texas A&M University

3 comments
sidmehta
There is a road on top of these columns. This means the top of the column must stay in place while the bottom part of the column moves. So this idea can only work for a limited range of earthquakes that are move the column sideways and not in any other direction (such as down or up).
Karmudjun
Very nice NIck! Every new construction technique designed to avoid earthquake damage expands our capacity to weather another 1906 San Francisco event. Who knows when the next massive quake will hit - and who knows what advanced techniques will allow people to build atop the former bays with layers of sediment ready to liquefy at a moment's notice! The gas (line) fires and collapsing buildings have been partially mitigated by other techniques, but losing the connecting infrastructure hampers - or kills - our first responders!

We can't seem to keep people from building in flood plains, above ancient sedimentary basins along fault lines, or atop the slopes of dormant volcanoes....although I don't know why. If we know the danger, why do municipalities allow such development with all the years of income and exploitation before a big event destroys all the 'house of cards' and requires monumental recovery efforts? Or massive firestorms eliminate national treasures? But since we humans are so foolish to believe our own biases, we need this type of research. And we'll just have to train more trauma specialists to deal with the PTSD and more engineers to implement novel constructions to replace the precarious municipalities. Sounds utterly American, or Italian. After all, we are from "the old country", why should WE change?
Kpar
Interesting. The idea of spending more money on a design that saves money on the back end does not appeal to the political class, however. They prefer to go cheap (to lower the apparent cost to the public), and worry about the future later, if at all (usually these things come due for renewal after the politician has retired). That is why US highways are not built to European standards, which last much longer. However, this design has seeds of its own success- these supports could be standardized and mass produced- a true modular system.