Retrofit Solution
Low-cost seismic fix stabilizes old buildings against earthquakes
A research team led by Akanshu Sharma, the Jack and Kay Hockema Associate Professor in Civil Engineering, has taken the next step in its work that involves retrofitting structures to make them more resilient to seismic activity. The added resilience is created by using metal triangular haunches connected using adhesive anchors as braces.
The added haunches are both practical and cost-effective, Sharma said. And — most importantly — they will greatly increase the chance of saving lives in the event of a natural disaster.
“While a majority of developed nations’ structures are being built for seismic resilience, for much of the rest of the world, that isn’t the case,” Sharma said. “Anywhere between 50 to 90 percent of existing concrete structures in developing countries are not designed appropriately against seismic activity.”
The team’s novel approach involves installing the haunches to reinforce beam-column joints. The haunches are attached with post-installed adhesive anchors secured with epoxy mortar, so material cost is relatively low. There is also an additional indirect cost savings by keeping the building’s functionality intact during installation of the haunches.
PhD student Margaritis Tonidis said both the effectiveness of the haunches and their practicality are equally important.
“We need to ensure any solution we pursue is financially viable and relatively easy to apply in practice,” Tonidis said.
In December 2024, Sharma’s team began the first round of testing by building a life-size, two-story structure in the Bowen Laboratory for Large-Scale Civil Engineering Research. The test included generating loads similar to those that occur during an earthquake and recording where points of failure occurred.
“In the first test we took a structure with nonseismic detailing, and we identified weak joints and joint failures to better understand exactly where and when a nonseismically designed structure begins to fail,” Tonidis said. “The results were extremely helpful as we prepared to create the retrofitted haunches for the next test.”
In May 2025, the team tested the structure again — this time with the haunches attached.
In the second test, the joint shear failure was successfully eliminated due to the presence of the haunches, which demonstrated the efficacy of the retrofit solution and its potential in improving the seismic performance of existing structures.
“The preliminary results are promising,” Tonidis said. “While further testing and research are necessary to refine the retrofitting procedure, we are confident that the current approach is heading in the right direction.”
“Strengthening of joints in existing structures is one of the most challenging aspects due to the limited to no access to the joints of real-life buildings. This test has clearly demonstrated that using haunch elements with post-installed anchors offers a low-cost, highly effective and low-invasive solution,” Sharma stated. Sharma says he and his team expect to publish a report on their findings before the end of 2025.