Existing Buildings Can Be Made More Earthquake-Resistant, fischer-Purdue Study Finds

The findings come as severe earthquakes in recent days have once again highlighted the vulnerability of people living in seismically active regions. Images of destroyed homes and the high number of casualties have renewed the pressing question of how such disasters can be prevented in the future or, at least, how their consequences can be mitigated.

A major part of the challenge lies in the existing building stock. While new buildings are now subject to strict seismic standards, millions of older structures worldwide were constructed long before modern earthquake-resistant design standards came into force. In many places where people live and work, the necessary protection is therefore lacking.

Around 500,000 earthquakes are recorded worldwide every year, according to the US Geological Survey. Densely populated regions along the Pacific Ring of Fire, the Mediterranean, the Himalayan region and Central America are particularly exposed to seismic risks. Human activities such as geothermal energy extraction, fracking and the construction of large reservoirs can also trigger earthquakes.

Demolishing and rebuilding all buildings at risk is not a realistic option because of the cost, time and resources involved. The research therefore focused on how existing buildings can be retrofitted to withstand seismic events more effectively and help protect human lives.

The fischer Group of Companies, together with its partner university Purdue University, USA, conducted the research using large-scale tests on full-scale reinforced concrete structures. The project was led by Prof Akanshu Sharma, Associate Professor at Purdue University and former Endowed Professor at the Institute of Materials Science at the University of Stuttgart.

The research focused on beam-column joints, which are the connection points between beams and columns. During an earthquake, these joints can become weak points in a structural system.

“These beam-column joints in RC frame structures are subjected to particularly high stresses and significant force caused by horizontal loading during an earthquake,” explains Dr Margaritis Tonidis, a former PhD Candidate at Purdue University and leading Project Engineer of the project. Failure of these joints can result in the collapse of an entire building.

The tested solution targets these critical points through haunch elements, in this case steel diagonal braces. These elements are integrated into the existing structural framework using injection mortar and threaded rods, specifically reinforcing the joints on site.

Dr Erik Johannes Stehle, Head of Development FiXperience at fischer, said the tests demonstrated that the earthquake resistance of existing buildings can be significantly increased when critical points in the load-bearing structure are specifically identified and reinforced. The approach also offers the advantage of requiring relatively little intervention in the existing structure, meaning residents and users do not have to face extensive alterations.

The tests demonstrated significantly improved performance under seismic loading, particularly at the joints. Following the successful scientific validation, the results are now being translated into practical application for existing buildings.

Mr. Mayank Kalra, Managing Director, fischer India, said India has a vast building stock, including structures constructed before current seismic design standards were introduced. He said the research is particularly relevant for India because of the country’s vulnerability to earthquakes across several regions.

According to Kalra, retrofitting existing buildings at critical structural points can provide a practical and more sustainable alternative to demolition and reconstruction while minimising disruption to occupants. He said the research represents an important step towards bringing scientifically validated retrofitting solutions closer to real-world application in India, with the potential to strengthen existing structures, protect lives and contribute to safer, more resilient communities.

The research indicates that targeted reinforcement of critical structural points can improve the seismic performance of older buildings without requiring extensive intervention, offering a scientifically validated route towards strengthening existing structures and reducing the potential consequences of earthquakes.