Extending the life spans of infrastructure

Apr 27, 2023

Extending the life spans of infrastructure 

Dr Wenjun Cao, Assistant Professor of Department of Civil Engineering

Many do not discover their passion until late in life, but Dr Wenjun Cao, Assistant Professor of Department of Civil Engineering, The University of Hong Kong (HKU), found her own calling while still a high school student.

She was mesmerised by the long, cable-stayed Sutong Yangtze River Bridge near her home town of Nantong, China, soon after its completion in 2008. The bridge cut down the transportation time between Shanghai and Nantong from five hours to two. More amazingly, Dr Cao saw the rapid economic growth the new infrastructure brought to the nearby economy.

It was no random choice when she decided to major in civil engineering at Tongji University. After graduated, she worked for five years as an engineer, lucky enough, as she recalled, to be put in charge of major projects including cable-stayed bridges, arch bridges and several viaducts.


Dr Cao worked on major projects as an engineer

She took on a different challenge – that of pursuing graduate studies after receiving an offer cum scholarship from the National University of Singapore and Singapore-ETH Centre. Having completed her doctoral studies one year ahead of schedule, she accepted an offer from the Delft University of Technology, also known as TU Delft, a world-leading engineering and technology university in the Netherlands.


Dr Cao (left two) and her students of the Delft University of Technology

Besides being a country with a record number of bridges, the Netherlands faces the issue of what to do with a rising number of old bridges approaching the end of their life cycles. It also aims to be a fully circular economy by 2050. Dr Cao’s time in the country was an eye-opening experience, exposing her to advanced research addressing those concerns.

Joining a comprehensive university

She joined HKU in 2022 after a two-year stint at TU Delft.

She enjoyed the free, open communications with colleagues and the collegial atmosphere in the Netherlands, but the chance to work at a comprehensive university like HKU appeals to her. She is looking forward to carrying out interdisciplinary research with staff from various faculties. “Here there are big facilities and a large number of international staff trained at top universities around the world. It is an ideal place for transdisciplinary research especially if you want to work together with say a business school or medical school. That will be a super advantage.”

It is also rare to find a university with strengths in engineering and a number of other disciplines, she adds. “I think HKU is a very good place for researchers.”

Her research serves the purpose of more than just environmental protection. Far more than that, it seeks to achieve feasible reuse of materials for the benefit of society. “Circular infrastructure has remained a relatively under-researched area. It needed a comprehensive approach for the area. It is my aim to set up a framework in which circularity is integrated into the design, construction, operation, maintenance and dismantling of infrastructure, starting with bridges.” she said.


Dr Cao joined HKU in 2022

Spearheading new research

Though the notion of circular economy is mentioned in China’s 14th Five-Year Plan as a national policy direction, it is far from being implemented in the area of civil engineering, Dr Cao said.

In Asia, she says, there is not much research on circular economy in the context of infrastructure. “In Hong Kong, there is research underway on the policy part, but not in structural, civil engineering.” She made it her goal to put the concept into practice in construction projects through smart design, data collection etc. Above all, it requires a revolutionary change in the approach to building structures.

“Smart design can help to efficiently take apart components and reuse the materials of bridges. With smart design and modular building, you can dismantle a bridge as easily as if it were made of Lego. And not just bridges but other types of infrastructure as well, such as roads and railways. That shows the potential of this research.’

“Normally what we have is a linear economy, which follows the ‘take-make-dispose’ cycle”. A circular economy aims to minimise the waste, circulate products and materials, and create value.

“You may ask how about down-cycling, that is, for example, crushing concrete into small pieces and using it as aggregates. The value in that product is declining still, but in a circular economy we try to use different technologies to catch the problems in advance or re-use part of the structure instead of demolishing the whole part to achieve the highest value.” 

Having a good design in the first place makes it easier and more efficient to identify suitable ways to deal with a structure years later. Methods that fall into this category include Design for Reuse, Design for Disaseembly and Deconstruction, Design for Repair, etc.

It is also possible to reuse structural components of a bridge, instead of mere construction materials. She is working on developing a circularity label for every civil infrastructural facility, similar to an energy label for every building.

She hopes that in the future, people will tell easily the circularity level of a structure or bridge through the labelling system.

“Based on the information provided we can estimate which parts of the bridge can be reused or repaired and how to go about it. Depending on the assessment, a bridge or a component can be labelled fit for repair, reuse, rebuild or recycling.”


Dr Cao (right two) was taking a bridge test for a project in Singapore

Digital twin as a powerful tool

Her other research focus - digital twin (DT) – a virtual model designed to accurately reflect a physical object – enables better understanding of the current condition of the object or structure.  It will help with the circularity assessment of existing civil infrastructure.

“Another feature of DT is it allows interdisciplinary interactions. We can connect it with different data sets related to, for example, the transportation systems, changes in the surrounding environment.” She said.

She also believes her work can help tackle climate change, again through reuse. “Less production of steel and concrete will lower CO2 emissions. “

The ample room for research in her field implies a huge potential for applications in the days ahead. Meantime, the young, visionary professor is expecting to work more with students and colleagues from across the university. “Besides circular economy, I just want to do some transdisciplinary work.”