‘It Boils Down To Life And Safety’: Fitness-For-Service Evaluations For Aging Infrastructure

The integrity of commercial buildings and infrastructure, including bridges, roads and public transportation, has always been vital to the U.S., but it has become a more prominent issue in recent years.

The federal government estimated that more than 45,000 bridges and 20% of roads across the country are in poor condition. Earlier this year, a parking garage that had a long history of hazardous conditions collapsed in Lower Manhattan, causing extensive damage, disruption and loss of life. In 2021, Champlain Towers South collapsed in Surfside, Florida, claiming the lives of 98 people. Experts have determined that tragedy was most likely due to major structural flaws such as improperly constructed and maintained concrete columns.

To safeguard lives, municipal officials, engineers, developers and contractors must ensure that any asset that has the potential to injure someone is maintained and regularly inspected. Owners looking to assess the integrity of their assets — and to see how much of the asset's life remains — are turning to SOCOTEC, an architectural, engineering and advisory consulting firm. 

“Fitness-for-service evaluations revolve around structural integrity, which boils down to life and safety,” SOCOTEC Director of Advanced Analysis Evan Schickel said. “As our infrastructure grows older, it becomes more susceptible to failures. It's always better to preemptively assess your structure and prepare for potential outcomes than to be surprised by a more serious issue.”

Schickel said the purpose of these quantitative evaluations is to assess the structural integrity of buildings and systems, as well as to set inspection criteria and intervals for the purpose of maintenance of integrity. Serviceability is also a large part of what the SOCOTEC team pays attention to in a fitness-for-service assessment.

“While some components of a structure may need to be inspected every year, others may only need to be checked on once every five years,” he said. “When we’re called into a project, we might determine the structure can tolerate a crack that's up to half an inch long, but at that point, you have to take action accordingly.”

Schickel said taking subsequent action may include repair procedures, part replacement or formulating a retrofit design to extend the life of a structure.

In aging assets, such as buildings or bridges that have existed for 50 or even 100 years, it is important to establish whether the structure has suffered any kind of damage or degradation — something that isn't always visible from the outside. Just because a crack or fracture cannot be seen doesn’t mean that it won’t lead to greater issues down the line.

Schickel said there are two main areas the team looks at when conducting fitness-for-service assessments: strength and fatigue. 

Strength is measured in terms of capacity, or the ability of a structure to support a certain load, whether from people, vehicles or environmental factors. When assessing strength of typical steel structures, there are two important failure modes that the team watches out for: brittle fractures, or the sudden release of energy, and plastic collapse, either the “hinge formation” or “buckling” of a structure. 

“These specific failures are sometimes due to fabrication defects, welding issues or some aspects that weren't in agreement with the drawings,” he said. “Dents, gouges and corrosion also have the ability to reduce the capacity of a given asset.” 

He said that about five years ago, the team worked on a sports stadium, one that urgently needed SOCOTEC’s structural integrity expertise. A canopy roof was being installed to cover parts of the stadium. But during the renovation, it was discovered that the large columns and load transfer mechanisms installed to support this canopy had internal defects, raising an immediate cause for concern.

“We were called in to conduct a detailed evaluation of those defects and determine whether or not these pieces were fit for their purpose or if they had to install new ones,” he said.

In addition to defects affecting strength, many structures are also susceptible to fatigue, Schickel said. Fatigue loads, or cyclic loads, can take a heavy toll on structures over time by reducing their usable life span.

“Imagine a day’s worth of traffic driving across a bridge,” he said. “There is repeated loading of that weight traveling down the bridge constantly. This can accumulate fatigue damage within the structure, causing cracks to initiate and propagate, leading to fractures, which could end up leading to major structural issues.”

The three areas that the SOCOTEC team evaluates in relation to fatigue are crack initiation, crack growth and determining the critical size of a crack that causes the structure to fail.

Schickel said the first step in this evaluation is to perform a complete review of a given asset, its design, service and repair history — in addition to its operating conditions, sources of loading and any unique factors that are special to the given component or asset being analyzed. Step 2 is to perform a detailed structural analysis via computer software, called a “stress or finite element analysis.” Lastly, SOCOTEC will evaluate the entire structure subjected to all kinds of loading consistent with what is expected, looking at areas of particularly high stress.

“We'll go out into the field and put instrumentation all over the structure,” he said. “We do detailed processing of all this data and through a number of steps of refining, isolating and processing, we're able to directly calculate the total fatigue life and remaining life of the structure.”

SOCOTEC plays a crucial role in these essential assessments, as it is referred to as a “one-stop shop” for all things engineering, he said. The team encompasses civil and structural engineers as well as mechanical and metallurgical/materials engineers. It also has a testing and inspection facility where specialized staff evaluate damaged or failed components at the microscopic level.

“It's very rewarding and exciting to always have a different problem, a different asset and a different project type to work on,” Schickel said. “It is most rewarding, however, to know that we are actively helping to prevent failures, prevent loss of life and limb, while helping our clients to either save money by extending the life of their structures or helping them plan for replacements at a time of their choosing.”

This article was produced in collaboration between SOCOTEC and Studio B. Bisnow news staff was not involved in the production of this content.

Studio B is Bisnow’s in-house content and design studio. To learn more about how Studio B can help your team, reach out to [email protected].