Infrastructure

In a study published in the Journal of Structural Engineering, Texas A&M University and the University of Colorado-Boulder researchers have conducted a comprehensive damage and repair assessment of a still-to-be-implemented bridge design using a panel of experts from academia and industry. The researchers said the expert feedback method offers a “unique and robust” technique for evaluating the feasibility of bridge designs that are still at an early research and development phase.

[Photo courtesy of Texas A&M University.]

“Bridges, particularly those in high-seismic regions, are vulnerable to damage and will need repairs at some point,” explained Dr. Petros Sideris, assistant professor in Texas A&M’s Zachry Department of Civil and Environmental Engineering, in a blog post.

“Now the question is what kind of repairs should be used for different types and levels of damage, what will be the cost of these repairs and how long will the repairs take — these are all unknowns for new bridge designs,” he added. “We have answered these questions for a novel bridge design using an approach that is seldomly used in structural engineering.”

Most bridges are monolithic systems made of concrete poured over forms that give the bridges their shape: a design strong enough to support their own weight and other loads, such as vehicle traffic. However, Sideris said if there is an unexpected occurrence of seismic activity, such structures could crack and remedying that damage would be exorbitantly expensive.

To overcome such shortcomings, Sideris and his team – with funding from the National Science Foundation – developed a new design called a hybrid sliding-rocking bridge. Instead of a monolithic design, these “sliding rocking” bridges are made of columns containing limb-inspired joints and segments. Hence, in the event of an earthquake, the joints allow some of the energy from the ground motion to diffuse while the segments move slightly, sliding over one another rather than bending or cracking.

Yet despite potential benefits of this design, no data existed about how it would behave in real-world situations. That is where the new testing procedure developed by Texas A&M and the University of Colorado-Boulder comes into play.

“To find the correct repair strategy, we need to know what the damages look like,” Sideris said. “Our bridge design is relatively new and so there is little scientific literature that we could refer to. And so, we took an unconventional approach to fill our gap in knowledge by recruiting a panel of experts in bridge damage and repair.”

Sideris, Dr. Abbie Liel at the University of Colorado-Boulder, and their respective research teams recruited a panel of eight experts from industry and academia to determine the damage states in experimentally tested hybrid sliding-rocking segment designed columns. Based on their evaluations of the observed damage, the panel provided repair strategies and estimated costs for repair.

The researchers then used that information to fix the broken columns, retested the columns under the same initial damage-causing conditions and compared the repaired column’s behavior to that of the original column through computational investigations.

The panel found that columns built with their design sustained less damage overall compared to bridges built with conventional designs. In fact, the columns showed very little damage even when subject to motions reminiscent of a powerful once-in-a-few-thousand-years earthquake. Furthermore, the damage could be repaired relatively quickly with grout and carbon fibers, suggesting that no special strategy was required for restoration. “Fixing bridges is a slow process and costs a significant amount of money, which then indirectly affects the community,” explained 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.”

When combined with fire-ravaged terrain, heavy rain creates a whole new set of highway maintenance issues.

[Above photo courtesy of Arizona DOT.]

Take California, for starters. Already in the midst of fighting several major wildfires, the state is already gearing up for potentially damaging weather/terrain scenarios that can develop due to post-fire conditions.

The California Department of Transportation dealt with one such situation three years ago when a mudslide covered portions of U.S. 50 following several heavy and wet winter storms.

In Arizona, the infamous Bush Fire in June – a human-triggered inferno that burned more than 193,000 acres of desert and vegetation in Tonto National Forest near the northeast suburbs or Phoenix ― left behind dry, rocky terrain that could not handle the rushing waters of a monsoon, since the fire melted away vital ground cover.

Thus the need arose to craft a faster response effort to address those specific conditions. As a result, the Arizona Department of Transportation created an emergency action plan that dispatches specialized highway crews that can deal with the impact that heavy rain causes on fire-scorched terrain.

Part of the good news, explained Kevin Duby, statewide road weather manager for the agency, is that the Arizona DOT created this response plan at minimal cost plan by piggybacking off an initiative of the Federal Highway Administration’s Pathfinder Program. An offshoot of the Every Day Counts innovation recognition initiative, the Pathfinder Program, keeps travelers informed, and improves safety, mobility and the movement of goods during storms via enhanced collaboration between federal, state, and local agencies.

“We utilized previous plans obtained by research on the topic, which resulted in better use of time and cost savings for taxpayers,” said Duby.

With the help of the National Weather Service or NWS, the Arizona DOT identified “areas of the watershed where problems could arise and cleaned out the drainage ditches,” Duby emphasized, noting that no major construction was necessary because cleared culverts were already in place.

“They can accommodate the water in the normal flow from the steep slopes of the Mazatzal Mountains,” he said; a range known locally as the Four Peak Mountains.

Duby added that the Arizona DOT “already had a great relationship” with NWS via several groups from within the agency, from regional districts to operations to public relations.

The depth of those collaborations proved more advantageous and timelier than originally imagined.

“The plan was completed on July 28,” Duby said. “Then about a week later we had a mudslide on State Route 188,” which connects the towns of Globe and Payson, near Roosevelt Lake, which had been identified as a flood problem area.

“We worked with NWS to come up with protocols when a storm was imminent,” Duby noted. “One was for the NWS to call our traffic operations center,” to warn representatives of the impact of the rain.

At that juncture, the traffic operations center and public information offices broadcast the information on social media. Once the flooding occurred, the Arizona DOT executed its plan and was able to respond quickly with heavy equipment in a pre-staging area. That included vehicles such as loaders, skid-steers, and backhoes; as well as barriers and portable message boards. The agency also identified alternate highway routes – notably State Route 87 and U.S. 60.

“Part of the initiative is to be proactive about getting messages out to the travelling public, with the best information we can offer,” Duby pointed out.

While he said there is also an estimated cost savings aside from avoiding the commuter delays due to the Arizona DOT’s approach, it also helped alleviate the environmental issues that are part of any major weather event.

Without the efforts of the parties involved, “taking care of that sudden real world event would have been more complicated,” explained Duby. “We had to be sure that all three Arizona DOT districts are in sync, because they all have separates staffs,” adding that Phoenix and Flagstaff – about two hours away – both have NWS offices, so keen communication between the two proved critical.

Today, the focus is on taking what’s been learned from the Bush Fire and the mudslide and use that information to prepare for the next potential weather disaster. “We’ve refined our approach and that’s making traveling safer for our citizens,” Duby emphasized.

The California Department of Transportation recently finalized and issued the last two of 12 district-based Climate Change Vulnerability Assessment Reports; studies designed to create a “comprehensive database” to help Caltrans evaluate, mitigate, and adapt to the effects of extreme weather events on the state transportation system.

[Above photo courtesy of Caltrans.]

“The completed assessments cover all 58 counties in the state and give California a comprehensive evaluation of climate change effects on the State Highway system,” explained Toks Omishakin, director of Caltrans, in a statement. “We are now integrating the findings into our planning process to better protect California’s citizens, economy and transportation investments.”

The final two reports cover Caltrans coastal district 1 and coastal district 5 and examine the potential impact of rising average temperatures, higher sea levels, storm surge, and precipitation on California’s transportation system – climate change trends that the agency said, in turn, increase incidences of flooding, drought, wildfires, coastal erosion and mudslides.

Caltrans said that understanding the impact of climate change helps the agency assess physical climate risk to the transportation system and work towards adapting infrastructure to be more “resilient” to those impacts. For example, the agency’s 12 climate reports project that by the year 2085:

• Sea levels will rise 5.5 feet along the California coast—affecting 130 miles of State Highway by accelerating soil erosion and cliff retreat.
• Increased severity and frequency of wildfires could threaten more than 7,000 miles of state highway.
• High temperatures on the central coast and in the northwest part of the state could rise by 6 to 12 degrees, increasing drought and wildfire potential.

Caltrans began publishing those climate change reports in December 2018 partly in response to Executive Order B-30-15 issued by outgoing Gov. Edmund G. Brown Jr. (D), which mandated the integration of climate change analysis into transportation investment decisions.

The Hawaii Department of Transportation is looking at a range of studies that examine how the potential for sea level rise (SLR) due to climate change could impact transportation infrastructure. 

The most recent study, published in March of 2020 examined how direct marine inundation – which is when sea water levels rising above the current land levels – could affect Hawaii’s infrastructure but also at the impact of groundwater inundation, known as GWI.

GWI describes flooding that occurs as groundwater is lifted above the elevation of the ground surface and buried infrastructure; a difficult flooding type to manage since groundwater flooding cannot be stopped by coastal barriers such as sea walls. 

That study – conducted by researchers at the University of Hawaii at Mānoa School of Ocean and Earth Science and Technology – predicts that sea level rise will likely cause large percentages of Hawaiian land area to be impacted GWI, with Shellie Habel, lead author of the study, noting that the results “highlight the need to readjust our thinking regarding the flooding that accompanies sea level rise.”

Ed Sniffen, Hawaii DOT’s deputy director for highways and chair of AASHTO’s Committee on Transportation System Security and Resilience, estimated in a previous report that it would cost around $15 billion to protect all of the state’s coastal highways from the rising seas. The figure assumed $7.5 million for every mile of road that will need to escape erosion in the next 50 to 100 years and $40 million for every mile of bridge.

The agency began a vulnerability study in December 2019 to develop a comprehensive inventory of “potential extreme weather impacts” to Hawaii’s highway system; impacts that include GWI, SLR, and other natural disasters such as rockfalls and landslides.

That’s in addition to a statewide assessment of SLR impacts conducted in 2017, which resulted in the Hawaii Sea Level Rise Vulnerability and Adaptation Report. That report predicted a 3.2-foot rise in global sea levels by 2100, one that could be reached as early as year 2060 under more recently published scenarios. Chronic flooding with 3.2 feet of SLR could result in approximately 25,800 acres of land in the Hawaii unusable, with roughly 34 percent of that potentially lost land containing a large amount of highway infrastructure in Maui, Oahu, and Kauai alone.

Currently, over 38 miles of major roads could be chronically flooded across the Hawaiian Islands, ranging from residential roads to sections of coastal highways such as Kamehameha Highway on Oahu. 

And much of that flooding could be from GWI rather than just direct marine inundation, thus not stoppable by traditional sea walls, which is why the Hawaii DOT is looking closely at creative engineering mitigation strategies for all flooding mechanisms for highways and bridge foundations.

Part of the agency’s flood mitigation planning is based on a study conducted for the Hawaii DOT by the University of Hawaii – called State Coastal Highway Program Report – released in August 2019. That report uses a new, detailed formula developed by the university to rank nearshore roads in order of urgency. Most of its suggested mitigation efforts focus on either “hardening” the roads and bridges or relocating them all together to higher ground. 

As a result, for the next two decades or so, the Hawaii DOT plans to strengthen and maintain the roadways as they are in place. For the future, it is also looking at elevating roadways and even relocating highways further inland and tunneling through parts of mountains to make that happen.  For instance, elevating the highway on Oahu’s Windward side could involve raising the road as high as nine feet. An alternative solution would be to relocate the highway further inland which would likely include tunneling through parts of the Koolau mountains at greater cost, the agency noted.