Catastrophic Bridge Collapses Explained
Let's investigate some unbelievable bridge failures and find out how they happened!Knowledge
We’ve all seen bridge collapses in the movies, triggered by earthquakes, or destroyed by tsunamis, and other mega forces of unstoppable power. However, it doesn’t take a giant monster to cause a collapse. From blatant design oversights to accidents caused by corruption, let's investigate some real-life bridge failures and the reasons they collapsed.
Harmony Ridge Trestle
Bridges in films tend to collapse after being shaken down, or swept away, but what about going up in flames? Back in 2013, that’s exactly what happened to the Harmony Ridge Trestle bridge in central Texas.
The 900 ft long, wooden trestle bridge that crosses over the Colorado River was built back in 1910. And despite being more than 100 years old it was still an active section of the Heart of Texas railroad, key for transporting goods from the nearby town of Brady.
However, the issue with wooden bridges built to withstand dry, rural conditions is that the wood making up the bridge needs protection. And 100 years ago, that solution came in a can of creosote; a kind of coal tar that preserves timber and protects it against insects and fungi.
The only problem is creosote is also incredibly flammable. This meant that when firefighters were called out to a small fire near the bridge back in May 2013, what they were confronted with by the time they got there was 900 ft of fiery timber!
The weight of the iron train tracks on top forced one of the burned-out pillars to collapse, which in turn dragged down the next one, and the next one until none of them were left standing! Firefighters spent a further 15 hours trying to put out the flames, but fighting against all that creosote was impossible.
Instead, they contained it and let it burn out on its own. While it’s still not known what exactly started the fire, it’s estimated to have cost a staggering $10 million to rebuild. Hopefully, this time round they used materials that are a little less flammable!
The Karakoram Highway is one of the most scenic and famous roads in East Asia, spanning more than 810 miles and connecting great cities like Abbottabad, Gilgit, and Dasu to the Chinese border. But back on the 10th of May 2022, traffic came to a standstill in one of the most mountainous stretches.
A section of The Hassanabad Bridge, an essential link between the northern areas of Pakistan and the rest of the country, had vanished. It didn’t seem possible! The stone and concrete bridge, built back in 1972, had stood solid for over 50 years. What could have made such a huge section of it disappear without a trace?
It didn’t take long before footage began to emerge online, revealing what had happened a little further upriver:
It turned out that heat waves sweeping the nation, with record high temperatures of up to 120 degrees Fahrenheit, had triggered the nearby Shisper Glacier to melt at an unprecedented rate. Which, in turn, created an ever-growing lake in the mountains throughout April.
That lake was covering over 33 hectares, more than 61 football fields worth of water! As the ice kept melting, it wasn’t long before the lake flooded, and water raced down the Hunza Valley tributary. And that’s when it met the Hassanabad Bridge:
You can see in the footage above that the onslaught of water almost immediately eroded the shoreline, where the bridge had one end of its foundation set. The more the earth holding the foundations in was eroded, the more exposed the foundations became, until the sheer force of the icy torrent knocked the end of the bridge down from the base!
Glass Bridge In China Breaks
Glass bridges have become incredibly popular across China in recent years, ranging in height from tens of feet to a staggering 1180 feet high. In 2016, there were around 60, but by 2021, there were more than 2,300! The only problem is that up till 2018, there were no specific legislations or technical requirements that glass bridge constructors had to adhere to.
All visitors had to know that they were safe were PR demonstrations; like driving cars over those bridges, or volunteers trying and failing to crack the strengthened glass with sledgehammers.
But it wasn’t the strength of the glass that failed back in 2021. On May 7th, a tourist was crossing a 328 ft high glass bridge in China’s Jilin province during a gale with windspeeds over 90 mph. But then, all of a sudden, almost all of the glass panels were blown off the bridge!
Stranded in the middle, the tourist held onto the railings for more than 40 minutes before eventually crawling to safety! It seemed the constructors had failed to secure the glass to the bridge itself, relying on the weight of it to keep it down instead. So when the wind picked up, each pane was simply blown off!
In 2018, technical standards were released stating glass bridges should be closed during bad weather but, apparently, the owners of the bridge missed that memo. It’s since re-opened, and no further cases of blowaway panels have been reported.
Tacoma Narrows Bridge Collapse
If you ask a structural engineer what the most famous and hilarious bridge failure in history is, they’ll all probably say the Tacoma Narrows Bridge Disaster.
Opened over the Tacoma Narrows strait, obviously, in Washington back in 1940, the suspension bridge once spanned nearly 6000 ft, and though it was narrow, it was just wide enough for two lanes of traffic and sidewalks on either side. Sounds perfect, but not quite. Take a look at what happened when the wind exceeded 35 mph:
This isn't normal, and less than 6 months after it’d opened, it collapsed. Luckily, people heard the concrete cracking before it collapsed, giving them enough time to flee their cars and run off the bridge. No one was hurt, save for one man’s cocker spaniel, Tubby, who was too terrified to leave a car on the bridge when it collapsed.
In most suspension bridges like those, trusses are built into the main stretch. Those are large metallic frames that are designed to break up the flow of the wind, allowing wind to pass through the bridge instead of batter against it. Trusses weren't built into the Tacoma Narrows bridge.
Instead, the H-shaped girders separated the flow and created wind vortexes that matched the sway of the main span of the bridge, an effect known as aeroelastic flutter, which gradually increased in power.
Basically, the bridge’s twisting in the wind induced more twisting! And then on November 7th, battling with 42 mph winds, the bridge finally took a twist too far and collapsed under the strain.
Puerto Rico PR-123
Do you remember the devastation that the Category 5 Hurricane Maria caused back in 2017? It was the most intense tropical cyclone of the year, with wind speeds of more than 175 mph. And Maria was not playing around when it hit Puerto Rico; the entire population lost electricity, and the majority lost access to clean water.
The storm was so powerful, it was lifting up entire cars in the street! Infrastructure across Puerto Rico was decimated, including a bridge built back in 1947 over the Río Grande de Arecibo.
Once the hurricane had died down, a temporary bridge was installed in its place. Which are modular bridges that aren’t designed to be long-term fixes. Rather, they’re cheaper solutions that can be installed quickly to re-establish essential travel across a country, though they are designed to last as long as 75 years under the right circumstances!
Puerto Rico installed several of those across the country following Hurricane Maria, including PR-123, each of which cost just $800,000. There were plans to build more permanent bridges once the country had recovered.
However, exactly 5 years later, in September 2022, Puerto Rico was dealt another blow, this time by Maria’s sister, Hurricane Fiona. In some areas, Fiona dumped a whopping 3 ft of rain in just 72 hours, leading to torrential floods which, as you can imagine, quickly overpowered the temporary bridges, like PR-123:
The pressure of the water literally snapped the entire structure in half! Those bridges weren’t meant to withstand raging tides! Another temporary bridge has since been installed, but it’s anyone’s guess as to how long this one will last!
Bear Creek Collapse
When you’re getting married, there are a hundred things that might go wrong on the big day. The cake might not arrive, the best man might lose the ring, and the bridge you’re crossing on the way to the venue might give out without any warning wait.
An Alaskan couple were driving down to Palmer for their wedding, but as they reached Bear Creek, they noticed a violent flash flood! Those are floods which occur when there’s a sudden excess of water that’s accumulated upstream, from either ice melt or rainfall. In this case, the flood was so torrential that it ripped through the river beds and banks!
The bridge sections themselves over the creek didn’t appear to be badly damaged, but the water washed away the earth supporting the asphalt road leading up to the bridge, which then collapsed.
So, despite what it looks like, technically the bridge didn’t collapse, the road did! Not sure that’s exactly comforting to the couple on their way to get married. They ended up having to double back on themselves, taking a detour that added an extra 4 hours onto their journey!
Bridge Collapses In China
Back in the 1990s, China saw an economic boost like no other. Thanks to market reforms, a huge building boom swept the nation. The government green-lit hundreds of construction projects, with many bridges among them to improve connectivity within the country. It was all going so well!
Until April 2011. At 5 a.m., a section of the Korla Peacock River bridge in Xinjiang failed, plunging a chunk of roadway into a riverbank. Thankfully, no one was hurt. But then in July, less than 2 months later, the Tongyu River bridge in Jiangsu collapsed.
Then just 3 days later, another Chinese river bridge fell apart, this time it was the Wuyishan Gongguan bridge in Fujian, the second time this particular bridge had collapsed! 3 collapses in one year definitely wasn’t good news, but it was about to get worse.
In August 2012, a recently built 330 ft section of an entrance ramp to the Yangmingtan Bridge in the city of Harbin, suddenly overturned. The bridge had cost $300 million to build and had only been opened in November 2011, less than a year before. So many bridge collapses in such a short space of time sparked panic.
The government initially said overloaded trucks were to blame, but the terrifying truth of the matter was that bridges all across China had actually been collapsing long before 2011. Back in July 2007, a section of the Jiujiang bridge in Guangdong Province was hit by a boat, which resulted in a section collapsing into the river, though it should have been able to sustain the damage.
In August 2007, an overloaded truck caused a bridge to collapse in Taiyuan, Shanxi. A few months later in October 2007, the viaduct of Minzu East Road in Baotou suddenly capsized, flipping just like the Yangmingtan Bridge entrance ramp after several overloaded trucks had apparently used it. And then in 2009, a 2,600 ft off-ramp bridge at the Gangtang Toll Station on the Jinjin Expressway collapsed, with overloaded trucks once again taking the blame.
So it wasn’t a new problem, but one that’d been ongoing for years. It begged one pretty big question, why were brand new, state-of-the-art, multimillion-dollar bridges collapsing when a few overloaded vehicles used them, or they had been lightly damaged? According to the Chinese court of public opinion, the only answer was corruption.
In 2016, transport official Chen Miangxian was charged with illegally accepting $4.4 million in bribes to divert hundreds of construction contracts to companies that used low-grade building materials. And that’s just the tip of the iceberg. 54% of the 12,759 bribery cases prosecuted in China between 2014 and 2017 related to construction projects.
Low-grade materials and rushed completion dates have left new bridges crumbling within the first few years of their erection! And it’s still having an impact to this day. In December 2021, a 1640 ft section of the Wuhuang Expressway overturned, in a manner all too similar to the 2000’s bridge flips.
One truck was accused of carrying nearly 200 tons, 400% more than the expressway allowed. That would mean it was carrying cargo that weighed the same as a mining truck! But the bridge itself was barely 10 years old. So, it would seem either those bridges have been built to sub-par standards, or the constant, repetitive use of overloaded trucks on those bridges really did cause their collapse.
The Minneapolis I-35W
China wasn’t the only country to suffer crippling bridge collapses back in 2007. Over the sea in the USA, Minnesota to be precise, August 1st was shaping up to be another very normal day. But at 6:05 pm, right at peak rush hour, disaster struck.
The I-35 W bridge over the Mississippi River suddenly gave way. And it wasn’t just one section, or a part of it, all 1064 ft of the main span fell some 115 ft into the river and banks below. From above, the scene looked utterly bizarre.
Water levels in the river were low, so the fractured segments laid out end to end looked more like a Google map glitch over a typical bridge collapse! How could such a huge span of a single bridge collapse all at once? For that, the Minnesota legislature quickly assembled a committee to investigate, but it wasn’t until January 2008 that they finally got some answers and not ones they liked.
The heart of the issue wasn’t down to something affecting the bridge, but the bridge’s original design. The bridge relied on ½ inch-thick steel gusset plates that were 30 ft wide and 20 ft high to connect each girder of the truss at node points.
When it was first opened back in 1967, it was deemed safe for trucks carrying the maximum legal load of 80,000 lbs. But over time it was increased to 136,000 lbs for overweight vehicles, as it was deemed the bridge could handle it. The only problem was that the gusset plates were actually too small to handle such an increase in weight, and so gradually, they started to fracture.
To make matters worse, at the time of the collapse, construction equipment weighing in at over 578,000 lbs was resting above the bridge’s weakest node. And then to add a final nail in the coffin of the design, over the years an additional 2 inches of concrete had been added to the road, increasing the bridge’s structural load by a whopping 20%.
Small signs began to show that this was taking its toll on the plates, with inspectors noticing the plates bowing ever so slightly back in 2003. But nothing was done. So, on August 1st, 2007, under all that weight, the gusset plate at the weakest node gave way.
Investigators later found not 1, not 2, but 8 of those gusset plates had then fractured, leading to the full collapse of the main span. Over the next 10 years, 172 of the state’s 20,000 bridges would be repaired or replaced to prevent this from ever happening again.
On October 1st, 2019, a disaster struck Taiwan’s Nanfang’ao fishing port. The 460 ft long, bifurcated single arch bridge, which had been completed back in 1998, was stretched over the mouth of the harbor and seemed as solid as ever. That was, until an oil tanker passed over it, and the entire bridge suddenly warped and collapsed 60 ft into the waters below!
Almost all of the 13 steel tendon cables attached to steel troughs in the roadway, which supported the weight of the bridge and road, suddenly snapped. 320 tons of steel and concrete, and an oil tanker, crashed some 60 ft into the water below, crushing three boats beneath it.
Two days after the crash, an investigation was launched. Initially, officials questioned whether a typhoon and earthquake, which had struck the area the day before, had anything to do with it. But the experts all said no. The bridge had stood for 20 years and withstood many typhoons and earthquakes, there had to have been something more going on beneath the steel and concrete. And they were right.
Engineers discovered water had been leaking into the steel troughs that anchored the tendons to the roadway, which didn’t have any drainage holes. Saltwater from the sea collected in those anchor points, gradually corroding them and weakening the entire structure. The tendons were so badly corroded in some places that cross sections revealed the tendons were just 22% functional!
When the first cable gave way, the next, which was just as badly corroded, also failed, with each tendon falling in turn like dominos. To make matters worse, there were no inspections carried out on this part of the bridge, so this fundamental design problem went undiscovered for almost 20 years.
After the discovery, every last bridge across Taiwan reliant on cable supports was checked for corrosion. For all the faults, at least something good came out of this disaster.
Since the 1970’s, Seoul, the capital city of South Korea, has witnessed a boom in construction projects. New complexes, districts, and skyscrapers have turned the sprawling landscape into a concrete jungle spanning both sides of the Han River. But one of its once most revered developments left a deep scar in the country’s collective memory: the Seongsu Bridge disaster.
Completed in 1979 after a little over 2 years of construction, the four lane bridge was opened at a glorious 63 ft wide and 3,810 ft long. So, less than half that of the Golden Gate bridge, but still long compared to previous bridges built across the Han. And unlike those bridges, it utilized Gerber Truss engineering, with steel trusses making up some 2200 ft of its overall length.
At the time it was hailed as an architectural marvel. But in the morning rush hour of October 21st, 1994, the unthinkable happened. Without warning, a 157 ft section suddenly collapsed while traffic was crossing it, falling 65 ft into the water below. It was the dry season, so with the water level only being around 10 ft, the bridge segment didn’t sink.
The dramatic scene sent shockwaves through South Korea. Initially, the government was quick to blame overloaded vehicles for the collapse, but the truth didn’t take long to come out once engineers inspected the bridge’s remains. The Gerber Truss design relied on a series of pins and welds to hold the suspended segments of the bridge in place.
It was discovered that the welding of the collapsed section, in the original design, was meant to be cast through the gap in the beams. However, because of some lax construction standards, it only coated the sides of the connecting beams. On the surface, they looked fine, but fatigue cracks developed around the weak weld.
Combined with the fact that inspectors couldn’t visually examine it meant that the damage went unseen for years. It was at those joints that stress fractures developed, eventually leading to the doomed section snapping and dropping on October 21st. Bad welding and shoddy inspections were to blame, turning the architectural marvel, into an architectural nightmare.
Ponte Morandi Bridge
At this point, we’ve gone through a lot of different reasons why bridges have collapsed, with negligence being the leading factor. But very few, if any, compare to the level of negligence that contributed to Genoa’s Ponte Morandi Bridge collapse back in August 2018.
A 3,900 ft viaduct over the Polcevera River, railway lines, and buildings beneath, it connected two sides of one of the city’s many valleys. Completed back in 1967, the bridge suffered a lot of issues from the get-go.
The cable-stayed design was characterized by its use of pre-stressed concrete, that is concrete that has been compressed during production to strengthen it. The only problem was the concrete wasn’t strengthened enough, meaning it was susceptible to cracks, water damage, and corrosion.
By the 1970s, the bridge required constant maintenance, because the creep of the concrete, that is deformation of the concrete under a sustained load, was so bad the vehicle deck was warped in all three dimensions!
Then in the 1990’s, it was found that the steel tendons in pillar 11 were massively corroded. It was reinforced with external steel cables, but none of the other pillars were checked for internal corrosion. In 2011, a report highlighted the accelerated decay of the bridge caused by heavy use.
By 2016, the Italian parliament had been informed multiple times that the bridge needed maintenance, as it was at the point of failing. But nothing was done. In 2017, an even more specific report anticipating the failure was released, noting anomalies in pillar 9.
Although it wasn’t until, June 2018 that ministers approved the works needed to fix it, costing it at some €20 million about $22 million. And even when they did, there was doubt the work would start before the summer for fear of impacting all the tourist traffic.
It was delay after delay after delay until the option to delay was taken out of their hands completely in the worst way possible. On August 1st, a crack in the road on the bridge was reported. But, as you probably guessed, nothing was done. There was no call to reduce the loads of vehicles on the bridge and it wasn’t closed.
Then, on August 14th, 2018, during a torrential rainstorm, a giant 690 ft section of the Ponte Morandi collapsed, with many vehicles on it, and the area, fondly referred to as Little Brooklyn, flattened underneath it.
The company responsible for maintaining the bridge, Atlantia, claimed that a landslide was to blame. But then CCTV emerged showing that it was none other than pillar 9 which gave way, and there was no landslide in sight. With such a troubled past and flawed design, it was eventually decided that the bridge would not be repaired, and the remnants were instead demolished in June 2019.
The Italian prime minister, Luigi Di Maio, made it clear that Atlantia was, in fact, to blame. A toxic mix of negligence, incompetence, and politics eventually ended up costing Atlantia more than €3.4 billion in legal disputes. And that’s just the bill so far. Though there’s not enough money in the world that can make up for that level of negligence!
I hope you were amazed at these catastrophic bridge collapses! Thanks for reading.