 DaveKamp wrote:
What needs to be kept in forefront:
If you make a graph of years, and start that graph at 1880, and increment it regularly to 1990, you will notice that there's a very steep rise in the number of bridges built in 1890, and another at 1910, and a skyrocket to 1930... plateau until 1950.... and then the volume fell off to about 25% from 1950 until 1975, then it fell off another 70% from 1975 through 1990.
Why?
To understand this, we need to realize why, and how, and the world events occurring during these times.
Most bridge-building prior to 1880 was for railroad use... and it was primarily wood trestles, as iron wasn't entirely suitable, and steel was still very expensive... and road-going vehicles were rated in 'real horsepower'... based on the size and quantity of horses in the TEAM... or oxen... or mules.
That doesn't mean big bridges weren't built... but they weren't built for MOTORCARS or MOTORTRUCKS.
The early automobile age arrived at the same time the cost of steel production started falling... and there's no small coincedence... steelmaking is an economy of scale... the more you make, the more efficient a process becomes, and the compartively less it will cost... and during the late 'teens, the steelmaking process improvements proliferated to industrial centers all over the US, and thus, the boom of steel production took off, which meant more materials available to build MORE INFRASTRUCTURE, which meant the cost to industrialize became much lower!!!
With more cars, came more people who wanted to drive, so more roads (study the Lincoln Highway history to see what that was all about), and more roads, meant more bridges too.
A phenominal amount of those bridges were prefabricated by outfits like American Bridge Company... they were basically 'kits', and teams of ironworkers travelled the country, set up work camps, and would assemble steel bridges in literally WEEKS... and those bridges are still seen all over our country.
The last really big bridge-building boom was during the interstate highway project. After that, the process fell way off... and with it, our huge steelmaking fell off a little, too.
Several factors have since reduced our steelmaking industry to only a tiny fraction of what it was THEN. Building new bridges now, is a much more costly circumstance than it was eight decades ago.
Most of the earliest bridges have been bypassed and replaced by larger, newer, stronger bridges... but even the replacements were eventually overrun by heavier, faster loading.
Fast forward 60 years... we still have that huge quantity of bridges, but we're not replacing them, and they are NOT locked in a sealed container. Concrete and steel do NOT last forever.
People get so used to a bridge being somewhere, and don't see what aging does to a civil structure.
Administrators try to 'economize' on solutions.... kick-the-can... squeak another year out... it's short-timer's syndrome all over again.
Politicians don't want big expendatures to fall 'on their watch'... so they keep it quiet until it suits their narrative to scream about it, then they use it as a whipping-stick against their adversaries, and when they finally put through an allocation of funds, they deal it out in pork, such that there's no real funding left to do anything more than a patch-up.
And then there's a failure... with lots of finger-pointing and shouting...
...and again, it's politicians.
A large volume of bridge failures occur because the foundations wash out... it's called scouring, and it occurs because a piling, amidst a flow of current, causes turbulence- eddies... whirlpools... and those whirlpools dig deep holes that undermine the foundation. The treatment (not cure!) for scouring, is applying riprap around the pilings which forces the eddies to work on riprap, rather than the riverbed. Unfortunately, applying riprap occupies area that water cannot flow through, thus, the constriction profile of the waterway occurs, which is also not a good thing... so they have to be careful, and frequent with their riprap, and they need to send divers down to inspect footings.
Bridges are not eternal, nor are they perfect. They need to be protected, maintained, inspected, and replaced.
well, that's the short version, but wowee you sure hit the nail on the head! It wasn't the inspector's fault whoever they were, this bridge was rated poor for the last several years, (one report says last 10 tears) and recommended for replacement but ignored. The rusted supports at Coke referred to were repaired, but so far, reports are not much more was done to address the poor rating
well, that's the short version, but wowee you sure hit the nail on the head! It wasn't the inspector's fault whoever they were, this bridge was rated poor for the last several years, (one report says last 10 tears) and recommended for replacement but ignored. The rusted supports at Coke referred to were repaired, but so far, reports are not much more was done to address the poor rating
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