Bay Bridge: How Supply Chain Mistakes Affect High-Strength Steel Rod

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BayBridge_550

The eastern span of the Bay Bridge.

Tests on a 25-foot, high-strength steel rod that secured the base of a tower on the eastern span of San Francisco’s new, $6.5 billion Bay Bridge recently showed widespread cracking, according to the San Francisco Chronicle.

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This is bad news for the 2,049-foot, two-span, self-anchored suspension bridge that was once one of heavy civil construction’s most decorated and talked about projects. Rust and microscopic cracking were found after one of the 424 high-strength steel rods, intended to keep the tower from being damaged in an earthquake, was removed for testing last year. The tests were needed after the tower on the eastern span listed too far to one side and had to be “crow-barred” back into its intended position by being pulled with cables from nearby Yerba Buena Island.

Improper Grouting

What’s even worse is that the reason the test was necessary in the first place was because the California Dept. of Transportation (CalTrans), the state agency that functions as the owner of the bridge, was worried that water exposure on the bottom of the steel rods led to the listing problem. The problem was even worse than they suspected, as the steel rod tested showed signs of corrosion on the top of the road, not just the bottom where it was exposed to water and corrosive hydrogen.

The bottoms of the rods were exposed to water because not enough grout had been pumped into protective sleeves designed to keep them dry once they were installed, CalTrans officials told members of the bridge project oversight committee. The corrosion at the top of the rod suggests that the problem with the rods goes beyond the areas exposed to water.

How did this happen? How can such a huge public works project be susceptible to these mistakes? Failure to control supply chain standards.

CalTrans Chose to Waive its Own Rules

According to the Chronicle, CalTrans decided to waive its own rule against using high-strength galvanized-steel rods and bolts on bridges when it came to construction of the eastern span during the design phase of the project in 2003.

Galvanization — a process by which the rods are coated with molten zinc — is understood as a threat to high-strength steel. The process carries the risk the rods can be exposed to hydrogen. Caltrans decided, however, that the extraordinary seismic demands placed on the eastern span, because of its unusual self-anchored design, required high-strength steel. CalTrans specified precautions to avoid hydrogen contamination during processing, but many of those steps were never followed.

The Buy American provisions, for instance,  for sourcing of federal projects were not followed.

Lack of Oversight

Caltrans belatedly learned it had no record of overseeing the manufacturing process or testing the tower rods before they were installed. The tower rods had been bathed in hydrochloric acid before being delivered to the bridge, a major no-no that CalTrans had specified against because it could expose the rods to hydrogen.

The rods were scraped en route from the Tennessee plant where they were galvanized in 2007. At a stopover in Texas, workers spray-painted the scrapes and other damage to the galvanization layer. Any damage to the threads from the scrapes could foster the cracking happening today.

Before the bridge opened in 2013, rust and other signs of corrosion had been visible on the rods in 2011, but that no one had checked them further.

Scope of Risk

The general contractor of the massive project, a joint venture of American Bridge and Fluor Enterprises, has denied responsibility for any of the supply problems for the steel rods and for a previous problem with cracked bolts and, if the stories about shipping problems and galvanizing of the rods are truly the cause, they do seem to be issues that are outside of a builder’s normal scope of work and are very much supply issues. It’s a cautionary tale that project owners need to verify their own standards are being met and their own supply chain practices are being implemented during construction –not after.

Comments (4)

  1. Thomas J Coyne jr says:

    This is not new. I believe we’ve been following this for a few years and have given it our all in trying to put some light on the issue with involvement from all over the world, I might add. The discussions have not been concluded as to the root causes or causes, but mainly 2 supposed reasons have come to light.
    1. There has definitely been Hydrogen embrittlement in the steel which has caused corrosion failure.
    2. Where did the hydrogen come from to cause such a catastrophic failure to all the structure? One opinion is that it comes in with the raw materials in the form of moisture and additional moisture can be added during all the various steel making processes. this can be overcome, somewhat, by a steel maker using better manufacturing and modern processes to make products that are critical in use. However the project group failed to evaluate this aspect, since they didn’t have anyone noticeable on staff qualified in steel making techniques and someone to evaluate the suppliers methods instead of just low price.
    I’m not sure what political influence was involved also in the selection process. Too late now except wait to see what happens and the additional cost it will end up on the tax payer’s plate.

  2. Kenneth says:

    What you buy cheaply can turn out to be highly costly. The purchaser should have had samples of the manufacture delivered so that cross sections could be inspected with a scanning electron microscope in order to determine the quality of the material and if there were any microscopic cracks, fissures, pitting, or what have you, the basic composition of the material. If the material is now found to be contaminated with any kind of pollutant which weakens molecular cohesion, then Cal Tran should stop paying on the contract and sue the manufacturer, period. Let their insurance company work out the matter. But don´t pay for crud. They should have been very careful from the beginning, after our companies screwed the Chinese on mortgage backed securities, we should have been expecting some pay back. They aren´t going to worry about dealing fairly with us when we have already demonstrated that we will screw them any way we can. It is embarrassing to have such a corrupt government.

  3. Sardonic says:

    Lol, the rods were made by an Ohio company called Dyson corporation. The Chinese parts are doing just fine…

    1. Jeff Yoders says:

      Sardonic,

      As the article clearly states, the problems occurred at the Tennessee plant where the rods were galvanized and then in shipping from Tennessee to California.

      -Jeff

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