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State Parks assessment of the Pilarcitos Bridge

This is a link to the assessment of the Pilarcitos Creek bridge on the Coastal Trail, as conducted by consultants for California State Parks. It says the bridge is essentially a total loss and that it can't be temporarily patched while a long-term solution is hatched.

Web Link

We want to thank Half Moon Bay interim city manager Stuart Schillinger for forwarding the assessment today...

State Parks officials are due to address the bridge issue at the Half Moon Bay City Council meeting, 7 p.m. on Aug. 19 at the Ted Adcock center.


Comments

Thanks Clay.

That report leaves me with only one question: Would the bridge have failed (after only 23 years) if the steel had been painted on a regular basis, and the wood correspondingly maintained? The GGB is much older and clearly not in trouble, maybe, just maybe, because it's regularly painted. Seems that someone dropped the ball here.


I think what you may be referring to is called "maintenance". It is a rarely exercised activity around these parts, but it is my understanding that a lot of things need it - from boats to bridges, cars to homes - if you buy it (or build it), it is my understanding that you should maintain it...but that's just rumor. I'm sure the State knows best.

Thanks Clay, I think. Very disappointing, very disappointing indeed.


I haven't researched this, but maybe someone with some more historic info or access to records could...

My understanding is the bridge was built with funds from Half Moon Bay and the Coastal Conservancy. Was there any clause in that funding agreement that required ongoing maintenance? Typically, grants include certain performance measures to ensure long term maintenance and stewardship of the resources and projects that the granting agencies are funding. Was the State legally required to maintain the bridge? And if so, are they now legally required to repair it?


The original plans called for ASTM A588 steel, also known as "weathering steel" or "Cor-Ten steel." There also appears to be a corrosion protection system in place.

Weathering steel works by forming a surface layer of rust that protects the members from further corrosion. The advantage of using it over water is that painting the structure isn't necessary to 't maintain it.

The High Bridge over the Mississippi River in St. Paul, MN is constructed of built up sections using A588 steel plate.

Web Link(St._Paul)#mediaviewer/File:Smithavebridge.jpg. It's still in service and the steel is in good shape.

The superstructure of the Antioch Bridge is also built of weathering steel. It had some problems with the protective layer of rust sloughing off then re-rusting, which resulted in section loss. Caltrans addressed the problem, but I don't know what they did to arrest the problem.

The HSS shapes, or "structural tubes" as they were called when that bridge was designed and built, may not be A588 steel. State Parks may want to retrieve samples and have them tested to see if the steel provided conforms to specifications.

It's also possible that there are corrosive elements other than salt spray associated with the site, or that the corrosion protection system failed or interfered with the "weathering" process of the A588 steel.

Whatever the case, I wouldn't be in a rush to rebuilt that bridge with steel until more is known about the actual steel used and why it corroded so quickly.


To follow up on a few of Franks helpful comments:

I contacted and then met with the bridge company that originally built the bridge about a month ago. (Jerry Steinberg was there too.)

The bridge was built with Cor-Ten Steel. It does have corrosion protection installed.

The cross truss supports were not sealed, they were open ended rectangular tube steel. Why they have essentially disintegrated is an extremely good question, but capping the ends so that the corrosion couldn't work from both sides and the ends probably would have helped.

There are three trusses, and the truss at the other end of the bridge has a ton of lateral movement in it when someone crosses, for reasons that are not clear.

The bridge could be made useable on a temporary basis. We looked at two or three different engineering solutions that would solve the issues as they currently sit, they wouldn't be pretty, but they would have minimal environmental impact, and could be implemented for very little real money.

Other than that I don't know what options we have. I haven't worked on this any further as the State bureaucracy is too immense to even contemplate trying to move in a positive direction, and I'm guessing the manufacturer isn't too interested in looking closely at what the hell happened either.

Cheers,

dce


^^^ The bridge could be made useable on a temporary basis. ^^^

A structural engineering firm has recommended against a temporary fix. They recommend replacement and doing more to keep the public off the bridge. Pursuing a temporary fix would be a waste of time.


We can't do both? Temporary fix while getting plans together for replacement?


With respect Frank...

Two Licensed Civil Engineers, both of whom walked the site for more than an hour, and one of whom worked for the company that manufactured the bridge, were both in agreement that the bridge could be made useable. (With the caveat that State Parks would have to review and approve any plans...)

Given that the State has no apparent funds available, that there is no timeline, and that the trail is a vital link for our community I must respectfully disagree with your statement.

Regards,

dce


Hmmmm....

The artist formerly known as Mr. The HoneyBadger and wonkazoo arguing about a bridge over Pilarcitos Creek...

Almost seems like old times!!

Cheers,

dce


Waiting for the State to do something - temporary or permanent - will ensure nothing will happen. State parks has deep institutional problems and unfunded mandates galore. Our community needs to come up with a solution working with the City, County parks, local nonprofits and the business/tourism community to come up with a solution that the State can either embrace or be compelled to


State Parks could use some of that money that they have hidden away.

I hope that someone gets an answer as to who was supposed to be responsible for maintenance.


pointing fingers at past maintenance responsibilities won't move this forward. Working together will. That mean, as Brian notes above, collaboration between individuals and Agencies is needed.

So far I have seen little interest from the State. Perhaps they feel that all eyes are on them, and they are, but uffish (among others) have a point. It seems the State is saying they won't trow good money after bad - fixing the bridge only to replace it. OK, I sort of get that. Maybe the State would be more amenable to work with if they felt that they had support and and understanding community that is willing to hold it together for use and just leave replacement to them.

That, of course, means that we would need to work with them for a good enough fix to last until replacement and the key there appears to be liability. It can be done.

It would be a real shame if all we could do is sit on our hands pointing fingers while waiting for the State to do something.


George, I mostly agree, but it is useful to understand the responsibility issue to insure that the ball doesn't get dropped again.

There need to be two separate teams on this. One, to come up with and implement a short term quick fix, and the other working on a permanent replacement. Until workers and equipment show up, the latter should not be allowed to interfere with the former.

Betcha these guys Web Link could have a new bridge up in a day or two.


The Structural Engineer that signed the report has far more weight with State Parks than two anonymous Civil Engineers. It's a waste of time challenging their conclusions or recommendations. Even if they're demonstrably wrong, State Parks can reasonably argue that they're not in a position to throw good money after bad. They want a new FRP member bridge: Web Link

In my view, it's better to work towards a final solution than on a temporary fix. That includes considering the wants and needs of State Parks.


Is it possible to approach the state with a citizen led effort to collect the funds and hire the original contractor for emergency repair on a very temporary basis,

the contractor takes the risk,

the bridge is only used by pedestrians anyway,

they shouldn't have been driving over it,

they can go around...

Could we as a community hold fundraisers etc?

Do you know how much cash lives in town?

We could if allowed provide a temporary compliant fix.

Out of the ordinary times call for out of the ordinary solutions


plus what the heck do we have state parks take over OUR beaches to do this to us?

OURS not theirs...


it would be a really fun and good opportunity for everyone to come together for a change,

the lion with the lamb and all that...

Everybody laughing and toasting the success!

A big old dinner with local appeal, invite our peninsulan neighbors, a big ol fete

2000x50 dollar plates of chow, I'd guess that we could easily fill up any sized venue on the coast,

make it a special outdoor fundraiser, you know we could if we tried,

100K probably will be a snap,

I'd bet many businesses would do it to keep the people coming, many citizens would do it because they like the trail,

and some would do it out of altruism.

We could fix that bridge if the original guys proposed a temporary fix, and we citizens pulled together.

How much money does the coast lose each day it's closed?

How much lost revenue is attributable to the coastal trail being closed?

I'm guessing the state parks don't care.

They get their share no matter what happens...


Neither of the engineers is or was anonymous- in fact one was identified earlier in this thread. And the State is right about one thing: The bridge cannot be salvaged- it is beyond saving.

What Frank ignores is that it may well be fine for him- given that he lives 100 miles away (or whatever) for the bridge to take three years to replace, but for those of us who live here this isn't a workable solution. Thus we need to find an alternative.

The one thing Frank is right about, and the inherent problem, is this: The bridge belongs to the State. Which means if we as a community want to "help" fix it, in whatever form, the State is not going to look kindly on our efforts. (See previous threads and press releases vis a vis the Main Street Bridge and "Concrete Peckers...")

No one at the State wants to own this problem, and my brief interaction with them showed that the lower-level managers were well aware that this was being watched by "higher-ups" at the State- none of whom is going to take ownership of the issue.

If someone like Jerry Hill wants to get involved we could have a working solution on the table within a week or two and a completed project likely within a month or less. Why someone on the Council hasn't reached out to him privately (and publicly) is beyond me.

We can vent all day long, but without someone at a higher level holding the State's feet to the fire we're simply not going to be able to get any forward movement on this.

Just my .02

Cheers,

dce


I remember when the state parks started being funded at a level that allowed more rangers and charging admission and parking and bathrooms etc.

Their big offer was they could provide for the functions of a public space-

they said they'd do it.

Jerry Hill is getting so much done-I'm not sure how much more he really needs to be handed to him at this time.

He says when he sees something wrong he tries to fix it.

I'm not sure how much time he could have for something like this.

I hope he's doing well :)


I don't care what you engineering types say or think you know. Anybody who believes that it is OK to build a steel bridge or a steel anything within a shout of the Pacific Ocean and expect it to last with out constant maintenance is living in a text-book world devoid of common sense or observations. Stainless steel would not last in that situation without maintenance.

-


Actually Barnus you make a great point- one that is relevant to both the Main Street Bridge and the pedestrian bridge on the Coastal Trail.

As best as I have been able to determine, between the years from 2000 to the present, the City of HMB spent exactly $0.00 to maintain the Main Street Bridge. Anecdotally we didn't spend much more than that in the previous 50 years either.

It is apparent that the pedestrian/Hernandez bridge got little better treatment. To place this in context, we spend roughly half a million per year on IT related expenses every year in HMB, and the Council has budgeted $15k for iPads and other nicknacks during the coming year. Yet even in the wake of the bridge debacle how much have they budgeted for basic maintenance and repair of the bridge?? Zero, zip, nada.

It seems that we love building shiny new things (Like a $32 million library as one possible example, or a $1.5 million EOC that we didn't need and essentially don't use as another example...) but we are incredibly myopic when it comes to taking care of those things once they have been built. As a result we end up spending far more in the end, and public infrastructure that people need on a daily basis degrades to the point where it is no longer usable- creating a real or imagined emergency and consequent stress.

That Fram oil-filter commercial from the 70's got it right, whether you are speaking about your car, a bridge, or our country: You can pay me now, or you can pay me later...

Regards, thanks for bringing up an important issue...

dce


I'm sorry, but I'm calling cheap shot. Most bridge engineers aren't going to live in the community which requires their services. No need to lower yourself with that snipe:

"What Frank ignores is that it may well be fine for him- given that he lives 100 miles away (or whatever) for the bridge to take three years to replace..."


But this is right on:

"Seems that we love building shiny new things .... but we are incredibly myopic when it comes to taking care of those things once they have been built."

Is maintenence money that hard to come by?

We need to take care of what we have and resolve the Coastal trail bridge and Seymour bridge problems before going into hock over a new latchkey library.


Sorry uffish, but I think you're wrong on this one.

My reference was to this comment from Frank: >>>It's a waste of time challenging their conclusions or recommendations.<<<

To which I reiterate: It is obviously fine for him to declare us to be wasting our time, but he really isn't in a position to judge, as he doesn't have to deal with the day to day issue at hand given his lack of proximity to the problem.

That and as far as I know no one has asked for his input on this subject, and for damn sure we don't require his services. His input is valued as always, but he doesn't live here, and he earns his living working as an engineer for a company that makes money "ignoring anonymous engineers" and "building new bridges." (That isn't meant to quantify anything he says as correct or incorrect, but fDrouillard is the antithesis of "unbiased" as far as this topic is concerned.

Anyway I respectfully think you're off base on this.

Regards,

dce


Hmm... the tone seems a bit... personal? His expertise on the MSB project was invaluable. Even if you felt something didn't apply in our case we've received an amazing amount of free information.

What can I say? I admire you both.

Carry on, lol....


Brilliant and highly relevant article (Rebel Architects: building a better world) here: Web Link

Money quote (and there is a photo in the article of one of his projects):

"That may be set to change. Santiago Cirugeda, a subversive architect from Seville, has shunned the glamour, and financial security, of luxury office space for the architecture of activism. In austerity-hit Spain, 500,000 new buildings lie derelict, unemployment is high and funding for community initiatives is minimal. Pulling these threads together, Cirugeda and his team – often working on the fringes of the law – use rapid building techniques, recycled materials and volunteer labour on abandoned municipal land for projects that people need."

Regards,

dce


Don't get me wrong Uff- I do admire Frank. He is bright, extremely intelligent and a determined and capable debater, and I for one have learned a great deal from him... (and he drives Muteff batsnockety crazy, which I must admit can have it's moments!! ;))

I am realistic about who he is though, and how he shapes his arguments- which is why I responded to his casual dismissal of an insurgent attempt to try to force or spur action locally on the Hernandez bridge.

Anyway as you said a moment ago... Time to move on I think...

dce


Haha, well put about FD's debating skills. I would hope to be so talented and entertaining. One thing we learned from the MSB discussion is that he really has no iron in the fire as to what we do here.

Thanks as always for your considerable efforts, DCE.


Plus,

what about the fledgling local outdoor economy?

Runners from the HMB International Marathon run through there don't they?

They aren't holding it this year,

but next it should be even better than last. Amazing people in an amazing event.

How will that work?

Plus all the other relay runs, triathlons etc.

How much money do they spend?

Who is in charge here?

State parks?

How much money today, Sunday August 10, 2014 will the local and regional economy lose today because some person at state parks is timid?


^^^ Is maintenence money that hard to come by? ^^^

Yes it is, particularly for public transportation projects. But that really is another topic.

^^^ which is why I responded to his casual dismissal of an insurgent attempt to try to force or spur action locally on the Hernandez bridge ^^^

Some people like to bully and harass authorities on bridge projects. Sometimes they are successful, and it encourages them to repeat their efforts on other project. To them, advising folks to consider the position, wants and needs of State Parks in arriving at a quick fix is a "dismissal of an insurgent attempt to try to force action."

Take your two engineers (at least one of which has plenty of egg to wash from their face for providing a structure that lasted less than 25 years) and submit a proposal to State Parks for their review and approval. If they approve your plan then good on you. But you may want to consider what you're up against before doing so and "poisoning the well" on other citizen efforts to work with State Parks. As a first step, you may want to consider who would likely review such a proposal.

^^^ I'm sorry, but I'm calling cheap shot. ^^^

It's called grandstanding. I don't think it's necessary or a good approach to take on this project.

HMB isn't the only community that is suffering from lack of service by State Parks. There are many other fixes State Parks can do that will improve the lives of more people for less money than what is required to reopen your local pedestrian bridge. Folks have been begging for years to have State Parks re-open public restrooms at just a few of the State Parks along the so-called Mendonoma Coast. Many of the elderly in those communities rely on those restrooms to make their 2-hour one-way trips inland to shop or see their doctors. Many of them are PIPs (previously important people) that know a thing or two about getting things done. Despite that, the potties remain closed.

State Parks clearly wanted a bridge that didn't require routine maintenance, especially painting which could cost millions to do over a sensitive riparian environment. That is why they opted for a "weathering steel" alternative in the first place. It is also now why they now want an FRP bridge (which has its own shortcomings).

State Parks clearly wants to avoid any liability by allowing access to a bridge in such bad shape. A temporary fix won't alleviate that liability.

There are problems with re-using the steel substructure units as well. They too are subject to corrosion and that corrosion has yet to be arrested.

I'm still gobsmacked by how quickly that steel truss rusted away. I would expect to see uniformly colored relatively large rust flakes with weathering steel, but I don't. State Parks should have some tags pulled from the existing structure then have them tested and certified. If it's not the steel specified then State Parks may have a cause for action against the prefab supplier, which could change the funding picture.

I don't particularly care for the way that Continental frames their pony trusses. There are better ways to frame the post-floorbeam connections to achieve a stiffer structure. That's something to be mindful of on any new structure.

One approach the community may want to consider is the walkway type built at Iguazu Falls in South America: Web Link

Those walkways were designed to be built in segments with minimum disrupts to the environment. Many short spans instead of four long spans. The segments are light enough that they can be transported and set in place by a few burly Turks. They would have one end designed to attach to the previously placed segment and a pedestal on the other end. The bridge could be designed to withstand overtopping in a 100-year flood. The segments could easily be strung together with prestressing cables anchored at the abutments, which would help resist EQ and stream flow forces.

Just a thought. Or two.


"Weathering steel works by forming a surface layer of rust that protects the members from further corrosion. The advantage of using it over water is that painting the structure isn't necessary to maintain it."

Interesting theory. No evidence around here that it works, at least not in salt air.

"The High Bridge over the Mississippi River in St. Paul, MN is constructed of built up sections using A588 steel plate. ... It's still in service and the steel is in good shape."

No salt air.

"The superstructure of the Antioch Bridge is also built of weathering steel. It had some problems with the protective layer of rust sloughing off then re-rusting, which resulted in section loss."

No salt air.

Any more?


While looking for something totally unrelated, I just stumbled across this 2013 Little Hoover Commission report "Beyond Crisis: Recapturing Excellence in California's State Park System". Web Link . Looks interesting, but I can't take time right now to read a 122 page report. For those who don't know, the LHC is sort of a civil grand jury at the State level. Just like county civil grand juries, it seems that all the LHC is chartered to do is write investigative "this needs to be fixed" reports, and they do it well.


Plenty, watchdog. Here's but one report that indicates weathering steel works fine in all environments, except Detroit where they salt the roads. Web Link

The problem with the Antioch bridge was salt spray during ocean transport of the segment: Web Link

Weathering steel should have performed much better that it did over Pilarcitos Creek. Something else is amiss, and it should be investigated before deciding on temporary repairs or replacement.


>>Weathering steel should have performed much better that it did over Pilarcitos Creek.<

I assume that's In The Book.


>>Weathering steel should have performed much better that it did over Pilarcitos Creek.<

I assume that's In The Book.


>>Weathering steel should have performed much better that it did over Pilarcitos Creek.<

I assume that's In The Book.


I've got a loaded day and haven't been able to respond to all of the good posts here. Frank- thank you for your early morning wisdom- it was essentially spot on.

I want to address one thing for purposes of clarity: The parts that we are speaking about were the rectangular floor beams, which were 1/4" thick 4"x6" rectangular steel sections approximately eight feet long and went from one side of the bridge to the other. These beams were spaced at roughly six-foot or eight foot intervals, and they were what supported the floor components.

And here's the thing about those pieces: They didn't just fail. In the worst sections they have essentially corroded away to non-existence. If I could upload a photo here I would, but in the section that failed there is only about four feet of beam left at most, the other four feet has not just failed- it has evaporated into thin air. (Or more accurately, lies in very small pieces below...)

These 1/4" steel beams didn't corrode to the point of failure- they corroded to the point of non-existence, and they did it in less than 20 years. Other beams on the span show varying progressions of this theme, delaminating in huge flakes and headed to the same end in a few years.

Frank is right (I think) in positing that something is amiss. Cor-Ten steel isn't impervious to corrosion, and it won't last forever, but it does (or should) severely retard the depth and annual progression of the corrosion. No charts I could find could provide any metric that would provide for 1/4" thick steel to simply disintegrate in 15-20 years.

Something else had to be going on here. No idea what, but if it was submerged in the creek the salt would have been washed off, and we have history that shows it only could have been submerged a couple of times in the 20 years of its existence.

Was it substandard or non-compliant steel?? No idea. But I've seen bubblegum stuck to the bottom of playground equipment that lasted longer...

Cheers,

dce


>>Weathering steel should have performed much better that it did over Pilarcitos Creek.<

I assume that's In The Book.


I've got a loaded day and haven't been able to respond to all of the good posts here. Frank- thank you for your early morning wisdom- it was essentially spot on.

I want to address one thing for purposes of clarity: The parts that we are speaking about were the rectangular floor beams, which were 1/4" thick 4"x6" rectangular steel sections approximately eight feet long and went from one side of the bridge to the other. These beams were spaced at roughly six-foot or eight foot intervals, and they were what supported the floor components.

And here's the thing about those pieces: They didn't just fail. In the worst sections they have essentially corroded away to non-existence. If I could upload a photo here I would, but in the section that failed there is only about four feet of beam left at most, the other four feet has not just failed- it has evaporated into thin air. (Or more accurately, lies in very small pieces below...)

These 1/4" steel beams didn't corrode to the point of failure- they corroded to the point of non-existence, and they did it in less than 20 years. Other beams on the span show varying progressions of this theme, delaminating in huge flakes and headed to the same end in a few years.

Frank is right (I think) in positing that something is amiss. Cor-Ten steel isn't impervious to corrosion, and it won't last forever, but it does (or should) severely retard the depth and annual progression of the corrosion. No charts I could find could provide any metric that would provide for 1/4" thick steel to simply disintegrate in 15-20 years.

Something else had to be going on here. No idea what, but if it was submerged in the creek the salt would have been washed off, and we have history that shows it only could have been submerged a couple of times in the 20 years of its existence.

Was it substandard or non-compliant steel?? No idea. But I've seen bubblegum stuck to the bottom of playground equipment that lasted longer...

Cheers,

dce


I don't understand. If weathering steel degrades after being exposed to salt (Antioch transport, Detroit road salting) then why would it work in a salt air environment?


I don't understand. If weathering steel degrades after being exposed to salt (Antioch transport, Detroit road salting) then why would it work in a salt air environment?


I've got a loaded day and haven't been able to respond to all of the good posts here. Frank- thank you for your early morning wisdom- it was essentially spot on.

I want to address one thing for purposes of clarity: The parts that we are speaking about were the rectangular floor beams, which were 1/4" thick 4"x6" rectangular steel sections approximately eight feet long and went from one side of the bridge to the other. These beams were spaced at roughly six-foot or eight foot intervals, and they were what supported the floor components.

And here's the thing about those pieces: They didn't just fail. In the worst sections they have essentially corroded away to non-existence. If I could upload a photo here I would, but in the section that failed there is only about four feet of beam left at most, the other four feet has not just failed- it has evaporated into thin air. (Or more accurately, lies in very small pieces below...)

These 1/4" steel beams didn't corrode to the point of failure- they corroded to the point of non-existence, and they did it in less than 20 years. Other beams on the span show varying progressions of this theme, delaminating in huge flakes and headed to the same end in a few years.

Frank is right (I think) in positing that something is amiss. Cor-Ten steel isn't impervious to corrosion, and it won't last forever, but it does (or should) severely retard the depth and annual progression of the corrosion. No charts I could find could provide any metric that would provide for 1/4" thick steel to simply disintegrate in 15-20 years.

Something else had to be going on here. No idea what, but if it was submerged in the creek the salt would have been washed off, and we have history that shows it only could have been submerged a couple of times in the 20 years of its existence.

Was it substandard or non-compliant steel?? No idea. But I've seen bubblegum stuck to the bottom of playground equipment that lasted longer...

Cheers,

dce


^^^ I assume that's In The Book. ^^^

???

^^^ If weathering steel degrades after being exposed to salt (Antioch transport, Detroit road salting) then why would it work in a salt air environment? ^^^

It forms a protective layer of rust when exposed to air, not just salt. When exposed to salt air, that protective layer of rust flakes off, then a new layer of rust forms and it eventually flakes off. Over enough cycles, it will completely consume a steel member.

What one normally does in that case is to choose members that have extra thickness. If you read through the B&B report, that is one of their recommendations if the bridge is rebuilt using weathering steel.

The stringers and plank supports on the existing bridge were only 1/8" thick when new. AASHTO calls for a minimum thickness at any structural component to be 5/16" ... plus any thickness needed to account for corrosion during its life cycle. Oops!

Dreaming up temporary fix or replacement schemes is both fun and challenging, but there are a few things that are more important that bridge users should be doing right now.

You already know that you should be organized. But what to do after organizing? For one, let both the Coastal Commission and State Parks know that the bridge is important to you and community and that it provides a vital link to and through coastal resources. Letters and public testimony are very useful in that regard. Next, look into whether State Parks owes HMB any special consideration regarding the bridge. For example, if the City paid for the bridge then turned it over to State Parks with the caveat that they're responsible for its maintenance, then you have a basis for demanding that they honor their commitments. If that scenario is accurate, ask your City Council for help, or offer yours if they already have such an effort underway.


Frank:-

You appear to be coming around to the "vaporization" of the Tube Steel 4x3x1/4” transverse floor beams. Also agree with your comments for the need of public support to the County, State Parks and Coastal Commission.

The Buehler report states:

Longitudinal Stringers TS 4x3x1/8" (TS =Tube Steel)

Transverse Floor Beams TS 6x4x1/4"

Chord Trusses TS 6x6x1/4"

Diagonals TS 3x2x1/8”

Posts TS 6x6x1/4”

i.e." The stringers and plank supports on the existing bridge were only 1/8" thick when new. AASHTO calls for a minimum thickness at any structural component to be 5/16"

... plus any thickness needed to account for corrosion during its life cycle. Oops!”

What were AASHTO standards in 1993?

Thus (I assume) under an older version of AASHTO standards (bridge built in 1993) this present stipulation on minimum thickness was not in code. Otherwise even the Chord members were under designed.

Maybe the failure of cor-ten in bridges encouraged AASHTO to modify standards?

Jerry Steinberg


^^^ What were AASHTO standards in 1993? ^^^

The 5/16" minimum thickness was a requirement back then, too, as was the requirement to account for section loss over the life of the bridge.

^^^ You appear to be coming around to the "vaporization" of the Tube Steel 4x3x1/4” transverse floor beams. ^^^

I'm not sure what you mean by that comment.

^^^ Maybe the failure of cor-ten in bridges encouraged AASHTO to modify standards? ^^^

Most are performing quite well, actually. See the link provided above.


Yes we do need a temporary fix, and would probably run about $5k in lumber. You run 2 x 12 x 9 footers every 12 inches across the span resting on the (strong)tubular sections and then cover with 1/2 inch plywood, this new section would run about six inches above the existing planks - place signs at either end with language absolving the state of liability if you choose to cross, etc - this should hold up for a few years and I was about to do so myself prior to the fence going up - anyone else tired of the state protecting us from ourselves?


So we're hearing the bridge wasn't built to legal standards at the time and the steel should have been at least 2.5X thicker PLUS additional thickness to account for loss through corrosion. So at least 1/2 inch sounds right knowing the rate of corrosion.

Shouldn't the bridge builder have known it was being built contrary to standards? Who OK'd the substandard design?


Hold on a minute. The owner may not have required that the bridge be built to AASHTO standards. I was simply noting that AASHTO standards establish a minimum thickness for steel primary structural elements.

That said, it would be good to know what standard of care the designer of the bridge used.


OK, so AASHTO standards aren't legally required then. What is legally required for a public pedestrian bridge? I'm assuming there must be something. Could have missed it here... thanks.


Hi Uff,

Couple of things: AASHTO and ASTM standards evolve over time. I don't know if Frank has the copy of either the Green Book or the ASTM guides he slept with back in 1993, but if he does I'd be interested in what they say.

Second: The plans call for Cor-Ten Steel. (Or the ASTM equivalent of Cor-Ten steel. So if it isn't Cor-Ten (or weathering) steel, someone probably did a no-no.

Third: Frank says the beams that disintegrated were spec'd at 1/8", but I believe (according to the plans, and the ones that remain intact) they were 1/4". Which is still less than 5/16", and far less than 5/16" plus weathering/corrosion buffer.

And...

Mr. (Mrs.??) Forlorn: Don't give up hope yet. Your kind of can-do attitude is what I've been trying to bring to the town in recent months. Granted fixing a bridge that belongs to the state is a problem, but in the end this is our community, and if we won't own it who will?? (Please don't go repair the bridge tonight- I think what I just wrote is already going to arouse comments, let's not make them worse!!)

Hopefully we can find a way to propose and implement a temporary repair that will meet the State's liability needs, and at the same time provide a useable structure until a new one can be provided for.

Regards to everyone,

dce


Thanks DCE for the info and for lighting a fire that will hopefully push this along faster and restore our Coastal Trail experience.

I'd like to know where things went wrong with specifying the materials so we can learn from this mistake.


David/Frank,

Bridge steel specifications appear to be listed in the General Notes Number 1 and 2 (difficult to read on computer screen ASTM specs etc.) in the B&B report Shop drawings of architect of record ,local Landscape Architect :- Callander Associates, San Mateo…

(Google search shows them still at same location on seventh avenue) They probably can pull a readable copy out of archives.

The Shop Drawings also confirm the plaque that is on the bridge that Continental bridge (Now part of CONTECH) was the material supplier.

If you go to link below and click on: Specifications-Continental Pedestrian Truss Bridge Specifications and scroll down to the steel spec 4.1.1 Unpainted weathering steel: (2014)

Web Link

“Bridges which are not to be painted shall be fabricated from high strength, low alloy, atmospheric corrosion resistant ASTM A847 cold formed welded square and rectangular tubing and /or ASTM A588 or ASTM A242, ASTM A606 plate and structural shapes (Fy=50,000 psi). The minimum corrosion index of atmospheric corrosion resistant steel as determined in accordance with ASTM G101 shall be 6.0”

Assume any “tags” pulled by Parks Department for partially vaporized floor beams would be tested for conformance with specs shown on drawings- to put to bed any question on materials used.

To lighten up a bit and enjoy you should check out video at:

Web Link

Jerry Steinberg


I'm not any kind of expert,

but a highly finished surface won't survive any better in the salt environment that close to the beach.

ANY thing will rot through,

ask the harbormaster scott grindy if there's metal you don't have to do something to to have it last even its service life.

Don't they attach zinc bars to metal to arrest electrolysis?

Whatever with the replacement-

that could take 3-5 years.

If the msb is going to take 5 at least just to repair it,

in this drought year it would be the best time to disturb the small patches to make anchorages.

Now's the besty time,

it'll take years.

So,

how about close collaboration between the appropriate agencies for a temporary and expertly crafted repair, utilizing the original contractor if possible to state a repair protocol, and propose the materials and labor list-

we're not talking about redesign and refurbish,

just a temporary compliant repair.

If the funding is a source of problems,

let's see the estimate, and go like heck to try and ^"get 'er done"^

if it is a potential conflict of interest due to possibly having the thing wrong in the first place, so what,

fix it first, then deal with the rest.


^^^ OK, so AASHTO standards aren't legally required then. What is legally required for a public pedestrian bridge? ^^^

That's usually established by the owner, and it's usually shown on the drawings and included in the project specifications. The standards could have been UBC, CBC (Uniform or California Building Code) or ANSI-ASCE. The loads used to design the bridge are usually shown on the drawings as well.


The Japanese have developed a "Coastal Weathering Steel" specifically for salty air environments: Web Link

As time permits I'll try to find out if and where it has been used in the US.


Interesting paper, FD, thanks. The addition of 3% Ni plus Cu reverse the usual diffusion of Na and Cl ions, so now the destructive Cl ions stay trapped in the outer oxidized region.

In case we buy this stuff, let's not get the discount brand... 2% doesn't work. :^)

By the way did anyone else catch the background comment about this research being needed because of Japan's declining population of workers?


For the adventurous, new guide specifications for FRP pedestrian bridges: Web Link


Web Link

Thanks for the links on FRP bridges, which led to more articles. This one is readable with lots of info and photos of a surprising number of large scale applications. Being a total layman this is all new to me (and I'd prefer to keep it that way, lol...).

I wouldn't want to see a composite materials replacement of the historic MSB, but for the little pedestrian bridge it might not be a bad solution.


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