Wood Bridge Inspection

[Ben29]

Hello! I am a structural engineer (buildings - not bridges). My in-laws own a house on a private island in Cape Cod. There are approximately 100 homes on this island.

There is a 60 ft long, single-span, laminated arch wood beam bridge, supported at each end by timber piles. The (4) laminated beams are 38" deep by 12" wide, spaced at 48"o/c. The bridge abutments are retained by timber bulkheads.

I believe it is one where only one car can pass at a time. Apparently there are no records for the construction of the bridge. My mother-in-law thinks that they had a major structural repair many years ago during a hurricane breach (she forgets the specifics).

Her HOA would like to put a reserve on the community dues to pay for future repairs. They are looking for an engineer to do a structural assessment & repair schedule for the bridge.

Apparently they are having a hard time finding an engineer who will return their call. They asked me if I would consider doing this work. Do you think its possible for a building engineer to inspect a small wooden bridge and do it well? Or should I punt?

 

[jhnblgr]

https://highways.dot.gov/fed-aid-essentials/videos/other-programs/infrastructure-national-bridge-inspection-standards

There are federal standards on bridge inspections and qualifications.

The bridge merits a in-depth inspection and level 1 load rating.

Underwater inspection is likely also required.

 

[LittleInch]

Got any pictures?

Wood rot below the water line on even more so in the tidal zone is probably the key issue plus delamination of the arch and rot or damage to the vehicle deck.

How old roughly?

what weight limit is on it now?

But wooden bridges don't last for ever so it's probably what is the cost of building a new one in 10, 15 or 20 years time which will be the bone of contention...

Your biggest issue is probably making the report so limiting in liability for you that no one can use it to do anything.

 

[BridgeSmith]

I would start by contacting the state DOT bridge department. Even privately-owned bridges that are open to the public are typically subject to inspection, load rating, and if necessary load posting. I suggest at least checking to see what info they have available.

I'd say you being able to do an effective inspection will hinge on your familiarity with general timber design and construction. If you have that, and can distinguish what is a structural issue and what is not, then you might consider doing the inspection and assessment of the condition of the bridge, and what it may take to restore it to its original structural condition.

Load rating, however, requires an understanding how the vehicle loading affects the bridge, the distribution of the wheel loads through the decking, etc. It could take a considerable amount of time get to a point where you're comfortable putting your stamp on a load rating (assuming the state would consider you qualified to do so).

 

[Ben29]

Thank you all for your input! It sounds like I should "stay in my lane". That being said, can anyone suggest a bridge inspection company in Massachusetts?

 

[JJ_Roy]

I worked on a project some time ago in southeast MA to move a superload across a private bridge and the load insurer required it to be inspected before the move.

I believe our company used Steer (sp?) Engineering from RI to do the inspection and write a report on short notice. None of the bigger firms wanted to do it and they were a pretty small shop looking for work. I can't vouch for their qualifications but the bridge didn't collapse when we moved the transformer over it!

BTW: You probably need to brace your in-laws (and the HOA) for the cost of just the inspection report.

Good luck.

 

[Ben29]

BTW: You probably need to brace your in-laws (and the HOA) for the cost of just the inspection report.

How much do you think it would be for the inspection? Ballpark?

 

[JJ_Roy]

There's others here that could probably give a better "guestimate", but this is probably a multi-$k job. Especially if they're looking for a formal report with repair schedule and indicative estimates.

All I know is HOA's aren't too keen on spending money that doesn't give them instant gratification (like flower beds, new rec room carpet, or freshly paved roadways).

A $10k for a 15MB .pdf file full of pictures and tables is useless to most non-engineers .

 

[Ben29]

Oh yes, I was expecting it to easily be 10K. My MIL was hoping there was a law forcing them to collect the money to do the biennial inspections, but apparently there is not. Everyone who owns a house on this island is "rich". Some celebrities on this island too...

 

[jhnblgr]

If the houses are insured and the fire department not located on the island, likely the insurance coverage will be dropped if the bridge is found unsafe or inadequate.

 

[LittleInch]

Oh yes, I was expecting it to easily be 10K. My MIL was hoping there was a law forcing them to collect the money to do the biennial inspections, but apparently there is not. Everyone who owns a house on this island is "rich". Some celebrities on this island too...

My experience of such people is that one of the reasons they are "rich" is that they expect " other people" to pay for everything....

It's not chappaquiddick is it??