Wood Trusses in a Corrosive Environment

[STR04]

All,

I'm designing a on a one story chemical building at a water treatment plant constructed with CMU walls and wood trusses. Some of the chemicals include chloride, fluoride, sodium chlorite & aluminum chlorohydrate. I’m thinking about specifying the wood trusses with stainless steel plates for corrosion protection. Does this sound reasonable? What might be some of the pitfalls with this system?

TIA

 

[msquared48]

Cost and availablity of rated connectors to name a couple. Any anchor bolt connectors at the truss ends to the CMU walls would have to be stainless too, as well as the CMU to truss wall ties.

Is the underside of the trusses to be closed off with a lid? If so, might want to vent the top portion with fans.

I might also think of a special protective coating for the inside of the CMU wall due to the presence of chloride and chlorohydrate.

Could also create a mechanical air flow system with a greater pressure in the roof (attic) if present, to prevent the chemicals from getting to the truss connections.

Mike McCann
McCann Engineering

 

[RARWOOD]

If the trusses are constructed of glulams and are spaced 6' or more on center then stainless steel may be your best bet. You might also find that hot-dip galvanized steel would work.

It is always helpful to talk to some one in the field with experience in the corrosion of metal in the environment you are designing for.

I've done glulam trusses in water treatment plants with primed steel and zinc plated hardware. I've also worked on jobs where a powder coated system or zinc rich paint system has been used.

One of my co-workers who worked with the construction of fertilizer buildings, would just add 1/8" to the required plate steel thickness. The idea was that the time it took the thicker plates to corrode, was longer then the life span of the building.

 

[connect2]

How big are the trusses? May experince with the truss plate institute and their members is they have little info on the structural capacity of post dipped galvanized plates. Every truss plate has a ton of ungalvanized surfaces. It's how the plates are manufactured. Agree with mike, isolate the trusses from the environment.

 

[STR04]

The trusses only span 30'. I’m sure TPI (Truss Plate Institute) would have some useful information.