Headers In Storm Shelter Wall

[KHoff]

Has anyone ever used a steel lintel in a CMU wall at the exterior of a storm shelter? I am designing a school and part of a classroom wing is intended to be used as a storm shelter. Since these are classrooms, the architect would prefer the storm shelter has windows consistent with the other classrooms. I am having difficulty getting a CMU lintel to work over these openings. I can get a steel lintel to work for the loading, but I am unsure if there is evidence the steel lintel could pass the debris impact criteria. Also, I am unsure if there are FEMA rated frames available where the manufacturer would approve welding to structural steel - they are typically intended to be anchored into concrete or CMU.

Thanks for your input.

 

[dik]

What is the span? Can you use 3 or 4 courses as a beam... matter of grouting solid and cutting the web down a bit to accommodate the top reinforcing... seen it done with a saw, or a hammer and chisel. Use a 'U' block for the bottom of the beam. If you're looking at a storm shelter, I'd avoid windows... flying glass is a real hazard.

Added: You can use steel, but the connection to the masonry may be a weak part of your protection wall.

Dik

 

[jayrod12]

Most CMU manufacturers now produce standard blocks with knock out webs. Saves the saw work.

 

[dik]

Thanks jayrod...

Dik

 

[KHoff]

The windows are FEMA rated, so they are designed to resist debris impact per the requirements of FEMA and ICC 500. I think we will try to use CMU, although it will likely require 5 or more courses.

I'm still curious if anyone has used a structural steel lintel. I was unable to find any information on debris impact or attachment of FEMA rated door/window frames with regard to structural steel.

 

[jayrod12]

What kind of steel lintel are you thinking? I would be inclined to think if you're talking a double angle lintel that sandwiches the wall then I would say it is at worst as good as straight CMU, but possibly better at debris impact resistance.

 

[KHoff]

In order to resist the required loading I would need a wide flange or HSS. For aesthetics, the steel lintel would be covered by soap blocks.

 

[concretemasonry]

Can you forget about the steel beam and use a deep masonry beam over the opening for the window system? That way you will have a uniform wall system that is about the best for projectile protection. There is plenty of documentation that has been accepted by FEMA for projectile protection. - As you know, projectiles are the greatest cause for tornado deaths.

Deep beam are nothing new for concrete masonry and few different shapes are required. If it is only 4' deep, the contractor would prefer to fill it all at once.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[dik]

The other Dick guy is correct and is pointing a way forward; I would avoid using a steel lintel... just another building material discontinuity, and masonry lintels can look really good... just like a wall.

OP: I didn't know there were FEMA rated windows... I live in a pretty safe place... no tornadoes, earthquakes, hurricanes... only -40C to contend with.

Dik