PEB building made of precast concrete and not steel, does it make sense?

[octagie]

Hi

I'm involved in a 4000 m2 warehouse project (50 m width with a intermediate column, 80 m long, 9 m height to eaves) and a contractor made an offer (turnkey) to do it with precast concrete columns, beams and purlins. The offer is sort of competitive (its more expensive than steel but does not need fire protection, plus I assume you have more thermal mass and greater durability). Does it make sense to you? I'm worried about the following:

1. The project is placed in a high seismicity region, and using concrete instead of steel would likely imply the design is governed by the earthquake and not the wind. I only can assume that they use large R values (7) for their desired ductility in order to be competitive with steel, meaning the damage in an earthquake will be significant. Have you worked on something similar to confirm this?

2. Considering most PEB manufacturers use steel, I'm worried there is not enough information on existing projects for this type of buildings and their behaviour. In steel almost all the details are already solved. In terms of state of the art in seismic design I would assume steel is already heavily studied, and precast concrete not at all. Is this the case? what's you view?

3. Why on earth would one use this solution? Apparently to save some money on fireproofing (they don't know the eurocode) and corrosion protection? Do you see any other benefit to it?

Do you have any comments?

 

[jayrod12]

Pre-cast building are prevalent here where I practice, Central Canada, due to speed mostly. Granted it's extremely low seismic so we don't have to worry about the additional mass.

 

[Ron247]

I am confused on how many of these you are making. Your reference of PEB I assume means "Pre-Engineered Building" as opposed to a PEMB meaning "Pre-Engineered Metal Building". Using Precast concrete components is not the same as pre-engineered in the concept of an entire building.

All structures are "pre-engineered", we don't build them and then do the engineering. PEMB would be more accurately called REMB (RE-Used Engineering Metal Building). The term has been used for years because metal building companies did multiple designs and shelved them for re-use. It was like buying a pair of pants, you determined the "size" you needed and went to that shelf or rack as opposed to having a Taylor make them for you. Moderns times have gone to computer design per order but the nickname Pre-Engineered Metal Building is still used. I have never heard of Re-Used concrete designs although it would be just as logical as PEMB. It would be harder to implement, but just as logical in the concept.

As far as your specific project, project criteria would determine what structural options make more sense to design around. Is your warehouse environment highly corrosive?

 

[Klitor]

nothing wrong with the system. I have designed such buildings in 0.25g regions.
If you need 60-90min fire rating,it could be competitive

 

[BUGGAR]

Although not post and beam construction, tilt up concrete construction of large warehouses is common in high seismic California. Of course, they are (usually) shearwall buildings.
I'm curious about the precast beams and purlins.

 

[jayrod12]

I'm curious about the purlins as well. Around here, a pre-fab concrete building generally uses planks for the flat surfaces, i.e. hollow-core or Tees (single or double).

 

[KootK]

I've done several warehouses with precast TT roofs and precast wall panels. The economics are whatever the suppliers say they are at the end of the day. I'd be pushing for precast wall panels instead of column and beam in a high seismic zone as moving all of that roof mass through a beam and column system won't be fun. Probably P-delta pancake under it's own self weight.

 

[Ron247]

The diaphragm and shearwall aspect is why I say it would be harder to implement PECBs. PEMBs only design the frame span in advance, not the length of the building. If you want a 100' long frame and a 1200' long building, they reuse the 100' frame as many times as needed on some spacing until they achieve a 1200' building. The PEMBs are rarely shearwall type applications. To do PRCBS, you would have to design the width and length together in your sizes to make available.

 

[octagie]

Sorry for not being clear.
This is a portal frame building with metal cladding and roof, extremely regular. typology is like the attached.
Environment is not corrosive at all.
Most of this buildings here are made with steel + fire protection. This building could perfectly be a Butler's or whatever.
Shear walls are for buildings with floors and all, and they would obviously be much more expensive, it doesn't make sense.

Questions for you:
1. How is this better in terms of speed than a steel building with bolted connections? Seems about the same constructive process, with smaller cranes (lighter elements) and without the need to deal with precast connections.
2. Those of you that have designed precast moment frames in seismic. Are this solutions proven ? has the practice of structural engineering validated this things? Most design in concrete here is done with shear walls, and moment frames are frowned upon.

PD: purlins have the shape of an hydraulic channel (stiffened channel).

 

[hokie66]

I would only say that I think you are wise to be skeptical. Concrete portal frames are rare, for good reason, mostly because of the difficulty of detailing efficient moment joints at the knee. Since yours is in a high seismic region, I wouldn't like it. Has the turnkey contractor allowed you contact with the design engineer?

 

[KootK]

With those beam spans and connection morphologies, I wonder if the lateral system isn't cantilevered column.

In what geographical region is the project?

 

[octagie]

I can't have direct contact with EOR.

I do have a sketch where lateral system appears to be fixed base (is this even possible? I would assume rotational stiffness is difficult to achieve) plus moment connection at the joints.

Project is in Peru.

 

[JLNJ]

Yes, a fixed base with precast columns is possible, but even if the building cost is competitive the footings will be significantly larger. Especially if it's a cantilevered column system.

We ran across a double tee precast cantilevered column system in a low-seismic area. Small (tiny) R Value + Large Mass At Roof = Gigantic Columns & Footings.

I don't know how you specify and be assured that you are getting a properly engineered building in Peru.