Live Load 4

[shp6]

I am currently working on an existing steel building. The composite floor was originally designed for 50 PSF of live load. The building owner now wants to add some heavy equipment to the floors. Based on my analysis, the floor beams need to be strengthened. However, the floor below belongs to other company and strengthening is impossible.

Now my question is can I limit the number of occupancy in these areas (rooms) in order to satisfy the original floor capacity? For example, if the floor can take 20 PSF after the heavy equipment and I limit the number of occupancy to 5 persons in each room and limit the furniture too. Does code allow to make this kind of arrangement? I checked ASCE-7 and IBC but have not found any code requirements.

Please comment on this approach. If you can reference any code that will be even better. Thank you.

 

[mfrad]

I would approach this problem differently. You represent the tenant who was guaranteed 50 psf live load capacity by the building owner. there is no such thing as a uniform load in an office setting. You have people and file cabinets that make up the 50 psf maximum. Some areas have a higher unit loaded area and others are less than 50 psf. If the actual 200 psf equipment is a small percentage of the room area you shouldn't have a problem by placing equipment near columns and girders of the floor system. You can then determine the moment diagram of actual loads placed and use the 20 psf for the walkway areas. If the moment and shear diagrams are less than the equivalent 50 psf M and V diagrams you are good to go. If it is slightly higher, try LRFD if you have the beam sizes etc. I would suggest making a floor plan of the equipment placement and loads for the tenants and owners record and submit them.

 

[shp6]

Thanks, mfrad.

That is the support I am looking for. That is exactly the approach I am going to.

The challenge is the computer racks have to go to some exact locations. According to my analysis, few beams under these racks are overstressed from 2% to 20%. I can live with a 5% or less overstress. However, I have to limit the live loads in order to satisfy these 20% overstress. If I can limit the live load to 20 PSF, these rooms are safe by code. Since these rooms are highly secured, there will be very few people in the rooms for maintenance only.

I feel comfortable to limit the live load but I need code support. Engineering judgement is one thing, CMA is even more importance as everyone else pointed it out.

So far, no one can find any code to allow this approach. I think I know what to do now.

Thank you all for give me your thoughts about this questions. We are engineers but also businessman/women. We need to satisfy codes also our clients. I don't like to run away projects or challenges. We need to provide "solutions" to our clients eventhough sometimes the solutions are a little bit out of ordinary. We are trained to provide solutions and that is why we are called consultants. Just a thought and share with you all. Thanks again.

 

[bvanhiel]

Hang the racks from the ceiling.

 

[lkjh345]

If your under IBC, try Table 1607.1 Part 26:

Office Buildings: ' File and omputer rooms shall be designed for heavier loads based on ANTICIPATED occupancy.'

I suppose, if you say that your limited occupancy is the ANTICIPATED occupancy, you are OK.

Still think you are in a grey area, and if the room has an access floor system you are under Table 1607.1 Part 2, and the whole room needs to be checked for a 100 PSF live load. But thats my opinion.

Keep in mind that any 'solution' we provide for our client must also meet the legally precsriped code that is in force in the jurisdiction we are working in. Its not a 'solution' if it doesn't meet the code.

 

[shp6]

Thanks to lkjh345. That is a positive approach for challenge questions. That is exactly the code language I am looking for. What I will do now is to write a letter to ICC to request an explaination for my case.

Excellent. Thanks again lkjh345.

 

[csd72]

shp6,

There are not solutions to every problem, it is one of the hardest things to tell a client but in some cases it is true.

csd

 

[VoyageofDiscovery]

Hi shp6,

I understand your position with regards to solutions for the Client, however I don't condone the end result of your position. Testing the Code wording such as "anticipated" on its own by semantics is a dangerous position. Minimums must still be adhered to while actual loads may govern.

VOD

 

[civilperson]

A client can not protect you after the building is sold and the next owner experiences a failure. You are the engineer responsible for good judgement, (i.e. following the code).