Working on a multi discipline existing building project cooling tower 1

[MechWang]

Hello all, just wondering how is your experience working with other discipline particularly structural engineers. I am just sharing my experience, I have worked on several cooling tower projects now and none of them have been executed because structural team says my proposed tower is always exceeding the existing cooling tower weight threshold of 5% in which the code allows, is this something you encounter on a frequent basis. I would like to get your thoughts on this thank you

 

[HVAC-Novice]

Can you cite the code that says you can increase weight by 5%? Because if that is the case, I just replace one tower with another 5% heavier, than the next 5% heavier etc. till I get a tower to be twice the weight.

Sometimes newer codes allow for different snow load and other assumptions. so that for newer code you sometimes can put up some more load. Some structures also may have been designed for more load. Maybe the original structure was designed for a 100-ton tower, but they only installed a 90 ton tower. therefore you now can install a heavier 100 ton tower. It all depends and is the structural engineer's job.

Structural engineer analyzes the structure and designs re-enforcements if needed. They take responsibility of that and have the final say. I don't question or double-check their work. If the new tower is too heavy, get a lighter one, or pay for structural upgrades. there really is no middle way I can see where.
I'm sure if you hire the 2 best structural engineers in the World, they will come up with slightly different conclusions. So, shop around till you find one who is more "lenient" (I'm kidding, go with the most conservative design, but I know this is what happens often)

 

[SAK9]

Structural loads have a huge factor of safety often 1.5 to 2.You would get much better advice if you post your question in the structural group forum Link

 

[MechWang]

Well, I have been on several buildings and when i talked to building management, MEP firm came in with the contractor and replace their cooling tower. What i notice is the existing concrete structures were never touched but brand new steel beam supports and isolators is what i saw. Does that mean some firms dont really consider looking or working with a structural engineer when they go and replace cooling towers?

 

[HVAC-Novice]

You have to ask those firms and review the documents they submitted to JHA. Those should be public record, so you can see them for a fee.

How would we as some random people on the Internet know what the projects you happen to know did? We don't even know what country you are in and what code is applicable....

 

[MechWang]

I just got the code reference and its for 2020 Florida existing building code section 707.2 Addition or replacement of roofing or replacement of equipment. This is the code that the structural engineer is referring to that i cannot increase the weight of the existing cooling tower by 5% which does’nt really make sense to me. Please let me know your thoughts on this.

 

[LittleInch]

This isn't for a PEMB is it?

What does this section refer to?

The full wording will let you know what this implies, what types of buildings it refers to or what needs to be done if you want to increase it further.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MechWang]

This is for cooling tower project that I am working on, is this something you typically encounter?

 

[HVAC-Novice]

What is your exact question? You seem to have a structural engineer who tells you what you can and cannot do. What do you want to know from this forum? If you want a second opinion, you need to hire a second structural engineer who would be willing to stamp a different design.

 

[LittleInch]

This is what the Florida code says (max 5% more load) - if you want something bigger you need to design for it.

This may or may not show that the existing structure can handle it or that it needs some reinforcement

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MechWang]

@hvac_novice, I am asking because most of work is on existing buildings and referring to building code existing buildings, have anyone experience this kind of conversation with a structural engineer and what compromise or solution you come up with. You mention either you lower the weight or increase the supports, have you done lowering the weight of the tower but risking reduced cooling tower evaporative heat rejection capacity or you tell the structural engineer figure it out im not changing my tower design?

 

[LittleInch]

In most instances you are far better working collaboratively and having conversations so that you BOTH understand each others issues. Then you can work together to create the optimum design for the money being spent.

So in your case you can explain why you need a bigger tower and the benefits tot he client that it will bring and the struc eng can explain his or her limitations either in allowable loads from the code with no work (the magic 5%) or what sort of additional load could be handled with no or some small mods or at what point would it need major money being spent.

The art of engineering is a compromise between competing issues. Your job, together with other specialists, is to find that compromise, or offer the client a set of alternatives for him to choose how he spends his money.

Coming on here basically just moaning about Structural Engineers won't get you very far.... IMHO.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.