Analysis of an Industrial Building
Analysis of an Industrial Building
(OP)
dear all,
while analyzing an industrial shed,
if the whole frames are made of steel, then boundary conditions at both ends of the columns can be fixed.
suppose if i am having RCC columns and steel roof, what should be the boundary conditions.
can we assign the base as hinge.
the loading at roof is around 200 kg/sq.m including Live load and suspended loads.
the area of the hanger is around 32000 sq.m
regards,
jeevan
while analyzing an industrial shed,
if the whole frames are made of steel, then boundary conditions at both ends of the columns can be fixed.
suppose if i am having RCC columns and steel roof, what should be the boundary conditions.
can we assign the base as hinge.
the loading at roof is around 200 kg/sq.m including Live load and suspended loads.
the area of the hanger is around 32000 sq.m
regards,
jeevan






RE: Analysis of an Industrial Building
"if the whole frames are made of steel, then boundary conditions at both ends of the columns can be fixed."
You have to provide a design that enforces those assumptions. A fixed base is difficult to design. There's a lot of anchor bolts, not to mention that the load has to be carried into the foundation. At the top, it's easier, but there's relative stiffnesses, sidesway, etc. to consider.
For a concrete frame, it's normally conservative and easier to implement, to assign a hinge at the base. But once again, you have to consistently consider this with respect to deflection, moments at the top, "k" factors for your columns, etc.
If this is your first large structure, is someone supervising you? These questions should go to him or her.
Your analysis needs to reflect your design and your design needs to reflect your analysis.
RE: Analysis of an Industrial Building
yes this is my first industrial building.
unfortunately i don't have a good supervisor to monitor me or to take any firm decision.
initially it was discussed and the base was made hinge, that resulted in huge reinforcement in columns.
then my seniors told me to make the base fixed.
so, i am still in a confusion that, which is the better way to follow while analyzing an industrial structure using any analysis software.
RE: Analysis of an Industrial Building
RE: Analysis of an Industrial Building
RE: Analysis of an Industrial Building
Jeevan: Either way, you're just shifting around the reinforcing. If it's pinned, you could (but usually don't, as AELLC says) reduce the reinforcing at the base to a minimum and just design for shear. But that results in higher moments at midspan.
Jeevan, you need to understand where the forces are and where they're going. I'm a little afaid that you're using the analysis software as a crutch, not a tool. Even though it's a big structure, do some hand calculations and approximations before you throw everything in the black box. Make sure your results make sense. I feel bad for you if your supervisors aren't helping. That makes things lonely.
RE: Analysis of an Industrial Building
When I read RCC columns and steel roof, I interpreted that as steel beams not rigidly (fixed) connected to the columns.
If he has grade beams as part of the foundation, that will take care of the column base fixity.
RE: Analysis of an Industrial Building
RE: Analysis of an Industrial Building
If it is concrete columns and steel roof, fixed base columns with pinned connections to the roof members would be my approach.
RE: Analysis of an Industrial Building
I have grade beams only in the pheripery.
Jed, I have done some manual designs for the roof plate girders and then I am going with the software. As you mention, I am driven by the software and I am not able to visualize the behaviour of the structure.
now i can conclude that base can be fixed and connection at roof shall be pinned, which may also be economical.
RE: Analysis of an Industrial Building
Why are you going for concrete columns in the first place ?
And what material is the wall cladding ?
RE: Analysis of an Industrial Building
For hangars I have used bracing around the perimeter and between the hangar bays. Use a moment frame across the front of the hangar and braces at the sides of the front of the building (at the exterior of the building adjacent to the last bay of hangar openings) if needed. Typically they are all steel buildings around where I am with very large foundation uplifts.
RE: Analysis of an Industrial Building
elevation bracings are not provided,
metal cladding with girts are given.
Suppose i am making the base pin, then my reinf. In rcc column is shooting up.
RE: Analysis of an Industrial Building
RE: Analysis of an Industrial Building
Dik
RE: Analysis of an Industrial Building
However steel plate girders in the roof doesn't make sense - why not steel trusses?
RE: Analysis of an Industrial Building
Based on his first post, I think he is talking in metres, not feet.
A bit of a plan would help in understanding the intended structure. I thought he was talking about an aircraft hangar, but if so, it must be for small planes.
With only a bit of information in defining the problem, poor advice is inevitable.
RE: Analysis of an Industrial Building
RE: Analysis of an Industrial Building
You can rigidly fix a concrete column to a foundation, but if the foundation cannot resist overturning it is, effectively, still a pin, albeit with the pin in the foundation instead of on it. If it is a large foundation, you can, as others have said, call it pinned for the reasons they offer.
If columns are pinned the top and the bottom and if there is no bracing, it isn't a structure, it is a mechanism and under horizontal load it will fall down.
Making a two directional moment connection to steel framing at the top of a concrete column is difficult, the size of the connections tends to be out of proportion for the size of the column.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Analysis of an Industrial Building
A bit odd (but still possible) to have concrete columns and steel rafters with pinned cols connected to footings.
How do you propose to connect the concrete columns to the rafters with a moment connection?