Damaged Column
Damaged Column
(OP)
We have a large assembly building. At one end we have a 10 ton bridge crane followed in series by several 5 ton bridge cranes. All have a lift height of 21 feet.
One of the columns between the 10 ton and the 5 ton next to it was damaged by a fork truck. About 6 inches off the floor. The column is a W10x77. One flange was dented in approximately 1-1/2" on one side of the web. On the other side of the web the flange bowed out approximately 1".
Aside from AISC Manual of Steel Construction Allowable Stress Design (page I-149, Permissible variations in cross section), are there any thumb rules or codes dealing with damaged columns?
One of the columns between the 10 ton and the 5 ton next to it was damaged by a fork truck. About 6 inches off the floor. The column is a W10x77. One flange was dented in approximately 1-1/2" on one side of the web. On the other side of the web the flange bowed out approximately 1".
Aside from AISC Manual of Steel Construction Allowable Stress Design (page I-149, Permissible variations in cross section), are there any thumb rules or codes dealing with damaged columns?






RE: Damaged Column
Dik
RE: Damaged Column
So i would go for the steel bracing in that portion. providing extra support to the column.
regards
Amanpreet
RE: Damaged Column
RE: Damaged Column
RE: Damaged Column
The purpose is to introduce in the beam carefully planned tensile stresses to pull the beam straight. The explanation is as follows:
Stresses are due to volume changes with heating and to decreasing yield strength at elevated temperature. Metal subject to thermal expansion while heated tends to be compressed by the surrounding cool structure. The heated volume has lower yield strength at high temperature, and then it is easily upset to shorter dimensions. Upon cooling the same material tends to contract in all directions and is now stressed in tension by the attached cool structure which did not move appreciably in the process.
See procedure and examples:
http://www.eng-tips.com/viewthread.cfm?qid=106922
ht
RE: Damaged Column
RE: Damaged Column
What if I welded a 1" thick plate between the outer edges of the flanges (1 flange bent, other flange straight) on both sides of the web. Would that do the job?
RE: Damaged Column
The flame straightened we did, left the members in place. We added temp supports and jacked them in position, unloaded the beam. The gray beard welder made it look easy.
I have see welders do to it on buckled plate to.
RE: Damaged Column
Or.. fabricate a plate- that's quick and easy. Split it into two plates and go on the inside of the flange.
Bottom line it's pucker factor and CYA- has the bay collapsed? You just want to be sure that the loads get to the foundation. And the existing section still has capacity (obviously). Get some plate and sleep well at night in a cost effective manner IMO. It's simply Area of steel- in the words of a boss- just kill it. You can spend tens of thousands of dollars in shoring, analysis and fabrication- or you can just slap some good ole' steel on there with proper development and analysis for change in C.G. and be done with it.
This is not a swiss watch or the Ritz, it's a steel column that's still standing in a factory. Just reinforce it and be done with it.
RE: Damaged Column
RE: Damaged Column
If you are over this, you must incorporate this into your repair or remove the stresses.
I would go for heat straightening, seen a few jobs where you could not even tell a member was dented or dinged.
RE: Damaged Column
RE: Damaged Column
Recently I saw a column (after it was fixed by the Client)that had been hit by a fork truck, three of the 4 anchor bolts had sheared and the column twisted over 90 degrees at the base and was still straight at the top.(roof up about 35 feet) The fix was to wack it with a sledge hammer and it sprung back. I'm glad I wasn't involved in that one!
So think about column protection with warehouse design.
RE: Damaged Column
The main reason for adding the heavy channels, was to protect the column so the third time they hit the column they would due less damage.
RE: Damaged Column
RE: Damaged Column
As this column supports cranes it is possible that the section is oversize for the building loads provided that the crane is ot used during the repair works.
Even with a straightened column welding on new plate/plates gives better certainty that the repair will perform adequately. I would be surprised if the re-bending actually achives the original profile. It is likely to be an approximation.
Concrete casing is a cheap way of giving extra protection to the columns but I'd be relucatant to rely on it for structural strength - As a fresh graduate, I attended site to examine a cast iron column where I'd asked for the casing to be removed for inspection. The casing turned out to be concrete but the contractor had indeed removed it and had shattered the cast iron in the process... You would know what the concrete was for but not necessarily other people.
RE: Damaged Column
RE: Damaged Column
I want more details on this one! :D
And how did the structure behave without the column?
RE: Damaged Column
RE: Damaged Column
OK - Here is some more detail.
The column was located in an old train shed near to a dock. The building had been coverted into small work shops at some previous date.
The company I worked for was the consulting engineer. We had been down to site to view the building. The column in question was one of several in a row, supporting the roof over. We couldn't get access to see the columns as the partitioning was in the way. We only wanted to know what the column detail was at floor level. I'd been told that this was important but can't remember why!
I asked the contractor the remove the casing to one column, assuming timber studs but turned up on site the next day to see a hole in the column bigger than my fist and clear surface damage elsewhere.
I phoned the office and explained what had happened and the boss spoke to the contractor and had him prop the roof.
The design progressed on the basis that we would replace a damaged column but we didn't let on how it had been damaged!
In the end the client changed his mind regarding the building and it was knocked down so the column was never replaced.
RE: Damaged Column