Deflected - Bent beam due to installation - Analysis / Repair Method
Deflected - Bent beam due to installation - Analysis / Repair Method
(OP)
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This is a temporary shoring installation situation. It is a square excavation sheeted and braced with walers. The walers have kicker/braces at each corner, basically 4 perimeter wales with corner braces, all welded. Due to the sheeting being slightly slanted the hole gets smaller as you go down. The contractor installing the bracing was pushing at the center of the waler and bent/curved the waler (due to the restraint at the corners). It has deflected 5" in the weak direction. The welds are not broken. Attached is a photo (remember the deflection is vertical not horizontal)
Is there a way to analyze or decide if the beam is acceptable or if it is acceptable if pushed back into place?
I've back calculated the stress due to the deflection assuming a curved shape similar to what a uniform load would produce and the stress is above the allowable. However I'm not sure this is an appropriate method. Any good suggestions for repair?
Thanks
This is a temporary shoring installation situation. It is a square excavation sheeted and braced with walers. The walers have kicker/braces at each corner, basically 4 perimeter wales with corner braces, all welded. Due to the sheeting being slightly slanted the hole gets smaller as you go down. The contractor installing the bracing was pushing at the center of the waler and bent/curved the waler (due to the restraint at the corners). It has deflected 5" in the weak direction. The welds are not broken. Attached is a photo (remember the deflection is vertical not horizontal)
Is there a way to analyze or decide if the beam is acceptable or if it is acceptable if pushed back into place?
I've back calculated the stress due to the deflection assuming a curved shape similar to what a uniform load would produce and the stress is above the allowable. However I'm not sure this is an appropriate method. Any good suggestions for repair?
Thanks






RE: Deflected - Bent beam due to installation - Analysis / Repair Method
As for analyzing, I suspect the true loads are not really known - just estimates.
www.SlideRuleEra.net
www.VacuumTubeEra.net
RE: Deflected - Bent beam due to installation - Analysis / Repair Method
As with any earth retention problem, true loads remain a mystery. The soils though are a very stiff which I suppose is another reason that the system should perform acceptably.
EIT
www.HowToEngineer.com
RE: Deflected - Bent beam due to installation - Analysis / Repair Method
www.SlideRuleEra.net
www.VacuumTubeEra.net
RE: Deflected - Bent beam due to installation - Analysis / Repair Method
Maybe have them weld it to the sheeting a closer intervals.
EIT
www.HowToEngineer.com
RE: Deflected - Bent beam due to installation - Analysis / Repair Method
Again the 5" is in the vertical direction so I back calculated. finding what uniform load causes 5" deflection then finding the moment associated with that uniform load and finally the stress from that moment.
The loads are technically zero for the soil when you include the cohesion, however I changed the input and added surcharge, etc and it is satisfactory. Spans are 16' center span with 5.5' each side. No nearby existing structures.
EIT
www.HowToEngineer.com
RE: Deflected - Bent beam due to installation - Analysis / Repair Method
Bending a wale (permanently) due to mishandling is common. Not at all good, but not as bad as deflection because of load.
www.SlideRuleEra.net
www.VacuumTubeEra.net
RE: Deflected - Bent beam due to installation - Analysis / Repair Method
"Bending a wale (permanently) due to mishandling is common. Not at all good, but not as bad as deflection because of load."
That's what I had figured. I see it from time to time but we don't get many calls about it. Maybe the project engineer on site is new or wanted reassurance.
EIT
www.HowToEngineer.com
RE: Deflected - Bent beam due to installation - Analysis / Repair Method
Maine EIT, Civil/Structural.
RE: Deflected - Bent beam due to installation - Analysis / Repair Method
EIT
www.HowToEngineer.com
RE: Deflected - Bent beam due to installation - Analysis / Repair Method
Based on my (limited) understanding residual stresses will only effect your buckling strength calculations. And then only if they exceed the residual stresses that a straight hot-rolled steel beam normally has. This is the reason for the 0.7Fy term in the lateral-torsional buckling equations for steel. Roughly if you keep your residual stresses below the 70% you should probably be acceptable.
You'll also have reductions in notch-toughness due to the tight radius of your bend. This probably isn't an issue unless you have major impact or fatigue issues which seems unlikely for a temporary beam.
Maine EIT, Civil/Structural.
RE: Deflected - Bent beam due to installation - Analysis / Repair Method
EIT
www.HowToEngineer.com
RE: Deflected - Bent beam due to installation - Analysis / Repair Method
I would be inclined to leave it alone also, for fear of doing more damage than good. Yes it has yielded, and been buckled, but you say no cracking or breaking of the main members or the welds. When (and if) it is loaded by the soil and sheeting will this tend to try to straighten the buckled member or make the buckle grow worse? This is a kinda subjective question, but how much has the new shape really changed the member section properties? The flg. has moved laterally by 4 or 5" and the web has bent and buckled a bit in the process, but you haven’t decreased the actual depth of the member by 20-30% have you? The buckling is actually fairly concentrated isn’t it, and if so, plastic deformation took place and regular deflection calcs., and regular stresses and loads causing this go out the window. As long as the anticipated loading doesn’t make the buckle grow, the member should be able to be loaded to yield again without significant problems. As SlideRuleEra suggested, these kinds of dings are fairly common in this kind of work. They just can’t seem to miss em with backhoe buckets and the like.
RE: Deflected - Bent beam due to installation - Analysis / Repair Method
EIT
www.HowToEngineer.com