Hello!
Anyone who likes to puzzle a bit might be able to help me?
I'm arguing with an insurance company that thinks it was unnecessary to replace an undersized beam, saying that it was indeed necessary. (Yes, I have reports from experts, a constructor, but only that the old one was undersized and that the new one is sufficient + how much from the max load the new one is designed for)
I want to illustrate to the handler how bad it was by showing how much the beam was overloaded in percentage by showing how undersized the old one was.
Span of the beam: 4.2 m
Old beam:
UNP160 beam (with a remaining deflection of 40mm)
New beam:
VKR200x100x6.3 and is dimensioned to be exposed to a maximum of 60% of what it can withstand. (I don't know what the load is, only the percentage)
Is there anyone proficient in strength calculation who can calculate what percentage of its maximum load the UNP160 was subjected to?
It should be possible to calculate backward from the 60% that the VKR beam is subjected to and what it is supposed to withstand.
Anyone who likes to puzzle a bit might be able to help me?
I'm arguing with an insurance company that thinks it was unnecessary to replace an undersized beam, saying that it was indeed necessary. (Yes, I have reports from experts, a constructor, but only that the old one was undersized and that the new one is sufficient + how much from the max load the new one is designed for)
I want to illustrate to the handler how bad it was by showing how much the beam was overloaded in percentage by showing how undersized the old one was.
Span of the beam: 4.2 m
Old beam:
UNP160 beam (with a remaining deflection of 40mm)
New beam:
VKR200x100x6.3 and is dimensioned to be exposed to a maximum of 60% of what it can withstand. (I don't know what the load is, only the percentage)
Is there anyone proficient in strength calculation who can calculate what percentage of its maximum load the UNP160 was subjected to?
It should be possible to calculate backward from the 60% that the VKR beam is subjected to and what it is supposed to withstand.
94.2%
The UNP160 has a Wx (bending resistance in the x-direction) of 116 mm^3, which is directly proportional to the moment it can withstand (Stress = Wx/Mb).
The VKR200x100x6.3 has a Wx of 183 mm^3, it is therefore 157% stronger.
This is directly proportional to the stress it can withstand (in this case where the bending moment is the same), which means that the load in your case, 60% on the VKR beam, is actually as much as 94.2% of the maximum load on the UNP160 beam (1.57*0.6=0.942 actually). Then whether these percentages are the load in relation to the yield strength with or without safety, I don't know. But it could be that it was very close to the yield strength then.
I can't exactly write out how I calculated it, but it's correct nonetheless. A bit too late in the evening now, but the numbers are true.
Source http://www.begroup.com/upload/Sweden/Broschyrer/Röda_Katalogen.pdf (There you can read more and find the numbers I mention, Wx (bending resistance).
The UNP160 has a Wx (bending resistance in the x-direction) of 116 mm^3, which is directly proportional to the moment it can withstand (Stress = Wx/Mb).
The VKR200x100x6.3 has a Wx of 183 mm^3, it is therefore 157% stronger.
This is directly proportional to the stress it can withstand (in this case where the bending moment is the same), which means that the load in your case, 60% on the VKR beam, is actually as much as 94.2% of the maximum load on the UNP160 beam (1.57*0.6=0.942 actually). Then whether these percentages are the load in relation to the yield strength with or without safety, I don't know. But it could be that it was very close to the yield strength then.
I can't exactly write out how I calculated it, but it's correct nonetheless. A bit too late in the evening now, but the numbers are true.
Source http://www.begroup.com/upload/Sweden/Broschyrer/Röda_Katalogen.pdf (There you can read more and find the numbers I mention, Wx (bending resistance).
One more thing that certainly affected it was that the UNP beam was positioned so that the load came in the y-direction, in other words like a "C".
Wy = 18.9
According to your way of calculating, the VKR is 973% stronger
9.73 * 6 = 580%
Did I get the numbers right?
If I have calculated correctly, if you calculate what the designer has calculated as the maximum load from weight from the roof, walls, etc., it is 5-6 times more than it should be able to handle. No wonder it was deformed.
Wy = 18.9
According to your way of calculating, the VKR is 973% stronger
9.73 * 6 = 580%
Did I get the numbers right?
If I have calculated correctly, if you calculate what the designer has calculated as the maximum load from weight from the roof, walls, etc., it is 5-6 times more than it should be able to handle. No wonder it was deformed.
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Hi,
I realized when I went to bed that I forgot to consider the material. My assumption only applies when using the same material, e.g., S355J2H. You can calculate the load it has been subjected to using the deflection if you consider it as freely supported (or fixed) at both ends and then a point load in the middle. Of course, it's also possible with distributed load, but it's a bit more complicated to calculate. So maybe a calculation will come here when inspiration strikes (and I find my formula collection).
That the UNP beam is mounted the "wrong" way (at least wrong in this case) is also something that should immediately indicate that it needs to be replaced due to under-dimensioning.
I think it's commonly said that beams are dimensioned after a maximum deflection of 7mm (?), but I think it depends on the span. In any case, 40mm is way too much. Here maybe a civil engineer can provide a better answer (I'm "only" a mechanical engineer).
I realized when I went to bed that I forgot to consider the material. My assumption only applies when using the same material, e.g., S355J2H. You can calculate the load it has been subjected to using the deflection if you consider it as freely supported (or fixed) at both ends and then a point load in the middle. Of course, it's also possible with distributed load, but it's a bit more complicated to calculate. So maybe a calculation will come here when inspiration strikes (and I find my formula collection).
That the UNP beam is mounted the "wrong" way (at least wrong in this case) is also something that should immediately indicate that it needs to be replaced due to under-dimensioning.
I think it's commonly said that beams are dimensioned after a maximum deflection of 7mm (?), but I think it depends on the span. In any case, 40mm is way too much. Here maybe a civil engineer can provide a better answer (I'm "only" a mechanical engineer).
okay thanks.
It is probably not the same material, considering that the beam is/was at least 50 years old. It would actually be interesting to know what load it has been subjected to, and in this case, it should be distributed since there is a wall directly on top that in turn supports the entire roof.
It is probably not the same material, considering that the beam is/was at least 50 years old. It would actually be interesting to know what load it has been subjected to, and in this case, it should be distributed since there is a wall directly on top that in turn supports the entire roof.
The maximum acceptable deflection is L/300, that is 14 mm in this case. (4200/300=14 mm)jarlen84 said: