Splicing I-beams

[2204z]

Can I-beams be spliced anywhere or should it be like the rebars in concrete beam where it shouldn't be in location of great moments? But if your I-beams are lacking in length.. how do you exactly make the splice coincide with regions of minimal moments?

And what's the best way to splice 2 ibeams pieces?

Also how many have tried the w8x18? what is moment capacity of it? where do you usually use this size? Just verifying some numbers.

 

[wannabeSE]

The questions are too broad. Typically, splices are avoided. If a beam splice is required, more information is required. Why is it being spliced? What are the loads on the beam? Can cover plates be used? Is bolting preferred? Will it be spliced in-situ, at the site, or in a fabrication shop? What are the qualifications and capabilities of the contractor? Etcetera.

While a splice with complete joint penetration welds typically provides the full moment capacity of the beam, it may not be the best option if other methods are less expensive. The moment capacity of a W8x18 depends on the unbraced length. W8x18 beams are typically used when they provide the best option, there isn't any one answer. I have probably specified this size for miscellaneous metals and supplemental steel.

 

[2204z]

The questions are too broad. Typically, splices are avoided. If a beam splice is required, more information is required. Why is it being spliced? What are the loads on the beam? Can cover plates be used? Is bolting preferred? Will it be spliced in-situ, at the site, or in a fabrication shop? What are the qualifications and capabilities of the contractor? Etcetera.

The column span is 7 meters.. the I-beam are only 6 meters hence they have to connected together which I refered to as splice. The loads are purlins and roofting material on top of the ibeam rafters to be spliced. It will be spliced at the site.

 

[KootK]

A steel beam can be spliced anywhere but it is gernarally easiest to splice where moments are not at peak values. To find regions of low moment, you'll need to perform a structural analysis and construct a moment diagram.

Some splicing options are shown below. For light loads, I'd probably go with a flush bolted end plate.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[BAretired]

W8x18 is too shallow for a 7m span.

BA

 

[2204z]

A steel beam can be spliced anywhere but it is gernarally easiest to splice where moments are not at peak values. To find regions of low moment, you'll need to perform a structural analysis and construct a moment diagram.

Some splicing options are shown below. For light loads, I'd probably go with a flush bolted end plate.

Kootk. What do you make of the following splice the contractor said they would do.

W8x18 is too shallow for a 7m span.

BAretired. The w8x18 is a perimeter beam and the load is only about 1 foot wall of concrete 4" in thickness (nothing else is connected to it). Is it still too shallow for a 7m span? What is the maximum load before one can say the w8x18 is too shallow?

 

[KootK]

The proposed contractor details don't show what parts will be connected and how those connections will be accomplished. Weld? bolts? Where and how much/many? More information is required.

Span to depth ratios for roof beams are usually about L/25 max. That may be the source of BA's concern.





I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[2204z]

The proposed contractor details don't show what parts will be connected and how those connections will be accomplished. Weld? bolts? Where and how much/many? More information is required.

Span to depth ratios for roof beams are usually about L/25 max. That may be the source of BA's concern.

There are details in the connections (such as I-beam framing into another I-beam perpendicularly which uses welding) except the splice between 2 I-beams. The designer assumes the following which many local contractors do by default. I'm asking if anyone use this and what do you make of it. We don't use expensive bolts for any splicing.

About span to depth ratios.. if L/25 and L=6 meters.. then L/25 = 6/25 = 0.24.. what is the normal?

 

[KootK]

I'm asking if anyone use this and what do you make of it. We don't use expensive bolts for any splicing.

In my area, bolting is generally much cheaper than welding. I've never used that detail but I don't see why it wouldn't work with proper weld design and fabrication. In your detail, I still don't understand what is welded to what and how. Are the web and both flanges groove welded together? If so, I would think that square cutting the spliced members would be more economical.

bout span to depth ratios.. if L/25 and L=6 meters.. then L/25 = 6/25 = 0.24.. what is the normal?

I thought that the span was 7m? If so, a normal beam depth would be 7000mm/25 = 300mm (rounded up). For 6m, 6000mm/25 = 250mm (rounded up). These rules of thumb can be exceeded if careful calculation justifies it.


I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[2204z]

In my area, bolting is generally much cheaper than welding. I've never used that detail but I don't see why it wouldn't work with proper weld design and fabrication. In your detail, I still don't understand what is welded to what and how. Are the web and both flanges groove welded together? If so, I would think that square cutting the spliced members would be more economical.

Yes, the web and both flanges groove welded together for more strength than just cutting it square and welding.

I thought that the span was 7m? If so, a normal beam depth would be 7000mm/25 = 300mm (rounded up). For 6m, 6000mm/25 = 250mm (rounded up). These rules of thumb can be exceeded if careful calculation justifies it.

A w8x18 wide flange is 8.14" depth and 5.25" width or about 200mm depth. If strict L/25 has to be followed.. then 6000mm/25=250mm or 10" depth is required and it needs a w10x22? If the loading is just light roof material supported on purlins.. it still needs to satisfy the L/25 rule? If it is not followed, would the w8x18 just deflect? But then it's maximum moment won't be reached by just light roofing.. would it.

 

[KootK]

Yes, the web and both flanges groove welded together for more strength than just cutting it square and welding.

That method wouldn't provide any more strength that just cutting it square and welding. The square cut, with full penetrations welds, should be able to develop the full plastic strength of the section.

A w8x18 wide flange is 8.14" depth and 5.25" width or about 200mm depth. If strict L/25 has to be followed.. then 6000mm/25=250mm or 10" depth is required and it needs a w10x22? If the loading is just light roof material supported on purlins.. it still needs to satisfy the L/25 rule? If it is not followed, would the w8x18 just deflect? But then it's maximum moment won't be reached by just light roofing.. would it.

Span to depth ratios are just rules of thumb that experienced engineers use to spot check for problems. As I said above, you can use any sized member you like so long as you've designed it carefully for both strength and deflection.


I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[2204z]

Thank you all for your assistance.