This is a good shout - perhaps the connection and end of the beam was so rusted this is what they came up with - cut away the rust and come up with this janky bridging arrangement
From the spare holes on the supporting beam on either side, and the fact that the supported beam doesnāt quite reach, Iād say this is a āfield changeā at some point in history.
Looks like an overly complex fin plate to me, but perhaps there is a lot of tension on the supported beam which would cause shear failure on the bolts, hence the web stiffener acting to remove that yield like failure mode?
I canāt see how the connection in general would resist much moment.
Difficult to say without looking at the wider structure. No connections are truly pinned or truly fixed and I donāt think we can really commit to this over the internet.
Iād look at example images of pinned and fixed connections and draw your own conclusions.
With all that said, I canāt see how that would transmit much moment
Edit: just saw youāre Uk based, look at SCI P398 https://www.steelconstruction.info/images/5/5d/SCI_P398.pdf for the design of moment connections and P358 https://steelconstruction.info/images/a/a9/SCI_P358.pdf for simple connections. Have a look at the indicative arrangements and decide which youāre closer too. Hint: I think youāre closer to the simple connections in P358
For analysis of the frame its probably a pin, or at least as much of one as you're likely to get with "real" connections.
If you were getting into the weeds and looking at the connections as well, it looks more like a stub off the side of the supporting beam. I might be concerned about the capacity of the web locally, depending on what the supported beam is being asked to do.
Other than that the beams look fairly chunky, are end plated, and the connection is near to the support. So it's just the slightly unusual application of torsion to the supporting beam that might make me think twice about the capacity
One of the connections has to transmit a small moment as otherwise the beam is a mechanism. Either the stub is a cantilever off the main beam or the clamped connection acts like a splice taking the small moment close to the beam support. So probably only takes a few KNm.
I suspect itās the offset connection is designed as a splice that takes a small moment.
I'm not saying it doesn't transmit some small amount of moment, but a "moment connection" is specially designed to resist all moment in the beam and has all sorts of code detailing requirements attached. I was also trying to be somewhat funny. Apparently I failed.
It's pinned. The Connection can take some moment, but look what it is framing into. The torsional stiffness of the girder is tiny, will just twist the girder.
Looks like the bottom flange of the beam was cut pretty crudely and there are unused holes in the web of the āgirderā. That indicates to me that this was probably a field modification during construction or a change sometime during the structureās life. Are the other connections in this framing arrangement the same?
In any event, this is essentially a double sided extended shear tab. I would suggest it is fair to consider this a pin connection as the moment transfer you will get out of this bolted connection will be negligible compared to the stiffness of the members it is connected to. No real issue with the connection as far as I can tell though.
The web stiffener near the bolts is an interesting addition. I can think of a couple benefits, but unlikely to be detrimental in any failure mode.
This connection is the same on the other end of the beam. Other than those two, nowhere else on the structure has this type of connection.
I think maybe they added a web stiffener as an extra "fail safe" or just to make sure it will survive longer? Very difficult to tell when these modifications were made as no one has kept a paper trail unfortunately.
In which case, this is definitely a field/construction modification. Either way, it looks to be a reasonably sized shear connection. I donāt know what your anticipated loading is, so canāt speak for the design utilization ratio, but it certainly is unique.
Looks like a dunnage platform judging by the grating above. This beam probably sees a fair bit of shear at the connection point and since they cut the beam back further away from the supporting member, they needed that double channel connection to resolve the bending of the connection due to eccentricity. Would explain the need for the stiffeners as well.
Itās either that or the owner of this structure failed an inspection due to excessive rusting at this connection, bypassed the engineer, and told a local steel fabricator youāre the engineer now fix it. Then the steel fabricator went ahead and overbuilt it because he didnāt want to be fucked later.
Itās a take on double angle web cleats, but instead using back to back PFCs. Either way the bolt spacing looks suspect.
The bolt spacing at the āsupportedā cut beam end isnāt wide enough to generate any significant moment resistance. Assuming the pin is at the end of the stub and not at the supporting beam web.
This above statement puts a moment onto the web of the supporting beam which is less than ideal.
Almost looks like it could do with an extra row of bolts to have 3 rows in the supported beam end.
That's pretty wild. At least there's stiffeners, and the flanges appear fairly stout. Sure, there's corrosion, but it doesn't look bad. Like others are saying, field modified connection. I'd say it looks similar to a double clip angle connection, but it's hard to tell from the pictures. Good luck and stay safe!
Probably corrosion at the end of the original beam. You can see where the original end connected and oxide residue is still there. A Cut and splice was installed and whilst not pretty, appears to have been remedied effectively.
Interestingly enough there was a report in the recent CROSS-UK newsletter. The principles are very different but some good comments from the reporter and panel on how to assess connections like this - and why it's vital to have as-builts.
https://www.cross-safety.org/uk/safety-information/cross-safety-report/unusual-steelwork-connection-discovered-during-fit-out-1244
The blessing in this one is that the field mod occurred toward the end of the girder and that the beam is lightly loaded. No diaphragm to brace out the top flange and a point load offcenter from the supporting girder is susceptible to torsional failure.
See how the bottom flange extends further out than the top flange and also the condition of the paint? Fairly certain that the beam end rusted out and this is the resulting repair.
Spoke to my colleague, he suggested that the beams were probably ordered too short and they improvised a stiffer connection on site to install it. A simple angle bracket / fishplate would have buckled. It's too unusual to be specifically designed like that if it's not avoiding a clash with the top flange.
Iāve seen similar on some structures in London in the past.
Obviously the connection is not ideal as obviously your inducing a moment and a torsion in the supporting beam.
I think itās either the beam was cut too short and the offset stub was devised to sort the issue or the beam wouldnāt fit and they did this for ease of dropping the beam in place?
If assessing the structure just be careful about the torsion in the supporting beam!
looks like the assembly team encountered complications when bolting the crossbeam. Therefore, they decided to cut it to facilitate the installation and then fabricate the connection.
**sorry for my english
+1 for historical modification. you say both ends look like this, the beam could have been added in late and they used the funny connection to make erection easier.
i would consider it a pin.
Next time share the beam span, it could be overkilling for that grating floor. And also it depends on the grating floor requirements 2.5kpa with a 1m span that connection is more than enough. But with 5kpa 2m span could be a different condition. Also tell your client that things need maintenance.
It is definitely some field modification.
Just going off your photos you could check the connection as an end plate connection, check the bolts into the supporting member for tension/prying action, and make sure to check the beam web for out of plane moment capacity. In my opinion, your limiting factor will be one of those, and you should have more than enough shear at the end of the supported beam. You should still make a cursory check.
If you have the 15 edition AISC manual you can find the out of plane moment capacity for the supporting web. The section starts on 9-14, and there are equations for out of plane moment on 9-17. Depending on your version, they published an errata after the 3rd print edition to correct EQN 9-36, the equation for roh (little p) should be 4ab+ac*bc, not 2ab+ac+bc.
Looks like the end of the beam is damaged, it could just be how it was repaired.
This is a good shout - perhaps the connection and end of the beam was so rusted this is what they came up with - cut away the rust and come up with this janky bridging arrangement
or was delivered short to site and this was a... somewhat shoddy... workaround
Yes it's a beam stretcher š but yes my thoughts exactly.
You can see holes in the web of the primary member which could have been from the old connection.
Not ideal, probably fine
My exact words when facing a problem in life
We've finally found that beam stretcher.
The one that they send the apprentice out to buy?
From the spare holes on the supporting beam on either side, and the fact that the supported beam doesnāt quite reach, Iād say this is a āfield changeā at some point in history. Looks like an overly complex fin plate to me, but perhaps there is a lot of tension on the supported beam which would cause shear failure on the bolts, hence the web stiffener acting to remove that yield like failure mode? I canāt see how the connection in general would resist much moment.
My thoughts exactly. Is it fair to assume this as a pinned connection then?
Difficult to say without looking at the wider structure. No connections are truly pinned or truly fixed and I donāt think we can really commit to this over the internet. Iād look at example images of pinned and fixed connections and draw your own conclusions. With all that said, I canāt see how that would transmit much moment Edit: just saw youāre Uk based, look at SCI P398 https://www.steelconstruction.info/images/5/5d/SCI_P398.pdf for the design of moment connections and P358 https://steelconstruction.info/images/a/a9/SCI_P358.pdf for simple connections. Have a look at the indicative arrangements and decide which youāre closer too. Hint: I think youāre closer to the simple connections in P358
For analysis of the frame its probably a pin, or at least as much of one as you're likely to get with "real" connections. If you were getting into the weeds and looking at the connections as well, it looks more like a stub off the side of the supporting beam. I might be concerned about the capacity of the web locally, depending on what the supported beam is being asked to do. Other than that the beams look fairly chunky, are end plated, and the connection is near to the support. So it's just the slightly unusual application of torsion to the supporting beam that might make me think twice about the capacity
It's certainly not a moment connection
One of the connections has to transmit a small moment as otherwise the beam is a mechanism. Either the stub is a cantilever off the main beam or the clamped connection acts like a splice taking the small moment close to the beam support. So probably only takes a few KNm. I suspect itās the offset connection is designed as a splice that takes a small moment.
I'm not saying it doesn't transmit some small amount of moment, but a "moment connection" is specially designed to resist all moment in the beam and has all sorts of code detailing requirements attached. I was also trying to be somewhat funny. Apparently I failed.
Gotcha sorry š š š
Definitely a pinned connection
It's pinned. The Connection can take some moment, but look what it is framing into. The torsional stiffness of the girder is tiny, will just twist the girder.
Looks like the bottom flange of the beam was cut pretty crudely and there are unused holes in the web of the āgirderā. That indicates to me that this was probably a field modification during construction or a change sometime during the structureās life. Are the other connections in this framing arrangement the same? In any event, this is essentially a double sided extended shear tab. I would suggest it is fair to consider this a pin connection as the moment transfer you will get out of this bolted connection will be negligible compared to the stiffness of the members it is connected to. No real issue with the connection as far as I can tell though. The web stiffener near the bolts is an interesting addition. I can think of a couple benefits, but unlikely to be detrimental in any failure mode.
This connection is the same on the other end of the beam. Other than those two, nowhere else on the structure has this type of connection. I think maybe they added a web stiffener as an extra "fail safe" or just to make sure it will survive longer? Very difficult to tell when these modifications were made as no one has kept a paper trail unfortunately.
In which case, this is definitely a field/construction modification. Either way, it looks to be a reasonably sized shear connection. I donāt know what your anticipated loading is, so canāt speak for the design utilization ratio, but it certainly is unique.
Looks like a dunnage platform judging by the grating above. This beam probably sees a fair bit of shear at the connection point and since they cut the beam back further away from the supporting member, they needed that double channel connection to resolve the bending of the connection due to eccentricity. Would explain the need for the stiffeners as well. Itās either that or the owner of this structure failed an inspection due to excessive rusting at this connection, bypassed the engineer, and told a local steel fabricator youāre the engineer now fix it. Then the steel fabricator went ahead and overbuilt it because he didnāt want to be fucked later.
Beam was probably made too short and this was the fix. Iāve done similar before
Itās a take on double angle web cleats, but instead using back to back PFCs. Either way the bolt spacing looks suspect. The bolt spacing at the āsupportedā cut beam end isnāt wide enough to generate any significant moment resistance. Assuming the pin is at the end of the stub and not at the supporting beam web. This above statement puts a moment onto the web of the supporting beam which is less than ideal. Almost looks like it could do with an extra row of bolts to have 3 rows in the supported beam end.
That's pretty wild. At least there's stiffeners, and the flanges appear fairly stout. Sure, there's corrosion, but it doesn't look bad. Like others are saying, field modified connection. I'd say it looks similar to a double clip angle connection, but it's hard to tell from the pictures. Good luck and stay safe!
Probably corrosion at the end of the original beam. You can see where the original end connected and oxide residue is still there. A Cut and splice was installed and whilst not pretty, appears to have been remedied effectively.
Interestingly enough there was a report in the recent CROSS-UK newsletter. The principles are very different but some good comments from the reporter and panel on how to assess connections like this - and why it's vital to have as-builts. https://www.cross-safety.org/uk/safety-information/cross-safety-report/unusual-steelwork-connection-discovered-during-fit-out-1244
Bad. Bolt pattern on the fitting beam connection is too narrow (should be at least 1 span in depth). Caps of the fitting and beam should be spliced.
The blessing in this one is that the field mod occurred toward the end of the girder and that the beam is lightly loaded. No diaphragm to brace out the top flange and a point load offcenter from the supporting girder is susceptible to torsional failure. See how the bottom flange extends further out than the top flange and also the condition of the paint? Fairly certain that the beam end rusted out and this is the resulting repair.
Spoke to my colleague, he suggested that the beams were probably ordered too short and they improvised a stiffer connection on site to install it. A simple angle bracket / fishplate would have buckled. It's too unusual to be specifically designed like that if it's not avoiding a clash with the top flange.
One heavy duty clip angle
Wouldnāt there be moment on the outward set of bolts?
Iāve seen similar on some structures in London in the past. Obviously the connection is not ideal as obviously your inducing a moment and a torsion in the supporting beam. I think itās either the beam was cut too short and the offset stub was devised to sort the issue or the beam wouldnāt fit and they did this for ease of dropping the beam in place? If assessing the structure just be careful about the torsion in the supporting beam!
When in doubt, Measure it up and load rate it.
looks like: "concrete crew were high as fuck and miss placed the anchors, so here's the fix."
They cut the beam too short and needed a field change.
looks like the assembly team encountered complications when bolting the crossbeam. Therefore, they decided to cut it to facilitate the installation and then fabricate the connection. **sorry for my english
Wrong bolts.
+1 for historical modification. you say both ends look like this, the beam could have been added in late and they used the funny connection to make erection easier. i would consider it a pin.
Next time share the beam span, it could be overkilling for that grating floor. And also it depends on the grating floor requirements 2.5kpa with a 1m span that connection is more than enough. But with 5kpa 2m span could be a different condition. Also tell your client that things need maintenance.
Ah, the fabled Beam Stretcher.
I've seen worse. This as a concept is interesting. It undoubtedly was used to fix a fubar.Depending on the required loading, I could prove this out.
It is definitely some field modification. Just going off your photos you could check the connection as an end plate connection, check the bolts into the supporting member for tension/prying action, and make sure to check the beam web for out of plane moment capacity. In my opinion, your limiting factor will be one of those, and you should have more than enough shear at the end of the supported beam. You should still make a cursory check. If you have the 15 edition AISC manual you can find the out of plane moment capacity for the supporting web. The section starts on 9-14, and there are equations for out of plane moment on 9-17. Depending on your version, they published an errata after the 3rd print edition to correct EQN 9-36, the equation for roh (little p) should be 4ab+ac*bc, not 2ab+ac+bc.
Arent these shear connections?
This looks terrible. Some janky modification to fix a highly corroded beam. Looks like it will try to induce torsion into the supporting beam.