Truss Connections

[strguy11]

I have a custom steel truss that I am designing. (HSS web members, and W section chords). What is typically done for the connections? Do most people just list the axial loads of the web members on the plans, and delegate the design to the fabricator, or do most just design and detail the connections themselves?

 

[hokie66]

I vote for designing the connections. While some fabricators may be capable of connection design, they may not use a type connection you are comfortable with. Do you know what type connections you want? If so, why not show them on your drawings?

 

[msquared48]

Definitely design the connections yourself.

Mike McCann
McCann Engineering

 

[JAE]

Design the connections yourself

 

[DaveAtkins]

I don't have a problem with allowing the fabricator to design the connections, but I would specify that the shop drawings and calculations must be prepared, signed and sealed by an engineer licensed in your jurisdiction--and that you must review them.

DaveAtkins

 

[jike]

Definitely design them yourself. With HSS sections, you will want to offset them (eccentric) at connections to avoid coping the tubes (quite common and efficient). This eccentricity should be taken into account in the design of the truss.

 

[archeng59]

design and detail the connections.

 

[nutte]

Did you include the time required for connection design in your original quote for the project? And are you experienced in the design of these types of connections? If the answer to either is "No," then I would suggest you show the type of connection you want and have the fabricator design the connections. Have them submit sealed calculations for review with the shop drawings.

Not to question your abilities, I have found that many engineers of record have little to no experience with connection design.

 

[csd72]

An eccentric connection may require a different member size. Personally I would design it or specify that all members are to meet at a single point.

 

[jike]

Eccentric connections can substantially lower the fabrication cost by eliminating special cuts. It also makes the welds quite simple. Often the same size members can used but, of course, should always be checked.

 

[strguy11]

After looking at these connections, I dont think I will have to offset the tubes. Based on the depth of my chord, and the angles of the members, it looks to me that when using a gusset and slotting the HSS member, no offset is needed. Based on this, it appears that the connection design would be relatively straight forward, so that myself, or the fabricator could do them.

What are you reasons for designing them yourself?

 

[JAE]

Mad, selfish, egocentric control.





No really, I just prefer to do them myself as this is what makes engineering fun! And avoids the nebulus "other person" doing design that I have to check anyway.

 

[hokie66]

My reason for designing connections is that I consider the connections the most important aspect of structural steel design, so I wouldn't want to leave the design of the most important elements to someone else.

Now I don't mean you have to detail all the connections. In your case, your gusset connections slotted into the hollow sections need to be defined on your drawings, but not detailed. The way I do it is to specify for each size web member the gusset thickness, slot length, and welding requirements to chord and web.

I think the comments jike made about eccentric connections was for the hollow sections to be directly welded to the chords. He is correct that it is cheap to do it that way, but depends on how hard the members are working. If you need to fully develop the hollow sections, backing bars would be required.

 

[jike]

Details are often when failures begin and generally not in the members. This is why I believe looking at the connections is fairly important. As hokie66 says, you may not need to design all the connections but enough to give a good idea to the fabricator how to build it.

Eccentric connections are typically used with gusset plates as hokie66 says. We often do this when there is architectural considerations.