T, Y, and K connections apply to connections that are tube to tube. Reading clause 2.25.1 and 2.25.2 may provide clarification as well as the figures found in later portion of clause 2 and the commentary.
The connections involved are pipe welded to pipe, box tube to box tube, etc.
A connection that is indirect, i.e., a tube to a plate such as that used as diagonal structural bracing in building construction has different design considerations. That is, the connection has an element (the plate) that acts as a hinge and provides some degree of movement, i.e., the plate can bend. This is not the case with tube to tube connections which has a high degree of restraint due to the inherent stiffness of the tubular members. The failure mode in a tube to tube connection is different because one or both of the members will fail by buckling, punching through the wall, tear out the wall of the main member, etc.
Designing a tube to tube connection is considerably more complex than a simple frame connection. A rigid design, i.e., a moment connection, can approximate some of the problems encountered with a tube to tube connection, but most are relatively simple to analyze when compared to the tube to tube connections. Punch shear is not a major consideration when analyzing a connection consisting of a wide flange beam to a wide flange used as a column. Typically the flange of the beam (the weak link) is thinner than the column flange. That is often not the case with a tube to tube connection where the wall thickness of one member is often the same or with only a minor difference in thickness.
Ultimately it is the engineer's responsibility to consider the failure mode that is most likely and design accordingly.
A tube/pipe to plate connection such as that depicted in AWS D1.1 Detail B of figure 4.20 is nothing more than a fillet weld around a round member. The member used in fabrication could be a hollow structural shape or it could be solid, it makes no difference. The connection could also be a CJP or a PJP groove detail which could be selected from any of the prequalified bevel or J-groove details found in figure 3.3 or 3.4 for indeed, they are nothing more than Tee joints welded from one side with backing. Life becomes a little more complex if the designer specifies the groove detail as CJP without backing.
Cause 3.13.5 ties the reader into figures 3.6 and 3.7 when welding round HSS to round HSS members and table 3.5 lists the dihedral angles that can be used for those joints. Figure 3.6 pops up again for box HSS members. Table 3.6 lists the local dihedral angle for prequalified tubular joints and is keyed into figures 3.8, 3.9, and 3.10. Notice the joint details for T, Y, and K connections found in figures 3.8, and 3.9 are keyed into table 3.5 and table 3.6 and figures 3.5, 3.6, or 3.7 which show HSS to HSS connections.
You can follow the thread that tie all of the tubulars together, but the bottom line is that the code has special provisions for tube to tube connections, for butt joints and then additional considerations for joints that make up tubular T, Y, and K connections where it is tube to tube with no connecting plates.
At least that is my understanding of the situation.
Best regards - Al
Thank you for your clarification, I also agreed with you that when they mention to TKY tubular connnection which also knows that it is connection between tubular to tubular.
But AWS D1.1's Annex K Term and Definition still makes me confusion
Tubular Connection: A connection in the portion of a structure that contains two or more intersecting member, at least one of which is a tubular member.
When in doubt, ask the Engineer whether he designed it as a tubular or not.
No one works in a vacuum.
Need some insights in AWS D1.1 2020 added new clause 10 supplements to clause 1 to 9.
In clause 10.
“The specific requirements of Clause 1 0 apply only to tubular connections as defined in 10.3 and Clause 3 . Such connections may be butt joints between tubulars, T- , Y- , K- connections of tubulars to tubulars , or tubulars welded to flat plates or flat elements of other members . Where this clause refers to rectangular tubulars, square tubulars are included unless noted.
10.1 .1 The scope of the term “tubular members” includes:
(1 ) Circular hollow structural sections (HSS ) ;
(2) Rectangular HSS;
(3 ) Square HSS ;
(4) Fabricated members built from flat plates and or shapes joined together with CJP longitudinal seams acting as chord members designed us ing the provisions of Clause 1 0. For design purposes , this clause shall be used with the applicable requirements of Clause 4, Part A. All provisions of Clause 1 0 apply to both static and cyclic applications, with the exception that the fatigue provisions of 1 0.2.3 , only apply to cyclic applications”.
Does it mean 18” pipe welded to plate CJP is considered TKY connections now? If the project contract was signed in 2019 before this, do I need to follow this new requirement?
Wow, you jumped in on an old post, but I don't blame you. Trying to post a new inquiry on this forum is mystifying.
You are bound to the code edition referenced the day the contract was signed. This can be complicated if you are bound to a building code that was in force when the contract was signed. For instance, in my home state we are obligated to meet AWS D1.1 1989 for ASD or 2000 for LFRD unless the Engineer specifies a more recent edition of a code in the contract documents (project specification or drawings for example.
You would not apply the requirements of AWS D1.1:2020 unless there was an agreement between the Engineer (representing the Owner) and the contractor to use the latest edition when construction starts. As mentioned, once the contracts are signed, the code editions in force on that day are "locked". I have seen exceptions while working on nuclear facilities and upgrades were mandated by the NRC, but that's an oddball.
From your description of the situation, you would be required to meet the requirements of edition of D1.1 referenced by the applicable building code or possibly D1.1:2015 if the Engineer references that particular code edition. If there is a question regarding what edition applied, ask the Engineer for clarification. No reputable Engineer is going to be offended by anyone asking for clarification.
I suggest you look at Table 4.1 in D1.1:2015 with regards to the diameter of the HSS. If you are welding a round HSS, a procedure on plate is acceptable on a round HSS if it is at least 24-inches in diameter. It would not be valid for square or rectangular HSS. Table 9.9 lists the positions used to qualify the WPS and the production positions qualified when the procedure is qualified using a HSS.
The diameter you cited is not qualified if plate was used for the purpose of qualifying the WPS, even in the 2015 edition of D1.1.
I hope this helps.
just confirmed with engineers the changes in 2020 will not be adapted in current project.
But i'm wondering T-K-Y connections apply to tube to tube OR tube to plate? am i going to qualify 6GR if tube to plate connection?
Are you qualifying the WPS or the welder? Just asking.
There are specific tests in D1.1 for qualifying the WPS and welder. In the case of qualifying the WPS, the butt joint is to demonstrate the procedure will meet the mechanical properties listed by the code. You may have to suppliment that with macro etch samples for the square and rectangular HSS whether they are hot formed or fabricated from plate.
I decided to qualify 6GR welders for tube to plate connection shown in figure.
Thanks for your info.