Questions about knifed connection and erection clearance

taha

New Member
1) what is knifed connection?
2) what is erection clearance?
3) in aisc manual , chap 10 page 10 it is written in the second line, if both angles are shopped attached to the beam web, the beam length can be shortened to provide for mill over run with shims furnished at the appropriate interval to fill the resulting gaps or to provide mill under run.
can you please explain in easy works with a little detail so i can understand the whole phenomenon, and i will be thankful if you will tell me the meaning of the next sentence after this.
 
Last edited by a moderator:

Mick West

Administrator
Staff member
1) A knife connection is where part of a girder (the "knife") goes between two angled metal plates ("knife plates") which are bolted or welded to the column (or beam).



2) the "erection clearance" is a gap that allows you to erect (put together) a connection. If measurements are too exact (designed so everything fits with no gap) then it can be impossible to get things into the right position.

3) This means that if the angles (e.g. the knife plates) are pre-attached to the beam (attached in the shop) they you should specify (ask for) the beam a bit (a few mm at most) shorter than you need it (give it some extra erection clearance) in case the shop overruns (makes it too long). Then if it ends up too short you can use a shim (thin metal plate, also called a "pack" or "shim pack") to make it longer. The shim would go between the knife plate and the column.

Why do you ask?
 
Last edited:

Mick West

Administrator
Staff member
Related to the above, the connection to column 79 in WTC7 were not knifed, and we just bolted to the seat plate and clip angle.



This is because they were not moment resisting connections - they did not have to resist any twisting force (moment) from wind loads, as they were interior connections and the exterior of the building was a moment frame.

In earthquake regions, interior connections like this would be moment connections. If it was a moment connection, then WTC7 probably would not have collapse (like the Interstate Bank in Los Angeles didn't), or at least not as quickly.
 
Last edited:

taha

New Member
thank you so much, i find this forum very helpful,
actually i am working on steel structure for my final year project at university, i talked with the head of a firm which is purely design office.
so they said me to go through to AISC and seismic manual . so i need to things to be clear. the project we have taken for final year project is the most hardest and difficult in the university. we are designing the steel structures of a power plant. and in university , we have only started steel subject 6 months before so i i know about 2 or less than 2 percent about the subject of what we are going to do.. we have finished 10 chapters of aisc manual. not methods . but the phenomenon and theories, so we will go to the head of the design office and we will start work on the real project.
 

Mick West

Administrator
Staff member
thank you so much, i find this forum very helpful,
actually i am working on steel structure for my final year project at university, i talked with the head of a firm which is purely design office.
so they said me to go through to AISC and seismic manual . so i need to things to be clear. the project we have taken for final year project is the most hardest and difficult in the university. we are designing the steel structures of a power plant. and in university , we have only started steel subject 6 months before so i i know about 2 or less than 2 percent about the subject of what we are going to do.. we have finished 10 chapters of aisc manual. not methods . but the phenomenon and theories, so we will go to the head of the design office and we will start work on the real project.
You are welcome. This is just a debunking site though, not really structural engineering. That is just incidental to debunking (explaining what is incorrect with) the 9/11 World Trade Center collapse theories. With respect, it seems like your questions are based on English not being your native language.
 

taha

New Member
You are welcome. This is just a debunking site though, not really structural engineering. That is just incidental to debunking (explaining what is incorrect with) the 9/11 World Trade Center collapse theories. With respect, it seems like your questions are based on English not being your native language.
english is my second language,
are you asking me to tell the reasons of the failing of WTC? or just telling that this site is for the discussion of the reasons of a falling or collapsing structures?
sorry i did not get it.
 

taha

New Member
shear plates are in yellow color in the above diagram ? i mean i have read that they are stiffeners? correct me if i am wrong.
 

Mick West

Administrator
Staff member
english is my second language,
are you asking me to tell the reasons of the failing of WTC? or just telling that this site is for the discussion of the reasons of a falling or collapsing structures?
sorry i did not get it.
I am telling you that this site is for the discussion of debunking. That is scientific skepticism. شكوكية علمية

It it not a problem that you are here. It is an an interesting topic.
 

Mick West

Administrator
Staff member
shear plates are in yellow color in the above diagram ? i mean i have read that they are stiffeners? correct me if i am wrong.
No, it's the blue end plate. It's a shear connection at the end of a beam. But "end shear plate" is not really a common term.

The yellow plates (transverse web stiffeners) stiffen the girder locally. The blue plate is creating (to a degree) a moment resisting connection and it stiffens the entire structure.
 

Mick West

Administrator
Staff member
Out of interest I was just reading AISC, and it defines a shear end-plate as having a plate length less than the supported beam depth. So the diagram above does not show that, the blue plate is actually an "extended end plate" or a "bolted moment end plate". Here's a better example of a simple shear end plate (the orange):



This slide show gives very good examples of the different connections:
http://www.slideshare.net/nadimnit/bracing-connections

And this is a good list:
http://www.steel-connections.com/lmc_types.htm
 
Last edited:

taha

New Member
NCSTAR_1-9_WTC7_unlocked.pdf_(SECURED)-20130505-122313.png
this diagram shows that seat is welded on supporting beam (horizontally), but other diagram shows them similar to angle. i have doubt in it.
 

Mick West

Administrator
Staff member
Not all shear end plate connections have a seat.

Some are just simply shear connections.

Some seated connection have no end plate, just the top and bottom bolts.
 

Mick West

Administrator
Staff member
View attachment 3260
this diagram shows that seat is welded on supporting beam (horizontally), but other diagram shows them similar to angle. i have doubt in it.
There are really two different connections shown there. The front and side projections have the beam at right angles. The section (top projection) does not.
 

taha

New Member
i mean.. the seat is welded to the web of the supporting beam, as shown in the figure above, on the very left side, at the top flange it is joined with clip angle, at bottom flange , bolts are fastened with seat, which is welded to the web of the supporting beam, and below the seat there is a plate.
but as shown in this photo
http://image.slidesharecdn.com/brac...72841-phpapp01/95/slide-14-728.jpg?1298676767
it looks like a clip angle.
i am little confused abut the components of connections and all tat stuff, i do not find a clear diagram which point all the components.
i studied 9 hours continusly yesterday searching and reading but still i am not clear in all the aspects.
 
Thread starter Related Articles Forum Replies Date
J Does google earth pro simulate refraction [No] Flat Earth 7
SFX Where to ask questions about posting? Site Feedback & News 5
A Augie Snyder's contrail/chemtrail questions Contrails and Chemtrails 18
K Did Elvis really say this about Andy Kaufman? Quotes Debunked 11
Vindog Vindog's Contrail Questions [Contrails Near Boston] Contrails and Chemtrails 561
Mick West Morgellons on Joe Rogan Questions Everything Health and Quackery 43
Mick West Joe Rogan Questions Everything: Weaponizing Weather Contrails and Chemtrails 100
Miss VocalCord Dutch Government answers chemtrail questions Contrails and Chemtrails 4
Jump Some chemtrail/contrail questions from Jump Contrails and Chemtrails 5
secretschizoid23 Questions about the chemtrail theory Contrails and Chemtrails 13
U Some Old Questions from Contrails in Airline Advertising Contrails and Chemtrails 4
U Some questions regarding chemtrails and debunking Contrails and Chemtrails 13
C Questions for the experts Contrails and Chemtrails 2
Rory Debunked: Study shows link between menstrual cycle and the moon Health and Quackery 30
Mick West Explained: Photo of "UFO" Used in Connection with Nimitz Incident [Balloon] UFO Videos and Reports from the US Navy 8
MikeC 95,000 kids, 20 years of science - no connection between Autism and MMR Health and Quackery 1
Steve Funk White House Fence Jumper, Omar J. Gonzalez, chemtrail connection? Conspiracy Theories 2
Mick West Debunked: Monsanto Patents and Chemtrails (Infowars' GMO-Chemtrail Connection) Contrails and Chemtrails 20
Tobes Email from former Connecticut state worker claiming lottery/Sandy Hook connection Sandy Hook 22
Mick West Bernard Eastlund's Connection to HAARP People Debunked 102

Related Articles

Top