Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: Bolting issues, generation II

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Charlie,

Many thanks for your time and valuable comments.

>Shear deformations occur on planes that are oriented 45-degrees with the
>axis of the bolt. So no matter if the bolt is loaded in shear, tension
>or combined tension and shear, the bolt has to elongate as it
>deforms...it sure couldn't shrink!

It may be hard to visualize this, so I use a very fansy skech below.

Assuming bolt axis is along a-a, shear deformation (exagereted here for the
sake of argument) on the bolt can only develop as shown, because end
rotation of the bolt head and nut is restrained by the plates in contact on
both sides. 

Now, distance b-b is the bolt grip after inelsatic shear deformation takes
place. Does not this mean additional elongation along the bolt length, i.e
extera tension due to shear? So why tension be lost rather than increased?


        _________________   
        |               |
        |               |
      a |               | a     
        |               |
        |               |
        -----------------         


        
        |\               
        | \              
      b |  \             
        |   \            
        |    \           
        \     \        
         \     \
          \     \
           \     \
            \     \
             \     \
              \     \  
               \     \
                \     \ 
                 \     \
                  \    |
                   \   |
                    \  | b
                     \ |
                      \| 



>I wouldn't claim that RCSC couldn't ever be wrong, but I can tell you
>from personal experience with the individuals that make up RCSC that it
>is a top-notch group of engineers and constructors who write a very
>practical and useful specification. They don't recommend or endorse
>anything without careful consideration and deliberation. G.L. Kulak
>(main author of the Guide to Design Criteria for Bolted and Riveted
>Joints) is one of the most technically knowledgable member of RCSC. So
>there isn't anything I'm aware of in either the RCSC Specification or
>the Guide that is based on luck.


Charlie, please do not get me wrong. I would not allow myself to question
the knowledge and credibility of RCSC. I have a great respect for you and
professor Kulak, and I know you all have more knowledge and experince than I
do. I honor Professor Kulak for his valubale contributions in many areas in
steel research, specially on joints and fasteners. I regret that he is
retired and it will be many years before we have another man like him in
Canada. I would be very lucky if I could follow in his footsteps in
research, or yours in practice.

It is only that I felt in this particular case, "MAYBE" RCSC is only
realying on this figure which is based on 6 data points from the tests
conducted in 50s or 60s by Fisher, or there must be explaininations on what
physically happen to bolt which looses its pretension after factored shear
load is applied.

Pordon me if my limited knowledge of mechanics of material would not allow
me to comprehend this any better.

Best regards,


Majid Sarraf


              ~      ~           ~ ___
                       [_________]-|__)
              __________OO______O__O_O___________________________
                  |==========================================|
                  |                                          |
                   \               Majid Sarraf             /
                    \       Ph.D Candidate/Lecturer        /
                     \   Department of Civil Engineering  /
                      |        University of Ottawa      |
                      |           Ottawa, Ontario        |
                      |            Canada K1N 6N5        |
                      |WEB SITE: www.uottawa.ca/~msarraf |
                      |   Tel:(613) 562-5800 Ext. 6159   |
                      |         Fax:(613) 562-5173       |
|                                  |
                       ~  ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~