yeild line theory for steel plates

huangyhg

yeild line theory for steel plates
hi all
as part of a steel connection design, i have to check a rectangular steel plate supported on 3 sides. the plate is 180mm x 195mm with a bolt hole in the middle.
the plates supports a fixed/continuous.
i would like to use the yield line theory to check the plate thickness to get a bit more economy.
does anyone have a typical design example.
many thanks
charlie.
your best bet is probably to look in some concrete design textbooks.  there are lots of steel design journal papers that show results from yla, but i've never seen one that someone could learn yla from.  the cool thing about looking at concrete design books is that it's actually far easier to do yla with steel because it's isotropic.
be sure to consider the deformation of the plate.  with some connections, it's possible to come up with a very thin plate, but it would take a huge displacement to achieve the yl mechanism.  in some cases, this is no good, of course.  it is impossible to get the deflection from the yla.  a fe model of the part is usually very fast and easy to build and use to check deformation.  approximate manual calcs can also be done to get the deflection.
thanks for the advice. i'm using a design guide from the reinforced concrete council called 'practical yield line design' downloaded from the net.
this uses the 'work' method where external energy expended by the displacement of loads is equated to the internal energy dissipated by the yield lines rotating.
from this i can get the moment on the plate.
i've managed to follow this through but just wanted to see if anyone had any examples to make sure i've got the method correct.
i understand what you mean about making the plate too thin will try and check using fe analysis package in the office.
attached is an example that can be used to verify your method.  i just made it up.  imagine that you have an old style column base plate with two anchor rods beside the web and the column's in uplift.  anchor rod forces are t each.  the equation gives the required plate thickness for the assumed yield line pattern.  the first term in the internal work is for the two panels to the left and right which rotate about an axis that's up and down on the screen.  used for illustration only.
many thanks 271828.
apologies but i have a bit of difficulty following your illustartion. i get the general 'jist' of it
attached is my effort, this follows a concrete design example, but is for a steel plate.
the deflection of the plate is taken as unity. the sagging moments are taken as being equal to the hogging moments.
l is the yield line length less the hole radius.
would it be possible to give this a look over. i was hoping to get a smaller answer.
many thanks for the assistance.
chas
no time to look through the whole example tonight, but i have one observation.  you're doing plastic analysis, so the internal moment should be the plastic moment not the first yield moment.
many thanks for taking the time to look this over. i appreciate the assistance.
the formula i've used are from the concrete design example i've followed...............so i'm not sure..........i suppose this explaines the reason for my post.
once again ...........many thanks
chas
chas10...
your calcs are neater than mine... fyi, the plastic section modulus is bd^2/4 and provides a slightly larger margin of safety.  great example.
dik
dik
many thanks for the assistance. if i use the plastic modulus it gets the plate thickness down to 21mm. which is nearer the number i was thinking about.
many thanks
good... just a caution voiced by someone in this thread... have to watch for deflections...
dik
one more thing.  folks don't generally subtract out for holes when doing yla.  might make a small difference in your favor also.