Why the joints in a Truss are considered as pinned while analyzing it, even if they are Welded joints ?
548986
The simple answer?  For ease of calculations.  When you load a pinned truss, the only forces which will exist are along the axis of the members.  When you load a welded truss, however, there will be some forces generated by the bending of the members.  This would make the amount of additional information and calculation almost prohibitively difficult for the average person.  In most situations, the answers you need for design and analysis are close enough to the "pinned" answers, so engineers do it that way.  Does this cause some error?  Sure, but engineering is just a way to apply modeling equations to the real world, and comes with some errors anyway.  That's (one of the reasons) why they design with safety margins and factors...
206156
Note that both of the above posters are right but the fact that it's a very specialized test wasn't emphasized. If you are thinking of testing a sample of a steel alloy you have currently you will need to get a sample machined to the diameter and thread specified by the ASTM standard as the previous poster mentioned.
472579
Depends on the structural design.  Shear will take place near to supports.  Load pressures will take place all the way down to the foundations (getting larger all the way.\n\nSome structures will tend to push out (like a pitched roof) and some will push down (like a flat roof). \n\nIf you need anything more specific drop me a note.
929977
I've never heard the term either.  My dad's a mechanic, and I've heard plenty about screws, and threads, and nuts and bolts and rivets...all types of fasteners.\n\nWhat does it matter if something was taken apart?  That's what screws are for--so you can unscrew it and screw it back together.  Unless something got messed up inside by opening it, I don't see what the big deal is.  If it wasn't supposed to be unscrewed, then the manufacturer should have glued it together or put in rivets or something instead of screws.\n\nNow, if the threads on the screws were messed up, or if it had the wrong kind of screws in the holes, it might be bad, but unless the hole the screws went into was messed up, just get the right screws and put them in the holes.  There's something called "thread-lock" which basically glues a screw in place--it flows around the screw and then the screw is stuck in the hole.  \n\nI don't get the problem.  The person should be more specific about the damage, and use standard terms any mechanic (or mechanic's daughter) would use.  If I don't recognize the term, I'm not saying it doesn't exist (I admit, there are a few words I don't know!) but it could just be a scam where somebody's trying to return it or get a refund for a "problem" that doesn't exist.
483029
Columns support the building and keep it standing up.  If the beams that connect between columns were stiff then the column connections would not be able to flex under earthquake loadings.  So, when the beams are allowed to flex it allows the side-to-side forces that earthquakes cause.
128277
Typically not. In engineering calculations we employ a strength allowable knockdown in the Heat-effected-zone near the weld.
1171597
It sounds like a Civil Engineering problem, maybe for steel structures? Well, regardless, I suggest going to the ASCE (Am. Society of Civil Engineers) web site. They should have some good examples including some mesh - free finite element method solutions. Should give strengths, buckling info, etc.
797646
I may be going out on a limb here, but as a non-engineer I would guess that a solid core door is solid, and a hollow core door is hollow. However, I could be missing something.
105883
First we note that the two bases of the trapezoid are parallel and the segment joining the midpoints of the altitudes is parallel and equidistant from the bases. Therefore the vertical displacement of the midpoints of the bases from the midpoints of the altitudes is equal.\n\nIf we also contruct the segment joining the midpoints of the bases we see this intersects our other segment at its midpoint. We have now cut our quadrilateral into four triangles and it is an easy task to show that opposite triangles are congruent using SAS.
588486
If you mill Aluminum plates to a very fine precision, and then stack the plates together they will become difficult to dislodge from each other.  The reason is not due to suction.  It is due to covalent bonds forming between the two slabs of metal!  Hard to believe isn't it!  I thought so too, even when I got a chance to see it first hand.
711713
You have to practice a lot to use them, very dangerous if you don't have the skill needed to handle them, I have plenty of practice and still freak out when I use them, I wouldn't recommend a novice to use pins, I think you're right, platform are better..☺
602032
it is 19.2 inches, and it  Has something to do with truss layout.
762462
Do you mean the FEA program if so the most important factor and the one that i used to always get wrong is node number and separation. Try a simple shape with fixed point load and pivot. First try with 10000's of nodes then try with 100's then with just 2 or 3 dependent on shape the difference to the results are big. Node choice comes with experience which i am lacking!!
148537
The term "double jointed" means having joints loose enough to snap in and out of regular position.  There is no difference in their bones, but in the tendons that connect, support and move those bones.
106060
Many physics priciples apply.\nYou got your tensil strength, this is your pulling streingth <- ->\nthen, your shear strenght _> <-(left one is lower)like holding a tooth pick between your thumb and index finger and pushing on the middle with your other hand\nand compretion strength -> <- \nthese factors determin wood's ability to withstand load. normaly, bridge trusses use triangles because it focuses on tensile and compretion strenght(whigh wood does well with)\nenginering sites are the best place to look up on these things
790576
You have to find basic wind speed, K1,K2,K3 factors, Design wind pressure, Gust factors, exposed area & solidity ratio, drag co-efficient.\nWind load on panel = ExpArea*Drag*Gust*Design Wind Pr.\nPanel load is distributed to nodes & you can analyse and find the axial forces (Comp & ten) treating these are truss members.\nThen design of these members is as explained in IS802.
238500
need to know the type of metal, then find the shear force & plug it into your equation.  don't forget to factor in each thread  (Basic solid mechanics)