At 4:24, the bending stress diagram for the drypack (concrete) under the base plate is questionable. There is no tension between the base plate and the drypack (concrete) except the anchor bolt tension force. The total stress diagram is also questionable. Usually it is assumed that the compression due to over-turning moment (OTM) is uniformly distributed under the base plate beyond the column flange at one side and the tension is resisted by the anchor bolts at the other side. Additional compresion due to column axial load is added to the compression due to OTM for base plate thickness design. There is no need to over analyze the stress distribution. For daily design, the anchor bolt and base plate design guide published by AISC should be used. A single equation can determine the required base plate thickness.
Awesome video !! This is the video am really looking for . I have one question here how will the design change if we add a stiffner in base plate . Can you explain ??
Hey Naveen. Introducing stiffeners will reduce the bending moment in the plate. Say you installed stiffeners aligned with the sides of the column flanges and extended these across the baseplate's full length. The moment developed in the plate due to the bolts/compressive block acting at a distance - previously - from the column flange would then be governed by the distance to the stiffener plate. Think of it this way - the load will distribute to the nearest and stiffest part, which would then become the stiffener plate. The governing distance for developing the moment, also known as the lever arm (termed 'z') would then reduce. Therefore, so would the moment [where Moment (M) = Force (F) x Lever Arm (z)]. Hope this helps you in some way.
It looks that B and N are plan dimensions of plate or concrete. However, when calculating the Moment of inertia is I = BH3/12 ...this means here you took H (thickness of concrete block) as N. Also, while calculating bending stress (Bending stress =My/I) (at 5:39/10.05 in the video) why are we considering y = N/ 2 and ..i thought may be the y should be half the depth of concrete block provided under the base plate. Please elaborate the N and B.. is it plan dimensions for base plate or dimension in elevation view for concrete block
Please think in terms of which face is fixed. here the square face (formed by sides B and N) is fixed, for us to have Bt3/12, the rectangular face (formed by sides B and t) must be fixed
@@deepakjohsh7748 Yeah. He is calculating the pressures on the BxN face at that point, the same you do when you calculate the pressure distribution at the bottom of a pad footing while interacting with the soil.
Thank you so much for this video. I've got a quick question, is there a conservative way to design a base plate on the action of a biaxial moment ? Or Do I have to a go with a " Matrix analysis " ? Maybe I can simply choose the enhanced moment for the design. Best regards!
Hey @TopDogEngineer at around 10:00 we're using qb1 and qb2, but I'm a little confused on x_1, x_end, and I. Are x_1 and x_end measured from the neutral axis, the fixed end of the cantilever, or other? Is the moment of inertia (I) the same for qb1 and qb2? Awesome video. Really helps, thanks!
While Converting stresses into distributed loads, there is a mistake I think. Although you use 1" strip to simplify, it really does not matter. We still have "t" which is the thickness of the base plate. And it was not considered while calculating the line loads.
it should be BN3/12 and not t3, this is decided based on which face is fixed/rested. here the square face (formed by sides B and N) is fixed, for us to have Bt3/12, the rectangular face (formed by sides B and t) must be fixed
