BSVBD
Structural
- Jul 23, 2015
- 463
I've never been mentored on this one!
I checked a previous thread where it was stated "Even though ACI 530 allows 0.25 F'm for bearing (375 psi for F'm =1,500), I have always use 250 psi bearing to design beam bearing plates on masonry... I wouldn't be surprised if many others also follow this practice."
For years i've used the max 0.25f'm=375 (or other based on R & h'/r and so on...) for my bearing plates. But that never takes into consideration the vertical steel. I can design a CMU column to support a large beam reaction, but the bearing plate, even when using 375 psi, for a large enough reaction, in some cases will exceed the required size of the CMU column. Therefore, in many cases, if the bearing plate exceeds, i will design a steel column to be placed inside of the hollow CMU.
Can we consider the vertical steel when designing bearing plates on CMU? I've not seen a bearing plate design or example that allows this.
Can i subtract the allowable bearing on the vertical steel from the total reaction and THEN apply the difference ONLY to the grouted CMU, and THEN divide by the 375?
I tend to think that the perimeter stress of the plate would cause the CMU to fail or at elast crack, but, i want other opinions.
Thank you!
I checked a previous thread where it was stated "Even though ACI 530 allows 0.25 F'm for bearing (375 psi for F'm =1,500), I have always use 250 psi bearing to design beam bearing plates on masonry... I wouldn't be surprised if many others also follow this practice."
For years i've used the max 0.25f'm=375 (or other based on R & h'/r and so on...) for my bearing plates. But that never takes into consideration the vertical steel. I can design a CMU column to support a large beam reaction, but the bearing plate, even when using 375 psi, for a large enough reaction, in some cases will exceed the required size of the CMU column. Therefore, in many cases, if the bearing plate exceeds, i will design a steel column to be placed inside of the hollow CMU.
Can we consider the vertical steel when designing bearing plates on CMU? I've not seen a bearing plate design or example that allows this.
Can i subtract the allowable bearing on the vertical steel from the total reaction and THEN apply the difference ONLY to the grouted CMU, and THEN divide by the 375?
I tend to think that the perimeter stress of the plate would cause the CMU to fail or at elast crack, but, i want other opinions.
Thank you!
