Related Resources: civil engineering

Structural Load Bearing Plates

 
To resist a beam reaction, the minimum bearing length N in the direction of the beam span for a bearing plate is determined by equations for prevention of local web yielding and web crippling. A larger N is generally desirable but is limited by the available wall thickness.
 
When the plate covers the full area of a concrete support, the area, in2 (mm2), required by the bearing plate is:
 
where  R = beam reaction, kip (kN), f 'c specified compressive strength of the concrete, ksi (MPa). When the plate covers less than the full area of the concrete support, then, as determined from Table A,
 

Table A
Allowable Bearing Stress, Fp
on Concrete and Masonry
 
where:
 
A2 full cross-sectional area of concrete support, in2 (mm2).

 

With N established, usually rounded to full inches (millimeters), the minimum width of plate B, in (mm), may be calculated by dividing A1 by N and then rounded off to full inches (millimeters), so that BN > or = A1. Actual bearing pressure f p, ksi (MPa), under the plate then is fp, ksi (MPa), under the plate is:

 
The plate thickness usually is determined with the assumption of cantilever bending of the plate:
 
 
where:
 
t =  minimum plate thickness, in (mm)
k = distance, in (mm), from beam bottom to top of web fillet
fb = allowable bending stress of plate, ksi (MPa)