Thursday, January 23, 2014

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Bearing Plates

To resist a beam reaction, the minimum bearing length N in the direction of the beam span for a bearing plate is deter- mined 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, in (mm ), required by the bearing plate is
1= R/0.35fc
R=beam reaction, kip (kN),
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 by following table
Bearing Plates formula
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 >=A1. Actual bearing pressure fp, ksi (MPa), under the plate then is
The plate thickness usually is determined with the assumption of cantilever bending of the plate:
Bearing Plates-2
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)


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