Roark's Eccentric Prism Calculator

What is the cross section?

A short prism carries a longitudinal compressive load P applied off-centre by an eccentricity e. The material cannot take tension — masonry, plain concrete, soil bearing, an unbonded base plate — so where the ordinary combined-stress formula would predict tension the section simply lifts off. Only the part of the section between the neutral axis NN and the most stressed fibre stays active, which drives the peak compressive stress well above P/A.