Thus the united pressures upon the two inclined supports always exceed the weight. In the last case, 2 3/4 tons exert a pressure of 2 1/2 and 2 tons, equal together to 4 1/2 tons; and in the former case, 1200 pounds exert a pressure of twice 720 pounds, equal to 1440 pounds. The smaller the angle of inclination to the horizontal, the greater will be the pressure upon the supports. So, in the frame of a roof, the strain upon the rafters decreases gradually with the increase of the angle of inclination to the horizon, the length of the rafter remaining the same.
This is true in comparing one system of framing with another; but in a system where the concentrated weight to be supported is not in the middle (see Fig. 23), and, in consequence, the supports are not inclined equally, the strain will be greatest upon that support which has the greatest inclination to the horizon.