Analysis and computer program for non-prismatic continuous beam and floor section

Abstract

This thesis is based on research by the VPI Agricultural Engineering Department in residential floor structures. Slope-deflection equations and computer programs were developed for theoretically analyzing continuous non-prismatic T-beams.

Residential floor systems were treated as a series of three-span continuous T-beams. Cross-sectional area of the stem of the T-beam was doubled over interior supports and for 3 ft. on either side.

Computer programs were used for calculating moment, shear, deflection, and rotation over supports for beams with simply supported ends and with one end cantilevered. The computer was also used for determining span ratios that would result in equal maximum deflections when all three spans were subjected to uniformly distributed loads.

Several tests were conducted on a full-scale 8 ft. by 48 ft. floor section. Deflection from the experimental tests on continuous joist alone and with plywood subfloor were statistically compared with theoretical deflections.

In one case the theoretical equation did not adequately describe the center span and had to be rewritten in order to show no significant difference between theoretical and experimental deflection. In one experiment symmetrical end spans did not act as replicates of each other 2 in which case the maximum experimental deflection was significantly larger than the theoretical deflection. In all other cases there was no significant difference in theoretical and experimental deflections.

It would require 33.9% more timber in nominal 2 in. thick lumber as simple beams to provide equal strength and stiffness as the experimental three-span continuous beam.