Bending Strength of Shallow Glued-Laminated Beams of a Uniform Grade

摘要

Bending tests of Douglas-fir and southern pine glulam beams of 2-, 4-, or 6-laminations revealed the following about the accuracy of the three methods for predicting near-minimum bending strengths: (1) The minimum strength ratio (SR) concept, method A, overestimated most of the near-minimum values; (2) No difference could be detected between the minimum SR concept, method B, and the K/G concept. These two methods also overestimated some of the near-minimum values. In addition, the data revealed no general trend of increase in the bending strength values from 2- to 4- to 6-laminations as both the K/G and method B concepts predict; and (3) A New prediction method was developed which suggests that better estimates of design bending strength values may be obtained by using the SR concept, method A, with an applied adjustment factor of 0.85. These results agree with the results of both J. W. Johnson and Fox, again suggesting that present prediction methods overestimate the strength of glulam beams without specially graded tension laminations.