Bending properties of wooden spaced beams II. Theoretical prediction and experimental verification of failure load

The bending properties of the spaced beam are affected by the conditions of size, number and position of the spacer-block. In this study, to derive the theoretical equation to expect the failure mode and failure load of the spaced beam constructed arbitrarily in regard to those conditions about the spacer-block, the spaced beam was substituted for the composite-beam model composed of the chord members and the diagonal members. In this model, two crossed diagonal members supposed at the position of each spacer-block of spaced beam combined with chord members with pin joint. The theoretical equation was derived under the following conditions. 1) The load is the center concentrated load, and the beam is the simply support beam. 2) The construction of the spaced beam is symmetric with respect to the center span. 3) The connections between the chord member and the spacer-block have recourse to the adhesive. Applicability of the theoretical equation derived in this study was verified by the results of bending test of the spaced beam, and applicability of the past theoretical equation derived by using rigid frame model was verified in the same way. The spaced beam specimens for the bending lest were constructed under 14 conditions in regard to the length, position, and number of the spacer-block. Consequently, good agreements were obtained between theoretically predicted and experimental results in regard to the failure modes and failure loads for almost all beams tested. It was confirmed that the theoretical equations suggested in this study were valid under the former conditions.