Estimation of Shear Strength and Pull-out Strength of Timber Joints Using Deformed Steel Bars for Civil Engineering Construction with Large Cross Sections.

In Akita prefecture, all wood type wooden check dams which are composed of wood members and lag screws have been studied and developed. The cost of the lag screws amounts to 20% to 30% of the entire construction cost. Therefore, as a substitute for the lag screws, we examined deformed steel bars which cost a tenth of the lag screws and would be very economical. Since pull-out force and shearing force can occur at joints of the wooden check dam simultaneously under design load conditions, the same performance would be required for the deformed steel bars as for the lag screws. In this study, we conducted pull-out and shear tests of the joints for different embedment depths of the deformed steel bar. Shear test results were compared with the yield capacity according to European yield theory. The results can be summarized as follows : In regard to shearing strength, the deformed steel bars give a performance equivalent to that of lag screws. In regard to pull-out strength, the deformed steel bar is a possible substitute for the lag screw. However, pull-out performance of the deformed steel bar is only about 80% of that of the lag screw. In order to expect the same pull-out performance as for lag screws, the pre-drilled hole diameter needs to be 14 mm and the embedment depth needs to be 200 mm.