Local buckling behavior and reinforced mechanisms of short circular timber columns confined with bamboo scrimber

Abstract

Developing sustainable high-performance bamboo scrimber (BS) as structural and reinforcing materials is significant. BS was used as reinforcing material to increase ancient timber columns' load-bearing capacity and safety via a damage-free strengthening method. The BS panels were fastened to the surface of the wooden columns by spaced steel strips. The spacing of the steel strips was the important factor in balancing the appearance of the confined reinforced timber columns with maximizing the strength of the confined panels. In this study, eight short circular wooden columns reinforced with BS with varying spacing of steel strips were fabricated and tested under axial compression. Each specimen's damage characteristics, load-carrying capacity performance, and strain coordination were analyzed and compared. The reinforcement method has a significant effect, and the reinforcement system of all specimens provides an additional load-bearing capacity of more than 48.3 % with about 38 % increase in cross-section area. The load-bearing capacity decreases significantly with increasing the spacing of steel strips. When the steel strips' distance is more than 363 mm (the corresponding slenderness ratio is 41), the confined panel showed significant buckling behavior from the beginning of loading. In contrast, the confined panels of the other circular reinforced timber column showed buckling and load drop only near the peak load, which takes full advantage of the strength of the BS material. The strain growth trends of the confined panels and core column were similar, although the strain of the confined panels' bending offsets some of the compressive strain, which was evidence that they were synergistically stressed under axial compression. The part of confined slats between the steel strips was intercepted as a compression bar, and the commonly used equation for the load-bearing capacity of a flexible bar was introduced. Various flex rod equations based on material properties were calculated and compared to the test results. The calculations showed that the buckling equation suggested by Euler and CSA086-19 had the best agreement with BS materials with similar proportional limits and ultimate strength. BS as a flex rod was suggested with a slenderness ratio not exceeding 32, and a general equation for calculating the steel strip spacing considering the material thickness was proposed for construction reference.