A recent article published in Sustainability explored the impact of novel cross-sectional configurations on low-cost bamboo composite (LCBC) structural members using both experimental and numerical methods.
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Background
Carbon-intensive materials like concrete and steel account for about one-third of the construction industry’s emissions. Structural timbers are promising sustainable alternatives but are in limited supply and require costly processing before structural use.
Bamboo, in contrast, is abundant in developing regions and has a high potential as a renewable material. Bamboo is an effective carbon sink and biodegradable, offering environmental advantages, but its raw form is vulnerable to environmental conditions and prone to brittle failure under seismic loads.
Bamboo composites, where bamboo is combined with other materials in a resin matrix, are being investigated as structural load-bearing members. These composites address some of the inherent weaknesses of raw bamboo.
This study examined four cross-sectional configurations of LCBC columns made from four bamboo species: Moso, Guadua, Madake, and Tali.
Methods
The bamboo species used were categorized by size: extra-large (Moso), large (Moso, Guadua, and Tali), medium (Madake), and small (Moso).
Seventeen stocky columns were fabricated with varying cross-sectional configurations—Russian doll (RD), big Russian doll (BRD), Hawser (HAW), and Scrimber (SCR)—and combined with four types of resins: commercial synthetic epoxy (EPX), experimental soft bio-based resin (BE1), commercial bio-epoxy (BE2), and commercial poly-furfuryl alcohol (PF1).
EPX was used as a benchmark to compare the bio-based resins, and BE1 was used to hold the smaller bamboo in the stay-in-place giant bamboo cast.
The compressive properties of LCBC specimens were measured on a compressive testing machine. The corresponding strain values were recorded using strain gauges on the outer layer of the exterior bamboo, while the longitudinal deformation was determined using linear variable differential transformers (LVDT).
Additionally, the compressive strengths of the LCBC specimens (HAW series) were predicted through theoretical analysis, which validated the findings from numerical simulations and experimental tests.
Finally, a three-dimensional finite element analysis (FEA) was performed using ABAQUS 2024 software to model the compression behavior of LCBC short columns. The constructed HAW-EXP-M and HAW-BE2-M models comprised full-culm Moso bamboo fibers embedded in EPX and BE2 resins. Static Riks method was used to determine the LCBC response to axial compressive loading.
Results and Discussion
The 17 different LCBC members exhibited varying compression strengths, with the highest values observed in the HAW (62 MPa) and SCR (60 MPa) configurations of the BE2 and PF1 series. In contrast, the BRD configuration showed the lowest compressive strength at 49 MPa, attributed to its higher Moso bamboo content (60 %) relative to the BE2 resin.
Accordingly, the SCR and HAW configurations achieved the highest moduli of elasticity, while the BRD configuration had the lowest. The BRD configuration could perform better with a resin that has compressive strength equal to or less than that of bamboo.
Most LCBC specimens experienced ultimate failure through longitudinal cracking on the outer layer, though the core matrix remained intact, except in the BRD sample. This suggests a reserve capacity in the structures due to the bamboo's outer layer. Columns using BE1 resin exhibited more cracking within the core matrix, while most cracking in other samples occurred on the outer surface.
For the HAW specimens, the measured compressive capacity averaged 0.88 times the theoretically predicted values, with a coefficient of variation (CoV) of 16 %, indicating reasonable alignment with theoretical expectations.
FEA analysis of the HAW-EPX-M samples showed only a 2 MPa difference between the axial stress at failure and experimental results, while the HAW-BE2-M samples exhibited a 3 MPa difference. The FEA-derived load, displacement, and stress-strain graphs closely matched experimental data, with only minor discrepancies.
Conclusion
The researchers conducted experimental, numerical, and theoretical analyses on 17 LCBC short columns, exploring various cross-sectional configurations, bio-resin matrices, and bamboo species. The LCBC columns with bio-based resins (HAW-BE2-M) demonstrated a notable compressive capacity of 67 MPa, while those with synthetic epoxy (HAW-EPX-M) reached a maximum compressive strength of 78 MPa.
Theoretical predictions for the HAW specimens showed reasonable accuracy, with a coefficient of variation (CoV) of 16 % compared to experimental results. The FEA performed using ABAQUS accurately captured the axial compression response of the HAW columns. Mesh refinement strategies with a 5 mm element size ensured the precision of the numerical model.
These findings contribute valuable insights that could aid in the design and development of LCBC structures for engineering applications.
Journal Reference
Padfield, C., Drury, B., Soltanieh, G., Rajabifard, M., & Mofidi, A. (2024). Innovative Cross-Sectional Configurations for Low-Cost Bamboo Composite (LCBC) Structural Columns. Sustainability, 16(17), 7451. DOI: 10.3390/su16177451, https://www.mdpi.com/2071-1050/16/17/7451
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