Structural testing and characterization of Sri Lankan yellow bamboo Bambusa vulgaris

Abstract

Bamboo is a woody grass belonging to the sub family Bambusoideae of the family Poaceae (Gramineae). The increasing need for sustainable building construction and the use of natural local materials have made bamboo a popular material. Sri Lanka is an island nation located south of the Indian peninsula. It is a tropical country with distinct dry and wet seasons. Sri Lanka has nearly 5000 ha of natural bamboo forests and another 5000 ha of domestically cultivated land, scattered mainly in the South Western zone which amounts to 0.5% of the total forest cover in Sri Lanka. However, with the restoration of cascading reservoir systems in the Eastern Province, there is potential to have many marginal lands converted to bamboo plantations hence allowing for the growth and harvesting of bamboo in a sustainable manner for use in construction as a structural material. Sri Lanka is home to ten endemic species of bamboo. In addition, several exotic species have been introduced to the country. The bamboo plant has a variety of uses. Industrial utilization of bamboo can be through primary or secondary value addition, which enhances the market value of bamboo. Bamboo in construction is found in either full-culm or engineered form. Bamboo is limited in its application through its durability and its tendency to split. Hence it needs to be processed and treated to ensure its long-term usage. Bamboo structures should be detailed appropriately for the full protection of treated bamboo. Bamboo used for construction has to undergo harvesting, grading, cleaning, preservative treatment, and storage. Determination of structural parameters of Sri Lankan bamboo could be based on ISO standards since other standards are often based on ISO standards themselves and are more suitable for bamboo species from those particular countries of those respective standards. To date, the mechanical characterization of Sri Lankan bamboo species has not been found in literature. The widespread availability of Bambusa Vulgaris (Sri Lankan Yellow bamboo) led to it being chosen for investigation in this study. All bamboo culm sections in this study were obtained from a single supplier with initial moisture content and dimensions obtained on delivery. Once culm data was measured for all culms, a random selection of culms underwent preservation treatment prior to testing. The mechanical characterization tests provided a set of structural parameters including; average strength values in compression, shear, flat ring flexure and tension for Bambusa Vulgaris (Sri Lankan Yellow bamboo). All Strength values tend to show gradual increase from bottom towards the top of the culm. Comparison of treated vs. untreated strength values across all four tests showed no significant increase in strength initially due to preservation treatment. Average densities of test samples tend to show a strong relationship with their respective strengths, whereas average diameter does not. Comparison of average strength values of Bambusa Vulgaris (Sri Lankan Yellow bamboo) with the same species from Kenya as well as relatable other species from Thailand revealed that the average strength values of Bambusa Vulgaris (Sri Lankan Yellow bamboo) to be lower compared to the respective average strength values of other species except in the case of tensile strength. Sri Lankan Bambusa Vulgaris showed characteristic strengths of 17.0N/mm 2 , 2.0N/mm 2 , 16.0N/mm 2 and 20.0N/mm for compressive strength, shear strength, bending strength in flat ring flexure and tensile strength respectively.