สมบัติของไม้ไผ่และพฤติกรรมของเสาไม้ไผ่กรอกปูนซีเมนต์มอร์ต้าร์ภายใต้การรับแรงในแนวราบสลับทิศ

Abstract

The objective of this research is to investigate the load-bearing capacity of bamboo, comprising 2 parts. Part 1 involved conducted tests to determine basic material properties, such as physical and mechanical properties, with the aim of predicting strengths and structural grading of bamboo. Part 2 involved tests on bamboo columns subjected to lateral static and cyclic loads, studying the impact of filling mortar in both single-culm and multiple-culm bamboo columns. The bamboo used in the research was the Sang Mon bamboo species (Dendrocalamus sericeus Munro), grown in plants in the northern region of Chiang Rai Province, Chiang Saen District. The bamboo used in the research underwent treatment and a drying process to reduce starch and remove water from the wood. In Part 1 of the study, the following physical properties were obtained: culm wall thickness ranged from 6.78 to 27.03 mm, outer diameter from 74.60 to 109.29 mm, moisture content from 10.03% to 19.70%, density at air-dry from 546.71 to 1,113.50 kg/m3, density at oven-dry from 485.86 to 1,001.36 kg/m3, density at 12%Mc from 544.16 to 1,121.52 kg/m3, linear mass at air-dry from 1.06 to 4.45 kg/m, linear mass at oven-dry from 0.94 to 3.80 kg/m, and linear mass at 12%Mc from 1.05 to 4.25 kg/m. The mechanical properties of bamboo tested according to ISO 22157 were as follows: compressive load capacity ranged from 71.98 to 256.93 kN, compressive strength from 36.23 to 71.92 MPa, tensile load capacity from 2,639.82 to 8,793.27 N, tensile strength from 75.66 to 233.79 MPa, shear load capacity from 4,306.96 to 18,630.20 N, shear strength from 0.93 to 3.88 MPa, bending load capacity from 6,030.11 to 29,022.08 N, modulus of rupture from 46.82 to 109.38 MPa, bending stiffness (EI) from 16.85 to 74.60 kN-m2, and modulus of elasticity from 11,153.80 to 23,868.51 MPa. In the grading process, Pearson correlation coefficient was analyzed. It was found that the physical properties suitable for grading, in order from highest to lowest relationship, were density (at air-dry and 12%Mc), linear mass (at air-dry and 12%Mc), moisture content, culm wall thickness, and outer diameter. The suitability depended on the types of mechanical properties compared to find relationships and predictions. A simple linear regression analysis was then performed to establish the relationship between the physical properties (independent variable) and the mechanical properties (dependent variable) for grading. In Part 2, the samples were divided into two groups: single-culm columns and 4-multi-culm columns, which could further be subdivided into either filled mortar or empty hollow sections. Two types of lateral loads were applied: static pushover load and cyclic load. For the single-culm column samples: the results of the static load test indicated that both the empty and mortar-filled columns exhibited comparable load-bearing capacities, with the mortar-filled columns demonstrating a slightly higher load-bearing capability. In the results of the cyclic load test, it was observed that the ductility factor and energy dissipation of single columns without mortar was greater than those of single columns with mortar. These findings suggest that bamboo columns without mortar exhibit greater flexibility and better earthquake resistance. Testing the 4-multi-culm column samples revealed that in the static load test, mortar-filled columns exhibited a slightly higher load-bearing capacity compared to non-mortar-filled columns. In the cyclic load test results, it was observed that the unfilled columns had higher ductility factors and greater energy dissipation than the mortar-filled columns. When comparing single columns and group columns, it was determined that group columns exhibited superior performance in static load tests compared to both single columns with and without mortar filling. However, in the cyclic load tests, the ductility factor of single columns surpassed that of group columns. Additionally, concerning energy dissipation, group columns outperformed single columns in terms of displacement.