Introduction

The communication towers are an essential source for providing connectivity in any region. However, they have still not reached most of the rural communities and localities of the country. The primary reason for this is that the steel used for making these towers is quite challenging to transport in the rural parts of the country. Steel is expensive, and the material's manufacturing process is hazardous to the environment.

Bamboo comes as a remedy to all these issues. Bamboo, a naturally grown construction material, can be easily found in rural areas, making it a sustainable and reliable material for constructing the tower. 

Bamboo generally has very good parallel-to-fibre structural properties, with allowable stresses in bending, compression and tension ranging between 10-20 MPa for most species of bamboo. Allowable shear stresses are relatively low at around 1.2 MPa which is further accentuated by bamboo’s tendency to split due to the weak parenchyma matrix. Hence the suggested characteristic tensile strengths perpendicular to the fibre are as low as 0.46 MPa. Because of these properties and the hollow nature of bamboo, joints are normally the most difficult aspect to design and also likely to be the weakest elements in the structure. It is therefore most efficient to use bamboo structural members mainly in axial tension or compression.

Characteristics of Suitable Structural Bamboo Species

The bamboo species that have traditionally been used for construction tend to have the following characteristics:

• Grow locally in abundance

• Stronger than other local species

• Large diameter (50mm–200mm)

• Grow relatively straight.

• Mature quickly (less than five years)

• Slightly more resistant to insects and fungi (lower starch content).

• Less susceptible to splitting

Design Optimization

To develop an efficient and structurally optimized tower geometry, parametric modelling and computational optimization techniques were employed. The tower geometry was parametrically modelled using Rhinoceros (Rhino) and Grasshopper, enabling systematic evaluation of different geometric configurations and structural parameters.

Galapagos, the evolutionary solver within Grasshopper, was used to optimize the tower configuration based on the defined design objectives and constraints. This optimization process helped identify an efficient structural form while maintaining the required geometric and structural requirements.

The bamboo tower is designed for

1. Self-weight of the bamboo members and connections

2. Dead loads due to the telecommunication equipment

3. Live loads due to maintenance and repair

4. Wind loads as per IS 802: (Part 1/Sec1) Use of Structural Steel in Overhead Transmission Line Towers — Code of Practice.

Structural Model Verification

The optimized tower configuration was subsequently modelled and independently evaluated using ETABS for structural analysis and verification. The ETABS model was used to assess the structural response under the governing load combinations and to verify the adequacy of the optimized configuration.