Literature Review

A lot of material was investigated in the literature review, the entirety the review is linked above, but the key things investigated were:

1. Mechanical properties of bamboo both engineered and natural

2. Previous investigations of bamboo reinforced concrete using both engineered and natural bamboo.

3. Challenges associated with the use of bamboo as a reinforcement for concrete.

Literature Review Take Aways

The main takeaway from the literature review was that “engineered bamboo”, a composite material made by stripping bamboo fibers and cold/heat pressing them with some sort of adhesive, is the most applicable for structural purposes.

Moreover, for the ensuing case study, the following material properties of engineered bamboo were used, referenced by research done by Alireza Javadian of the ETH Future Cities Laboratory:

longitudinal engineered bamboo; stirrup engineered bamboo

• Tensile Strength: 346 MPa; 275 MPa

• Modulus of Elasticity Tension: 33,100 MPa; 30,800 MPa

• Modulus of Rupture: 262 MPa; 244 MPa

• Modulus of Elasticity Flexure: 29,200 MPa; 24,900 MPa

• Compressive Strength Along Fiber: 162 MPa; 137 MPa

[more information on engineered bamboo can be found in the final paper]

Case Study

The study will analyzed a simple portal frame structure for both gravity loads and a lateral earthquake load. Once the loads on the frame were analyzed, the structure's primary beam was sized using both bamboo and steel and then each sections embodied carbon was compared.

The location of the case structure was Addis Ababa, Ethiopia. This location was picked because Ethiopia is one of the few countries in Africa where bamboo grows; other viable locations are Asia or South America. Furthermore, Ethiopia is a country that imports much of its steel and has a high demand for low-rise residential housing; thus, the use of bamboo as reinforcement would be a significant benefit and almost immediately applicable in the country, especially as it continues to modernize and expand.

Proposed Structure

The proposed structure was a 10 meter wide, 50 meter long, and 6.625 meter tall storage warehouse. The structure had a repeated concrete moment resisting frame, with non-load bearing hollow block walls and a corrugated steel plate roof supported on hollow rectangular steel purlins. This structure was suggested because it is a widely used low cost, high volume space used in developing countries like Ethiopia.

Analysis

For the system analysis, both hand calculations using the simplified portal frame analysis was done along with a computational analysis using Karamba.

The codes used to conduct the portal frame analysis were ASCE 7-16 Minimum Design Loads for Buildings and Other Structures, Ethiopian Building Code of Seismic Activity (ES8-15), and 2007 UN Earthquake Risk in Africa.

Following the derivation of the earthquake load, portal frame analysis was calculated by hand and in Karamba to verify the results.

Detailed calculations on how the equivalent lateral force was derived using the code are in Appendix B of the final paper. Detailed calculations of the portal frame analysis, including shear, moment, and axial force diagrams, can be found in Appendix C of the final paper.

Section Design

For the sizing of the concrete members the following assumptions were made:

1. Engineered bamboo lateral and transverse reinforcement will be
   used with material properties of those found in paper [22] and
   given in table 7

2. Bamboo reinforced members will be designed according to ACI
   440.1R-15.

3. Concrete reinforced members will be designed to ACI 318M-11

4. Bamboo Reinforcement sizes will be assumed to follow standard
   steel rebar sizes.

Detailed steps to the sizing of the bamboo-section according to ACI 440.1R-15 are in Appendix D of the final paper. Detailed steps to the sizing of the concrete section according to ACI 318M-11 are in Appendix E of the final paper.

Discussion & Conclusion

As a forewarning, it is essential to note that while this case study shows positive results, two broad assumptions are made. First and foremost, bamboo reinforced concreted challenges were ignored, such as debonding, shrinkage, and creep. Secondly, embodied carbon values were estimates based on research, as Life Cycle Analysis techniques are still being adopted for most construction materials. 

In light of the assumptions made, the results of this study show many positive results. In comparing the beams, the bamboo reinforced beam shows a 6.5% reduction in weight compared to its steel-reinforced counterpart (5669.2 kg vs. 6065.666 kg). While not a massive reduction, it's neither negligible, as a 6.5% reduction per beam summed over an entire structure makes a significant effect. More importantly, and perhaps more exciting is the reduction in embodied carbon. The bamboo reinforced beam showed a nearly 44 % reduction in embodied carbon compared to the steel-reinforced section (723.26 kg vs. 1291.31 kg). This excitement is not just because of the considerable reduction, but the fact that the embodied carbon ratio (1.7 kg CO2/kg steel) was an underestimate of the actual value. The value used does not take into account the significant amount of carbon is produced in the transportation of steel to developing nations such as Ethiopia who do not produce steel. 

In conclusion, this case study shows that if the current challenges with bamboo reinforcement are solved and improved, RCD using engineering bamboo is worth serious consideration in the developing world.