**6. Design standards for bamboo structure calculations**

The current bamboo construction standards published in 2004 by the International Organization for Standardization (ISO) were the first step in the attempt to standardize the use of bamboo in construction [15, 16, 30]. These standards are essentially based on the existing traditional knowledge with an adaptation of the existing ISO timber and timber testing standards for bamboo [31]. These standards cover the basis for design and testing of bamboo and bamboo products and can be used as a basis for further standardization of bamboo as a structural material used in soil bioengineering. ISO 22156: Bamboo, structural design [30], provides basic design guidance for full culm bamboo construction. This standard is supported by ISO 22157-1 Bamboo, determination of physical and mechanical properties, part 1: requirements [15], which specify the test methods necessary for design, and ISO 22157-2 [16], which is essentially a laboratory manual for determining the structural properties of bamboo.

#### **6.1. ISO 22156: bamboo: structural design**

This international standard is based on limit state design and on the structure's performance; it is only concerned with the requirements for mechanical resistance, serviceability and durability of structures [30]. Execution (work on-site and fabrication of components off site and their erection on-site) is covered to the extent that is necessary to indicate the quality of construction materials and products which should be used and the standard of workmanship on-site needed to comply with the assumptions of the design rules. Bamboo construction design concepts shall be based on calculations, relevant permissible stresses verifying that no relevant limit state or no stress is exceeded. Exclusions are made for design based on previous generations' experience or design based on evaluation reports on structures that survived natural disasters (e.g. hurricanes, earthquakes, etc.) undamaged. In this standard, the limit state design is based on the characteristic value of a material property (5 percentile property, estimated from test results [15], with 75% confidence that it represents the sampled population). The standard advises that special attention is given to differences between materials originating from different sites to account for natural variability. The standard assumes that bamboo will behave as a linear elastic material with service classes dependent on the local environmental conditions (e.g. temperature, humidity) during the structure lifetime. This means that bamboo material is expected to behave elastically until failure, while the plastic behaviour is considered insignificant. In terms of schematization; the bamboo culms are supposed to be analysed as not perfectly straight, tapered, hollow-tube structures with variable thickness.

for the use of bamboo elements as soil reinforcement, providing that there is an appropriate evidence (test results) that the bamboo will function as reinforcement during the structure's expected service lifetime, with special attention to the lifetime of the bamboo in the organic environment. Types of tests and the frequency of testing are not specified in this standard.

The Use of Bamboo for Erosion Control and Slope Stabilization: Soil Bioengineering Works

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The environmental conditions (temperature, humidity, moisture content, soil/water characteristics and composition, surrounding flora/fauna, etc.) must be taken into account at the design stage to assess their effect on the durability of the structure but also to enable the design of material protection techniques. The durability of each structure is expected to vary based on the particular materials and the environmental conditions. The standard does not prescribe methods for assessing the durability but suggests considering a range of factors (e.g. environment, service life, use, performance criteria, workmanship, maintenance, etc.) when

In terms of quality assurance, the design with bamboo structural elements should be carried out by suitably qualified and experienced personnel. Similarly, qualified and experienced personnel should carry out the supervision and quality control during construction. The structures should be used as per the design briefly and adequately maintained. This standard specifies quality control for mainly factory-produced bamboo and products using a quality assurance manual (QAM). For the purposes of eco-engineering works, the standard can be interpreted including material specifications (including incoming material, inspection, and acceptance requirements), quality assurance inspection testing and acceptance procedures, sampling and inspection frequencies and procedures to be followed upon failure to meet specifications or upon out-of-control conditions. The QAM should be supplemented by rel-

evant records, including inspection and test records, test data, corrective actions, etc.

tionship between mechanical properties and factors for quality control functions.

results and test report requirements are specified for each test.

**6.2. ISO 22157-1 bamboo: determination of physical and mechanical properties: part** 

This standard specifies the test methods for evaluating the following characteristic physical and strength properties of bamboo: moisture content, mass per volume (density), shrinkage, compression, bending, shear and tension. This data is needed for establishing characteristic strength functions and determination of allowable stresses, as well as for establishing the rela-

The standard prescribes the acceptable precision of testing measurements, the sampling and storage of test samples and reporting requirements. The measurements specified in the standard include determination of moisture content, mass (by volume), shrinkage, strength in compression (including nominal modulus of elasticity), strength in bending (including loaddeflection curves and modulus of elasticity), strength in shear and strength in tension. The principles, apparatus, preparation of test specimens, procedure, calculation and expression of

**6.3. ISO 22157-2 bamboo: determination of physical and mechanical properties: part** 

The purpose of this standard, originally written as a technical report is to disseminate best practice test methods in order to make these globally available but also to outline the 'how

making such assessments.

**1: requirements**

**2: laboratory manual**

Similarly as for timber structures, the design shall be verified if no possible limit state is exceeded when partial safety factors and loads/actions relevant to the location of the structure have been applied. Alternative to this approach, allowable stress approaches can be adopted with suitable modification for differences between laboratory and in situ results (0.5), duration of the load (1.0–1.5) and a default value of the factor of safety of 2.25. In these analyses, the conventional structural analysis methods can be used with the bamboo initial curvature, diameter and wall thickness as inputs. The joints/supports of bamboo structures should be located near the nodes (which, in reality, are not spaced at constant intervals) and should be considered to act as a hinge, unless substantive data exist to justify a spring or a fixed joint.

Reflecting the use of bamboo structural members in bioengineering, this standard prescribes the design of beams (predominantly loaded in bending), columns (predominantly axially loaded), joints and assemblies (trusses). All beam elements should be symmetrically loaded, and the loads should be applied preferably close to or at the nodes. All axially loaded bamboo elements should preferably be constructed using the best available straight bamboo culms to avoid buckling. For both types of elements, standard structural calculation methods apply, taking into account the effects of any combination of stresses that may occur during the structure/element lifetime. The joints between the elements should be rigid and provide structural continuity between them, including force transmission and deflection limitation.

In the section on sound construction practices, this standard advises that the designer is in charge of ensuring that 'sound construction practices are taken into account', covering mostly the moisture content change of structural bamboo. It also suggests that special care should be taken to ensure the workmanship (on-site and for products coming from the factory) is according to the assumptions listed in the appendix of the standard. Special provision is made for the use of bamboo elements as soil reinforcement, providing that there is an appropriate evidence (test results) that the bamboo will function as reinforcement during the structure's expected service lifetime, with special attention to the lifetime of the bamboo in the organic environment. Types of tests and the frequency of testing are not specified in this standard.

**6.1. ISO 22156: bamboo: structural design**

118 Bamboo - Current and Future Prospects

This international standard is based on limit state design and on the structure's performance; it is only concerned with the requirements for mechanical resistance, serviceability and durability of structures [30]. Execution (work on-site and fabrication of components off site and their erection on-site) is covered to the extent that is necessary to indicate the quality of construction materials and products which should be used and the standard of workmanship on-site needed to comply with the assumptions of the design rules. Bamboo construction design concepts shall be based on calculations, relevant permissible stresses verifying that no relevant limit state or no stress is exceeded. Exclusions are made for design based on previous generations' experience or design based on evaluation reports on structures that survived natural disasters (e.g. hurricanes, earthquakes, etc.) undamaged. In this standard, the limit state design is based on the characteristic value of a material property (5 percentile property, estimated from test results [15], with 75% confidence that it represents the sampled population). The standard advises that special attention is given to differences between materials originating from different sites to account for natural variability. The standard assumes that bamboo will behave as a linear elastic material with service classes dependent on the local environmental conditions (e.g. temperature, humidity) during the structure lifetime. This means that bamboo material is expected to behave elastically until failure, while the plastic behaviour is considered insignificant. In terms of schematization; the bamboo culms are supposed to be analysed as not perfectly straight, tapered, hollow-tube structures with variable thickness.

Similarly as for timber structures, the design shall be verified if no possible limit state is exceeded when partial safety factors and loads/actions relevant to the location of the structure have been applied. Alternative to this approach, allowable stress approaches can be adopted with suitable modification for differences between laboratory and in situ results (0.5), duration of the load (1.0–1.5) and a default value of the factor of safety of 2.25. In these analyses, the conventional structural analysis methods can be used with the bamboo initial curvature, diameter and wall thickness as inputs. The joints/supports of bamboo structures should be located near the nodes (which, in reality, are not spaced at constant intervals) and should be considered to act as a hinge, unless substantive data exist to justify a spring or a fixed joint.

Reflecting the use of bamboo structural members in bioengineering, this standard prescribes the design of beams (predominantly loaded in bending), columns (predominantly axially loaded), joints and assemblies (trusses). All beam elements should be symmetrically loaded, and the loads should be applied preferably close to or at the nodes. All axially loaded bamboo elements should preferably be constructed using the best available straight bamboo culms to avoid buckling. For both types of elements, standard structural calculation methods apply, taking into account the effects of any combination of stresses that may occur during the structure/element lifetime. The joints between the elements should be rigid and provide structural

In the section on sound construction practices, this standard advises that the designer is in charge of ensuring that 'sound construction practices are taken into account', covering mostly the moisture content change of structural bamboo. It also suggests that special care should be taken to ensure the workmanship (on-site and for products coming from the factory) is according to the assumptions listed in the appendix of the standard. Special provision is made

continuity between them, including force transmission and deflection limitation.

The environmental conditions (temperature, humidity, moisture content, soil/water characteristics and composition, surrounding flora/fauna, etc.) must be taken into account at the design stage to assess their effect on the durability of the structure but also to enable the design of material protection techniques. The durability of each structure is expected to vary based on the particular materials and the environmental conditions. The standard does not prescribe methods for assessing the durability but suggests considering a range of factors (e.g. environment, service life, use, performance criteria, workmanship, maintenance, etc.) when making such assessments.

In terms of quality assurance, the design with bamboo structural elements should be carried out by suitably qualified and experienced personnel. Similarly, qualified and experienced personnel should carry out the supervision and quality control during construction. The structures should be used as per the design briefly and adequately maintained. This standard specifies quality control for mainly factory-produced bamboo and products using a quality assurance manual (QAM). For the purposes of eco-engineering works, the standard can be interpreted including material specifications (including incoming material, inspection, and acceptance requirements), quality assurance inspection testing and acceptance procedures, sampling and inspection frequencies and procedures to be followed upon failure to meet specifications or upon out-of-control conditions. The QAM should be supplemented by relevant records, including inspection and test records, test data, corrective actions, etc.
