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Bahrin, N. A., Kamarudin, M. K., Mansor, H., Sahol-Hamid, Y., Ahmad, Z., and Lopez, L. F. (2023). “Mechanical characterization of bamboo pole for building engineering: A review,” BioResources 18(3), 6583-6613.

Abstract

Bamboo is a sustainable and cost-effective alternative to traditional construction materials. Despite the fact that three species are well known for structural applications, namely Dendrocalamus asper, Gigantochloa scortechinii, and Gigantochloa levis, the scientific data for their mechanical characterization is scarcely available and widely dispersed. In addition, a systematic literature review appraising the study advancement of mechanical characterization of bamboo had been unavailable. This paper bridges this gap by conducting a systematic literature review (SLR) of the available literature of mechanical characterization of bamboo pole. A total of 54 relevant articles were retrieved from Scopus and snowballing and then put forward through bibliometric analysis using VOSviewer. The results showed that the distribution of data for physical and mechanical characterization of aforementioned species was scattered due to the different location (origin), age, and initial moisture content recorded during empirical work among the researchers. This review’s importance and distinctiveness lie in its synthesis of the existing literature on bamboo mechanical characterization. The findings provide a point of reference for both academia and industry by bridging the scarcity of current bamboo engineering data and outlining future possibilities for bamboo research in the building and construction domain.


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Mechanical Characterization of Bamboo Pole for Building Engineering: A Review

N. A. Bahrin,a M. K. Kamarudin,a,b,* H. Mansor,a,b Y. Sahol-Hamid,a,b Z. Ahmad,a and L. F. Lopez c

Bamboo is a sustainable and cost-effective alternative to traditional construction materials. Despite the fact that three species are well known for structural applications, namely Dendrocalamus asper, Gigantochloa scortechinii, and Gigantochloa levis, the scientific data for their mechanical characterization is scarcely available and widely dispersed. In addition, a systematic literature review appraising the study advancement of mechanical characterization of bamboo had been unavailable. This paper bridges this gap by conducting a systematic literature review (SLR) of the available literature of mechanical characterization of bamboo pole. A total of 54 relevant articles were retrieved from Scopus and snowballing and then put forward through bibliometric analysis using VOSviewer. The results showed that the distribution of data for physical and mechanical characterization of aforementioned species was scattered due to the different location (origin), age, and initial moisture content recorded during empirical work among the researchers. This review’s importance and distinctiveness lie in its synthesis of the existing literature on bamboo mechanical characterization. The findings provide a point of reference for both academia and industry by bridging the scarcity of current bamboo engineering data and outlining future possibilities for bamboo research in the building and construction domain.

DOI: 10.15376/biores.18.3.Bahrin

Keywords: Systematic literature review; Bamboo mechanical properties; Physical properties; Dendrocalamus asper; Gigantochloa scortechinii

Contact information: a: School of Civil Engineering, College of Engineering, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia; b: Innovative Hybrid Composite Structures Research Group, College of Engineering, Universiti Teknologi MARA, Shah Alam, Selangor, 40450, Malaysia; c: Base Bahay Foundation Inc., UPRC III Bldg., 2289 Pasong Tamo Extension, Makati, Philippines;

* Corresponding author: mkhairul3965@uitm.edu.my

INTRODUCTION

Bamboo is a natural fiber composite used for household application, furniture, and food (Azmy et al. 1991; Yap et al. 2017). This natural fiber could substitute the synthetic fiber reinforced plastic because it is more durable, economical, and sustainable for green building (Mansor et al. 2019). An et al. (2020) found out that the mechanical strength of material bamboo (bamboo fiber) is an excellent fit for paper products. Also, bamboo is a promising material for producing bicycle frames and fabrics because of its mechanical strength applicability (Tausif et al. 2014; Jakovljevic et al. 2017). In addition, the developed CTNF-BACNF nanocomposite has good mechanical properties, thermal stability, and biodegradability, and is promising for food packaging (Hai et al. 2019). Bamboo is the fastest growing plant; it matures within 3 to 4 years (Wahab et al. 2012). Physical characteristics of bamboo such as age, height, moisture content, thickness, diameter, relative density, and shrinkage depend on the species, soil, climate conditions, and harvesting technique (Lee et al. 1994). Although the physical properties have been scarcely investigated (Liese 1985; Amada et al. 1997; Azmy et al. 2009; Asari and Suratman 2010; Wahab et al. 2010; Mohamed et al. 2011; Sakaray et al. 2012; Waranyu et al. 2013; Anokye et al. 2014a; Ye and Fu 2018), mutual data derivation has proposed that the age and height of bamboo have different effects depending on the bamboo species.

Several studies showed that moisture content affects the mechanical strength properties. In air-dry conditions, a moisture content of 12% is the nominal value (Chinese Standard Agency 2007). However, this suggestion is still open for discussion because the mechanical characterization needs to be justified (Janssen 1985; Godbole et al. 1986; Hisham et al. 2006; Hamdan et al. 2009; Wakchaure and Kute 2012; Anokye et al. 2014b; Awalluddin et al. 2017; Li et al. 2017; Ismail et al. 2019). The grading properties of bamboo consist of thickness, diameter, and density. The thickness of the bamboo wall culm is the average of four measurements taken around the circumference of the culm at angular spacings of 90º (ISO/TC 165 N 1120 2018). The thickness of bamboo decreases along the culm height (Amada et al. 1997; Awalluddin et al. 2017). The wall thickness at the base of all culms seemed bigger and thicker against the age factor (Mohamed et al. 2011), although this result is debated (Hisham et al. 2006). The mean diameter-at-breast-height (DBH) is different for each species and age (Mohamed et al. 2011), but the Gigantochloa species shows the same mean DBH, which is insignificant against age factor (Asari and Suratman 2010). There is a correlation between bamboo species and density, such that Gigantochloa scortechinii has recorded a higher density than the Bambusa vulgaris (Hisham et al. 2006; Nordahlia et al. 2012; Anokye et al. 2014a). The density is inversely proportional to the moisture content (Hamdan et al. 2009; Wahab et al. 2012; Anokye et al. 2014a; Awalluddin et al. 2017; Yap et al. 2017). Scientific data for shrinkage (radial, tangential, and volumetric) has been recorded (Wahab et al. 2012; Razak et al. 2013; Edi Suhaimi et al. 2014), though further exploration is needed.

The recorded shear strength for bamboo has suggested the increment in strength from green to air-dry conditions due to the reduction of moisture content (Rafidah et al. 2010; Wahab et al. 2012). Mokhtar et al. (2018) has suggested a different perspective with specific allocation of green and air-dried condition in proclaiming the bamboo shear strength. Studies on bamboo tensile strength have suggested that Dendrocalamus asper is the top of the list (Awalluddin et al. 2017; Amatosa and Lorento 2018; Jais et al. 2020), while Gigantochloa levis shows higher tensile strength than Gigantochloa scortechinii. However, more investigation is needed to expand the quality of deducing this outcome for bamboo strength grading in the future. Studies that observed the compressive strength of bamboo have suggested that the optimized moisture content to achieve compression strength fairly ranges between 12% to 15% (Awalluddin et al. 2017; Mokhtar et al. 2018).

The vast amount of bamboo research makes it difficult to evaluate the dimension of the knowledge discovered, in particular synthesizing the mechanical characterization of bamboo pole, its critical domains, and emerging trends. The findings have focused on the silo mentality context of physical and mechanical properties of bamboo without further synthesizing the extending overall mechanical characterization aspects of bamboo. Such an exercise on bamboo engineering is important to provide a point of reference for guide scholars and practitioners to enable mainstreaming of bamboo material knowledge and practice.

To address the above-mentioned deficiency, a schematic literature review is established in the present work to explore more justification and knowledge exploration related to mechanical characterization of bamboo pole, specifically, Dendrocalamus asper, Gigantochloa scortechinii, and Gigantochloa levis. Hence, this paper aims to perform a bibliometric analysis of the documents published related to bamboo strength specification as to review the current research status using VOSviewer. The purposes of this systematic literature review are as follows: (1) to summarize the trends in bamboo research of specified species from the perspective of a co-occurrence network; (2) to determine physico-mechanical characterization of bamboo; and (3) to identify bamboo failure mechanisms in correlation with the physical and mechanical properties of bamboo as a future research roadmap. This paper is structured to review the physical and mechanical characterization of bamboo poles from previous compilation of related literature.

RESEARCH METHOD

A schematic literature review (SLR) was used in this study to review the specified species bamboo pole’s mechanical characterization critically. All the data was obtained from previous studies. Hence, there is no experimental work and finite element analysis conducted in this research. This method employs a thorough review strategy to capture works focusing on the specific context and further synthesizing the findings into several perspectives depending on each study’s objective. Osei-Kyei et al. (2015) used a three-stage search approach to undertake a content analysis of the mechanical characterization of the specified species bamboo pole. The three stages comprise identifying database and journal selection, targeted article selection, and content analysis. A framework of this approach is shown in Fig. 1.

Identification (Database and Journal Selection)

In stage 1, all the journals were searched and downloaded from the Scopus database, as it tends to have the most significant search engines in regard to their breadth and precision of coverage. Scopus has been used in many recent reviews in bamboo studies. For example, it was used to review the strength parameters of parallel to fiber (de Jesus et al. 2021), water absorption behavior of bamboo (Salih et al. 2019), and interactive buckling of bamboo structure (Awalluddin et al. 2019). In order to carry out the search, the Scopus search engine was utilized by using “titles/abstract/keyword” as the first step. The keywords of “bamboo”, “culm”, “mechanical characterization”, “mechanical properties”, “physical characterization”, “physical properties”, and “strength of bamboo” were considered when doing the first search to identify papers. “Article or Review” was selected as the document type during setup. The search string TITLE-ABS-KEY (“bamboo” OR “culm” OR “mechanical characterization” OR “mechanical properties” OR “physical characterization” OR “physical properties” AND “strength of bamboo”) was employed to find results for all bamboo species used in structural applications.

Because this study analyzed mechanical characterization related to bamboo literature, the keywords were intentionally diverse to capture a comprehensive picture of the features of bamboo that are relevant to its mechanical and physical characterization. After the keywords were entered, the screening of the publication source was restricted to only looking at English-language journals. The publication date also was limited to the past 16 years, from 2005 to 2021. The journals and proceedings were taken as the sample in this study due to the lack of articles related to bamboo studies. The original search yielded a total of 195 publications, which were narrowed down to 125 articles. Table 1 displays the various publications that were deemed acceptable following the initial screening.

Fig. 1. Methodology for conducting a systematic review

Targeted Article Selection

In stage 2, the process selection of articles was carried out in order to examine the articles. This method reduced unrelated articles and focused more on the main objective of the study. Three inclusion criteria were applied to the article selection process.

To begin, the article must be focused on physical and mechanical characterization of the bamboo pole. The physical characterization must include one of the criteria, which are age, height, moisture content, thickness, diameter, specific density, and shrinkage. Meanwhile, the scope for mechanical characterization was shear strength, tensile strength, compression strength, modulus of rupture, and modulus of elasticity.

Second, the article should have at least one species of bamboo related to Dendrocalamus asper (Buluh betong), Gigantochloa scortechinii (Buluh semantan), and Gigantochloa levis (Buluh beting). Lastly, the article should include any relevant information on physical and mechanical characterization of three bamboo poles species.

A list of all publications that did not meet the aforementioned standards was compiled. Due to this screening, papers that were not relevant, such as articles that focused on alternative contexts, like engineered bamboo, were eliminated. While study of properties through-thickness of bamboo (inner, middle, and outer) are beyond the scope of this study. Consequently, the contents of the articles were examined, and the number of the articles was reduced to 40, which were then used for the content analysis in determining the mechanical characterization of specified species bamboo poles.

Table 1. The Breakdown of the Number of Articles in Stage 1

As there was still a lack of articles found, additional related articles that were not captured by the Scopus database were identified using the “snowball” method. The term “snowball” means that certain studies were found due to their being cited in other works that had been found according to the search procedure outlined above. As a result, 14 articles were identified using the same criteria through the snowballing method. This method was carried out to supplement the results of the first two-stage search in order to have a complete view of the papers that merited further study. The snowball exercise is sufficient since it provides the option to include significant state-of-the-art works connected to the subject (Li et al. 2019).

Content Analysis

The qualitative research method was used in this study. Qualitative research collects data, information and analyzes non-numerical data to understand concepts, opinions, or experiences.

In stage 3, following the identification and selection of articles, a comprehensive examination of their content was conducted. A total of 54 articles were used in determining the mechanical characterization of the specified species bamboo pole. It is important to note that any numerical data or a detailed description of the topic related to the mechanical characterization of specified species bamboo poles were figured out based on the total number of articles that were taken into consideration for the content analysis. The information in the articles was extracted and reviewed based on the scope of this study.

The selected articles were reviewed based on the following contents. The findings of the bibliometric analysis consisted of the physical (age, height, diameter, thickness, moisture content, density, and shrinkage), mechanical characterization (shear strength, tensile strength, compressive strength, and bending strength), and the failure mechanism of three species bamboo pole. VOSviewer software was used for the bibliometric analysis. Due to the limited resources, this free-accessible software was merely considered. Additionally, this VOSviewer can visualize the networks at a big scale and speed by using manual methods or software tools. It also has text mining capability, by which network maps of co-occurring keywords sourced from abstracts and bodies of research articles can be constructed. The criteria of the three-stage search approach can only be undertaken visually by VOSviewer, as can be seen from other researcher’s work (Che Ibrahim et al. 2021). The results were compared and summarized by the specific category.

RESULTS AND DISCUSSION

Bibliometric Analysis Result

Analysis of co-authorship

Regarding the statistics in Table 2, the five major quantitative measurements of selected authors who published more than two articles consist of the number of articles, total citations, average publication year, average citations, and average normalization citations. The measurements present the research output and influence of the given authors on the research fields. The analysis indicates that 13 authors got involved in more than one article. In addition, 56 total citations were recorded as the highest citations of articles. The total citations measure the influence and impact of the research work.

Table 2. Detailed Information of the Selected Authors

The average publication year of authors showed that the articles were developed between the year 2007 to 2013. It is worth noting that essentially more research studies in characterizing the mechanical properties of bamboo poles are needed for the specified species that is useful for building construction.

Analysis of co-occurrence of keywords

Contents of the 54 target articles were analysed following the initial inspection of keywords. Main keywords addressed in each article were extracted as shown in Table 3.

Table 3. Main Keywords of Mechanical Characterization of Bamboo Poles

The keywords ‘Gigantochloa scortechinii’ and ‘Mechanical properties’ have received high attention in this research field, with 15 occurrences. That was followed by moisture content, with 13 occurrences, while physical properties and tensile strength had the same occurrence, which is 8, respectively. Besides, the average publication year illustrates that the most related study topics of the mechanical characterization of bamboo poles were raised around these five years, 2012 to 2017. The highest average year published was in 2012 with keywords ‘moisture content’, ‘Gigantochloa scortechinii’, ‘Bambusa’, ‘Gigantochloa’, and ‘durability’. In contrast, tensile strength keywords record as the lowest average year published was in 2018. This shows that the significance of related research topics has been reduced over the years. Based on Fig. 2, a large node size indicates high occurrence of the items, and a thick connection line indicates close relationship between two items. Different colors divide nodes into different clusters. The keywords consist of four clusters such as Gigantochloa scortechinii, mechanical properties, physical properties, and tensile strength, and are seen through the large node of different colors. The network visualization of co-occurrence of keyword analysis indicates that the interconnections of keywords between the clusters are strongly connected.

Analysis of countries’ activeness

In Table 4, the details of countries or regions for the research origins of published mechanical characterization of bamboo poles are listed along with the number of articles, total citations, average publication year, average citations, and average norm citations.

Fig. 2. Network visualization of co-occurrence of keyword analysis

Table 4. Countries or Regions of Mechanical Characterization of Malaysian Bamboo Poles

Malaysia has the largest representation, with the highest number of articles and total citations. This is followed by the Philippines and Indonesia with the same score of 5 number of articles but the different number of citations, 96 and 5 citations, respectively. The distribution of countries shows that the studies related to the mechanical characterization of bamboo poles of that specified species still are lacking in research and are not expanding. This also has been mentioned by Awalluddin et al. (2017) that one of the factors that contributes to low utilization of bamboo properties is a low number of relevant studies by the researchers. Most of the countries that encourage research in the field are within the Southeast Asia region, although it is worth noting that Germany stands out as one of the European countries that has shown interest in exploring technical data of the mechanical properties of bamboo pole, specifically for the aforementioned bamboo species.

Content Analysis Result

Physical characterization (age, height, moisture content, grading properties)

Based on the reviewed sources, Dendrocalamus asper is the tallest bamboo (17.3 m). Gigantochloa scortechinii is 15.3 m shorter. Gigantochloa levis is the shortest, at 8.9 m. The three bamboo species have a wider error bar, indicating a faulty data distribution. Age and location affect bamboo height. Table 5 displays bamboo height at various ages. The researchers revealed that Gigantochloa scortechinii grows to 11.5 m, 12.3 m, and 13.9 m in age. Other bamboo investigations supported the conclusion (Wahab et al. 2010; Nordahlia et al. 2019). This shows that bamboo species height controls bamboo maturity. A four-year-old bamboo was reported at 25 m in Selangor, Malaysia, and 22.5 m in Bukidnon, Philippines. This shows that soil type impacted bamboo height. The average height of the three bamboo species varied greatly. Dendrocalamus asper had the thickest bamboo at 12.4 mm. This was followed by Gigantochloa levis (11.6 mm) and Gigantochloa scortechinii (8.1 mm). A low error bar for bamboo species is shown in Fig. 3a. This indicates that the data distribution is not precise. Location influenced bamboo thickness variation. Dendrocalamus asper is 16 mm thick in Selangor and 18.5 mm thick in Bukidnon. Dendrocalamus asper thickness was 11.5 mm at three years, 18.5 mm at four years, and 10.4 mm at seven years (Aguinsatan et al. 2019; Da Silva et al. 2019; Kadivar et al. 2019).

Fig. 3. Average of the physical characterization of three bamboo species

Table 5. Age, Height, Thickness, and Diameter of the Three Bamboo Species by Target Journals