The use of materials such as the Guadua cane is of particular interest in present days since it can be used as a main construction material of social housing, replacing reinforced concrete (RC) and structural steel (SS). Both of these have been widely used for their high strength, availability, and our understanding of their mechanical properties and performance. Extensive literature studies reporting the behavior of RC and SS, stressing their good performance, can be found (Betancourt Rodríguez, 2017), which has led to pertinent comprehensive design standards. However, a major disadvantage of concrete and steel is the environmental impact of their production and use. This has motivated scholars to investigate alternative construction materials that have a lower carbon footprint. An example of such a material is bamboo, which is naturally available in continents such as Asia, Africa, America, and Oceania (Manandhar et al., 2019), with more than 25 species used in construction (Scurlock et al., 2000; Benton, 2015). Bamboo is lighter than concrete, with a high strength-to-mass ratio (Blankendaal et al., 2014). Moreover, it is a low-cost material and a natural resource that can form ready-to-use structural members, resulting in a reduced carbon footprint compared to its traditional counterparts (González and Gutiérrez, 2005).

The construction industry plays a significant role in the worldwide economy, thus requiring a substantial quantity of materials, whose production imposes a high toll on the environment (Koca, 2019). For instance, in the United States, the construction sector is responsible for 41% of the total energy consumption and 38% of the total gas emissions (Basbagill et al., 2013). Furthermore, the 2018 global report on the construction industry showed that buildings are responsible for 36% of the global resource and energy consumption and 39% of the worldwide gas emissions (Morsi et al., 2022).

The adoption of alternative materials such as bamboo at a larger scale shows potential to help mitigate environmental impacts produced by the construction industry. The principal environmental cost of the Guadua cane lies in transporting it (Van der Lugt et al., 2006). For example, maritime transport of Guadua accounts for an environmental impact of 92.9 mPt (millipoints) per kg Guadua, and processing, preservation, and ground transportation of Guadua have impacts of 3.2, 1.6, and 6.5 mPt per kg of Guadua, respectively (Van der Lugt et al., 2006). Therefore, bamboo can be 20 times more favorable to the environment than alternative materials such as concrete or steel, in addition to being less expensive, even when it is not readily available and needs to be imported (Van der Lugt et al., 2006). Furthermore, a study on the life cycle assessment (LCA) of bamboo buildings indicates low environmental impact (30 kg CO₂Eq/m²) for both single-story and multi-story buildings, as opposed to concrete or brick buildings (240 kg CO₂Eq/m²) (Escamilla et al., 2018). Additionally, in some exceptional cases, such as those of short transport distances, Guadua structures can even have a negative carbon footprint (i.e., reduction of CO₂ in the atmosphere) (Escamilla et al., 2018).

An encouraging symptom of the feasibility of bamboo as a structural solution is its ubiquitous use in traditional architecture in areas where it is endemic and abundant. Good examples are bahareque structural systems, which are common in the traditional architecture of many Latin American countries, such as Ecuador and Colombia. Bahareque, or cement–bamboo frame systems, are walls made from bamboo and plaster, which have been adopted for centuries as solutions for low-rise buildings, although their use in construction has been mostly empirical (Alzate and Osorio, 2014).

A recent survey focused on social housing projects in the city of Cuenca, Ecuador, Palacios, and Angumba showed that within a sample of construction professionals of the city, 46% have built houses using the bahareque technique and 84% of the surveyed professionals think that the adoption of bahareque systems for housing of social interest is a feasible alternative because its construction is less time-consuming than that of concrete structures, and based on the performance of historical buildings that use similar construction techniques, the lifespan of bahareque structures can be as long as that of concrete structures (Palacios and Angumba, 2021).

Kakkad compared three structural solutions for a school in India: bahareque (locally known as Ikra), a reinforced brick masonry system, and a confined brick masonry system. The study evaluated the seismic strength and stress via finite element analysis and showed that the seismic strength of the bahareque option was 11.7% higher than that of the confined masonry option and 13% higher than that of the reinforced masonry option (Kakkad, 2011). This study suggests that the higher seismic performance of bahareque could be attributed to its ductility, flexibility, and lightweight.

Similarly, Varum et al. studied the seismic behavior of buildings in Nepal after the Gorkha earthquake, concluding that, despite the fact that constructions with materials such as adobe, bamboo, or wood are scarce in this region, they were found to be the least damaged when compared to reinforced concrete buildings, which sustained severe damage in many cases (Varum et al., 2018).

Mite et al. evaluated a two-story housing solution of social interest built using bahareque, considering particularly the Ecuadorian design regulations. The structure was subjected to a nonlinear time history analysis to evaluate its seismic behavior under 10 different seismic records. The study showed that, for houses of two or fewer stories using structural panels with Guadua canes as diagonals, they did not exceed their maximum resistance and presented deformations that compromised neither the structure nor the nonstructural components (Mite et al., 2022).

In this paper, an evaluation of the performance of a two-story bahareque house, compared to a similar structure made of RC, is studied. The selected structure is a single-family, two-story house of social interest, designed according to the Ecuadorian standard and following international guidelines established in standards such as ACI 318-19, ASCE 7-16, IBC 2018, ASCE 41, and FEMA P58. We compare these two structural solutions in terms of seismic performance, cost, and environmental impact by conducting a nonlinear static analysis (pushover) and a life cycle assessment. Ultimately, the study aims to encourage the adoption of bahareque as a sustainable and sound structural solution by disproving the widespread notion that it is of inferior performance and mechanical characteristics compared to concrete.

The considered structure is an existing two-story house located in Guayaquil, Ecuador. The structure’s plan geometry and 3D view are presented in Figures 1, 2, respectively. The first-floor level is at 2.43 m height, and the roof level is at 4.75 m height. A 3D model of the building in the structural analysis software program ETABS (CSI, 2019) is also developed here. The seismic demands are considered according to the Ecuadorian seismic structural code (NEC-SE-DS, 2014). The applied gravitational loads comply with the Ecuadorian construction code (NEC-SE-CG, 2015) and include live loads (the dwelling house load is 2 kN/m², and the roof live load is 0.7 kN/m²). The dead loads are described in Table 1.

First, a spectral analysis was performed for the design of the structural elements. Then, using the design information obtained in the nonlinear static analysis, the equivalent linearization method was adopted, as follows in FEMA-440, 2005. Two cases are examined; in the first, the structure is made of reinforced concrete (RC), and in the second, the same structure is built using the bahareque structural system.

The performance levels of the RC framed and bahareque systems are determined from the performance seismic levels, according to (Vision, 2000), which are shown in Figure 3. The performance points obtained from the nonlinear static analysis are compared in the capacity curve of each model. In addition, the performance level due to the rare earthquake is determined by placing the performance points on both capacity curves, which are divided into sections based on the roof displacement. In this study, the objective is to compare the rare earthquake and the performance point with the building performance level recommended by Vision, 2000. Since this is a residential-type building, it would be expected that, for the aforementioned earthquake, the performance level would not exceed the life safety level.

With respect to the seismic performance, the inter-story drift is the main parameter to relate the lateral stiffness of both systems. Additionally, inter-story drift could be directly related to the damage of nonstructural elements and repair costs. The structural weight is also related to the seismic lateral force. The results of these parameters are shown in Table 10.

The results presented show that in the short direction (X), the reinforced concrete framed system has a smaller inter-story drift. However, in the long direction (Y), the inter-story drift is smaller on the bahareque system. This is due to the diagonal bamboo elements, which could be an advantage of the bahareque system over the RC system since it is easier to put a diagonal element with bamboo. Diagonal elements increase the lateral stiffness of the bahareque system and improve its response. In addition, the fact that RC is greater in one direction while the bahareque option is more similar in both directions points to a better torsional response (i.e., a more equilibrated stiffness distribution among the two perpendicular directions). The leftover in both cases was the increase in stiffness generated by the nonstructural walls in the structure considered.

The performance levels are evaluated for both cases. For the case of the RC framed system, the results are shown in Figure 11. The earthquake used for this analysis is the 475-year return period (or 10 percent probability of exceedance in 50 years) event. This house is considered an ordinary building, according to Vision, 2000, and this type of structure should be at least within the life safety performance level. The results suggest that this structure complies with the functional performance-based seismic level.

As shown in Figure 12, the seismic performance level is located within the operational zone, which means that this structure complies with the recommendations of Vision, 2000. Thus, results suggest that the bahareque system shows a better seismic performance level than the RC framed system.

A cost comparison between the RC frame and the bahareque house, according to Ecuadorian costs, reveals that for an RC house, which is the most common system used in Ecuador, the total direct cost of the project is US$ 12,045.44, whereas for the case of the bahareque house, the cost reaches US$ 7,660.06. These results clearly show that a bahareque house is approximately 36% cheaper than a traditional RC house.

The displacement in the top vs base shear of three structures is presented in Figure 13. The first structure consists of a timber shear wall that obtained a maximum base shear of 43 kN and an approximate displacement of 160 mm (Bedon et al., 2015), while the other two structures consist of walls made of bamboo frames and diagonals with the difference that our structure consists of two floors, and the third one consists in a vernacular construction of a single floor supporting a roof (Sharma, 2010). The maximum base shears are 17 kN and 4 kN, and displacements are 200 and 150 mm, respectively. In the first case, since the wall is made entirely of wood logs, it has the behavior of a shear wall, so it can withstand greater lateral forces with less displacement, while in the other two, their resistant structures are made of bamboo frames and bracing that lighten the weight of the structure. Therefore, they receive lower lateral forces with higher displacements.

This study evaluates the bahareque technique as an alternative, sustainable structural solution. Specifically, the study determines the seismic performance of a two-story social housing structure made of reinforced concrete and compares it with the corresponding performance of a similar structure made of Guadua canes, following the bahareque technique. To that end, the study adopts the nonlinear static (pushover). Additionally, the study performs a life cycle analysis of both structures to determine their environmental impacts.

The nonlinear static analysis yielded the following results: for the reinforced concrete house, a displacement of 63 mm with a base shear force of 304 kN, showing a performance level of life safety, which suggests that there will be structural damage that does not compromise the stability of the structure, safeguarding the life of the occupants, while damage to nonstructural elements such as masonry is expected. For the bahareque house, a displacement of 38 mm due to a force of 7.85 kN was observed. In this case, it is expected that there will be no damage to the main structure or to any nonstructural elements, demonstrating one of the advantages of these structures, which, being lightweight, receive a lower seismic load and also have the capacity to release energy.

The components of the main structure were considered for a life cycle assessment and were analyzed from the following viewpoints: manufacture, transportation of the material to the construction site, quantities of materials, and the design period. The results showed that the reinforced concrete house has a greater amount of embodied carbon, while the Guadua house obtained an A++ rating, certifying that it is an ecological building and that the structural element that showed the greatest environmental impact was its foundation, which is made of RC.

With regard to the budget, all items were considered, corresponding to the construction of the main structure of the designed homes. The result implies that a house of bahareque is 40% less expensive than a house of concrete and that its construction time is approximately half. This would imply savings in labor and a much more efficient start-up.

This research has analyzed one of the most widely used materials in the South American region due to its ancestral applications in construction, which is currently one of the main inputs for the construction of any type of building. However, its potential has not been considered for the construction of low-cost social housing that needs to provide all the necessary services to ensure habitability. As a future direction of research, a parametric analysis is proposed where the mechanical properties of other bamboo specimens existing in the world are considered.