THE ADAPTABILITY OF FORM, STRUCTURE, AND MATERIAL OF UMA PANGGU IN BIMA REGENCY IN THE CONTEXT OF LOCAL SEISMIC CULTURE

• Main Author: Dwi Hariyanto, Agus
• Format: Dissertations
• Language: Indonesia
• Subjects: Arsitektur
• Online Access: https://digilib.itb.ac.id/gdl/view/62262
• Institution: Institut Teknologi Bandung

Bima Regency is an earthquake-prone area because it is located on Sumbawa Island, flanked by two earthquake fault lines in the north and south of the island. In addition, there are two active volcanoes, namely Mount Tambora and Sangeang. So, tectonic and volcanic earthquakes can be a disaster threat in the region. A study on the adaptability of Bima's vernacular architecture to its earthquake-prone environment is needed to develop knowledge about the factors that support the adaptability of uma panggu in the context of local seismic culture. The aims of this research are: (1) to find out the characteristics of the shape, structure, and material of the uma panggu in the context of local seismic culture; (2) to prove the effectiveness of traditional techniques on the uma panggu structure in supporting the performance of the structure against earthquakes; (3) to get the adaptability pattern by formulating the causal relationship between form and material factors with the structure's performance. This mix-method research was carried out in three stages. The first is qualitative research using a case study approach. Experimental quantitative research is applied for the second stage. Then the third is quantitative, using a correlational approach. Field observation is used in the first stage to identify the character of uma panggu in terms of form, structure, and material. Furthermore, some local wood is tested for strength and durability. Experimental modeling using digital simulation was carried out in the second phase to determine the effectiveness of traditional techniques. Statistical analysis was carried out in the third stage to determine the causal relationship between the shape and material of the uma panggu with the structure's performance against earthquakes. The results of the analysis are formulated to determine the pattern of adaptability. Factors that support the seismic adaptability of the uma panggu, namely: (1) the characteristics of the form and structure; (2) the quality of the wood material used as needed; (3) structural layout with minimal eccentricity; (4) synergies between components in the structure through the application of the ceko technique and the friction foundation technique; (5) The significance of the causal relationship between form, material, and structural performance. The first to fourth factors support the integration of form, material, and structure in the existence of local seismic culture. The fifth factor supports integration in the causal relationship between the form, material, and structure. The uma panggu’s characteristics of form and structure are adaptive to the seismic-prone area. The floor plan has a simple basic shape, making it more stable during an earthquake. The wall with a knock-down system supports the flexibility of the post during an earthquake. The synergy between components occurs in stage structures that have consistent structures and constructions. Using wooden pegs in the connection between the stilt structure components allows energy dissipation during an earthquake. The quality of wood materials is utilized according to structural and non-structural functions, even for the wooden pegs as a minor structural element. The wooden peg use supa wood (Caesalpinia sappan) and luhu wood (Schoutenia ovata). The specific gravity, flexural strength, and shear strength of the two kinds of wood are almost equivalent to teakwood (Tectona grandis), but their modulus of elasticity is much lower. This property is advantageous because the post is not easily broken and is ductile. The dimensional stability of supa wood in the tangential and radial directions is better than luhu wood. Its resistance to termites is also better than luhu wood. Supa wood is classified as durable class I against subterranean termites (Coptotermes Curvignathus Holmgren) and dry-wood termites (Cryptotermes Cynocephalus Light). Luhu wood is classified as durable class III for subterranean termite attack and durable class I for dry-wood termite attack. This finding strengthens the evidence that local seismic culture in wood selection still exists and is sustainable. The structural layout of uma panggu has minimal eccentricity. Small-scale eccentricity occurs in the Y-axis direction, which is dominant in the 16-post model. The synergy between the components in the stilt structure is proven to exist. The diagonal bar (ceko) is effective and significant in reducing deformation and stress. In addition, the average maximum stress in the existing model does not exceed the allowable stress for wood quality category A with strength class II. The foundation with friction support applies a seismic isolation system to be more adaptive and effectively reduce internal stresses compared to the fixed support. So, the pile foundation placed on a flat stone effectively supports the structure's performance during an earthquake. A significant causality relationship forms an integrated pattern of forms, materials, and structures that support the seismic adaptability of uma panggu. The building size of uma panggu is correlated with the number of pillars because the distances between the pillars tend to be the same. So, the more the number of pillars, the more mass the weight increases, so the buildings are more susceptible to earthquake forces. On the other hand, the smaller the number of piles, the lighter the mass, the higher the seismic adaptability. The taller the uma panggu building, the more vulnerable it is to earthquakes. On the other hand, the lower the building, the more adaptive it is. This research contributes to knowledge of local seismic culture from the aspect of form, material, and structure of wooden houses on stilts in Indonesia. In addition, this study has succeeded in proposing a prediction model for the level of seismic adaptability in uma panggu in a software called PAdLe-UP.