Confined masonry construction has been practiced in Indonesia since before the December 26, 2004, Great Sumatra earthquake and the Indian Ocean tsunami (magnitude around 9.0) (EERI, 2006a).
In the town of Banda Aceh, Sumatra, Indonesia, located 240 km away from the earthquake epicenter, confined masonry buildings constituted around 70% of the housing stock. These buildings were one-to-two-storeys high, built with brick masonry walls, tie-columns and tie-beams (also known as “practical columns” and “practical beams” in Indonesia), and covered by CGI sheet roofs. Since these buildings were non-engineered, the provision of reinforcement in confining elements was made on an empirical basis. According to Boen (2005), buildings of this type did not collapse due to the earthquake shaking (although some damage in the walls was observed) – most of the damage was caused by the subsequent tsunami.
Although the traditional post-and-beam timber construction has a good performance record in the past earthquakes, confined masonry seems to be the construction technology of choice for more prosperous communities and those of a higher social status (Meisl et al. 2006). Confined masonry buildings were also subjected to the March 28, 2005, Northern Sumatra earthquake of magnitude 8.7 (EERI, 2005). Buildings of this type were used for housing, schools, and community health centres. These buildings survived the shaking without collapse, although some cracking in the walls was observed. Cross-sectional dimensions for typical tie-columns were 120 mm by 120 mm with four 8 mm bars and 6 mm stirrups at 200 mm spacing (Boen, 2006). Confined masonry construction was exposed to the May 27, 2006 Central Java earthquake (magnitude 6.3). Some confined masonry houses remained undamaged on the edge of heavily damaged Pleret. Damage was observed due to the absence of connections between the tie-beams and tie-columns,(Build Change, 2007). Confined masonry construction was also affected by the September 12 and 13, 2007, Bengkulu earthquakes in Indonesia (EERI, 2007 a). The epicentre was off Sumatra island and the magnitudes were 8.4 and 7.9 respectively. Confined masonry was widely used for housing construction in the affected area. The walls were built of clay brick masonry and the confinement was provided by timber or RC tie-columns and tie-beams. Causes of damage in confined masonry construction were: inadequate connections between confining elements; poor quality of workmanship related to masonry construction; excessive openings resulting in out-of-plane failures; and slender walls leading to out-of-plane failure (typically 130 mm thick and over 3 m high in some cases). Overall, the performance of confined masonry construction in these earthquakes points out to the importance of construction quality and detailing of connections between the confining elements.
Guidelines, Codes, and Standards
- Build Change Construction Manual Constructing Seismically Resistant Masonry Houses (Boen)
- Build Change Construction Checklist
- Build Change Design Calculations
- Case Study: Design and Construction of Confined Masonry Homes in Indonesia, Tim Hart, J. Pazdon, L. Blaisdell, E. Hausler Strand, Paper #694
- From Brzev, Svetlana. Earthquake-Resistant Confined Masonry Construction. 2nd ed. Kanpur: NICEE, 2007. Print. EERI (2006a).
- Special Issue on the Great Sumatra Earthquakes and Indian Ocean Tsunamis of 26 December 2004 and 28 March 2005.
- Earthquake Spectra, Vol. 22, No S3, June 2006. Boen, T. (2005).
- Sumatra Earthquake 26 Dec 2004. Earthquake Engineering Research Institute, Oakland, California (www.eeri.org) Meisl, CS., Safaie, S., Elwood, KJ., Gupta, R., and Kowsari, R. (2006).
- Housing Reconstruction in Northern Sumatra after the December 2004 Great Sumatra Earthquake and Tsunami. Special Issue on the Great Sumatra Earthquakes and Indian Ocean Tsunamis of 26 December 2004 and 28 March 2005, Earthquake Spectra,Vol. 22, No SS, pp. 777-802. EERI (2005).
- The Northern Sumatra Earthquake of March 28, 2005. EERI Special Earthquake Report. Newsletter. Earthquake Engineering Research Institute, California, August 2005. Boen, T. (2006).
- Structural Damage in the March 2005 Nias-Simeulue Earthquake. Special Issue on the Great Sumatra Earthquakes and Indian Ocean Tsunamis of 26 December 2004 and 28 March 2005, Earthquake Spectra, Vol. 22, No S3, pp. S419-S434. Build Change (2007).
- Central Java Earthquake 27 May 2006. PowerPoint presentation (unpublished). EERI (2007a). Observations from the Southern Sumatra Earthquakes of September 12-13, 2007. EERI Special Earthquake Report. Newsletter. Earthquake Engineering Research Institute, Oakland, California, November 2007.