BASE ISOLATION in TRADITIONAL BUILDING LESSON LEARNED from NIAS MARCH 28, 2005 EARTHQUAKE
While modern buildings in Nias collapsed due to the March 28, 2005 strong earthquake (8.7 on Richter scale), the traditional northern Nias house (omo hada) survived without any damage. Omo hada has an oval plan with a raised platform consisting of wooden beam and plank supported by a complex arrangement of posts (ehomo) and x type bracing (diwa). The posts are not fixed on the ground, but rest on top of stone foundations. This kind of friction type support is also evident in other traditional houses in Indonesia. In this study, the behaviour of omo hada under spectrum consistent ground acceleration is studied. The supports of the traditional house are modeled as coulomb friction model and fixed support. Results of analysis show that the friction type support acts as base isolation. The presence of sliding at the friction type support significantly reduces the internal forces in the structure.