Kajian Indeks Kerusakan pada Struktur Bangunan Baja Berdasarkan Pendekatan Energi Akibat Gempa Kuat

Abstract

Every structure which is made from any materials has mechanic strength limitation. This is explained by many theories as it is described in the graph of stressdeformation that material will fall down because its load has exceeded its strength limitation. It is known that during a structure serving age, the structure undergoes damage such as it is caused by earthquake. These damages bring about the change in the nature of the structural system, and the use of damage index enables the quantity of damage. Drift or inter-story drift is generally used as the criteria for finding out the structure behavior which has caused by earthquake. However, some researches have found that the cumulative plastic deformation has more significant influence than drift or inter-story drift in the level of structural damage. The cumulative plastic deformation can be considered through the concept of energy, especially through plastic dissipation hysteresis energy demand. This thesis analyzed damage index, based on energy in which there were two equations were used: Bozórquez equation and Cosenza equation. There were three types of structure model: SMRF 4, SMRF 7, and SMRF 10. These three structures would be analyzed in four earthquakes in which the earthquakes were scaled against planned earthquakes, according to earthquake mapping in Indonesia in 2010. The result of the research showed that damage index was directly correlated with incoming energy on structure. The biggest value of damage index for Bozórquez equation in SMRF 4 was 0.147 (lightly damaged), in SMRF 7 was 0.079 (lightly damaged), and in SMRF 10 was 0.154 (lightly damaged). The three structures were affected by Kobe earthquake. For Cosenza equation, in SMRF 4 was 0.170 (lightly damaged), in SMRF 7 was 0.176 (lightly damaged), and in SMRF10 was 0.260 (moderately damaged). The three structures were affected by Kobe earthquake.

Setiap struktur yang terbuat dari material apapun memiliki batas kekuatan mekanik. Hal ini dijelaskan oleh berbagai teori, dimana digambarkan dalam grafik stress-deformation bahwa material akan runtuh akibat pemberian beban yang melebihi kekuatan batasnya. Diketahui selama umur layan bangunan, struktur mengalami kerusakan, seperti yang diakibatkan oleh beban gempa. Kerusakankerusakan ini mengakibatkan perubahan dalam sifat-sifat dari sistem struktur. penggunaan indeks kerusakan memungkinkan kuantifikasi kerusakan. Drift atau Inter-story drift secara umum digunakan sebagai kriteria untuk melihat perilaku struktur akibat gempa. Namun, beberapa penelitian menyatakan bahwa kumulatif deformasi plastis lebih kuat pengaruhnya dibandingkan dengan drift dan inter-story drift dalam tingkat kerusakan struktur. Kumulatif deformasi plastis dapat dipertimbangkan melalui konsep energi, khususnya melalui plastis dissipasi histeresis energi demand. Dalam tesis ini akan dibahas indeks kerusakan berdasarkan energi, dimana ada dua persamaan yang digunakan yaitu persamaan Boz rquez dan Cosenza. Model bangunan yang digunakan ada 3 jenis yaitu SMRF 4, SMRF 7, dan SMRF 10. Ketiga bangunan ini akan di analisa terhadap 4 gempa, dimana gempa-gempa tersebut diskalakan terhadap gempa rencana yang sesuai dengan peta gempa Indonesia 2010. Dari penelitian yang dilakukan, dapat dilihat bahwa indeks kerusakan berhubungan langsung dengan enegi masuk terhadap struktur. Nilai indeks kerusakan terbesar untuk persamaan Boz rquez pada SMRF 4 sebesar 0.147 (rusak ringan), SMRF 7 sebesar 0.079 (rusak ringan), dan SMRF 10 sebesar 0.154 (rusak ringan), ketiga bangunan tersebut dipengaruhi oleh gempa Kobe. Untuk persamaan Cosenza, pada SMRF 4 sebesar 0.170 (rusak ringan), SMRF 7 sebesar 0.176 (rusak ringan), dan SMRF 10 sebesar 0.260 (rusak sedang), ketiganya diakibatkan oleh gempa Kobe.