Pembentukan tanah tempatan adalah salah satu faktor yang mempengaruhi kerosakan seismik terhadap bangunan. Gerakan tanah berbeza di lokasi yang berlainan mengikut keadaan tanah setempat. Pelbagai kerosakan diperhatikan selepas gempa bumi Sabah bermagnitud 6.0 melanda Ranau pada tahun 2015. Kesan struktur tanah terhadap kerosakan struktur masih belum disiasat. Oleh itu, pengukuran mikrogegaran tatasusunan dan titik tunggal telah dijalankan untuk menganggar struktur tanah di SMK Ranau dan Hospital Ranau. Kesan struktur tanah terhadap sambutan struktur bangunan di tapak telah dinilai. Struktur tanah kedua-dua tapak tersebut dianggarkan menggunakan kaedah Autokorelasi Ruangan (SPAC) untuk SMK Ranau dan kaedah keelipsan gelombang Rayleigh untuk Hospital Ranau. Struktur tanah SMK Ranau dan Hospital Ranau telah dianggarkan dan masing-masing dikelaskan sebagai tanah jenis B dan C. Struktur tanah yang dianggarkan kemudiannya diubahsuai kepada jenis tanah lain dan sambutan tanah bagi setiap jenis tanah dianalisis dengan menggunakan Analisis Sambutan Gempa Bumi Lelurus Setara (EERA). Tanah jenis B, C dan D dibandingkan dari segi pecutan permukaan tanah dan hasilnya menunjukkan bahawa tanah jenis D memberikan sambutan tanah dan faktor amplifikasi tanah tertinggi kerana ia menunjukkan pecutan permukaan tanah puncak terbesar, diikuti oleh tanah jenis C dan B. Bagi sambutan struktur yang disimulasikan oleh STERA 3D, hanyutan tingkat maksimum, anjakan tingkat maksimum, daya ricih tingkat maksimum dan ricih dasar-hanyutan atas digunakan untuk menyiasat sambutan struktur bangunan di atas struktur tanah yang berbeza. Di SMK Ranau, tanah jenis D memberi sambutan struktur terbesar, diikuti dengan tanah jenis C dan B. Kerosakan stuktur yang lebih teruk adalah dijangkakan jika bangunan ini berada di atas tanah jenis C atau D. Bagi Hospital Ranau, kecuali untuk anjakan tingkat maksimum yang terbesar untuk tanah jenis D, sambutan struktur lain menunjukkan tanah jenis C memberikan impak terbesar, diikuti dengan tanah jenis D dan sambutan terendah diberikan oleh tanah jenis B. Kerosakan Hospital Ranau adalah dipengaruhi oleh penguatan tapak terhadap gerakan bumi.
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Local soil formation is one of the factors that affect the seismic damage of building. Ground motion varies in different locations according to the local ground condition. Various extents of structural damages were observed after a 6.0 magnitude Sabah earthquake hit Ranau in 2015. The effect of ground structure to structural damage has not been investigated. Therefore, microtremor array and single point measurement were conducted to estimate the ground structure at SMK Ranau and Hospital Ranau. The impact of ground structure to structural response of buildings at the site was evaluated. The ground structures of both sites were estimated using Spatial Autocorrelation (SPAC) method for SMK Ranau and Rayleigh wave ellipticity method for Hospital Ranau. Ground structures of SMK Ranau and Hospital Ranau were estimated and classified as ground types B and C, respectively. The estimated ground structures were then modified to other ground types and the ground response of each ground type was analysed using Equivalent-linear Earthquake Response Analysis (EERA). Ground types B, C and D were compared in term of ground surface acceleration and results shows that ground type D gave the largest ground response and amplification factor as it showed the largest peak ground surface acceleration, followed by ground types C and B. For structural response simulated by STERA 3D software, the maximum storey drift, maximum storey displacement, maximum storey shear force and the base shear-top drift were used to investigate the structural response of building on different ground structures. In SMK Ranau, ground type D gave the largest structural responses, followed by ground types C and B. It is expected that more severe damage could happen if the building is located on ground types C and D. For Hospital Ranau, except for the maximum storey displacement which shows the largest for ground type D, the other structural responses show that ground type C gave the largest impact, followed by ground type D and the least response is given by ground type B. The damage of Hospital Ranau is influenced by the site amplification of ground motion.
Estimation of ground structure and its impact on structural damage of building / Tng Kah Lok