Dynamic characteristics and seismic performance of reinforced concrete buildings experiencing 5 June 2015 and 8 March 2018 Sabah earthquakes
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Date
2019-06
Authors
Ho Kar Meng
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Abstract
Staff quarters of S.M.K. Ranau and officer quarters of Hospital Ranau that were
damaged during a Sabah earthquake with a magnitude of 6.0 on 5 June 2015 were
repaired in 2016. However, an earthquake with a magnitude of 5.2 struck Ranau, Sabah
again on 8 March 2018, thus it is unknown for the present condition of both buildings.
This dissertation presents the results on dynamic characteristics of these buildings
experiencing both Sabah earthquake events based on microtremor observations in
January 2016, April 2017 and November 2018. The modal frequencies and vibration
mode shapes of the buildings were determined by using the Nakamura method and Time
Domain Decomposition method, respectively. Due to the absence of the study on
dynamic characteristics of both buildings before 2015 Sabah earthquake, computational
analyses were performed using ETABS based on the architectural plan and on-site
measurement in order to simulate the building condition before the earthquake. The
results show that the fundamental frequencies for staff quarters of S.M.K. Ranau and
officer quarters of Hospital Ranau reduced up to 20 % after 2015 Sabah earthquake. This
reduction is significant and consistent with moderate damages suffered by both buildings.
For the case after 2018 Sabah earthquake, the fundamental frequencies of both buildings
reduced less than 2.5 %. This implies that both buildings may suffered very minor
damages during the earthquake. Seismic performances of both buildings under the design
load stipulated in Malaysia National Annex to MS EN 1998-1:2015 were obtained
through numerical simulation by using modal response spectrum analysis. Under the
design acceleration of 0.16 g, the maximum interstorey drift occurs at the first floor due
to soft storey effect. The maximum interstorey drift for the staff quarters of S.M.K. Ranau
exceeded the damage limitation as specified in Eurocode 8. The results also showed that
the column jacketing applied to staff quarters of S.M.K. Ranau during repair in 2016
increased the fundamental frequency and reduced the maximum storey displacement and interstorey drift, but this also increased the maximum storey shear force and overturning moment at the ground floor.