Parametric Analysis of the Effect of Concrete Quality on the Seismic Deflection Response of Low, Mid, and High-Rise Reinforced Concrete Buildings Based on SNI 1726:2019

This study aims to parametrically analyse the effect of concrete quality variations on the seismic response of reinforced concrete buildings in the low, medium and high categories, referring to SNI 1726:2019. The high seismic activity in Indonesia demands an in-depth understanding of the behaviour of structures in earthquakes, particularly with respect to deformation. This study quantitatively investigates the impact of five concrete grade variations (fc' 20, 25, 30, 35, and 40 MPa) on the maximum lateral deviation of the roof, the maximum inter-storey deviation ratio (IDR) and its location, and the IDR distribution profile. The research methodology involves response spectrum analysis on 15 three-dimensional building models (3, 6, and 12 storeys) using ETABS software. To maintain consistency, typical plans and dimensions of structural elements were kept constant across model heights, so that the influence of concrete grade could be isolated. The results show that increasing the concrete grade from 20 MPa to 40 MPa consistently increases the stiffness of the structure, which is characterised by a decrease in the fundamental natural vibrating period by about 15.9%. Consequently, there is a reduction in the maximum lateral deviation of the roof between 26.2% and 29.3% and a decrease in the maximum IDR between 18.8% and 21.3%. Building height affects the deformation pattern, with the maximum IDR occurring at the top floor in low-rise buildings, and shifting to the mid-high floors in medium and high-rise buildings. Although an increase in concrete quality is effective in reducing deformations, for the Banyumas (KDS D, SRPMK) seismic configuration and conditions analysed, an increase in fc' up to 40 MPa is often not sufficient to meet the SNI 1726:2019 permissible IDR limit, especially in low- and medium-rise buildings.