Vibration-based temporary monitoring of a 253 m tall skew-plan building in Istanbul

Abstract

A 253 m tall office building in Istanbul with a parallelogram footprint, which has 62 stories in total, 54 tower stories above and 8 podium stories below grade, was monitored using 92 channels of accelerometers deployed on 20 different floors for about 4 days. The structural system of the building consists of reinforced concrete (RC) core shear walls with peripheral composite columns and two-story tall RC outriggers between floors 29 and 31. First 12 natural vibration periods and mode shapes of the building together with the modal directions for the translational modes were identified from the ambient vibration records. These dynamic properties were reproduced with the three-dimensional finite element model developed using gross section properties for all structural members without a need for model updating. The fundamental period of the building at the time of testing, 5.3 s, is expected to lengthen to 5.9 s and 7.8 s upon cracking in structural members for the prescribed service-level and design-level evaluations, respectively, in line with the recent performance-based design guidelines for tall buildings. Damping ratios for the first six vibration modes, with median values of 0.6% and coefficients of variation in the order of 0.3–0.4, were identified through statistical analysis using the random decrement technique. The simulated peak floor accelerations, when the building was subjected to the 2019 Mw 5.8 Marmara Sea earthquake ground motions recorded in the vicinity of the building, showed that ASCE 7-16 in-structure floor acceleration amplifications are exceeded at the lower floors but not reached at the upper floors.