Summary
Computational modeling, in addition to data analytics, plays an important role in structural health monitoring (SHM). The high‐fidelity computational model based on the design and construction information provide important dynamics information of the structure and, more importantly, can be updated against field measurements for SHM purposes such as damage detection, response prediction, and reliability assessment. In this paper, we present a unique skyscraper (Al‐Hamra Tower) located in Kuwait City and its high‐fidelity computational model using ETABS for structural health monitoring applications. The tower is made of cast‐in‐place reinforced concrete with a core of shear walls and two curved shear walls running the height of the building (approximately 413 m with 86 floors in total). Interesting static and dynamic characteristics of the tower are described. System identification, interferometry‐based wave propagation analysis, and wave‐based damage detection are performed using synthetic data. This work mainly presents the phase of numerical investigations, which serves as a basis for correlating the field monitoring data to the model of the building in future work.
Portland cement emits bright near-infrared photoluminescence that can be excited by light wavelengths ranging from at least 500–1000 nm. The emission has a peak wavelength near 1140 nm and a width of approximately 30 nm. Its source is suggested to be small particles of silicon associated with calcium silicate phases. The luminescence peak wavelength appears independent of the cement hydration state, aggregates, and mechanical strain but increases weakly with increasing temperature. It varies slightly with the type of cement, suggesting a new non-contact method for identifying cement formulations. After a thin opaque coating is applied to a cement or concrete surface, subsequent formation of microcracks exposes the substrate’s near-infrared emission, revealing the fracture locations, pattern, and progression. This damage would escape detection in normal imaging inspections. Near-infrared luminescence imaging may therefore provide a new tool for non-destructive testing of cement-based structures.
The response of a 413-meter-tall building to the 12 November, 2017, Mw 7.3 earthquake 642km from the building is measured with a GPS receiver located near the top of the building and operating with a 1 Hz sampling rate. Nearby GPS and seismic stations measure the ground motion near the building. The ground motions have amplitudes of ~40 mm while the top of the building moves by up to 160 mm. The building motion continues with levels greater than the noise level of the GPS measurement for about 15 minutes after the earthquake. After the ground motion excitation ends, the building motion decays with a time constant of ~2 minutes and the beat between the two lowest frequency modes of deformation of the building can be seen. There are two large amplitude peaks in the building motion with magnitudes of 120 and 160 mm. The timing of the peaks is consistent with ground excitation in a 8.3-6.5 second period (120-180 mHz) band which covers the 7.25 and 5.81 second periods (138 and 172 mHz frequencies) of the fundamental modes of the building. The ground motions in this band show two large pulses of the excitation which have timing consistent with the large amplitude building signals. The response of the top of the building is amplified by an order magnitude over the ground motions in this band. There is no apparent permanent displacement of the top of the tower.
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