Fiber optics are increasingly being used in structural health monitoring applications. In addition to the well-known advantages, they most reliably transmit the stress–strain condition of the structure in the long term. This article presents the results of structural health monitoring on the embedding of fiber optics in the upper layer of the raft over the entire area of a high-rise building in Astana city (Kazakhstan), including the 75-storey 320 m block R. Temperature and strain data were collected constantly via a distributed fiber optic strain sensing system (DFOSS). The analysis of strains in fiber optic chainage indicated that the compression strains were observed over the entire area of the building, with values from −20 to −40 µε and with progression of the compression loaded up to −80 µε along the core wall closer to the eastern facade of the building. Tension strains were concentrated along the extreme axes of the building, with a predominance in the southern part of the R block, as well as in the immediate vicinity of the columns, in a range of −20 to −40 µε, with separate spots from −40 to −60 µε. Individual patches of tension strains near the columns have been explained by the increased deflection of the raft under the application of a concentrated load (columns). Fiber optic monitoring results at the time of testing did not exceed the permitted values for high-rise building operation; however, they characterized the general picture of the strain in the raft plane and made it possible to determine the initiation of cracks in concrete at an early stage.

Distributed fiber-optic sensing (DFOS) with intentionally spaced mechanical fixity points was experimentally evaluated for the structural health monitoring (SHM) of reinforced concrete (RC) members. A full-scale four-point bending test was conducted on a 12 m RC beam (400 × 400 mm) instrumented with a single-mode DFOS cable incorporating internal anchors at 2 m intervals and bonded externally with structural epoxy. Brillouin time-domain analysis (BOTDA) provided distributed strain measurements at approximately 0.5 m spatial resolution, with all cables calibrated to ±15,000 µε. Under stepwise monotonic loading, the system captured smooth, repeatable strain baselines and clearly resolved localized tensile peaks associated with crack initiation and propagation. Long-gauge averages exhibited a near-linear load–strain response (R² ≈ 0.99) consistent with discrete foil and vibrating-wire strain gauges. Even after cracking, the DFOS signal remained continuous, while some discrete sensors showed saturation or scatter. Temperature compensation via a parallel fiber ensured thermally stable interpretation during load holds. The fixed-point configuration mitigated local debonding effects and yielded unbiased long-gauge strain data suitable for assessing serviceability and differential settlement. Overall, the results confirm the suitability of fixed-point DFOS as a durable, SHM-ready sensing approach for RC foundation elements and as a dense data source for emerging digital-twin frameworks.

The structural monitoring of high-rise building foundations requires measurement systems that can register spatially distributed deformation and temperature effects during construction and at the early stage of service. This paper presents a field case study of a distributed fiber optic sensing (DFOS) system installed in the raft foundation of a high-rise building complex. The study is focused not on general crack detection, but on the practical commissioning of the sensing line, interpretation of initial measurements, and preparation of a reference dataset for subsequent long-term observation.The monitoring object is the raft foundation beneath Block R of Abu Dhabi Plaza in Astana, Kazakhstan. Measurements were obtained along the same horizontal sensing route using Brillouin Optical Time Domain Analysis (BOTDA). Two commissioning stages were compared in order to evaluate the repeatability of the installed system and to separate temporary con-struction-stage influences from the stable response of the foundation slab.The analysis showed that signal variability during the first measurement stage was mainly associated with ongoing construction operations, including concrete casting and related thermal-mechanical disturbances. In the second stage, after the completion of active works on the monitored section, the measured strain and temperature responses became significantly more stable. The proposed approach demonstrates how DFOS data can be converted from raw distributed measurements into a practical monitoring basis for reinforced concrete substructures. The results are relevant for commissio-ning control, baseline formation, diagnostic comparison of future measure-ments.

The structural monitoring of high-rise building foundations requires measurement systems that can register spatially distributed deformation and temperature effects during construction and at the early stage of service. This paper presents a field case study of a distributed fiber optic sensing (DFOS) system installed in the raft foundation of a high-rise building complex. The study is focused not on general crack detection, but on the practical commissioning of the sensing line, interpretation of initial measurements, and preparation of a reference dataset for subsequent long-term observation.The monitoring object is the raft foundation beneath Block R of Abu Dhabi Plaza in Astana, Kazakhstan. Measurements were obtained along the same horizontal sensing route using Brillouin Optical Time Domain Analysis (BOTDA). Two commissioning stages were compared in order to evaluate the repeatability of the installed system and to separate temporary con-struction-stage influences from the stable response of the foundation slab.The analysis showed that signal variability during the first measurement stage was mainly associated with ongoing construction operations, including concrete casting and related thermal-mechanical disturbances. In the second stage, after the completion of active works on the monitored section, the measured strain and temperature responses became significantly more stable. The proposed approach demonstrates how DFOS data can be converted from raw distributed measurements into a practical monitoring basis for reinforced concrete substructures. The results are relevant for commissio-ning control, baseline formation, diagnostic comparison of future measure-ments.