Browsing by Author "Herbers, Max"

Filter results by typing the first few letters
Now showing 1 - 5 of 5
  • ItemOpen Access
    Crack monitoring with DFOS: Distributed strain measurements with various DFOS/adhesive combinations and model development for strain peak prediction
    (Technische Universität Dresden, 2025-07-10) Herbers, Max; Richter, Bertram; Marx, Steffen
    Coherent optical frequency domain reflectometry (c-OFDR) enables continuous and automated crack monitoring in concrete structures due to its high spatial resolution and long sensing range. However, the selection of a suitable DFOS/adhesive combination (DAC) remains a key challenge and is typically based on empirical knowledge. As a result, the monitoring quality is highly dependent on the user’s experience. Inappropriate choices can result in undetected cracks, degraded signal quality, miscalculated crack widths, or even fiber breakage. This study proposes a semi-analytical model for predicting strain curves for arbitrary crack patterns, based on experimentally derived parameters, such as sensitivity, strain lag parameter, and the extent of bond disturbance due to transverse cracking. The model was validated using strain measurements from tests on reinforced concrete specimens with multiple cracks. With only a few input parameters, it enables accurate representation of crack-induced strain peaks and allows for the consideration of measurement limitations typical for c-OFDR systems. Based on this, design charts and an open source software tool were developed to support practitioners in the systematic selection of DACs, tailored to the expected crack pattern.
  • ItemOpen Access
    Investigations on prestressing wire breaks in a post-tensioned prefabricated girder – Distributed fiber optic strain data and Python scripts
    (Technische Universität Dresden, 2025-05-06) Richter, Bertram; Will, Elias; Herbers, Max
    This data set contains distributed fiber optic strain data and Python scripts for evaluation. The data was collected 2022-10-04 during experiments on a decommissioned bridge girder of type BTE 311.080.12. These prefabricated and post-tensioned girders were produced in the former GDR. In the experiments, tendons were deliberately damaged by cutting wires. Two locations on opposite lateral sites of the girder 1 m from the girder's middle were selected: C1 and C2. The data shows strain changes measured with a distributed fiber optic sensor (DFOS) installed in the underside of the girder. The DFOS was routed in three segments along the free span of the girder.
  • ItemOpen Access
    Monitoring Data of the openLAB Research Bridge (2024-02-01 to 2024-10-31) and building information
    (Technische Universität Dresden, 2025-01-15) Jansen, Andreas; Richter, Bertram; Röder, Robert; Herbers, Max; Marx, Steffen
    This dataset presents Structural Health Monitoring (SHM) data from the openLAB research bridge, a large-scale laboratory structure located in Bautzen, Germany. Following an initial one-year reference phase, the bridge will undergo a series of load tests designed to induce significant structural damage. This open-access dataset provides researchers with a rare opportunity to validate SHM methodologies under near-real-world conditions. The current publication includes data from the undamaged bridge, covering the period from 2024-02-01 to 2024-10-31. Additional repositories will be published periodically as new data become available. The bridge is equipped with a comprehensive monitoring system featuring fiber optic and electrical sensors that capture both structural behavior and environmental conditions (e.g., air temperature, humidity, and solar radiation). In this initial release, data is sourced from an electrical Gantner Instruments measurement system (Q.station 101T, with various Q.bloxx modules). The dataset includes measurements of acceleration, tilt, air temperature, humidity, and solar radiation. Data is recorded continuously at 10-minute intervals, with additional triggered measurements during non-damaging load tests conducted with a test vehicle or in response to increased vibration activity. The repository provides the data in Comma Separated Values (CSV) format. Each file includes a header specifying the names of the data columns. Additional details, such as units and sampling frequency, are provided in this README file. Each CSV file contains a Timestamp column that records the time of each sample as a datetime string in ISO 8601 format, without time zone information. All timestamps are in Coordinated Universal Time (UTC). Sensor data is represented as decimal numbers. The data is accompanied with structural plans of the bridge and the installed monitoring system. This dataset is available at [10.25532/OPARA-660](https://doi.org/10.25532/OPARA-660).
  • ItemOpen Access
    Monitoring Data of the openLAB Research Bridge – Load Test on PE 2.1
    (Technische Universität Dresden, 2025-07-14) Herbers, Max; Richter, Bertram; Walker, Maria; Marx, Steffen
    Between May 5 and 7, 2025, extensive experiments were carried out on the openLAB research bridge. The test program was structured as follows: • Day 1: Static and dynamic measurements in the reference state • Day 2: Loading of the bridge using hydraulic jacks up to the ultimate limit state (yielding of prestressing steel) • Day 3: Local damage of prestressing tendons (cutting wires at several locations) The present dataset contains force and displacement measurements from the load test conducted on Day 2. The load was applied locally to precast element (PE) 2.1 (Field 2, PE axis 1) using two hydraulic jacks and increased up to 400 kN. Displacements were measured at five different positions along PE axis 1. Details on the measurement setup can be found in the attached file readme.txt. Additional information on the project, the bridge and reference-phase measurements is available under the following references: https://doi.org/10.1016/j.dib.2025.111624 https://onlinelibrary.wiley.com/doi/10.1002/best.202300094 Herbers, M., Richter, B., Jan-Hauke, B., Al-Zuriqat, T., Smarsly, K., & Marx, S. (2024, November). openLAB – A large-scale demonstrator for advancing digital twin developments of bridges. In 2024 fib Symposium (pp. 2057–2067). (see attachment) Value of the data: • Validation and calibration of finite element models (FEM) • Comparison with geodetic measurement methods (e.g., total station, drone survey) • Basis for interpreting data from additional monitoring systems (e.g., distributed fiber optic sensing, acceleration measurements, acoustic emission monitoring, etc.) The provided Python script enables data import, post-processing, and visualization of the measurement data (see example figures).
  • ItemOpen Access
    Strain curves measured with different DFOS types and varying spatial resolution by an ODiSI 6108
    (Technische Universität Dresden, 2024-03-15) Herbers, Max
    Based on the principle of coherent optical frequency domain reflectometery (c-OFDR), cracks in concrete structures can be precisely localized and their widths determined due to the high spatial resolution in the sub-millimeter range. However, with longer distributed fiber optic sensors (DFOS) lengths, as is common in structural health monitoring, the spatial resolution is reduced. Experimental studies were carried out to investigate the influence of the spatial resolution on the measurement quality in the area of large strain gradients. Four different DFOS, two robust and two filigree DFOS types, were subsequently installed on a 4 m long reinforced concrete beam. In a displacement controlled 4-point bending test, crack widths of up to 0.5 mm were measured with four different gage pitch (gp).