Deformation Monitoring for Chinese Traditional Timber Buildings Using Fiber Bragg Grating Sensors

Real-Time Structural Monitoring of the Multi-Point Hoisting of a Long-Span Converter Station Steel Structure

In the process of using a long-span converter station steel structure, engineering disasters can easily occur. Structural monitoring is an important method to reduce hoisting risk. In previous engineering cases, the structural monitoring of long-span converter station steel structure hoisting is rare. Thus, no relevant hoisting experience can be referenced. Traditional monitoring methods have a small scope of application, making it difficult to coordinate monitoring and construction control. In the monitoring process, many problems arise, such as complicated installation processes, large-scale data processing, and large-scale installation errors. With a real-time structural monitoring system, the mechanical changes in the long-span converter station steel structure during the hoisting process can be monitored in real-time in order to achieve real-time warning of engineering disasters, timely identification of engineering issues, and allow for rapid decision-making, thus avoiding the occurrence of engineering disasters. Based on this concept, automatic monitoring and manual measurement of the mechanical changes in the longest long-span converter station steel structure in the world is carried out, and the monitoring results were compared with the corresponding numerical simulation results in order to develop a real-time structural monitoring system for the whole long-span converter station steel structure's multi-point lifting process. This approach collects the monitoring data and outputs the deflection, stress, strain, wind force, and temperature of the long-span converter station steel structure in real-time, enabling real-time monitoring to ensure the safety of the lifting process. This research offers a new method and basis for the structural monitoring of the multi-point hoisting of a long-span converter station steel structure.

Cuistow: Chinese Unique Inlay Bristow: A Novel Arthroscopic Surgical Procedure for Treatment of Recurrent Anterior Shoulder Instability with a Minimum 3-Year Follow-Up

BACKGROUND

The prevalence of nonunion after the Latarjet procedure remains high. The purpose of the present study was to investigate healing and clinical outcomes after a novel arthroscopic coracoid process transfer procedure.

METHODS

Sixty-three patients who underwent the arthroscopic inlay Bristow procedure combined with Bankart repair were identified, and 51 patients who met the inclusion criteria were enrolled in this study. The key feature of this technique was that the coracoid process was trimmed and fixed into a trough (5 to 10 mm deep) in the glenoid neck with a metal screw. Bone graft union and positioning accuracy were assessed with use of postoperative computed tomography (CT) imaging. Clinical examinations, return to sport, and functional scores (American Shoulder and Elbow Surgeons [ASES] and Rowe scores) were recorded.

RESULTS

The mean duration of follow-up (and standard deviation) was 41.5 ± 7.7 months (range, 36 to 48 months). Postoperative CT scans showed that the position of coracoid graft was at 4:10 (from 3:50 to 5:00) (referencing the right shoulder) in the sagittal view. The α angle was 16.4° ± 9.5°, with 4 (7.8%) of 51 screws being over-angulated (α > 25°). On the axial view, the graft position was considered to be flush in 33 patients (64.7%), medial in 11 (21.6%), congruent in 7 (13.7%), and lateral or too medial in none. At 1 year, the coracoid graft had healed in 49 patients (96.1%) and had failed to unite in 2 patients. CT scanning, performed for 47 patients, showed grade-0 osteolysis in 9 patients, grade-1 osteolysis in 21 patients, and grade-2 osteolysis in 17 patients. At the time of the latest follow-up, there was a significant increase in the Rowe score (from 35.5 ± 8.3 to 95.7 ± 7.2) and the ASES score (from 71.2 ± 9.7 to 91.5 ± 4.4), and 87.0% of patients were able to return to sport. No arthropathy was observed in any patient.

CONCLUSIONS

After a minimum 3-year follow-up, the arthroscopic inlay Bristow procedure resulted in a high rate of graft healing, excellent clinical outcomes, and a high rate of return to sports.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Structural Instability-Enabled Mechanical Sensors Using Fiber Bragg Grating

Structural health monitoring (SHM) has been extensively used in civil infrastructures to assess structural condition and situation. Here, we develop a novel type of mechanical sensing technique using the structural instability of cylindrical cells detected by fiber Bragg grating (FBG). The cylinders are fabricated using a 3D printing technique, which are coiled by the FBG wires to detect the transverse deformation. Structural instability under axial compression is obtained in the experiments and the force–displacement relations are validated by the numerical simulations with satisfactory agreements. The wavelength variation of the FBG, caused by the structural instability, is observed and compared with the predefined threshold. Defining the variation larger than the threshold as “1” and smaller as “0”, the pattern recognition algorithm is used to convert the FBG results into binary data, which can, therefore, be analyzed to indicate the structural conditions. In the end, we envision the potential applications of the reported sensing technique, such as wireless sensors for structural health monitoring (SHM) in civil infrastructures.

Laboratory and In-Situ Testing of Integrated FBG Sensors for SHM for Concrete and Timber Structures

Long-term structural health monitoring (SHM) plays an important role in the safety of public transport infrastructure such as bridges or tunnels and warns in the event of any emerging problem. This article describes development and testing of system based on fiber Bragg grating (FBG) sensors that can detect changes in strain and temperature. The first phase of the research has been focused on the development of new fiber optic sensors for the monitoring of concrete structures and their investigation in laboratory conditions. The work also shows novel applicability of the same FBG technology for glulam structures. Mechanical loading tests of the concrete beam as well as glulam beam with embedded sensors were carried out. Data measured by developed fiber optic sensors were compared with the readings from reference sensors as well as with the analytically calculated values. The achieved results proved good agreement between the measured data, analytical data and reference methods. In second phase of the research, the pilot installation of the sensors was carried out on the newly constructed prestressed-concrete bridge. The bridge was monitored throughout pre-stressing phase and monitoring continued after the completion of the construction works. Problems with the fragility of the sensors occurred during the measurements, but the obtained results provide a good basis for further improvement of the system.

Real-Time Wood Behaviour: The Use of Strain Gauges for Preventive Conservation Applications

Within the heritage field, the application of strain gauges on wood surfaces is a little-explored but inexpensive and effective method to analyse the environmental appropriateness of rooms for the wooden heritage collections they contain. This contribution proposes a wood sensor connected to a data logger to identify short moments with an elevated risk of harm. Two experiments were performed to obtain insights pertaining to the applicability of wood sensors to evaluate preservation conditions. (1) The representativeness of strain gauges on dummies was tested for their use in evaluating the preservation conditions of a range of wooden objects exposed to the same environment. For this, three situations were mimicked: a bare wood surface, a wood surface covered with a preparation layer, and a wood surface covered with a preparation and varnish layer. (2) The usability of strain gauges to monitor the wood behaviour in real-time measurements was tested with a monitoring campaign of almost two years in a church where a new heating system was installed. The results of both experiments are promising, and the authors encourage a broader application of strain gauges in the heritage field.

Structural Health Monitoring System Based on FBG Sensing Technique for Chinese Ancient Timber Buildings

Due to the long-term service, Chinese ancient timber buildings show varying degrees of wear. Thus, structural health monitoring (SHM) for these cultural and historical treasures is desperately needed to evaluate the service status. Although there are some FBG sensing-based SHM systems, they are not suitable for Chinese ancient timber buildings due to the differences in architectural types, structural loads, materials, and environment. Besides, a technical gap in Fiber Bragg grating (FBG) sensing-based column inclination monitoring exists. To overcome these weaknesses, this paper develops an FBG sensing-based structural health monitoring system for Chinese ancient Chuan-dou-type timber buildings that aims at monitoring structural deformation, i.e., beam deflection and column inclination, temperature, humidity, and fire around the building. An in-situ test and simulation analyses were conducted to verify the effectiveness of the developed SHM system. To validate the long-term-operation of the developed SHM system, monitoring data within 15 months were analyzed. The results show good agreement between the developed SHM system in this paper and other methods. In addition, the SHM system operated well in the first year after its deployment. This implies that the developed SHM system is applicable and effective in the health state monitoring of Chinese ancient Chuan-dou-type timber buildings, laying a foundation for damage prognosis of such types of timber buildings.

Efficient Sensor Placement Optimization for Shape Deformation Sensing of Antenna Structures with Fiber Bragg Grating Strain Sensors

This paper investigates the problem of an optimal sensor placement for better shape deformation sensing of a new antenna structure with embedded or attached Fiber Bragg grating (FBG) strain sensors. In this paper, the deformation shape of the antenna structure is reconstructed using a strain–displacement transformation, according to the measured discrete strain data from limited FBG strain sensors. Moreover, a two-stage sensor placement method is proposed using a derived relative reconstruction error equation. In this method, the initial sensor locations are determined using the principal component analysis based on orthogonal trigonometric (i.e., QR) decomposition, and then a new location is sequentially added into the initial sensor locations one by one by minimizing the relative reconstruction error considering information redundancy. The numerical simulations are conducted, and the comparisons show that the proposed method is advantageous in terms of the sensor distribution and computational cost. Experimental validation is performed using an antenna experimental platform equipped with an optimal FBG strain sensor configuration, and the reconstruction results show good agreements with those measured directly from displacement sensors. The proposed method has a large potential for the strain sensor placement of complex structures, and the proposed antenna structure with FBG strain sensors can be applied to the future wing-skin antenna or flexible space-based antenna.