Structural Safety Performance Research Articles

Parametric Study on Structural Performance According to the Condition Grade of Open-cut Electric Power Tunnel

In this study, the structural performance of electric power tunnels was evaluated based on the type and degree of damage. For experimental performance evaluation, a power structure test specimen was designed with a state safety performance of grade D corresponding to a concrete damage area ratio of 44% and structural safety performance of grade D with a reduced cross-section of 25% of the main reinforcement of the upper slab. The electric power structures with grade D state safety performance and structural safety performance exhibited 63% load-bearing capacity compared to those without damage. Cracks occurred on the outside of the structure under the experimental conditions simulating the overburden load, implying the possibility of corrosion of the outer reinforcing bars of the real structure. Finite element analysis showed that reducing the area of the outer main rebar of the upper slab caused more significant reduction in the load-bearing capacity than that of the inner main rebar.

Investigation of an Ancient Wooden Cantilever Covered Bridge in China: Construction Form and Mechanical Properties

Wooden cantilever-covered bridges are typical Chinese constructions due to their structural style and architectural decoration. Yanzi bridge, an ancient wooden cantilever-covered bridge with more than 220 years of history in Anhua, China, has attracted increasing attention in recent years. In this study, its construction form and cultural background were investigated, and the structural components, original materials and mechanical behavior of the bridge were investigated in detail. First, the same type of raw material used for the Yanzi bridge, namely, pinus koraiensis, was tested to better understand its mechanical properties. Then, a finite element model was built to simulate the mechanical behavior of the bridge, and the stress state and internal forces of the cantilever system were obtained. According to the numerical results, when the loads are transferred downward and evened by the beams in the same layers of the cantilevers, the maximum deflection of the bridge of 12.8 mm meets the requirements of not exceeding L/600 in the specification, and the maximum normal stress of 1.35 MPa is much less than the ultimate tensile strength of the wood. This indicates that the structural safety performance of the ancient wooden cantilever-covered bridge is acceptable. Finally, a small amount of tiny damage of the bridge was observed and presented in the paper. This damage is not severe enough to cause brittle collapse, but care and maintenance are necessary to preserve this old historical bridge.

Theoretical model of the three - Stage parameter fire curve considering the contribution of combustible materials

Fire resistance is a critical factor constraining structural safety performance, specifically for Cross Laminated Timber (CLT) structures. Due to wood being a combustible material, the exposed wood will participate in combustion, increasing the fire load density and char rates, thereby causing more severe fire risks. In order to investigate the effect of exposed wood on fire temperature, this paper summarized 32 char rate data from 11 CLT room fire tests and fitted the relationship between wood exposure area and char rate, establishes a theoretical formula for the proportion of fire load burned outside the room to the total fire load, and it also establishes a theoretical formula for the three-stage parameter fire curve, which considers the contribution of combustible materials to fire load and char rate, as well as the transition from ventilation controlled to fuel controlled during the cooling stage of the fire. The accuracy of the three-stage parameter fire curve was verified through comparison with test results. Sensitivity analysis was conducted on the main parameters that affect the three-stage parameter fire curve. The results showed that the degree of influence of each factor on the maximum temperature of the fire and the time to reach the maximum temperature was as follows: fire load density > vent height > vent width > wood exposure area.

Resource-constrained bridge maintenance optimization by harmonizing structural safety and maintenance duration

Bridges are progressively experiencing significant structural wear and challenges in their maintenance procedures. To address this issue, it's crucial to clarify the order of maintenance activities during the bridge maintenance process and the impact of maintenance resources on structural safety performance. This understanding allows for the precise establishment of a model that captures the changes in structural safety performance in relation to the bridge maintenance duration that are resource-constrained. This paper proposes a resource-constrained bridge maintenance optimization method where neither the structural safety performance loss nor the duration holds a dominant advantage. An Adjusted NSGA-II (Adj-NSGA-II) method is employed to determine the total structural safety performance loss and total duration throughout the bridge's operational cycle. The results show that the number of construction workers in the mathematical model proposed will have different degrees of influence on the change of the total construction duration under the similar total structural safety performance. The proposed method not only enhances the scientific management capabilities of decision-makers in bridge maintenance planning but also provides a framework that can be applied to maintain other structural forms.

Intelligent analysis of corrosion characteristics of steel pipe piles of offshore construction wharfs based on computer vision

The lower part of offshore construction wharfs is mostly a steel structure system composed of steel pipe piles, whose corrosion level directly affects the structural safety performance of steel wharfs in service. The currently common corrosion detection methods can only sample and inspect steel pile after it has been dismantled, making it impractical for in-service monitoring during the operational period of the steel pile. In this paper, a deep learning-based image classification model is first established to recognize the type of corroded area on steel pipe piles. The model achieves a recognition accuracy of 99.14 % in automatically identifying different types of corroded areas, including full immersion zone, tidal range zone, and splash zone. Subsequently, digital image processing technology is utilized to automatically calculate the corroded area of steel pipe piles. The method proposed in this paper can obtain the key information, such as type of corrosion area and area of the steel pipe pile corrosion area, without damaging their structural performance during the service. With this data, the mechanical performance of steel pipe piles can be analyzed, and the structural safety of the in-service steel pipe piles can be determined, thereby ensuring the safety of the construction wharf.

An Intelligent Evaluation Method for Service Safety of Cable Net Structures under Multiple Factors

Various uncertainties often influence the serviceability of cable net structures, which can impact their structural safety performance. The accurate identification of sensitive factors during the structure’s service life and the determination of its serviceability state is crucial for achieving intelligent serviceability safety. In this paper, based on the digital twin model, a multi-factor-based assessment method for the serviceability safety of cable net structures was proposed. Firstly, the assessment method for serviceability safety under multi-factor influence was described in detail, outlining the specific workflow. Secondly, key indicators that affect the structural safety state are selected, and their range of variation is determined. Subsequently, a comprehensive dataset of sample data, considering long-term multi-factor influence, was constructed, through combined simulation using MATLAB 2021 and ANSYS 15.0. Finally, a support-vector-regression-based structural safety assessment model was established and validated.

Photogrammetry-based bending monitoring and load identification of steel truss structures

The bending of steel truss structures is an important gauge for detecting, identifying, and evaluating potential issues with structural safety performance. The limitations and high cost of traditional monitoring methods make it challenging to carry out stable long-term monitoring. Therefore, this paper developed a displacement monitoring system for steel truss structures which fulfill the requirements of having low cost, high stability, and ease of operation. The system is based on the improved sub-pixel positioning technology, achieving precise positioning in unfavorable conditions such as long structure-camera distance, angle skew, and dim light. Then, this system was calibrated through field experiment and compared with other measurement systems. Finally, a load identification method was developed to identify discrepancies between the true load and the design load. This method uses optimization functions to identify the true load applied in the experiment, and the optimization parameter obtained by a genetic algorithm iteration is output as the optimal solution. The results suggest that the photogrammetric system performs well in practical engineering applications and can provide advantages including high precision, low cost, simple operation, etc. Results obtained by the load identification method agree well with measurements obtained from the actual structure, and can serve as a tool for evaluating the mechanical properties of similar structures. This method monitors potential risks of steel truss structures, and greatly improve the stability and safety of such structures.

Investigation on seepage field distribution and structural safety performance of small interval tunnel in water-rich region

The complicated interaction between seepage field and stress field of tunnels in water-rich region has an important impact on the stratum deformation stability, structural safety performance, groundwater resources and ecological environment protection, etc. Especially for large-span urban tunnel with small spacing, the seepage funnels of the two holes will partially overlap and affect each other, making the seepage field distribution much more complex, and the difficulties in prediction water drainage and safety performance of supporting structure increase sharply. In this paper, in order to investigate the seepage field distribution and its influence on the structural mechanical behavior of small interval tunnel in water-rich region, using the self-developed seepage model test equipment, tests under different hydrostatic head heights were carried out on the Kexuecheng Tunnel, which is a typical small interval tunnel under complex hydrogeological environment in Chongqing, China. According to the test results, with the increase of buried depth and water level, the water pressure at each monitoring point gradually increased. For small interval tunnel, the average water pressure on the inner side decreased by 10–15 % compared with the outer side. Benefiting from the grouting circle can effectively block the supply of pore water in the rock mass, the water pressure behind the lining can be significantly reduced by 32 %–42 %. But with the increase of the hydrostatic height, the proportion of water pressure that can be shared by the grouting circle decreased gradually, and further aggravated the asymmetric distribution of the water pressure on lining structure. Meanwhile, the water pressure evolution curve shown a W-shaped distribution in horizontal direction and a V-shaped descend funnel along the tunnel axis, the predicted seepage influence range may increase to over 60–70 m under high water pressure. Contrary to the asymmetric distribution of water pressure, the earth pressure at the inner side was about 10 % higher than that at the outer side. Influenced by the tunnel excavation unloading effect, the closer to the tunnel face, the smaller the surrounding rock pressure. The minimum safety factors of the lining structure under water level of 0, 30, 40 and 50 m were 4.28, 3.85, 3.41 and 2.98, the structural safety performance significantly decreased with the increase of the hydrostatic head height.

Dynamic prediction method of structural safety performance of stereo garage driven by multi-source information

Dynamic prediction method of structural safety performance of stereo garage driven by multi-source information

Structural engineering applications of recycled aggregate concrete: Seismic performance, guidelines, projects and demonstrations

In this paper, the most-concerned questions of recycled aggregate concrete (RAC) application, i.e., the structural safety performance, the availability of design code and project experience, and ecological and economic costs, are overviewed, aiming to find the answer to whether it is feasible to apply RAC in main structural components technically and practically. Firstly, RAC structural performances were analyzed. The failure pattern, load-carrying capacity, energy dissipation capacity, and ductility of the RAC structures were compared with those of natural aggregate concrete (NAC). The results confirm the safety of the RAC structures in most scenarios. Secondly, the specifications and standards for RAC structures of different countries, the attitude of engineering participants, the optimum preparation methods of recycled aggregates, and the projects using RAC are reviewed. Finally, the ecological and economic benefits of applying RAC to replace NAC in structures are investigated, showing a reduction in the projects' overall cost and promotion of social advantages due to its sustainable, low-carbon, and resource-efficient features. The authors hope that this research will serve as a stimulus to promote the applications of RAC in structural engineering and address the problems posed by C&D waste and the scarcity of natural aggregates.

A robust structural vibration recognition system based on computer vision

Vibration-based structural health monitoring (SHM) systems are useful tools for assessing structural safety performance quantitatively. When employing traditional contact sensors, achieving high-resolution spatial measurements for large-scale structures is challenging, and fixed contact sensors may also lose dependability when the lifetime of the host structure is surpassed. Researchers have paid close attention to computer vision because it is noncontact, saves time and effort, is inexpensive, and has high efficiency in giving visual perception. In advanced noncontact measurements, digital cameras can capture the vibration information of structures remotely and swiftly. Thus, this work studies a system for recognizing structural vibration. The system ensures acquiring high-quality structural vibration signals by the following: 1) Establishing a novel image preprocessing, which includes visual partitioning measurement and image enhancement techniques; 2) initial recognition of structural vibration using phase-based optical flow estimation (POFE), which introduces 2-D Gabor wavelets to extract the independent phase information of the image to track the natural texture targets on the surface of the structure; 3) extracting the practical vibration information of the structure using mode decomposition to remove the complex environment of the camera vibration and other noises; 4) employing phase-based motion magnification (PMM) techniques to magnify small vibration signals, and then recognizing the complete information on the vibration time range of the structure. The research results of the laboratory experiments and field testing conducted under three different cases reveal that the system can recognize structural vibration in complicated environments.

Key Component Capture and Safety Intelligent Analysis of Beam String Structure Based on Digital Twins

In the construction process of beam string structures, the environmental effect and corresponding mechanical properties of the structure are complex. The problem of the misjudgment of structural safety performance caused by the uncertainty of a structural mechanical parameter analysis under various factors needs to be solved. In this study, a method for capturing key components and an intelligent safety analysis of beam string structures based on digital twins (DTs) was proposed. Combined with the characteristics of DTs mapping feedback, a component capture and security analysis framework was formed. Driven by twin framework, multi-source data for structural safety analysis were obtained and the parameter association mechanism established. Considering the space-time evolution and the interaction between the virtual and real elements of the construction process, a multidimensional model was established. Driven by the Dempster–Shafer (D–S) evidence theory, the fusion of structural mechanics parameters was carried out. The safety of the structure was analyzed intelligently by capturing key structural components, thereby providing a basis for the safety maintenance of the structure. The integration of DTs modeling and multi-source data improves the accuracy and intelligence of structural construction safety analysis. In the analysis process, capturing the key components of the structure is the core step. Taking the construction process of a string supported beam roof (symmetrical structure) in a convention and exhibition center as an example, the outlined research method was applied. Based on DTs and D–S evidence theory, the variation degree of mechanical parameters of various components under temperature was determined. By comprehensively investigating the changes of various mechanical parameters, the key components of the structure were captured. Thus, the intelligent analysis of structural safety was realized. The comparison of data verified that the intelligent method can effectively analyze the safety performance of the structure.

Intelligent Analysis for Safety-Influencing Factors of Prestressed Steel Structures Based on Digital Twins and Random Forest

The structure of a prestressed steel structure is complex, which can result in insufficient control accuracy and the low efficiency of the structural safety. The traditional analysis method only obtains the mechanical parameters of the structure and it cannot obtain the key factors that affect the structural safety. In order to improve the intelligence level of the structural safety performance analysis, this study proposes an intelligent analysis for the safety-influencing factors of prestressed steel structures that is based on digital twins (DTs) and random forest (RF). Firstly, the high-precision twin modeling is carried out by the weighted average method. The design parameters and the mechanical parameters of the structure are extracted in real time in the twin model, and the parameters are classified by the RF. The fusion mechanism of the DTs and RF is formed, and the intelligent analysis model of the structural safety factors is established. Driven by the analysis model, the correlation mechanism between the design parameters and the mechanical parameters is formed. The safety state of the structure is judged by the mechanical parameters, and the key design parameters that affect the various mechanical parameters are analyzed. Through the integration of the design parameters and mechanical parameters, the intelligent analysis process of the safety-influencing factors of prestressed steel structures is formed. Finally, an intelligent analysis of the importance of the safety-influencing factors is carried out with the string-supported beam structure as the test object. Driven by the integration of DTs and RF, the key design parameters that affect the various mechanical parameters are accurately obtained, which provides a basis for the intelligent control of the structural safety.

Intelligent Safety Assessment of Prestressed Steel Structures Based on Digital Twins

In the development process of intelligent construction, the safety assessment of prestressed steel structures as an important research direction has become more and more attractive in academia. Digital twins (DTs) is the key technology to realize intelligent construction. The virtual and real interaction of the DTs can provide an efficient management and control mechanism for the construction process. This research proposes an intelligent safety assessment method of prestressed steel structures based on DTs. In this research method, the structural safety assessment is divided into two aspects: performance analysis and maintenance. By analyzing the characteristics of the construction safety assessment, a DTs framework for construction safety assessment is built. Driven by the DTs framework, a physical space model and a virtual space model are constructed. On the basis of virtual and actual interaction, multidimensional information fusion of time and space is carried out to realize the analysis of structural safety performance. On this basis, the paper establishes a Bow-tie model for the maintenance modeling of unsafe construction events. Moreover, the theoretical method formed is applied to the construction of a symmetrical structure (wheel–spoke cable truss). The validity of the method is verified by comparing the cable force calculated by the theoretical method and measured on site. The assessment method driven by the DTs ensures the structural safety and improves the intelligence level of safety management and control of the structure construction.

Study on Risk Analysis and Structural Safety Performance of Material Ropeway Construction of Transmission Line

Material ropeway transport runs through the whole construction process of transmission line. It is operated frequently with long working period and its structural components are easy to produce fatigue, wear, deformation and other defects. The result is to form safety risks and cause personal and property losses, which is the focus of construction safety. This paper first summarizes the common construction safety risk factors of material ropeway and analyzes the causes of the risk points. Then, safety assessment method of material ropeway of transmission line is proposed. The method considers with the coupling dynamic factor of working ropes and running car and the states of carrying rope, pulling rope, trestle, saddle, anchor underground, etc. is analysed in whole process of transportation. The safety evaluation method is suitable for different topographic conditions and structural types of material ropeway, which provides technical means for the construction check and evaluation of material ropeway.

Intelligent Discrimination Method Based on Digital Twins for Analyzing Sensitivity of Mechanical Parameters of Prestressed Cables

The information collected on large-span prestressed cables by field sensors is susceptible to interference, which leads to inaccurate collection of structural and mechanical parameters of large-span prestressed cables, resulting in misjudgment of structural safety performance. This paper proposes an intelligent judgment method for improving the sensitivity of analyzing mechanical parameters of prestressed cables based on digital twins (DTs). The safety performance of the structure was evaluated by analyzing the mechanical parameters. First, the information during prestressed cable tensioning is dynamically sensed, thereby establishing a multidimensional model of structural analysis. The virtual model is processed by the model modification rule to improve the robustness of the simulation; thus, a DT framework for the sensitivity judgment of the mechanical parameters of the cable is built. In the twin model, the simulation data of the real structure were extracted. Probabilistic analysis was performed using the Dempster–Shafer(D–S) evidence theory to discriminate the sensitivity of mechanical parameters of each cable node under the action of external forces with high accuracy and intelligence. Sensitivity analysis provides a reliable basis for the safety performance assessment of structures. Taking the wheel–spoke-type cable truss as an example, the application of DTs and D–S evidence theory to the sensitivity determination of cable mechanical parameters under temperature fully verified that the proposed intelligent method can effectively evaluate the safety performance of the actual structure.

Prediction of Fatigue Strength of Extra-Large Container Ships Based on Spectrum Analysis

Wang, J.T.; Jiang, B.C., and Guo, Y.L., 2020. Prediction of fatigue strength of extra-large container ships based on spectrum analysis. In: Al-Tarawneh, O. and Megahed, A. (eds.), Recent Developments of Port, Marine, and Ocean Engineering. Journal of Coastal Research, Special Issue No. 110, pp. 146–149. Coconut Creek (Florida), ISSN 0749-0208.With the rapid development of maritime transportation industry, container ships have quickly become the mainstream ship model due to their advantages of fast shipping speed, high handling efficiency, and low operating costs. At the same time, their large-opening structure has resulted in poor performance in bending strength, torsional strength and other mechanical properties. In order to ensure the structural safety performance of extra-large container ships, it is necessary to conduct an in-depth research on its fatigue damage and strength life. Based on the spectrum analysis, this paper takes the model 8601ETP extra-large container ship as an example, and adopts finite element modeling to obtain distribution range of the alternating stress; it also uses SN curve and linear cumulative damage theory to predict the fatigue damage and strength life of the container ship. The research results show that the fatigue damage of the extra-large container ship at full load is significantly more severe than that at no load; the degree of structural damage at the position of the keyhole is greater than that at the position of the hatch corner, so it is the hotspot for the fatigue damage analysis and strength check of extra-large container ships. This study provides certain theoretical reference and data support for improving the safety performance of large container ships, and it also enriches the theory of fatigue strength evaluation.

Impacts of geological conditions on instability causes and mechanical behavior of large-scale tunnels: a case study from the Sichuan–Tibet highway, China

Tunneling in complicated geological conditions frequently encounters problems with squeezing ground, large ground deformation, rockbursts, asymmetric deformation, non-linear rheology of surrounding rock, water inrush, and failure of supporting structures. In this paper, the Sichuan–Tibet highway, which is located at the north-west edge of the Sichuan basin and the eastern margin of the Qinghai–Tibet plateau, serves as a case study to investigate potential hazard sources for tunnels constructed in complex and difficult mountainous areas. Consideration first is given to the following 5 sets of conditions: crossing a fault zone, shallow tunnels in soft rock, crossing a landslide deposit, and deep tunnels in hard and soft rock formations. A program of field tests was performed to study the changes in rock pressure and the performance of support structures in different geological conditions. The results confirmed that the squeezing of rock depended upon a combination of the surrounding rock strength and the in situ stress field; fracture zones and water conditions reduced the integrity and mechanical properties of the surrounding rocks; topography and bedding structure can induce asymmetric mechanical behavior of the supporting structures during construction. Meanwhile, time-dependent rock deformation may have greater adverse impacts on the structural safety performance of tunnel during their operation.

Post‐installation adaptation of offshore wind turbine controls

AbstractThe cost of offshore wind energy can be reduced by incorporating control strategies to reduce the support structures' load effects into the structural design process. While effective in reducing the cost of support structures, load‐reducing controls produce potentially costly side effects in other wind turbine components and subsystems. This paper proposes a methodology to mitigate these side effects at the wind farm level. The interaction between the foundation and the surrounding soil is a major source of uncertainty in estimating the safety margins of support structures. The safety margins are generally closely correlated with the modal properties (natural frequencies, damping ratios). This admits the possibility of using modal identification techniques to reassess the structural safety after installing and commissioning the wind farm. Since design standards require conservative design margins, the post‐installation safety assessment is likely to reveal better than expected structural safety performance. Thus, if load‐reducing controls have been adopted in the structural design process, it is likely permissible to reduce the use of these during actual operation. Here, the probabilistic outcome of such a two‐stage controls adaptation is analyzed. The analysis considers the structural design of a 10 MW monopile offshore wind turbine under uncertainty in the site‐specific soil conditions. Two control strategies are considered in separate analyses: (a) tower feedback control to increase the support structure's fatigue life and (b) peak shaving to increase the support structure's serviceability capacity. The results show that a post‐installation adaptation can reduce the farm‐level side‐effects of load‐reducing controls by up to an order of magnitude.

Assessment of emerging metallic structures technologies through test and analysis of fuselage structure

In partnership with Arconic and Embraer, the Federal Aviation Administration (FAA) is assessing emerging metallic structures technologies (EMST) using the FAA’s Full-Scale Aircraft Structural Test Evaluation and Research facility. In this collaborative effort, full-scale fuselage panel test data will be obtained to assess the effect of EMST fuselage concepts on damage tolerance performance as compared to the current baseline aluminum fuselage structures located on the crown of a typical single-aisle aircraft forward of the wing. Several technologies will be considered in the scope of the project, including advanced aluminum–lithium alloys, selective reinforcement using fiber metal laminates, and advanced joining processes, such as friction stir welding. Data from this study will be used to verify improved weight and structural safety performance of EMST and to assess the adequacy of existing airworthiness standards and guidance needed for the implementation of arising technologies and their impact on future designs. Results from the first baseline panel test are presented in this paper and will be compared to future tests on advanced panels containing varying EMST to assess the damage-tolerance performance.