The Fractional Diagnosis of Multi-Span Continuous Bridge’s Structural Damage Based on Neural Network and Genetic Algorithm

2011 ◽  
Vol 71-78 ◽  
pp. 1298-1304 ◽  
Author(s):  
Shun Guo Li ◽  
Hui Li
Keyword(s):  
Structural Damage ◽  
Traffic Accidents ◽  
Damage Index ◽  
Element Model ◽  
Bridge Engineering ◽  
Bridge Structure ◽  
Concrete Carbonation ◽  
Detection Approach ◽  
Set Up ◽  
The Impact

The natural environmental erosion and human factors such as the impact of traffic accidents, crack propagation, concrete carbonation and etc, make the bridge’s damage more serious. Therefore, the bridge damage diagnosis has become a hot field of bridge engineering issues. This paper put forward the fractional diagnosis method of multi-span bridge structure reflecting the structural cracks and carbonation damage. In this paper, adopting the optimization equivalent method, the finite element model of damaged structure is set up according to the damaging characteristic of multi-span continuous bridge structure. A damage index of strain mode with practical meanings is adopted which can reflect local damage. Basing on this index, fractional-step detection method of structural damage is presented. The first step is to identify the damage region, then locate the detailed damage location and degree; Performance of the proposed damage detection approach is demonstrated with analysis of a multi-span continuous bridge. The result turns up trumps.

FEM Free Damage Detection of Beam Structures Using the Deflections Estimated by Modal Flexibility Matrix

2021 ◽  
pp. 2150128
Author(s):  
Wen-Yu He ◽  
Wei-Xin Ren ◽  
Lei Cao ◽  
Quan Wang
Keyword(s):  
Damage Detection ◽  
Structural Damage ◽  
Damage Index ◽  
Element Model ◽  
Mode Shapes ◽  
Beam Structures ◽  
Flexibility Matrix ◽  
Damage Quantification ◽  
Modal Flexibility ◽  
The Cost

The deflection of the beam estimated from modal flexibility matrix (MFM) indirectly is used in structural damage detection due to the fact that deflection is less sensitive to experimental noise than the element in MFM. However, the requirement for mass-normalized mode shapes (MMSs) with a high spatial resolution and the difficulty in damage quantification restricts the practicability of MFM-based deflection damage detection. A damage detection method using the deflections estimated from MFM is proposed for beam structures. The MMSs of beams are identified by using a parked vehicle. The MFM is then formulated to estimate the positive-bending-inspection-load (PBIL) caused deflection. The change of deflection curvature (CDC) is defined as a damage index to localize damage. The relationship between the damage severity and the deflection curvatures is further investigated and a damage quantification approach is proposed accordingly. Numerical and experimental examples indicated that the presented approach can detect damages with adequate accuracy at the cost of limited number of sensors. No finite element model (FEM) is required during the whole detection process.

Interaction of external head impact parameters on region and volume of strain for collisions in sport

2018 ◽  
Vol 233 (2) ◽  
pp. 258-267 ◽  
Author(s):  
R Anna Oeur ◽  
Michael D Gilchrist ◽  
Thomas Blaine Hoshizaki
Keyword(s):  
Brain Injuries ◽  
Element Model ◽  
Brain Regions ◽  
Peak Strain ◽  
Centre Of Gravity ◽  
Impact Parameters ◽  
Four Levels ◽  
Set Up ◽  
The Impact ◽  
Strain Responses

Collisions with the head are the primary cause of concussion in contact sports. Head impacts can be further characterized by velocity, striking mass, compliance, and location (direction). The purpose of this study was to describe the interaction effects of these parameters on peak strain in four brain regions and the volume of strain for collision impacts. A pendulum test set-up was used to deliver impacts to an adult Hybrid III headform according to four levels of mass (3, 9, 15, and 21 kg), four velocities (1.5, 3.0, 4.5, and 6.0 m/s), two impact locations (through the centre of gravity and a non-centre of gravity), and three levels of compliance simulating unprotected, helmeted, and well-padded conditions in sport. Headform accelerations were input into a brain finite element model to obtain peak strain in the frontal, temporal, parietal, and occipital lobes and the volume of the brain experiencing 0.10, 0.15, 0.20, and 0.25 strains. Centre-of-gravity impacts created the highest strains (peak and volume) under low compliance and non-centre-of-gravity impacts produced greater strain responses under medium and high compliance conditions. The temporal lobe was the region that consistently displayed the highest peak strains, which may be due to the proximity of the impact locations to this region. Interactions between mass and velocity displayed effects where the 9-kg mass had higher peak and volumes of strain than the 15-kg mass at velocities of 3.0 and 4.5 m/s. This study demonstrates the important role of interacting impact parameters on increasing strain responses that are relevant to the spectrum of diffuse brain injuries, including concussion.

scholarly journals Seismic Damage Model of Bridge Piers Subjected to Biaxial Loading Considering the Impact of Energy Dissipation

2019 ◽  
Vol 9 (7) ◽  
pp. 1481 ◽  
Author(s):  
Shangshun Lin ◽  
Zhanghua Xia ◽  
Jian Xia
Keyword(s):  
Energy Dissipation ◽  
Structural Damage ◽  
Biaxial Loading ◽  
Mechanical Performance ◽  
Damage Model ◽  
Damage Index ◽  
Seismic Damage ◽  
Bridge Piers ◽  
Dissipated Energy ◽  
The Impact

The large degradation of the mechanical performance of hollow reinforced concrete (RC) bridge piers subjected to multi-dimensional earthquakes has not been thoroughly assessed. This paper aims to improve the existing seismic damage model to assess the seismic properties of tall, hollow RC piers subjected to pseudo-static, biaxial loading. Cyclic bilateral loading tests on fourteen 1/14-scale pier specimens with different slenderness ratios, axial load ratios, and transverse reinforcement ratios were carried out to investigate the damage propagation and the cumulative dissipated energy with displacement loads. By considering the influence of energy dissipation on structural damage, a new damage model (M-Usami model) was developed to assess the damage characteristics of hollow RC piers. The results present four consecutive damage stages during the loading process: (a) cracking on concrete surface, (b) yielding of longitudinal reinforcements; (c) spalling of concrete, and (d) collapsing of pier after the concrete crushed and the longitudinal bars ruptured due to the flexural failure. The damage level caused by the seismic waves can be reduced by designing specimens with a good seismic energy dissipation capacity. The theoretical damage index values calculated by the M-Usami model agreed well with the experimental observations. The developed M-Usami model can provide insights into the approaches to assessing the seismic damage of hollow RC piers subjected to bilateral seismic excitations.

scholarly journals Research on Blade-Casing Rub-Impact Mechanism by Experiment and Simulation in Aeroengines

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Jie Hong ◽  
Tianrang Li ◽  
Zhichao Liang ◽  
Dayi Zhang ◽  
Yanhong Ma
Keyword(s):  
High Speed ◽  
High Performance ◽  
Element Model ◽  
Physical Parameters ◽  
Test Rig ◽  
Calculation Results ◽  
Rotor Support ◽  
Blade Tip ◽  
Set Up ◽  
The Impact

Aeroengines pursue high performance, and compressing blade-casing clearance has become one of the main ways to improve turbomachinery efficiency. Rub-impact faults occur frequently with clearance decreasing. A high-speed rotor-support-casing test rig was set up, and the mechanism tests of light and heavy rub-impact were carried out. A finite element model of the test rig was established, and the calculation results were in good agreement with the experimental results under both kinds of rub-impact conditions. Based on the actual blade-casing structure model, the effects of the major physical parameters including imbalance and material characteristics were investigated. During the rub-impact, the highest stress occurs at the blade tip first and then it is transmitted to the blade root. Deformation on the impact blade tip generates easily with decreased yield strength, and stress concentration at the blade tip occurs obviously with weaker stiffness. The agreement of the computation results with the experimental data indicates the method could be used to estimate rub-impact characteristics and is effective in design and analyses process.

scholarly journals Identification of Damage on Sluice Hoist Beams Using Local Mode Evoked by Swept Frequency Excitation

Sensors ◽  
2021 ◽  
Vol 21 (19) ◽  
pp. 6357
Author(s):  
Qingyang Wei ◽  
Hao Xu ◽  
Yifei Li ◽  
Li Chen ◽  
Drahomír Novák ◽  
...  
Keyword(s):  
Damage Detection ◽  
Structural Damage ◽  
Large Scale ◽  
Damage Index ◽  
Three Dimensional ◽  
Element Model ◽  
Local Mode ◽  
Structural Systems ◽  
Significant Shift ◽  
Frequency Excitation

As a global vibration characteristic, natural frequency often suffers from insufficient sensitivity to structural damage, which is associated with local variations of structural material or geometric properties. Such a drawback is particularly significant when dealing with the large scale and complexity of sluice structural systems. To this end, a damage detection method in sluice hoist beams is proposed that relies on the utilization of the local primary frequency (LPF), which is obtained based on the swept frequency excitation (SFE) technique and local resonance response band (LRRB) selection. Using this method, the local mode of the target sluice hoist beam can be effectively excited, while the vibrations of other components in the system are suppressed. As a result, the damage will cause a significant shift in the LPF of the sluice hoist beam at the local mode. A damage index was constructed to quantitatively reflect the damage degree of the sluice hoist beam. The accuracy and reliability of the proposed method were verified on a three-dimensional finite element model of a sluice system, with the noise resistance increased from 0.05 to 0.2 based on the hammer impact method. The proposed method exhibits promising potential for damage detection in complex structural systems.

Study of Carbon Fiber/Polycarbonate (CF/PC) Material Sandwich Structure for Vehicle Hood

2011 ◽  
Vol 287-290 ◽  
pp. 472-476
Author(s):  
Tso Liang Teng ◽  
Cho Chung Liang ◽  
Chien Jong Shih ◽  
Manh Trung Nguyen
Keyword(s):  
Carbon Fiber ◽  
Sandwich Structure ◽  
Traffic Accidents ◽  
Element Model ◽  
Fiber Reinforced ◽  
Vehicle Model ◽  
Carbon Fiber Reinforced ◽  
Safety Characteristic ◽  
The Impact ◽  
The Finite Element Model

Traffic accidents are the worldwide problem. Based on many reports in the word, the front parts of vehicle is the most likely to strike at pedestrians when the accident occurs. And the fatal injuries almost occurred to pedestrians when their head impact to the vehicle hood. So it’s necessary to reduce the pedestrian injuries as much as possible to enhance the safety characteristic, one of the most importance criteria for vehicles manufactures. In this study, the effect of sandwich structure with material of carbon fiber reinforced polycarbonate (CF/PC) will be concerned as vehicle bonnet change. The finite element model of headform impactor and Honda vehicle model was analyzed detail by LS-DYNA as simulation. The impact between headform impactor and original vehicle model or the carbon fiber reinforced polycarbonate material bonnet vehicle model was executed and the comparison result was shown. This study, the European Enhanced Vehicle-safety Committee/ Working Group 17 (EEVC/WG17) and NCAP requirements was adopted.

scholarly journals Characterization and Imaging of Localized Thickness Loss in GFRP with Ka-Band Microwave Open-Ended Waveguides

2020 ◽  
Author(s):  
Jinhua Hu ◽  
Yong Li ◽  
Jianguo Tan ◽  
Wenjia Li ◽  
Zhenmao Chen
Keyword(s):  
Ultrasonic Testing ◽  
Impact Damage ◽  
Element Model ◽  
Fibre Reinforcement ◽  
Destructive Testing ◽  
Ka Band ◽  
Thickness Loss ◽  
Set Up ◽  
The Impact ◽  
Non Destructive

Glass Fibre Reinforcement Plastic (GFRP) is widely used in engineering fields including aerospace, marine and construction, etc. During practical service, it is prone to the impact damage leading to the Localized Thickness Loss (LTL) which severely influences the integrity and safety of GFRP. To detect and evaluate LTL in GFRP, common Non-Destructive Testing (NDT) techniques such as ultrasonic testing and thermography are usually applied. Complementary to these methods, microwave NDT has been found to be one of the promising techniques in quantitative evaluation of GFRP. In this paper, the characterization and imaging of LTL in GFRP by microwave NDT are intensively investigated. A 2D Finite Element Model (FEM) with the Ka-band open-ended waveguide and GFRP sample subject to LTL has been set up and adopted for analysis of field characteristics and testing signals. Following that, an experimental investigation is conducted to further study the feasibility of LTL imaging by microwave NDT with the Ka-band open-ended waveguide. The results from simulations and experiments indicate the applicability of Ka-band microwave open-ended waveguide for detection and evaluation of LTL in GFRP.

Non-baseline method for damage detection in truss structures using displacement and strain measurements

2018 ◽  
Vol 22 (3) ◽  
pp. 818-830 ◽  
Author(s):  
Peng Ren ◽  
Zhi Zhou ◽  
Jinping Ou
Keyword(s):  
Damage Detection ◽  
Structural Damage ◽  
Experimental Studies ◽  
Measurement Data ◽  
Element Model ◽  
Truss Structures ◽  
Detection Methods ◽  
Detection Approach ◽  
Potential Development ◽  
System States

Realistic problems restrict the application of many existing structural damage detection methods. Due to the requirement of a comparison between two system states, lack of appropriate baseline data may become one of the limitations to undertake structural health monitoring strategy. This article suggests a non-baseline damage detection approach based on the mixed measurements and the transmissibility concept and demonstrates it in truss structures. The algorithm uses the measurement data from the strains of the truss elements and the displacements of the truss joints, in which the displacements are utilized to estimate the baseline strains based on the transmissibility matrix from an initial finite element model. Wavelet-based damage-sensitive features are extracted from both estimated and measured strains to detect damages of the target elements. Numerical and experimental studies are performed to investigate the feasibility and effectiveness of the proposed approach. It is concluded from the instances that the robustness of the algorithm is realized when handling the measurement noise, modeling errors and the operational condition variability. These permit the potential development of the damage detection method for real structures in site.

scholarly journals Localization of structural damage based on its dynamic analysis

2019 ◽  
pp. 170-176
Author(s):  
Solon Zenkov
Keyword(s):  
Structural Damage ◽  
Direct Method ◽  
Damage Index ◽  
Element Model ◽  
Fatigue Tests ◽  
Vibration Modes ◽  
Shape Variation ◽  
Index Method ◽  
Dog Bone ◽  
Physical Tests

This paper gives the results of analytical and experimental data on localization of structural damage, obtained through comparison of vibration modes for intact and damaged structure. The paper studies a standard dog-bone sample used for highcycle fatigue tests, the analysis being performed for its finite-element model. Necking damage of the sample was simulated by step-by-step elimination of elements from the model. Physical tests were performed as per the same approach. This paper studies the following damage localization methods: direct method of shape variation; shape curvature method and damage index method. The analysis of vibration shapes performed as per various approaches yielded damage locations and made it possible to identify the most accurate of above-mentioned methods.

Damage Identification of Multi-Box Steel-Concrete Composite Bridges Based on Modal Curvature Difference Method

2012 ◽  
Vol 226-228 ◽  
pp. 1689-1692 ◽  
Author(s):  
Yi Qiang Xiang ◽  
Li Si Liu ◽  
Yu Liang He
Keyword(s):  
Difference Method ◽  
Structural Damage ◽  
Damage Identification ◽  
Damage Index ◽  
Element Model ◽  
Before And After ◽  
Composite Bridges ◽  
Modal Curvature ◽  
Composite Bridge ◽  
The Difference

Based on the data from dynamic analysis of a 40m-span multi-box steel-concrete composite bridge and the difference value of its modal curvature before and after the structural damage, this paper detects the damage locations in steel-concrete composite bridge by modal curvature difference method (MCDM). Here we adopt the updated finite element model in last work as analytical model, taking concrete density and elastic modulus as updating parameters and modal frequency+MAC as reference data. The results indicate that the modal curvature difference method can well locate the damages in steel-concrete composite bridge, especially the damage in concrete. But the change rate of frequency as damage index is insensitive to the bridge damage and the method can’t be applied solely for practical.

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