scholarly journals Microseismic Signal Characterization and Numerical Simulation of Concrete Beam Subjected to Three-Point Bending Fracture

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Nuwen Xu ◽  
Feng Dai ◽  
Chun Sha ◽  
Yingcheng Lei ◽  
Biao Li
Keyword(s):  
Concrete Beam ◽  
Process Analysis ◽  
Failure Process ◽  
Microseismic Monitoring ◽  
Bending Test ◽  
Hydropower Station ◽  
Mass Concrete ◽  
Physical Test ◽  
Deformation And Failure ◽  
Three Point Bending

To study the generation mechanism and failure mode of cracks in mass concrete, microseismic monitoring is conducted on the fracture processes of the three-point bending roller compacted concrete (RCC) beam of Guanyinyan hydropower station. The spectrum characteristics of microseismic signals in different deformation and failure stages of the concrete beam are analyzed, and the identification method of the fracture stages and crack propagation precursors of concrete beam is established. Meanwhile, the Realistic Failure Process Analysis code (RFPA) is adopted to simulate and analyze the entire failure processes of concrete beam from its cracks initiation, development, propagation, and coalescence, until macroscopic fractures formation subjected to three-point bending test. The relation curve of the load, loaded displacement, and acoustic emission (AE) of concrete beam in the three-point bending test is also obtained. It is found that the failure characteristics of concrete beam obtained from numerical experiments agree well with the field physical test results. The heterogeneity of concrete is the major cause of zigzag propagation paths of beam cracks subjected to three-point bending tests. The results lay foundation for further exploring the formation mechanism of dam concrete cracks of Guanyinyan hydropower station.

scholarly journals Deformation and Failure Behavior of Wooden Sandwich Composites with Taiji Honeycomb Core under a Three-Point Bending Test

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2325 ◽  
Author(s):  
Jingxin Hao ◽  
Xinfeng Wu ◽  
Gloria Oporto ◽  
Jingxin Wang ◽  
Gregory Dahle ◽  
...  
Keyword(s):  
Shear Failure ◽  
Dominant Role ◽  
Honeycomb Structure ◽  
Structure Design ◽  
Bending Test ◽  
Failure Behavior ◽  
Sandwich Composites ◽  
Honeycomb Core ◽  
Deformation And Failure ◽  
Three Point Bending

A new type of Taiji honeycomb structure bonded outside with wood-based laminates was characterized from a mechanical standpoint. Both theoretical and experimental methods were employed to analyze comprehensively the deformation behavior and failure mechanism under a three-point bending test. The analytical analysis reveals that a Taiji honeycomb has 3.5 times higher strength in compression and 3.44 times higher strength in shear compared with a traditional hexagonal honeycomb. Considering the strength-weight issue, the novel structure also displays an increase in compression strength of 1.75 times and shear strength of 1.72 times. Under a three-point bending test, indentation and core shear failure played the dominant role for the total failure of a wooden sandwich with Taiji honeycomb core. Typical face yield was not observed due to limited thickness-span ratio of specimens. Large spans weaken the loading level due to the contribution of global bending stress in the compressive skin to indentation failure. A set of analytical equations between mechanical properties and key structure parameters were developed to accurately predict the threshold stresses corresponding to the onset of those deformation events, which offer critical new knowledge for the rational structure design of wooden sandwich composites.

Numerical Simulation on AE Characteristics of Rock and Concrete Materials

2007 ◽  
Vol 353-358 ◽  
pp. 961-964 ◽  
Author(s):  
Yu Mei Kang ◽  
Chun An Tang ◽  
Zheng Zhao Liang ◽  
Gen Gye Chen
Keyword(s):  
Crack Propagation ◽  
Failure Process ◽  
Great Influence ◽  
Space Distribution ◽  
Bending Test ◽  
Propagation Path ◽  
Notch Depth ◽  
Crack Propagation Path ◽  
Three Point Bending ◽  
Simulation Results

Based on physical model of three-point-bending test, the AE characteristics of three-point-bending beams with different relative notch depth during the entire loading period was simulated by using RFPA3D(realistic failure process analysis) code. Simulation results show that the relative notch depth affects the AE characteristics significantly. With increasing relative notch depth, the occurrence of AE events decreases remarkably. The stress distribution figures, elastic modulus photo and AE relative energy time-space distribution figures as well as an analysis on the failure process are also provided. Based on the analysis of simulation results, it is concluded that the heterogeneity of rock and concrete has great influence on the crack propagation path, which leads the crack propagation path becoming curvilinear.

scholarly journals Relationship between Movement Laws of the Overlaying Strata and Time Space of the Mined-Out Volume

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Xiang Yu ◽  
Kang Zhao ◽  
Qing Wang ◽  
Yajing Yan ◽  
Yongjun Zhang ◽  
...  
Keyword(s):  
Rock Mass ◽  
Process Analysis ◽  
Failure Process ◽  
Failure Behavior ◽  
Overburden Rock ◽  
Deformation And Failure ◽  
Working Face ◽  
Time Space ◽  
Rock Failure Process ◽  
Function Relationship

The study and accurate prediction of the movement of overburden rock mass and surface subsidence are crucial for a safe production in metal mines. This study investigates the relationship between the movement laws of overlaying strata and the time space of a mined-out volume using Rock Failure Process Analysis (RFPA) System. Furthermore, the movement, deformation, and failure laws of overlaying strata are examined in different positions when a goaf volume is certain and the failure behavior of the overlaying strata. This study analyzes the similarities and differences of the overlaying strata comparatively. Results show that, regardless of the movement range or subsidence value of the overlying rock mass, a power function relationship is observed between them and working face advancement. Setting the equation shows that the scope of the overlying rock mass is significant when the ratio of a certain position distance roof to the working face distance is small. The results provide a reference for controlling the displacement of the overlying rock mass and treating goaf.

scholarly journals Research on the Law of Large-Scale Deformation and Failure of Soft Rock Based on Microseismic Monitoring

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Feng Chen ◽  
Tianhui Ma ◽  
Chun’an Tang ◽  
Yanhong Du ◽  
Zhichao Li ◽  
...  
Keyword(s):  
Monitoring System ◽  
Large Scale ◽  
Failure Process ◽  
Soft Rock ◽  
Microseismic Monitoring ◽  
Surrounding Rock ◽  
Deformation And Failure ◽  
Microseismic Events ◽  
Rock Tunnel ◽  
Microseismic Event

Based on the existing Canadian ESG microseismic monitoring system, a mobile microseismic monitoring system for a soft rock tunnel has been successfully constructed through continuous exploration and improvement to study the large-scale nucleation and development of microfractures in the soft rock of the Yangshan Tunnel. All-weather, continuous real-time monitoring is conducted while the tunnel is excavated through drilling and blasting, and the waveform characteristics of microseismic events are analysed. Through the recorded microseismic monitoring data, the variation characteristics of various parameters (e.g., the temporal, spatial, and magnitude distributions of the microseismic events, the frequency of microseismic events, and the microseismic event density and energy) are separately studied during the process of large-scale deformation instability and failure of the soft rock tunnel. The relationship between the deterioration of the rock mass and the microseismic activity during this failure process is consequently discussed. The research results show that a microseismic monitoring system can be used to detect precursors; namely, the microseismic event frequency and energy both will appear “lull” and “active” periods during the whole failure process of soft rock tunnel. Two peaks are observed during the evolution of failure. When the second peak occurs, it is accompanied by the destruction of the surrounding rock. The extent and strength of the damage within the surrounding rock can be delineated by the spatial, temporal, and magnitude distributions of the microseismic events and a microseismic event density nephogram. The results of microseismic analysis confirm that a microseismic monitoring system can be used to monitor the large-scale deformation and failure processes of a soft rock tunnel and provide early warning for on-site construction workers to ensure the smooth development of the project.

Influence of the Reinforcement’s Number on the Mechanical Properties of the Reinforced Concrete Beam

2010 ◽  
Vol 105-106 ◽  
pp. 723-728 ◽  
Author(s):  
Wei Hong Li ◽  
Xue Yang
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beam ◽  
Concrete Beams ◽  
Process Analysis ◽  
Failure Process ◽  
Reinforced Concrete Beam ◽  
Reinforced Concrete Beams ◽  
Practical Significance ◽  
Gradual Failure ◽  
Set Up

Basing on the experimental data collected, the mechanical model of reinforced concrete beams’ gradual failure has been set up, to test differ reinforced components with loads and study the process of split. At last the influence of reinforcement’s number on components’ intensity and failure process are analyzed by using MFPA2D (Material Failure Process Analysis) software, started with the analysis of formula cracks after experiments. The results showed that the number of reinforcement is not the more the better. When ultra-reinforced beam appears, its mechanical capacity enhances but the bars won’t do their best, furthermore, it is uneconomical. Accordingly, less-reinforced beam should also be avoided for safe. Everything possible should be made to avoid ultra-reinforced beam and less-reinforced beam in engineering. By all means, this conclusion has practical significance during our practice.

Influence of Protective Layer Thickness on the Mechanical Properties of Reinforced Concrete Beam

2010 ◽  
Vol 177 ◽  
pp. 549-553
Author(s):  
Wei Hong Li ◽  
Feng Hai Ma
Keyword(s):  
Mechanical Properties ◽  
Reinforced Concrete ◽  
Layer Thickness ◽  
Concrete Beam ◽  
Process Analysis ◽  
Failure Process ◽  
Protective Layer ◽  
Reinforced Concrete Beam ◽  
Four Point Bending ◽  
Reinforced Concrete Member

In this paper, MFPA (Material Failure Process Analysis) is utilized to simulate the failure process of reinforced concrete member under the situation of four-point bending. The influence which protective layer thickness does on the mechanical properties of reinforced concrete beam is mainly studied. Results indicate that the increase of the protective layer thickness will reduce the sectional effective height of the beam, which decrease the bearing capacity of the member either. Therefore, choosing the protective layer thickness properly will make the member having preferable properties. In this study, what also be found is that generally it is more reasonable when protective layer is within 90 mm. However, it is necessary for the protective layer thickness to be confirmed by relevant specifications and standards on the premise above.

Numerical Simulation of Crack Development in Reinforced Concrete Beam with Different Shear Span Ratios

2014 ◽  
Vol 536-537 ◽  
pp. 1435-1438
Author(s):  
Juan Xia Zhang ◽  
Zhong Hui Chen ◽  
Xian Zhang Guo ◽  
Chun An Tang ◽  
Zheng Zhao Liang
Keyword(s):  
Numerical Simulation ◽  
Reinforced Concrete ◽  
Concrete Beam ◽  
Process Analysis ◽  
Failure Process ◽  
Reinforced Concrete Beam ◽  
Numerical Code ◽  
Shear Span ◽  
Distribution Rule ◽  
Complete Failure

The periodically distributed fracture spacing phenomenon exists in the failure process of the pure bending region of the reinforced concrete beam. A numerical code RFPA3D (3D Realistic Failure Process Analysis) is used to investigate the crack distribution rule of reinforced concrete beam with different shear span ratios. The displacement-controlled loading scheme was used to simulate the complete failure process of reinforced concrete beam. The numerical simulation results were agreed well with the theoretical analysis and experiment observations. The study is focused on the failure process of the reinforced concrete beam and the effects of the shear span ratio on the failure mode.

scholarly journals Smart Aggregate-Piezoceramic Patch Combination for Health Monitoring of Concrete Structures

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Jinlei Zhao ◽  
Tengfei Bao ◽  
Shanying Chen ◽  
Tribikram Kundu
Keyword(s):  
Health Monitoring ◽  
Concrete Beam ◽  
Damage Index ◽  
Concrete Structures ◽  
Signal Amplitude ◽  
Bending Test ◽  
Three Point Bending ◽  
Recorded Signal ◽  
Amplitude Fluctuations ◽  
Smart Aggregate

A new method combining an embedded smart aggregate and surface mounted piezoceramic patches is introduced for health monitoring of concrete structures. The smart aggregate is embedded in a concrete beam as an actuator (or transmitter), and piezoceramic patches are attached on the surface of the concrete beam as sensors. Two tests using the smart aggregate and the piezoceramic patches are conducted. The first test investigates the sensitivity of the recorded signal amplitude-frequency relation on the piezoceramic patches. To explain the significant amplitude fluctuations in the results, the possibility of resonance occurring in the piezoceramic patches in a certain frequency range is verified through finite element modeling. In the second test, a damage index is proposed to evaluate the health of concrete structures and a three-point bending test is conducted to induce damage in the concrete beam. It is observed that, with increasing severity of damage in the concrete beam, the recorded signal amplitude at the patches decreases gradually while the value of the damage index increases significantly. The experimental results show that the proposed method is an effective tool for health monitoring of concrete structures.

scholarly journals Additive Manufacturing-Based In Situ Consolidation of Continuous Carbon Fibre-Reinforced Polycarbonate

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2450
Author(s):  
Andreas Borowski ◽  
Christian Vogel ◽  
Thomas Behnisch ◽  
Vinzenz Geske ◽  
Maik Gude ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Carbon Fibre ◽  
Bending Test ◽  
Thermoplastic Composites ◽  
Experimental Investigations ◽  
Material Structure ◽  
Three Point Bending ◽  
Continuous Fibre ◽  
Local Material

Continuous carbon fibre-reinforced thermoplastic composites have convincing anisotropic properties, which can be used to strengthen structural components in a local, variable and efficient way. In this study, an additive manufacturing (AM) process is introduced to fabricate in situ consolidated continuous fibre-reinforced polycarbonate. Specimens with three different nozzle temperatures were in situ consolidated and tested in a three-point bending test. Computed tomography (CT) is used for a detailed analysis of the local material structure and resulting material porosity, thus the results can be put into context with process parameters. In addition, a highly curved test structure was fabricated that demonstrates the limits of the process and dependent fibre strand folding behaviours. These experimental investigations present the potential and the challenges of additive manufacturing-based in situ consolidated continuous fibre-reinforced polycarbonate.

scholarly journals Research on Supporting Method for High Stressed Soft Rock Roadway in Gentle Dipping Strata of Red Shale

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 423
Author(s):  
Chunde Ma ◽  
Jiaqing Xu ◽  
Guanshuang Tan ◽  
Weibin Xie ◽  
Zhihai Lv
Keyword(s):  
Failure Process ◽  
High Stress ◽  
Soft Rock ◽  
In Situ Stress ◽  
Mechanical Parameters ◽  
Deformation And Failure ◽  
Deep Mine ◽  
Plastic Energy ◽  
Roadway Stability ◽  
Phosphate Mine

Red shale is widely distributed among the deep mine areas of Kaiyang Phosphate Mine, which is the biggest underground phosphate mine of China. Because of the effect of various factors, such as high stress, ground water and so on, trackless transport roadways in deep mine areas were difficult to effectively support for a long time by using traditional supporting design methods. To deal with this problem, some innovative works were carried out in this paper. First, mineral composition and microstructure, anisotropic, hydraulic mechanical properties and other mechanical parameters of red shale were tested in a laboratory to reveal its deformation and failure characteristics from the aspect of lithology. Then, some numerical simulation about the failure process of the roadways in layered red shale strata was implemented to investigate the change regulation of stress and strain in the surrounding rock, according to the real rock mechanical parameters and in-situ stress data. Therefore, based on the composite failure law and existing support problems of red shale roadways, some effective methods and techniques were adopted, especially a kind of new wave-type bolt that was used to relieve rock expansion and plastic energy to prevent concentration of stress and excess deformation. The field experiment shows the superiorities in new techniques have been verified and successfully applied to safeguard roadway stability.

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