Fatigue Test Studies on Reinforced Concrete Hollow Slab Girder

2013 ◽  
Vol 787 ◽  
pp. 825-828
Author(s):  
Hong Bing Zhu ◽  
Yao Zhao ◽  
Bo Xia
Keyword(s):  
Reinforced Concrete ◽  
Rapid Development ◽  
Fatigue Loading ◽  
Development Stage ◽  
Damage Development ◽  
Highway Engineering ◽  
Three Stages ◽  
Last Stage ◽  
Number Of Cycles ◽  
Stable Stage

Reinforced Concrete (RC) Hollow Slab Girder is widely used in Highway Engineering, and fatigue load is an essential aspect of causing damage. In order to accurately calculate the distribution and development laws of RC hollow slab girder fatigue strain, experiment on Amplitude fatigue with five experimental beams were done in the laboratory. The beams obviously presented a rule of three stages: the damage development is fast in fore period and later period; but the hazard from fatigue in the midterm developed steadily relatively. The destruction of fatigue damage is the steel brittle fracture. Fatigue failure could be divided into three periods: rapid development stage, stable stage and destruction stage. In last stage one or two main cracks continues to expand, the rest stop growing and gradually closed, it fatigue fractured at the main crack. With the increase of the number of cycles of fatigue loading, the growth rate slowed down into a relatively stable stage, when approaching destruction there is relatively substantially growth.

Evolution of Cracks in Nano-CaCO3 Modified Pre-Disintegrated Carbonaceous Mudstone Under Cyclic Wetting and Drying

2020 ◽  
Vol 20 (8) ◽  
pp. 5117-5122
Author(s):  
Ling Zeng ◽  
Yurong Yuan ◽  
Junhui Zhang
Keyword(s):  
Electron Microscopy ◽  
Rapid Development ◽  
Development Stage ◽  
Crack Evolution ◽  
Wetting And Drying ◽  
Ph Values ◽  
Three Stages ◽  
Final Crack ◽  
Scanning Electron ◽  
Stable Stage

To explore the evolution of cracks in the pre-disintegrated carbonaceous mudstone, wetting-drying tests were carried out on nano-CaCO3 modified pre-disintegrated carbonaceous mudstone samples. The samples were prepared with aqueous solutions of different pH values. Scanning electron microscopy (SEM) was performed to clarify the mechanism of crack evolution of pre-disintegrated carbonaceous mudstone modified by nano-CaCO3. The results showed that development of shrinkage and cracks was basically divided into three stages, i.e., the gestation stage, the rapid development stage and the stable stage. For the samples without nano-CaCO3, the final crack rates and pore sizes of samples with pH = 3 and pH = 11 were larger than corresponding values of the sample with pH= 7. Moreover, final crack rate and pore size significantly decreased with the addition of nano-CaCO3 suggesting that nano-CaCO3 can effectively improve cracking resistance of pre-disintegrated carbonaceous mudstone.

Fatigue Damage Evaluation in CFRP Woven Fabric Composites Through Dynamic Modulus Measurements

2004 ◽  
Author(s):  
Hideaki Kasano ◽  
Osamu Hasegawa ◽  
Chiaki Miyasaka
Keyword(s):  
Fatigue Damage ◽  
Material Properties ◽  
Elastic Moduli ◽  
Fatigue Loading ◽  
Damage Function ◽  
Fatigue Tests ◽  
Woven Fabric ◽  
Damage Development ◽  
Dynamic Elastic Moduli ◽  
Number Of Cycles

Advanced fiber reinforced composite materials offer substantial advantages over metallic materials for the structural applications subjected to fatigue loading. With the increasing use of these composites, it is required to understand their mechanical response to cyclic loading [1–4]. Our major concern in this work is to macroscopically evaluate the damage development in composites during fatigue loading. For this purpose, we examine what effect the fatigue damage may have on the material properties and how they can be related mathematically to each other. In general, as the damage initiates in composite materials and grows during cyclic loading, material properties such as modulus, residual strength and strain would vary and, in many cases, they may be significantly reduced because of the progressive accumulation of cracks. Therefore, the damage can be characterized by the change in material properties, which is expected to be available for non-destructive evaluation of the fatigue damage development in composites. Here, the tensiontension fatigue tests are firstly conducted on the plain woven fabric carbon fiber composites for different loading levels. In the fatigue tests, the dynamic elastic moduli are measured on real-time, which will decrease with an increasing number of cycles due to the degradation of stiffness. Then, the damage fimction presenting the damage development during fatigue loading is determined from the dynamic elastic moduli thus obtained, from which the damage function is formulated in terms of a number of cycles and an applied loading level. Finally, the damage function is shown to be applied for predicting the remaining fifetime of the CFRP composites subjected to two-stress level fatigue loading.

scholarly journals The Progress of Global Antimicrobial Resistance Governance and Its Implication to China: A Review

Antibiotics ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1356
Author(s):  
Jia Yin ◽  
Yu Wang ◽  
Xueran Xu ◽  
Yinqi Liu ◽  
Lu Yao ◽  
...  
Keyword(s):  
Antimicrobial Resistance ◽  
Central Government ◽  
Rapid Development ◽  
Development Stage ◽  
Policy Recommendations ◽  
Official Document ◽  
Global Trend ◽  
Global Action ◽  
Three Stages ◽  
Catch Up

China has great potential for engaging in global actions on antimicrobial resistance (AMR) control. This study aims to summarize the process of global AMR governance and provide relevant policy recommendations on how China could take more initiative in the global AMR governance. We searched for academic articles and official document published or issued before December 2020 in e-journal databases, official websites of major organizations, and the relevant national ministries. This review revealed that global action on AMR control has experienced three stages: (1) The beginning stage (1980s and 1990s) when actions were mainly sponsored by high-income countries and AMR surveillance was focused on hospitals; (2) The rapid development stage (2000–2010) when global AMR governance began to concentrate on joint actions in multi-sectors, and developing countries were gradually involved in global actions; (3) The comprehensive stage (2011 to present) when global actions on AMR have covered various fields in different countries. China’s AMR governance has fallen behind at the beginning but recently began to catch up with the global trend. The central government should take a far-fetched view, act decisively and positively towards the global efforts of addressing AMR to play a more active and greater role on the international stage.

scholarly journals Evolution of Guangzhou Biomedical Industry Innovation Network Structure and Its Proximity Mechanism

2020 ◽  
Vol 12 (6) ◽  
pp. 2456
Author(s):  
Kaihuang Zhang ◽  
Qinglan Qian ◽  
Yijing Zhao
Keyword(s):  
Topological Structure ◽  
Rapid Development ◽  
Development Stage ◽  
Innovation Network ◽  
Policy Recommendations ◽  
Biomedical Industry ◽  
Three Stages ◽  
Innovation Cooperation ◽  
Different Characteristics ◽  
The Relationship

The topological structure and multidimensional proximity evolution mechanism of Guangzhou biomedical industry innovation network are studied by using cooperative patents and cooperative papers from 1998 to 2018 with Ucinet and PLS-SEM. Research shows: ① The evolution of the Guangzhou Biomedical Industry Innovation Network can be divided into three stages, which are the primary budding stage of 1998–2005, the steady development stage of 2006–2012, and the rapid development stage of 2013–2018; ② the number of subjects in the innovation network is increasing, and the types of subjects are constantly increasing. The innovation network has gone from small to large, from closed to open, and from simple to complex. Patents and papers cooperation networks show different characteristics at various stages; ③ the relationship between geographical proximity, cognitive proximity, organizational proximity, and innovation network differs in stages. The interaction of proximity varies with the content of innovation cooperation. Based on this result, we have put forward policy recommendations for different innovative content.

scholarly journals Experimental Research on Fatigue Behavior of Existing Reinforced Concrete Beams

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Guangzhen Qu ◽  
Pingming Huang ◽  
Guangli Zhou ◽  
Sizhong Lv
Keyword(s):  
Reinforced Concrete ◽  
Fatigue Test ◽  
Fatigue Behavior ◽  
Fatigue Loading ◽  
Reinforced Concrete Beams ◽  
Damage Development ◽  
Initial State ◽  
Loading Test ◽  
Butt Weld ◽  
Hollow Beams

In order to obtain the law of the fatigue damage development of reinforced concrete hollow beams that has been in service for 24 years, its solid hollow beams were removed and transported to the laboratory for loading test. Two beams were selected for static loading to obtain the ultimate flexural bearing capacity, and three beams were, respectively, subjected to constant-amplitude fatigue loading with different load amplitudes. The static and dynamic behaviors of the beams were monitored in the fatigue test. The fatigue failure of the beams showed that the outermost rebar at the butt weld fractured at first, and the crack width at the fracture position of the steel bar was about 0.3 mm, which was largest in all cracks. After a rebar was broken, midspan deflection and flexibility increased by approximately 20% and 10%, respectively, relative to the initial state. The damage developed rapidly in the following range: (1) the first 10,000 fatigue cycles; (2) after fatigue fracture of the rebar; and in the intermediate stage of fatigue test, the damage development was relatively stable. As the loading amplitude increased, the stiffness degradation and the cumulative damage that occured under the same loading cycle were more significant.

scholarly journals Theoretical and Experimental Fatigue Strength Calculations of Lips Compensating Circumferential Backlash in Gear Pumps

Energies ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 251
Author(s):  
Piotr Osiński ◽  
Grzegorz Chruścielski ◽  
Leszek Korusiewicz
Keyword(s):  
Maximum Stress ◽  
Theoretical Calculations ◽  
Fatigue Loading ◽  
Minimum Thickness ◽  
Bending Tests ◽  
External Gear Pumps ◽  
Gear Pumps ◽  
In Series ◽  
Number Of Cycles ◽  
Technical Solutions

This article presents theoretical and experimental calculations of the minimum thickness of a compensation lip used in external gear pumps. Pumps of this type are innovative technical solutions in which circumferential backlash (clearance) compensation is used to improve their volumetric and overall efficiency. However, constructing a prototype of such a pump requires long-lasting research, and the compensation lip is its key object, due to the fact that it is an element influenced by a notch and that it operates in unfavorable conditions of strong fatigue stresses. The theoretical calculations presented in this article are based on identifying maximum stress values in a fatigue cycle and on implementing the stress failure condition and the conditions related to the required value of the fatigue safety factor. The experimental research focuses on static bending tests of the lips as well as on the fatigue loading of the lips in series of tests at increasing stress values until lip failure due to fatigue. The tests allowed the minimum lip thickness to be found for the assumed number of fatigue cycles, which is 2.5 times the number of cycles used in wear margin tests.

scholarly journals Recent Advances in Phase-Sensitive Optical Time Domain Reflectometry (Ф-OTDR)

2021 ◽  
Vol 11 (1) ◽  
pp. 1-30
Author(s):  
Yunjiang Rao ◽  
Zinan Wang ◽  
Huijuan Wu ◽  
Zengling Ran ◽  
Bing Han
Keyword(s):  
Fiber Optics ◽  
Time Domain ◽  
Acoustic Waves ◽  
Rapid Development ◽  
Development Stage ◽  
Time Domain Reflectometry ◽  
Rayleigh Backscattering ◽  
Optical Time Domain Reflectometry ◽  
Phase Sensitive ◽  
Optical Time

AbstractPhase-sensitive optical time domain reflectometry (Ф-OTDR) is an effective way to detect vibrations and acoustic waves with high sensitivity, by interrogating coherent Rayleigh backscattering light in sensing fiber. In particular, fiber-optic distributed acoustic sensing (DAS) based on the Ф-OTDR with phase demodulation has been extensively studied and widely used in intrusion detection, borehole seismic acquisition, structure health monitoring, etc., in recent years, with superior advantages such as long sensing range, fast response speed, wide sensing bandwidth, low operation cost and long service lifetime. Significant advances in research and development (R&D) of Ф-OTDR have been made since 2014. In this review, we present a historical review of Ф-OTDR and then summarize the recent progress of Ф-OTDR in the Fiber Optics Research Center (FORC) at University of Electronic Science and Technology of China (UESTC), which is the first group to carry out R&D of Ф-OTDR and invent ultra-sensitive DAS (uDAS) seismometer in China which is elected as one of the ten most significant technology advances of PetroChina in 2019. It can be seen that the Ф-OTDR/DAS technology is currently under its rapid development stage and would reach its climax in the next 5 years.

Study of the low cycle fatigue of 12Cr18Ni10Ti steel based on fractal analysis and artificial intelligence approaches

2021 ◽  
Vol 87 (9) ◽  
pp. 59-67
Author(s):  
A. A. Khlybov ◽  
Yu. G. Kabaldin ◽  
M. S. Anosov ◽  
D. A. Ryabov ◽  
D. A. Shatagin
Keyword(s):  
Neural Network ◽  
Growth Rate ◽  
Fractal Dimension ◽  
Low Temperatures ◽  
Main Crack ◽  
Fatigue Loading ◽  
Wide Range ◽  
Lower Temperature ◽  
Number Of Cycles ◽  
Dimension Index

The evolution of the structure and assessment of the age limit of steel 12Cr18Ni10Ti upon fatigue loading is considered using neural network modeling and approaches of fractal analysis of the microstructure. An algorithm for processing images of the microstructures has been developed to improve their quality. An indicator of the fractal dimension of the image is used as a quantitative indicator for assessing the evolution of the microstructure of the surface metal layer. A quantitative assessment of the structures at different stress amplitudes is carried out in a wide range of low temperatures using the fractal dimension index. Correlation of the fractal dimension index with the run of the sample material is shown. The appearance of the main crack was observed in the range of 0.7 - 0.8 from the number of cycles to failure, after which the crack growth rate increased. At a lower temperature, the main crack is formed later, but further loading results in a higher crack growth rate. Formation of the secondary phases in austenitic steel at a lower temperature occurred at earlier stages than that at a temperature of t = +20°C, which led to hardening of the material. An artificial neural network (ANN) has been developed and trained for assessing structural changes in metal proceeding from the fractal dimensionality of the microstructure images at different stages of fatigue loading. The developed neural network made it possible to estimate with a sufficiently high accuracy the number of cycles before damage of the sample and the residual life of the material. Thus, the developed ANN can be used to assess the current state of the material in a wide range of low temperatures.

scholarly journals Transcriptome analysis of lateral buds from Phyllostachys edulis rhizome during germination and early shoot stages

2020 ◽  
Author(s):  
Yuting Shou ◽  
Yihua Zhu ◽  
Yulong Ding
Keyword(s):  
Signaling Pathways ◽  
High Throughput Sequencing ◽  
Stem Elongation ◽  
Rapid Development ◽  
Development Stage ◽  
Fast Growth ◽  
Moso Bamboo ◽  
Phyllostachys Edulis ◽  
Lateral Buds ◽  
Meristem Development

Abstract Background: The vegetative growth is an important stage for plants when they conduct photosynthesis, accumulate and collect all resources needed and prepare for reproduction stage. Bamboo is one of the fastest growing plant species. The rapid growth of Phyllostachys edulis results from the expansion of intercalary meristem at the basal part of nodes, which are differentiated from the apical meristem of rhizome lateral buds. However, little is known about the major signaling pathways and players involved during this rapid development stage of bamboo. To study this question, we adopted the high-throughput sequencing technology and compared the transcriptomes of Moso bamboo rhizome buds in germination stage and late development stage. Results: We found that the development of Moso bamboo rhizome lateral buds was coordinated by multiple pathways, including meristem development, sugar metabolism and phytohormone signaling. Phytohormones have fundamental impacts on the plant development. We found the evidence of several major hormones participating in the development of Moso bamboo rhizome lateral bud. Furthermore, we showed direct evidence that Gibberellic Acids (GA) signaling participated in the Moso bamboo stem elongation. Conclusion: Significant changes occur in various signaling pathways during the development of rhizome lateral buds. It is crucial to understand how these changes are translated to Phyllostachys edulis fast growth. These results expand our knowledge on the Moso bamboo internodes fast growth and provide research basis for further study.

scholarly journals Utilization of the Tiktok Video Application as a Means of Showing Existence And Self-Disclosure of Teenagers on Social Media

2021 ◽  
Vol 04 (09) ◽  
Author(s):  
Esty Wulandari ◽  
Keyword(s):  
Social Media ◽  
Rapid Development ◽  
Self Disclosure ◽  
Social Penetration Theory ◽  
Video Application ◽  
The Social ◽  
Social Penetration ◽  
Use Of Social Media ◽  
Share Information ◽  
Stable Stage

Along with the rapid development of technology, the current use of social media by the community is also increasing. One of the social media that is currently on the rise is the TikTok application. TikTok application users come from various backgrounds and ages, including teenagers. Video-based TikTok features accompanied by music, writing, and pictures are considered attractive so that they are liked by teenagers as a means of showing their existence and self-disclosure. TikTok is also currently developing as a way to share information. The theory applied by the researcher was Alman and Taylor's Social Penetration Theory. In addition to such theory, this paper are supported and strengthened by the concepts of Self-Disclosure, Social Media, Teenagers, TikTok, and also Self-Existence. This paper was a qualitative descritpive study which applied a qualitative study method. This paper involved several informants namely teenagers who were also the users of the TikTok application. The inclusion criteria here were teenagers who had a TikTok account, were active on TikTok, and used TikTok as part of their existence and self-disclosure. The results of this study explored the process of self-disclosure and also the existence carried out by the informants in accordance with the stages proposed in the social penetration theory. Informants passed through the stages of self-disclosure sequentially from the orientation stage to the stable stage so that the existence of teenagers in presenting themselves on social media could be observed.

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