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Simulation of top-down crack propagation in asphalt pavements

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第3期11卷 223-230页

作者： Hui LUO Hong-ping ZHU Yu MIAO Chuan-yao CHEN School of Civil Engineering and Mechanics Huazhong University of Science and TechnologyWuhan 430074China Hubei Key Laboratory of Control Structure Huazhong University of Science and TechnologyWuhan 430074China

Top-down crack in asphalt pavements has been reported as a widespread mode of failure.A solid understanding of the mechanisms of crack growth is essential to predict pavement performance in the context of thickness design,as well as in the design and optimization of *** the coupled element free Galerkin (EFG) and finite element (FE) method,top-down crack propagation in asphalt pavements is numerically simulated on the basis of fracture mechanics.A parametric study is conducted to isolate the effects of overlay thickness and stiffness,base thickness and stiffness on top-down crack propagation in asphalt *** results show that longitudinal wheel loads are disadvantageous to top-down crack because it increases the compound stress intensity factor (SIF) at the tip of top-down crack and shortens the crack path,and thus the fatigue life *** SIF experiences a process "sharply ascending—slowly descending—slowly ascending—sharply ascending again" with the crack *** thicker the overlay or the base,the lower the SIF; the greater the overlay stiffness,the higher the *** crack path is hardly affected by stiffness of the overlay and base.

关键词： Road engineering Top-down crack Coupled element free Galerkin (EFG) and finite element (FE) method Stress intensity factor (SIF) Crack propagating path

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AN IMPEDANCE ANALYSIS FOR CRACK DETECTION IN THE TIMOSHENKO BEAM BASED ON THE ANTI-RESONANCE TECHNIQUE

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Acta Mechanica Solida Sinica 2007年第3期20卷 228-235页

作者： Wang Dansheng Zhu Hongping Chen Chuanyao Xia Yong School of Civil Engineering ＆ Mechanics Huazhong University of Science and Technology Wuhan 430074 China Hubei Key laboratory of Control Structure Huazhong University of Science and Technology Wuhan 430074 China

An alternative technique for crack detection in a Timoshenko beam based on the first anti-resonant frequency is presented in this paper. Unlike the natural frequency, the anti-resonant frequency is a local parameter rather than a global parameter of structures, thus the proposed technique can be used to locate the structural defects. An impedance analysis of a cracked beam stimulated by a harmonic force based on the Timoshenko beam formulation is investigated. In order to characterize the local discontinuity due to cracks, a rotational spring model based on fracture mechanics is proposed to model the crack. Subsequently, the proposed method is verified by a numerical example of a simply-supported beam with a crack. The effect of the crack size on the anti-resonant frequency is investigated. The position of the crack of the simply-supported beam is also determined by the anti-resonance technique. The proposed technique is further applied to the ＂contaminated＂ anti-resonant frequency to detect crack damage, which is obtained by adding 1-3% noise to the calculated data. It is found that the proposed technique is effective and free from the environment noise. Finally, an experimental study is performed, which further verifies the validity of the proposed crack identification technique.

关键词： impedance analysis crack detection Timoshenko beam anti-resonant frequency

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Compacting Deformation Engineering Characteristics of Weathered Soft Rock Mixture in Subgrade

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Journal of China University of Geosciences 2008年第3期19卷 298-306页

作者：李小青金清平 School of Civil Engineering & Mechanics Huazhong University of Science & Technology Wuhan 430074 China Hubei Key Laboratory of Control Structure Huazhong University of Science & Technology Wuhan 430074 China

The engineering characteristics of weathered soft rock are important contents of soft rock mechanics. They also play a significant role in compacting deformation, which has been known to exert a significant amount of influence on the stability of highway filling subgrade engineering. In an effort to investigate this aspect of the problem, compacting tests and unconfined compressive strength tests have been carried out on weathered argillaceous slate and pelitic siltstone rocks, which are broken and graded before the test. The testing results indicate that the relationships of both between stress and strain and between axial strain and tangent modulus are exponential relationships; the size of the grain plays some influence on the deformation modulus, whereas the water content impacts the compressive strength greatly, which shows quadratic function; the unconfined compressive strength is linear with the dry density of loose soft rock mixtures. Therefore, the water content must be controlled in both the design and the construction of subgrade engineering of soft rock filling, and at the same time some effective measures should be taken to reach the requirement of compaction.

关键词： subgrade weathered soft rock mixture compaction deformation engineering characteristics.

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Identification of small crack in beam structures using anti-resonant frequency and wavelet analysis

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key Engineering Materials 2009年 413-414卷 63-70页

作者： Wang, Dansheng Shen, Danyan Zhu, Hongping School of Civil Engineering and Mechanics Huazhong University of Science and Technology China Hubei Key Laboratory of Control Structure Huazhong University of Science and Technology Wuhan 430074 China

Structural crack identification has been received considerable attention in recent decade. A lot of different techniques like acoustic emission, ultrasonic, or X-ray, etc have been used for structural crack detection. However, it is still difficult to identify the small crack in structures. A new method for identification of small crack in beam structures using the first anti-resonant frequency curve is proposed in this paper. The method makes use of the driving-point mechanical impedance characteristics of beam structures and a simplified rotational spring model to model the edge crack of beam. After the first anti-resonant frequency curve is obtained, signal process based on wavelet transformation will be carried out and the small crack in beam structures can be explored. The proposed method is validated by a numerical example of cracked beam with pinned-pinned or fixed-free boundary. It is concluded that not only the location of beam crack can be determined, but also the extent of crack damage can be identified qualitatively based on the first anti-resonant frequency curve and wavelet analysis.

关键词： Wavelet analysis

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Multi-dynamic displacement measurement based on digital image processing technology

Multi-dynamic displacement measurement based on digital imag...

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2010 2nd International Conference on Industrial Mechatronics and Automation, ICIMA 2010

作者： Li, Penghui Wen, Yinping Zhao, Wenguang Zhu, Hongping Hubei Key Laboratory of Control Structure School of Civil Engineering and Mechanics Huazhong University of Science and Technology Wuhan Hubei China

ISBN: (纸本)9781424476541

The multi-point dynamic-displacement data of structure is an important parameter for structural health monitoring. The difficulties of traditional multi-dynamic displacement measurement are reference point selecting and massive data processing. A novel multi-dynamic displacement measurement system was developed based on digital image processing technology. The calibration method based on surface fitting and window-centroid tracking algorithm was applied to determine the relationship between the object space and pixel coordinate system. The displacement data was acquired by comparing the change of the centroid pixel. The expectations based on wavelet coefficients were used for sub-pixel edge detection, measurement accuracy can reach 0.02 pixels. The dynamic displacement of four-layer steel frame structure was monitored on the shaking table. The results show that the system can achieve the monitoring of multi-channel 2-D dynamic displacements, the accuracy of displacement survey can reach ***. © 2010 IEEE.

关键词： Calibration

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Simulation of galloping and wind-induced vibration control

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Noise and Vibration Worldwide 2010年第10期41卷 15-21页

作者： Li, Li Cao, Huajin Ye, Kun Jiang, Yicheng School of Civil Engineering and Mechanics Huazhong Univ. of Sci. and Tech Wuhan Hubei 430074 China Hubei Key Laboratory of Control Structure Huazhong Univ. of Sci. and Tech. Wuhan Hubei 430074 China

A nonlinear finite element model of transmission tower-line coupling system including transmission tower-cable-insulator is established based on ANSYS. The restarting technology is proposed to solve the vertical, horizontal and torsional galloping of the transmission conductors and the wind-induced vibration of the transmission towers. A program is developed to simulate the wind velocity;the galloping of the transmission tower line coupling system is performed to get the amplitude of the transmissions and the internal forces of the transmission towers. The calculations are performed under the condition that four fixed schemes of lead viscoelastic dampers (LVDs) to control the transmission towers wind-induced vibration, and the schemes of the damper have been optimized.

关键词： Towers

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Finite element analysis of tunnel-soil-building interaction using displacement controlled model

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WSEAS Transactions on Applied and Theoretical Mechanics 2008年第3期3卷 73-82页

作者： Keshuan, Ma Lieyun, Ding Huazhong University of Science and Technology Department of Civil Engineering Nanyang Institute of Technology Nanyang Henan 473004 China Huazhong University of Science and Technology Hubei Key Laboratory of Control Structure Nanyang Institute of Technology Nanyang Henan 473004 China Nanyang Institute of Technology Nanyang Henan 473004 China Huazhong University of Science and Technology Department of Civil Engineering Wuhan Hubei 430074 China Huazhong University of Science and Technology Hubei Key Laboratory of Control Structure Wuhan Hubei 430074 China

Using some building affected by the river-crossing highway tunnels of Wuhan as engineering background, this paper investigates the interaction between the tunneling in soft soils and adjacent structures. A full three-dimensional finite element model, which takes into account the presence of the building during the excavation of the tunnel, is well analyzed. The soil behavior discussed in this paper is assumed to be governed by an elastic perfectly-plastic constitutive relation based on the widely adopted Mohr-Coulomb criterion with a non-associative flow rule. The paper consists of three parts. The first part presents the 3-D finite element numerical model, and the second part provides a full analysis of the construction of a shallow tunnel close to a five level building. Comparison between the full couple model analysis and the full 3D free-field analysis is given in the final part. The corresponding comparison results provide a fundamental guidance for the shield tunnel design and construction.

关键词： Shielding

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Pseudo strain energy density-based structural damage identification

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key Engineering Materials 2009年 413-414卷 71-78页

作者： Xiaoqiang, Chen Hongping, Zhu Dansheng, Wang School of Civil Engineering and Mechanics Huazhong University of Science and Technology Wuhan 430074 China Hubei Key Laboratory of Control Structure Huazhong University of Science and Technology Wuhan 430074 China

In this paper, a new time-domain method for detecting structural local damage has been developed, which is based on the measured strain signals. The "pseudo strain energy density (PSED)" is defined and used to build two major damage indexes, the "average pseudo strain energy density" (APSED) and the "average pseudo strain energy density changing rate" (APSEDR). A probability and mathematical statistics technique is utilized to derive a standardized damage index. Afterwards, these indexes are used to establish the damage identification strategies for beam structures and plate structures respectively. Furthermore, the wavelet packet transform is used to pre-process the measured dynamic strain signals. Then, the effectivity of the new damage identification method is confirmed by numerical simulations. Finally, a laboratory beam model experiment is conducted to verify this method examine the feasibility and applicability of the new method.

关键词： Damage detection

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Experimental study on anti-impact performance of RHST and PCFST columns under lateral impact 16th

Experimental study on anti-impact performance of RHST and PC...

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16th International Symposium on Tubular structures, ISTS 2017

作者： Zhu, A.Z. Xu, W. Gao, K. Zhu, H.P. Gao, F. Hubei Key Laboratory of Control Structure School of Civil Engineering and Mechanics Huazhong University of Science and Technology Wuhan China

ISBN: (纸本)9780815381341

Three Rectangular Hollow Steel Tubular (RHST) and nine Partially Concrete-Filled Steel Tubular (PCFST) column specimens were tested under lateral impact. Length of the column is 1500 mm. Steel with a nominal yield strength of 345 MPa was applied to fabricate the cold-formed steel tubes. Self-consolidating concrete with nominal cubic compressive strength of 30 MPa was applied to fill the tubes partially. The concrete filling height, the impact direction and the impact energy are the main factors considered in this study. The typical displacement and strain responses, as well as the failure modes of the specimens were all analysed. The result showed that the PCFST specimens had much better anti-impact performance than the RHST specimens. The concrete filling height affected the failure mode significantly especially when the specimen was tested under a larger impact energy. The impact direction and energy also affected the anti-impact performance of the specimen significantly. © 2018 Taylor & Francis Group, London.

关键词： Compressive strength

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Numerical simulation of lightning location based on Monte Carlo method

Numerical simulation of lightning location based on Monte Ca...

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International Conference on Management and Service Science, MASS 2009

作者： Hu, Z.X. Wen, Yin Ping Zhao, W.G. Zhu, H.P. Liu, S.L. Hubei Key Laboratory of Control Structure School of Civil Engineering and Mechanics Huazhong University of Science and Technology Wuhan China

ISBN: (纸本)9781424446391

Currently, lightning location system (LLS) is one of the important bases for urban lightning protection. A key factor of the TDOA technology prevalently adopted in LLS is the time error of detection stations. According to the stochastic property of the time error measured by detection stations, the lightning information containing error is simulated using Monte Carlo method. The location error is determined through the results of many times revolving of a particular lightning point, and error ellipse is plotted based on the location error. The results can guide the lightning location network construction and the location error analysis. ©2009 IEEE.

关键词： Stochastic systems

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