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Statistical damage detection method for frame structures using a confidence interval

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Earthquake engineering and engineering Vibration 2010年第1期9卷 133-140页

作者： Li Weiming,Zhu Hongping~(++),Luo Hanbin~(++) and Xia Yong~(++) school of civil engineering and Mechanics,Huazhong University of Science and Technology,Wuhan 430074,China ~+PhD Candidate ++ Professor school of civil engineering and Mechanics Huazhong University of Science and Technology Wuhan China

A novel damage detection method is applied to a 3-story frame structure, to obtain statistical quantification control criterion of the existence, location and identification of damage. The mean, standard deviation, and exponentially weighted moving average （EWMA） are applied to detect damage information according to statistical process control （SPC） theory. It is concluded that the detection is insignificant with the mean and EWMA because the structural response is not independent and is not a normal distribution. On the other hand, the damage information is detected well with the standard deviation because the influence of the data distribution is not pronounced with this parameter. A suitable moderate confidence level is explored for more significant damage location and quantification detection, and the impact of noise is investigated to illustrate the robustness of the method.

关键词： damage detection standard deviation statistical method confidence interval noise

Prediction of undrained shear strength using extreme gradient boosting and random forest based on Bayesian optimization

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Geoscience Frontiers 2021年第1期12卷 469-477页

作者： Wengang Zhang Chongzhi Wu Haiyi Zhong Yongqin Li Lin Wang school of civil engineering Chongqing UniversityChongqing 400045China

Accurate assessment of undrained shear strength(USS)for soft sensitive clays is a great concern in geotechnical engineering *** study applies novel data-driven extreme gradient boosting(XGBoost)and random forest(RF)ensemble learning methods for capturing the relationships between the USS and various basic soil *** on the soil data sets from TC304 database,a general approach is developed to predict the USS of soft clays using the two machine learning methods above,where five feature variables including the preconsolidation stress(PS),vertical effective stress(VES),liquid limit(LL),plastic limit(PL)and natural water content(W)are *** reduce the dependence on the rule of thumb and inefficient brute-force search,the Bayesian optimization method is applied to determine the appropriate model hyper-parameters of both XGBoost and *** developed models are comprehensively compared with three comparison machine learning methods and two transformation models with respect to predictive accuracy and robustness under 5-fold cross-validation(CV).It is shown that XGBoost-based and RF-based methods outperform these ***,the XGBoostbased model provides feature importance ranks,which makes it a promising tool in the prediction of geotechnical parameters and enhances the interpretability of model.

关键词： Undrained shear strength Extreme gradient boosting Random forest Bayesian optimization k-fold CV

Seismic Behavior of Specially Shaped Column Joints with X-Shaped Reinforcement

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Transactions of Tianjin University 2013年第2期19卷 110-117页

作者：戎贤张健新李艳艳 school of civil engineering Hebei University of Technology civil engineering Technology Research Center of Hebei Province

To investigate the seismic behavior of specially shaped column joints with X-shaped reinforcement,two groups of specimens with or without X-shaped reinforcement in joint core region were tested under constant axial compression load and low reversed cyclic loading,which imitated low to moderate earthquake *** seismic behavior of specially shaped column joints with X-shaped reinforcement in terms of bearing capacity,displacement,ductility,hysteretic curve,stiffness degradation and energy dissipation was studied and compared to that without Xshaped reinforcement in joint core *** the damage estimation model,the accumulated damage was *** shearing capacity formula of specially shaped column joints reinforced by X-shaped reinforcement was proposed with a simple *** test results show that X-shaped reinforcement is an effective measure for improving the seismic behavior of specially shaped column joints including deformation behavior,ductility and hysteretic *** specimens were damaged with gradual stiffness *** addition,X-shaped reinforcement in the joint core region is an effective way to lighten the degree of cumulated *** good seismic performance obtained from the specially shaped column joint with X-shaped reinforcement can be used in engineering *** test value is higher than the calculated value,which indicates that the formula is safe for the design of specially shaped column joints.

关键词：抗震性能异形柱柱节点 X形加固承载力公式低周反复荷载特殊形状

Coupling of high order multiplication perturbation method and reduction method for variable coefcient singular perturbation problems

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Applied Mathematics and Mechanics(English Edition) 2014年第1期35卷 97-104页

作者：张文志黄培彦 school of civil and Transportation engineering South China University of Technology

Based on the precise integration method （PIM）, a coupling technique of the high order multiplication perturbation method （HOMPM） and the reduction method is proposed to solve variable coefficient singularly perturbed two-point boundary value prob lems （TPBVPs） with one boundary layer. First, the inhomogeneous ordinary differential equations （ODEs） are transformed into the homogeneous ODEs by variable coefficient dimensional expansion. Then, the whole interval is divided evenly, and the transfer ma trix in each sub-interval is worked out through the HOMPM. Finally, a group of algebraic equations are given based on the relationship between the neighboring sub-intervals, which are solved by the reduction method. Numerical results show that the present method is highly efficient.

关键词： high order multiplication perturbation method (HOMPM) reductionmethod variable coefficient singular perturbation problem two-point boundary valueproblem

A New Method for Determining Threshold in Using PGCEVD to Calculate Return Values of Typhoon Wave Height

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China Ocean engineering 2012年第2期26卷 251-260页

作者：罗耀朱良生胡金鹏 school of civil engineering and Transportation South China University of Technology

In using the PGCEVD （Poisson-Gumbel Compound Extreme Value Distribution） model to calculate return values of typhoon wave height, the quantitative selection of the threshold has blocked its application. By analyzing the principle of the threshold selection of PGCEVD model and in combination of the change point statistical methods, this paper proposes a new method for quantitative calculation of the threshold in PGCEVD model. Eleven samples from five engineering points in several coastal waters of Guangdong and Hainan, China, are calculated and analyzed by using PGCEVD model and the traditional Pearson type III distribution （P-III） model, respectively. By comparing the results of the two models, it is shown that the new method of selecting the optimal threshold is feasible. PGCEVD model has more stable results than that of P-III model and can be used for the return wave height in every direction.

关键词： POT Compound Extreme Value Distribution Pearson type II1 mean change point extreme wave height

Unanswered questions in unsaturated soil mechanics

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Science China(Technological Sciences) 2013年第5期56卷 1257-1272页

作者： SHENG DaiChao ZHANG Sheng YU ZhiWu school of civil engineering Central South University The University of Newcastle

The last two to three decades have seen significant advances in the mechanics of unsaturated *** is now widely recognized that the fundamental principles in soil mechanics must cover both saturated and unsaturated ***,there is still a great deal of uncertainties in the geotechnical community about how soil mechanics principles well-established for saturated soils can be extended to unsaturated *** is even wide skepticism about the necessity of such extension in engineering *** paper discusses some common pitfalls related to the fundamental principles that govern the volume change,shear strength and hydromechanical behaviour of unsaturated *** also attempts to address the issue of engineering relevance of unsaturated soil mechanics.

关键词：非饱和土力学饱和土壤工程实践不确定性力学原理体积变化力学行为剪切强度

Multibody dynamic analysis using a rotation-free shell element with corotational frame

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Acta Mechanica Sinica 2018年第4期34卷 769-780页

作者： Jiabei Shi Zhuyong Liu Jiazhen Hong school of Naval Architecture Ocean and Civil EngineeringShanghai Jiao Tong University

Rotation-free shell formulation is a simple and effective method to model a shell with large deformation. Moreover, it can be compatible with the existing theories of finite element method. However, a rotation-free shell is seldom employed in multibody systems. Using a derivative of rigid body motion, an efficient nonlinear shell model is proposed based on the rotation-free shell element and corotational frame. The bending and membrane strains of the shell have been simplified by isolating deformational displacements from the detailed description of rigid body motion. The consistent stiffness matrix can be obtained easily in this form of shell model. To model the multibody system consisting of the presented shells, joint kinematic constraints including translational and rotational constraints are deduced in the context of geometric nonlinear rotation-free element. A simple node-to-surface contact discretization and penalty method are adopted for contacts between shells. A series of analyses for multibody system dynamics are presented to validate the proposed formulation. Furthermore,the deployment of a large scaled solar array is presented to verify the comprehensive performance of the nonlinear shell model.

关键词： Flexible multibody dynamics Rotation-free shell Corotational frame Geometric nonlinearity

A Train-Bridge Dynamic Interaction Analysis Method and Its Experimental Validation

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engineering 2016年第4期2卷 528-536页

作者： Nan Zhang Yuan Tian He Xia school of civil engineering BeijingJiaotong University Beijing 100044 China

The train-bridge dynamic interaction problem began with the development of railway technology, and requires an evaluation method for bridge design in order to ensure the safety and stability of the bridge and the running train. This problem is studied using theoretical analysis, numerical simulation, and experimental study. In the train-bridge dynamic interaction system proposed in this paper, the train vehicle model is established by the rigid-body dynamics method, the bridge model is established by the finite element method, and the wheel/rail vertical and lateral interaction are simulated by the corresponding assumption and the Kalker linear creep theory, respectively. Track irregularity, structure deformation, wind load, collision load, structural damage, foundation scouring, and earthquake action are regarded as the excitation for the system. The train-bridge dynamic interaction system is solved by inter-history iteration. A case study of the dynamic response of a CRH380BL high-speed train running through a standard-design bridge in China is discussed. The dynamic responses of the vehicle and of the bridge subsystems are obtained for speeds ranging from 200 km-b-1 to 400 km.h-1, and the vibration mechanism are analyzed.

关键词： Train-bridge dynamic interaction Wheel/rail relationship Inter-history iteration Field measurement Experimental validation

FURTHER INVESTIGATION OF INTERACTION BETWEEN INTERFACE MACROCRACK AND PARALLEL MICROCRACKS IN BIMATERIAL ANISOTROPIC SOLIDS

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Acta Mechanica Sinica 1999年第3期15卷 255-264页

作者：田文叶陈宜亨 school of civil engineering and Mechanics Xi'an Jiaotong UniversityXi'an 710049China

In this paper, with the aid of superimposing technique and the Pseudo Traction Method (PTM), the interaction problem between an interface macrocrack and parallel microcracks in the process zone in bimaterial anisotropic solids is reduced to a system of integral equations. After the integral equations are solved numerically, a conservation law among three kinds ofJ-integrals is obtained which are induced from the interface macrocrack tip, the microcrack and the remote field, respectively. This conservation law reveals that the microcrack shielding effect in such materials could be considered as the redistribution of the remoteJ-integral.

关键词： J-integral bimaterial anisotropic solids interface macrocrack microcrack