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A 1D time-domain method for in-plane wave motions in a layered half-space

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Acta Mechanica Sinica 2007年第6期23卷 673-680页

作者： jingbo liu Yan Wang Department of Civil Engineering Tsinghua University 100084 Beijing China

A 1D finite element method in time domain is developed in this paper and applied to calculate in-plane wave motions of free field exited by SV or P wave oblique incidence in an elastic layered half-space. First, the layered half-space is discretized on the basis of the propagation characteristic of elastic wave according to the Snell law. Then, the finite element method with lumped mass and the central difference method are incorporated to establish 2D wave motion equations, which can be transformed into 1D equations by discretization principle and explicit finite element method. By solving the 1D equations, the displacements of nodes in any vertical line can be obtained, and the wave motions in layered half-space are finally determined based on the characteristic of traveling wave. Both the theoretical analysis and the numerical results demonstrate that the proposed method has high accuracy and good stability.

关键词： In-plane wave Oblique incidence Time-domain method Snell law

Longitudinal integral response deformation method for the seismic analysis of a tunnel structure

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Earthquake Engineering and Engineering Vibration 2021年第4期20卷 887-904页

作者： liu jingbo Wang Dongyang Bao Xin Department of Civil Engineering Tsinghua UniversityBeijing 100084China

For the longitudinal seismic response analysis of a tunnel structure under asynchronous earthquake excitations,a longitudinal integral response deformation method classified as a practical approach is proposed in this *** determinations of the structural critical moments when maximal deformations and internal forces in the longitudinal direction occur are deduced as *** applying the proposed method,the static analysis of the free-field computation model subjected to the least favorable free-field deformation at the tunnel buried depth is performed first to calculate the equivalent input seismic ***,the equivalent input seismic loads are imposed on the integral tunnel-foundation computation model to conduct the static ***,the critical longitudinal seismic responses of the tunnel are *** applicability of the new method is verified by comparing the seismic responses of a shield tunnel structure in Beijing,determined by the proposed procedure and by a dynamic time-history analysis under a series of obliquely incident out-of-plane and in-plane *** results show that the proposed method has a clear concept with high accuracy and simple ***,this method provides a feasible way to determine the critical moments of the longitudinal seismic responses of a tunnel ***,the proposed method can be effectively applied to analyze the seismic response of a long-line underground structure subjected to non-uniform excitations.

关键词： underground tunnel longitudinal integral response deformation method asynchronous seismic excitation critical moment

A unified viscous-spring artificial boundary for 3-D static and dynamic applications

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Science China(Technological Sciences) 2005年第5期48卷 570-584页

作者： liu jingbo LI Bin Department of Civil Engineering Tsinghua University Beijing 100084 China Department of Civil Engineering Tsinghua University Beijing 100084 China

A method to develop unified artificial boundaries for problems coupling static effect and dynamic effect is proposed. Based on the dynamic viscous-spring artificial boundary and the fundamental solution of static problems in elastic half space, a unified viscous-spring artificial boundary for 3-D static and dynamic applications is established.

关键词： artificial boundary, half space, open system, soil-structure interaction.

A robust three-stage approach to large-scale urban scene recognition

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Science China(Information Sciences) 2017年第10期60卷 239-251页

作者： Jinglu WANG Yonghua LU jingbo liu Long QUAN Department of Computer Science and Engineering The Hong Kong University of Science and Technology School of Resource and Environmental Sciences Wuhan University

To obtain the ultimate high-level description of urban scenes, we propose a three-stage approach to recognizing the 3D reconstructed scene with efficient representations. First, we develop a joint semantic labeling method to obtain a semantic labeling of the triangular mesh-based representation by exploiting both image features and geometric features. The labeling is formulated over a conditional random field(CRF) that incorporates local spacial smoothness and multi-view consistency. Then, based on the labeled reconstructed meshes, we refine the man-made object segmentation in the recomposed global orthographic map with a graph partition algorithm, and propagate the coherent segmentation to the entire 3D meshes. Finally, we propose to generate a compact, abstracted geometric representation for each man-made object which is more visually appealing than the original cluttered models. This abstraction algorithm also leverages CRF formation to partition building footprints into minimal sets of structural linear features which are then used to construct profiles for large-scale scenes. The proposed recognition approach is able to robustly handle reconstructions with poor geometry and connectivity, thanks to the higher order CRF formulations which impose the ubiquitous regularity priors in urban scenes. Each stage performs an individual and uncoupling task. The intensive experiments have demonstrated the superior performance of our approach in robustness, accuracy and applicability.

关键词： 3D reconstruction urban scene recongition semantic segmentation CRF

Phosphorus nutrition of growing pigs

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Animal Nutrition 2022年第2期9卷 127-137页

作者： Hengxiao Zhai Olayiwola Adeola jingbo liu Southwest University of Science and Technology MianyangChina DSM China Animal Nutrition Research Center BazhouChina Department of Animal Sciences Purdue UniversityWest LafayetteUnited States

Phosphorus(P)is an essential nutrient for diverse biological processes,which aggregate to the animal's requirement for P,and nutritionists strive to meet this requirement *** P demand for a growing pig comprises requirements for maintenance and tissue *** P in feed ingredients,however,must be digested and absorbed before its ultimate partition between the 2 aforementioned requirement *** from various sources could behave differently during digestion and absorption,which results in their disparate bioavailability for *** system of standardized total tract digestibility reflects true total tract digestibility of P and feed ingredient effects on specific endogenous P loss with relative ease of implementation,and this system guarantees satisfactory additivity in digestible P among the ingredients in a dietdthe foundation for diet *** basal endogenous P loss,which is much easier to measure than the specific endogenous P loss,is considered as part of the pig's maintenance *** this arrangement,a digestibility framework is established both for measuring the P-providing capacity of various feed ingredients and for describing the pig's P *** framework entails basic understanding of the function,digestion,absorption,excretion,and homeostasis of P as support *** the workings of this framework enables potential integration of factors such as environment conditions and disease status in future P requirement *** current review discusses dietary sources,digestion,absorption,bioavailability and requirement of P for growing pigs to understand the status quo,revealing the points of consensus as well as those of debate,and to encourage further investigation to provide more clarity.

关键词： Bioavailability Digestibility Phosphorus Pig Requirement

Pushover analysis of underground structures:Method and application

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Science China(Technological Sciences) 2014年第2期57卷 423-437页

作者： liu jingbo WANG WenHui DASGUPTA Gautam Institute Department of Civil Engineering Tsinghua University Department of Civil Engineering and Engineering Mechanics Columbia UniversityNew York NY 10027 USA

Pushover analysis is common because of its conceptual simplicity and computational attractiveness in computing seismic *** that traditional pushover analysis is restricted in underground structures due to the stark differences in the seismic response characteristics of surface structures,this paper proposes a pushover analysis method for underground structures and its application in seismic damage ***,three types of force distribution are presented based on ground response ***,the target displacements and analysis models are established according to force-based and performance-based ***,the pushover analysis procedure for underground structures is ***,the applicability of pushover analysis to underground structures is verified by comparing the responses of a Chongwenmen subway station determined by the proposed procedure and by nonlinear response history *** addition,two other points are made:that the inverted triangular distribution of effective earthquake acceleration is more practical than the other two distributions,and that performance-based design is more effective than force-based ***,a cyclic reversal loading pattern based on one cycle of reversal loads as an earthquake event is presented and applied to the seismic damage assessment of underground *** results show that the proposed pushover analysis can be effectively applied to the seismic design and damage assessment of underground structures.

关键词： underground structure pushover analysis seismic demand seismic damage assessment

Tectonic Boundary and Ceasing Time of Amalgamation between the North China Craton and the North Qinling Belt

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Journal of Earth Science 2018年第5期29卷 1074-1080页

作者： jingbo liu Neng-Song Chen Wen Su State Key Laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences College of Earth and Planetary Sciences University of the Chinese Academy of Sciences School of Earth Sciences Center for Global Tectonics China University of GeosciencesWuhan

The Qinling orogenic belt is a composite orogen, consisting of the north and south Qinling belts with different collision ages. The North Qinling belt is composed of several petro-tectonic units, including the Kuanping, Erlangping, Qinling and Danfeng groups with numerous granitoid plutons from Neoproterzoic to Middle Devonian. To the north of the Kuanping Group, a mylonitized granite body in the Luanchuan Group was determined to have the magmatic age of 850 Ma, which is the northernmost Neoprotozoic granite body. The volcanic rocks of the Dahongkou Formation from the Luanchuan Group had the eruptive age of -1 600 Ma, obtained from zircon U-Pb LA-ICP-MS analysis. The detrital zircons in meta-sandstones from the Taowan Group have three populations of-920-1 400, -1 600-2 100, and 〉2 200 Ma ages, whereas those from the Kuanping Group shows six populations with the peaks of -590, -767, -952, -1 590, -2 485, and -3 200 Ma. These data suggest that the boundary between the North China Craton and the North Qinling belt cannot simply be constrained by using the events determined from zircon U-Pb ages. The granitoid plutons with the magmatic age of 430 Ma were strongly deformed, while those with the magmatic age of -390 Ma show no or less deformation, indicating that the deformation of amalgamation between the North China Craton and the North Qinling belt ceased between 390 and 430 Ma.

关键词： Qinling orogenic belt Taowan Group Kuanping Group granitoid zircon age.

Eclogites and their country gneisses: studies on inclusions in the accessory minerals of country gneisses

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Chinese Science Bulletin 1998年第1期43卷 65-68页

作者： jingbo liu Yin Wu Lianjie Guo Chinese Acad Sci Inst Geol Beijing 100029 Peoples R China

The mineral inclusions in accessory minerals of the country gneisses have been studied in order to interpret relation between eclogites and their country gneissic rocks. Omphacite inclusions have been identified in titanite and zircon, which indicates that the present mineral assemblages of country gneisses are the last retrograded assemblages and eclogites and their country gneissic rocks probably have a same metamorphic history.

关键词： eclogite inclusion omphacite.

Seismic fragility analysis of composite frame structure based on performance

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Earthquake Science 2010年第1期23卷 45-52页

作者： jingbo liu Yangbing liu Heng liu Department ofCivilEngineering Tsinghua University Beo'ing 100084 China College of Civil Engineering Chongqing University Chongqing 400045 China

Steel-concrete composite structures that share the advantages of both steel structure and concrete structure have been developed rapidly and used widely. It has been a popular structure in high-rise buildings in recent years. Although more and more composite structures have been used in earthquake area, only a few literatures about fragility analysis of this type of structure are available. In this paper, a fragility analysis method based on performance is proposed, in which both the uncertainty due to variability in structures and ground motion are considered. Seismic fragility analysis is performed for a 15-story composite beam-concrete-filled square steel tube column frame by the proposed method. The top-drift-angle and the story-drift-angle are used as quantitative indexes to define the four different performance levels. Then seismic demand probability analysis is carried out and fragility curves are derived to assess the seismic performance of this type of structure.

关键词： composite structure performance level seismic demand fragility curve