检索结果-南通市图书馆

Damage alarming for bridge expansion joints using novelty detection technique based on long-term monitoring data

在线全文

学校读者我要写书评

暂无评论

Journal of Central South university 2013年第1期20卷 226-235页

作者：缪长青邓扬丁幼亮李爱群 School of civil engineering Southeast University School of civil engineering and architecture Changsha University of Science and Technology

Damage alarming and safety evaluation using long-term monitoring data is an area of significant research activity for long-span bridges. In order to extend the research in this field, the damage alarming technique for bridge expansion joints based on long-term monitoring data was developed. The effects of environmental factors on the expansion joint displacement were analyzed. Multiple linear regression models were obtained to describe the correlation between displacements and the dominant environmental factors. The damage alarming index was defined based on the multiple regression models. At last, the X-bar control chart was utilized to detect the abnormal change of the displacements. Analysis results reveal that temperature and traffic condition are the dominant environmental factors to influence the displacement. When the confidence level of X-bar control chart is set to be 0.003, the false-positive indications of damage can be avoided. The damage sensitivity analysis shows that the proper X-bar control chart can detect 0.1 cm damage-induced change of the expansion joint displacement. It is reasonably believed that the proposed technique is robust against false-positive indication of damage and suitable to alarm the possible future damage of the expansion joints.

关键词： damage alarming expansion joint temperature traffic condition control chart suspension bridge

engineering punching shear strength of flat slabs predicted by nature-inspired metaheuristic optimized regression system

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and civil engineering 2024年第4期18卷 551-567页

作者： Dinh-Nhat TRUONG Van-Lan TO Gia Toai TRUONG Hyoun-Seung JANG Department of civil engineering University of Architecture Ho Chi Minh CityHo Chi Minh City 700000Vietnam Faculty of civil engineering and Technology Dong A UniversityDa Nang City 550000Vietnam School of architecture Seoul National University of Science and TechnologySeoul 01811Republic of Korea

Reinforced concrete(RC)flat slabs,a popular choice in construction due to their flexibility,are susceptible to sudden and brittle punching shear *** design methods often exhibit significant bias and *** estimation of punching shear strength in RC flat slabs is crucial for effective concrete structure design and *** study introduces a novel computation method,the jellyfish-least square support vector machine(JS-LSSVR)hybrid model,to predict punching shear *** combining machine learning(LSSVR)with jellyfish swarm(JS)intelligence,this hybrid model ensures precise and reliable *** model’s development utilizes a real-world experimental data *** with seven established optimizers,including artificial bee colony(ABC),differential evolution(DE),genetic algorithm(GA),and others,as well as existing machine learning(ML)-based models and design codes,validates the superiority of the JS-LSSVR hybrid *** innovative approach significantly enhances prediction accuracy,providing valuable support for civil engineers in estimating RC flat slab punching shear strength.

关键词： punching shear strength reinforced concrete flat slabs machine learning jellyfish search support vector machine

Ultrasonic testing and microscopic analysis on concrete under sulfate attack and cyclic environment

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Central South university 2014年第12期21卷 4723-4731页

作者：姜磊牛荻涛孙迎召费倩男 College of civil engineering Xi’an University of Architecture and Technology

The damage process of concrete exposed to sodium sulfate attack and drying-wetting cycles was investigated. The water to binder(W/B) ratio and the concentration of sulfate solution were taken as variable parameters. Through the experiment, visual change, relative dynamic modulus of elasticity(RDME) and the surface damage layer thickness of concrete were ***, SEM and thermal analysis were used to investigate the changing of microstructure and corrosion products of *** test results show that the ultrasonic velocity is related to the damage layer of concrete. It approves that an increase in damage layer thickness reduces the compactness and the ultrasonic velocity. The deterioration degree of concrete could be estimated effectively by measuring the surface damage layer and the RDME of concrete. It is also found that the content of gypsum in concrete is less than that of ettringite in test, and some gypsum is checked only after a certain corrosion extent. When the concrete is with high W/B ratio or exposed to high concentration of sulfate solution, the content of ettringite first increases and then decreases with corrosion time. However, the content of gypsum increases at a steady rate. The content of corrosion products does not correspond well with the observations of RDME change, and extensive amount of corrosion products can be formed before obvious damage occurs.

关键词： sulfate attack drying-wetting cycles damage layer thickness thermal analysis

Unified elastoplastic finite difference and its application

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2013年第4期34卷 457-474页

作者：马宗源廖红建党发宁 School of civil engineering and architecture Xi'an University of Technology Department of civil engineering Xi'an Jiaotong University

Two elastoplastic constitutive models based on the unified strength the- ory （UST） are established and implemented in an explicit finite difference code, fast Lagrangian analysis of continua （FLAC/FLAC3D）, which includes an associated/non- associated flow rule, strain-hardening/softening, and solutions of singularities. Those two constitutive models are appropriate for metallic and strength-different （SD） materials, respectively. Two verification examples are used to compare the computation results and test data using the two-dimensional finite difference code FLAC and the finite element code ANSYS, and the two constitutive models proposed in this paper are verified. Two application examples, the large deformation of a prismatic bar and the strain-softening be- havior of soft rock under a complex stress state, are analyzed using the three-dimensional code FLAC3D. The two new elastoplastic constitutive models proposed in this paper can be used in bearing capacity evaluation or stability analysis of structures built of metallic or SD materials. The effect of the intermediate principal stress on metallic or SD mate- rial structures under complex stress states, including large deformation, three-dimensional and non-association problems, can be analyzed easily using the two constitutive models proposed in this paper.

关键词： elastoplastic constitutive model unified strength theory explicit finite difference effect of intermediate principal stress

SPH numerical investigation of the characteristics of an oscillating hydraulic jump at an abrupt drop

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2018年第1期30卷 106-113页

作者： Diana De Padova Michele Mossa Stefano Sibilla Department of civil Environmental Land Building Engineering and ChemistryPolytechnic University of Bari Department of civil engineering and architecture University of Pavia

This paper shows the results of the smooth particle hydrodynamics（SPH） modelling of the hydraulic jump at an abrupt drop,where the transition from supercritical to subcritical flow is characterised by several flow patterns depending upon the inflow and tailwater conditions. SPH simulations are obtained by a pseudo-compressible XSPH scheme with pressure smoothing; turbulent stresses are represented either by an algebraic mixing-length model, or by a two-equation k-ε model. The numerical model is applied to analyse the occurrence of oscillatory flow conditions between two different jump types characterised by quasi-periodic oscillation,and the results are compared with experiments performed at the hydraulics laboratory of Bari Technical university. The purpose of this paper is to obtain a deeper understanding of the physical features of a flow which is in general difficult to be reproduced numerically,owing to its unstable character： in particular, vorticity and turbulent kinetic energy fields, velocity, water depth and pressure spectra downstream of the jump, and velocity and pressure cross-correlations can be computed and analysed.

关键词： Hydraulic jumps smoothed particle hydrodynamics(SPH) models oscillating characteristics

Structure and behavior of floor system of two super high-speed railway Changjiang composite bridges

在线全文

学校读者我要写书评

暂无评论

Journal of Central South university 2011年第2期18卷 542-549页

作者：张晔芝张敏 School of civil engineering and architecture Central South University

Wuhan Tianxingzhou Changjiang (WTC) Bridge and Nanjing Dashengguan Changjiang (NDC) Bridge are two super high-speed railway 3-trusses composite bridges. This is the first time of using three trusses in such large bridges in the world. These two types of railway floor systems of the two bridges have never been used in China before. The problem how to conform the deformations and stress levels of the railway floor system of WTC Bridge was studied. After finite element analysis and comparison,the plan of arranging one expansion stringer every two panels in railway floor system were proposed and good effect was obtained. Because of the application of three trusses,the allocation of the loads acted on the deck in three trusses is different and varies in different places of NDC Bridge. This problem was studied by model experiment and 3D finite element analysis. The results of 3D FEM analysis coincide with the model test results. The allocation rule of the loads acting on the deck in three trusses was presented. Because of the application of monolithic decks,the stiffness and structural integrity of NDC Bridge are high.

关键词： high-speed railway composite mechanics characteristics floor system Wuhan Tianxingzhou Changjiang Bridge Nanjing Dashengguan Changjiang Bridge

Vertical vibrations of elastic foundation resting on saturated half-space

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2007年第9期28卷 1199-1207页

作者：王国才王哲孟凡丽 School of civil engineering and architecture Zhejiang University of Technology

This paper is mainly concerned with the dynamic response of an elastic foundation of finite height bounded to the surface of a saturated half-space. The foundation is subjected to time-harmonic vertical loadings. First, the transform solutions for the governing equations of the saturated media are obtained. Then, based on the assumption that the contact between the foundation and the half-space is fully relaxed and the halfspace is completely pervious or impervious, this dynamic mixed boundary-value problem can lead to dual integral equations, which can be further reduced to the Predhohn integral equations of the second kind and solved by numerical procedures. In the numerical extortples, the dynamic colnpliances, displacements and pore pressure are developed for a wide range of frequencies and material/geometrical properties of the saturated soil-foundation system. In most of the cases, the dynamic behavior of an elastic foundation resting on the saturated media significantly differs from that of a rigid disc on the saturated half-space. The solutions obtained can be used to study a variety of wave propagation problems and dynamic soil-structure interactions.

关键词： saturated media elastic foundation vertical vibration dynamic colnplialice dual integral equations

Long-term Durability of Cement-based Materials with Very Low w/b

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan university of Technology(Materials Science) 2008年第3期23卷 303-308页

作者：谢友均龙广成 School of civil engineering and architecture Central South University

To investigate the durability, especially the long-term stability of cement-based materials with very low w/b, the air permeability test, carbonation test, capillary absorption rate test and dilation potential test were adopted under long-term heat treatment condition. Microstructure of these materials is also analyzed by scanning electronic microscopy （SEM） and mercury intrusion porosimeter （MIP） in order to further unveil its mechanism and interrelation between microstructure and its properties. The results indicate that in the area investigated, cement-based material with w/b 0.17, like RPC, possesses low porosity and excellent durability. Moreover, its porosity will further decrease under long-term heat treatment compared with normal heat treatment. Its long-term durability is much superior to that of other cement-based materials with w/b 0.25 or 0.35 as high strength concrete（HSC）.

关键词： cement-based material durability dilatability potential air permeability carbonation capillary absorption

Effects of binder strength and aggregate size on the compressive strength and void ratio of porous concrete

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2009年第6期16卷 714-719页

作者： P. Chindaprasirt S. Hatanaka N. Mishima Y. Yuasa T. Chareerat Department of civil engineering Faculty of Engineering Khon Kaen University Department of architecture Faculty of Engineering Mie University Industrial Research division Mie Prefecture Science and Technology Promotion Center Department of civil and Environmental engineering Faculty of Science and Engineering Kasetsart University

To test the influence of binder strength, porous concretes with 4 binder strengths between 30.0-135.0 MPa and 5 void ratios between 15%-35% were tested. The results indicated that for the same aggregate, the rates of strength reduction due to the increases in void ratio were the same for binders with different strengths. To study the influence of aggregate size, 3 single size aggregates with nominal sizes of 5.0, 13.0 and 20.0 mm （Nos. 7, 6 and 5 according to JIS A 5001） were used to make porous concrete. The strengths of porous concrete are found to be dependent on aggregate size. The rate of strength reduction of porous concrete with small aggregate size is found to be higher than that with larger aggregate size. At the same void ratio, the strength of porous concrete with large aggregate is larger than that with small aggregate. The general equations for porous concrete are related to compressive strength and void ratio for different binder strengths and aggregate sizes.

关键词： cement paste porous concrete compressive strength void ratio