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  • 工程力学
    Engineering Mechanics
    (月刊,1984年创刊)
    主管单位:中国科学技术协会
    主办单位:中国力学学会
    主  编:陆新征
    编辑出版:《工程力学》编辑部
    ISSN 1000-4750 CN 11-2595/O3
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A PHILOSOPHIC REVIEW OF STRUCTURAL MECHANICS METHODS
LONG Yu-qiu
Engineering Mechanics    2019, 36 (4): 1-7.   DOI: 10.6052/j.issn.1000-4750.2019.01.ST13
Abstract326)      PDF(pc) (482KB)(307)       Save
The methodology of structural mechanics is reviewed. Five problems are discussed:1) the keynote of the methodology of structural mechanics, 2) features of the structural mechanics methods, 3) the dominant features of the virtual work method and the energy method, 4) the equivalent relationship between the virtual work method and the energy method, and 5) the adjoint theorem between the equilibrium matrix and the geometric matrix.
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EARTHQUAKE ENGINEERING: FROM EARTHQUAKE RESISTANCE, ENERGY DISSIPATION, AND ISOLATION, TO RESILIENCE
ZHOU Ying, WU Hao, GU An-qi
Engineering Mechanics    2019, 36 (6): 1-12.   DOI: 10.6052/j.issn.1000-4750.2018.07.ST09
Abstract257)      PDF(pc) (3410KB)(295)       Save
In recent years, the research on earthquake engineering in our country showed a tendency of development from earthquake resistance, energy dissipation, and isolation to resilience. Earthquake resilience can be defined as the capability of restoring the function for a structure, a system or a city after it has been interrupted by an earthquake event. In respect of structures, an earthquake resilient structure should not only protect life safety during a seismic event, but also restore its function quickly enough after the earthquake in order to minimize the influence to immediate occupancy. The fundamental concepts of earthquake resilience are introduced first. After that, the characteristics of an earthquake resilient structure and its uniqueness compared to a conventional structure are addressed over the aspects of seismic fortification objective, design code and standard, structural systems, design methods, performance indexes and project applications. Lastly, the direction of future development for earthquake resilient structures is forecasted.
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EXPERIMENTAL STUDY ON THE DYNAMIC EFFECTS IN PROGRESSIVE COLLAPSE OF BEAM-COLUMN CONCRETE SUBSTRUCTURES
XIAO Yu-zhe, LI Yi, LU Xin-zheng, REN Pei-qi, HE Hao-xiang
Engineering Mechanics    2019, 36 (5): 44-52.   DOI: 10.6052/j.issn.1000-4750.2018.04.0189
Accepted: 01 April 2019

Abstract167)      PDF(pc) (751KB)(147)       Save
Progressive collapse is a nonlinear dynamic behavior of structure systems. The key issue in establishing the simplified method for the practical engineering design is to evaluate the dynamic effect accurately. To investigate the dynamic progressive collapse mechanism and the dynamic effect of reinforced concrete substructures, one static and four dynamic experiments were conducted on four specimens, which had the identical dimensions and material properties. The results indicated that the stress concentration and asymmetric deformation in the dynamic tests were severer than those in the static test due to the high strain rate effect. Thus, the cracks developed intensively at the beam ends and the concrete spalling area caused by compression was relatively small in dynamic tests. The general dynamic resistance, in which the effects of dynamic damage and high strain rate to the structural resistance were inherently considered, was able to accurately predict the resistance demand in the real progressive collapse process. In addition, the dynamic amplification effect was enhanced by the effect of dynamic damage and high strain rate, thus the practical dynamic amplification factors were larger than the predicted values of the conventional theory.
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NUMERICAL SIMULATION ON DYNAMIC COMPRESSIVE BEHAVIOR OF ULTRA-HIGH TOUGHNESS CEMENTITIOUS-COMPOSITES
XU Shi-lang, CHEN Chao, LI Qing-hua, ZHAO Xin
Engineering Mechanics    2019, 36 (9): 50-59.   DOI: 10.6052/j.issn.1000-4750.2018.03.0147
Accepted: 12 July 2019

Abstract125)      PDF(pc) (2326KB)(142)       Save
Investigates the dynamic compressive behavior of PVA fiber reinforced ultra-high toughness cementitious-composites (PVA-UHTCC) using Split Hopkinson Pressure Bar (SHPB) test based on HJC constitutive model. Firstly, 21 parameters of HJC model are determined and the numerical simulation is verified. Then dynamic compressive stress-strain curves under 5 different strain rates are obtained for analyzing the strain-rate effects on Dynamic Increase Factor (DIF). The failure modes of specimens under different strain rates are also researched. The results show that with the increase of strain rate, DIF increases and the strain-hardening dominated behavior will transform into a strain-softening dominated behavior. Besides, PVA-UHTCC shows an obvious different strain-rate sensitivity in the different range of strain rates. Thusly, a functional expression between DIF and lgε is proposed. Compared with Steel Fiber Reinforced Cementitious Composites (SFRCC) and normal concrete, PVA-UHTCC has a lower strain-rate sensitivity. Finally, the crack propagation mechanism and failure modes are observed at LS-DYNA software to furtherly understand the dynamic compressive behavior of PVA-UHTCC.
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REVIEW ON ASEISMIC BEHAVIOR OF PRECAST PIERS: NEW MATERIAL, NEW CONCEPT, AND NEW APPLICATION
WANG Jing-quan, WANG Zhen, GAO Yu-feng, ZHU Jun-zheng
Engineering Mechanics    2019, 36 (3): 1-23.   DOI: 10.6052/j.issn.1000-4750.2018.10.ST03
Abstract214)      PDF(pc) (17514KB)(225)       Save
With accelerated bridge construction, the precast pier system has been widely applied in non and low seismic zone, but limited in moderate and high seismic zone by lack of knowledge about its aseismic performance. This paper classifies precast pier systems into two types: emulative precast piers and nonemulative precast piers, based on their aseismic performance. On one hand, the emulative precast pier is further categorized into grouted sleeve connection, grouted steel corrugated duct connection, pocket connection, socket connection, and cast-in-place wet joint connection by the type of connection. On the other hand, the nonemulative precast pier is further categorized into two types based on whether special energy dissipation device is used or not. The research about aseismic performance and typical engineering application are systematically reviewed for each of these categories. Three high performance materials, including Ultra high-performance concrete, fiber reinforced polymer and shape memory alloy, are reported for the research status of their application in the precast pier system to improve their aseismic performance. The proper way is pointed out to apply the three high performance materials in the precast pier system. Two methods are summarized to apply the new concept of earthquake resilience in the precast pier system, which are an external replaceable energy dissipation device and an internal energy dissipation bar with mechanical connection. The research review is conduct for the aseismic performance of precast piers using the two-connection ways. Based on the summarization of the aseismic performance of a precast pier system, the precast pier system is proposed to apply in the four types of bridges, including higher aseismic requirement, larger stiffness requirement, longer service life requirement, and stricter environmental protection requirement. The new issues caused by the new application fields are pointed out.
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SEISMIC FRAGILITY MODELS AND FORWARD-BACKWARD PROBABILISTIC RISK ANALYSIS IN SECOND-GENERATION PERFORMANCE-BASED EARTHQUAKE ENGINEERING
Lü Da-gang, LIU Yang, YU Xiao-hui
Engineering Mechanics    2019, 36 (9): 1-11,24.   DOI: 10.6052/j.issn.1000-4750.2018.07.ST08
Accepted: 22 January 2019

Abstract168)      PDF(pc) (631KB)(135)       Save
The seismic fragility in 2nd-generation performance-based earthquake engineering (PBEE) generally refers to the seismic capacities of both structural components and non-structural components. However, this concept is different from the definition and the content of seismic fragility in traditional seismic risk theory. To clarify the differences between the two fragility definitions, the definition and its probabilistic model for seismic fragility in traditional seismic risk theory are firstly introduced. And then, five seismic fragility models in 2nd-generation PBEE are identified:seismic demand fragility model, seismic capacity fragility model, seismic damage fragility model, seismic loss fragility model, and seismic decision fragility model. The differences and their relationships of the five seismic fragility models are pointed out. The analytical formulations for the probability models and their distribution parameters in a seismic demand fragility model and a seismic damage fragility model are derived. On the basis of the above theoretical deduce, the concepts of forward PBEE and backward PBEE are put forward according to the directions of uncertainty propagation. Through this new concept, the risk integration equation in 2nd-generation PBEE can be solved by different methods. By integrating the approximate formulation of seismic hazard and the analytical formulations of fragility probability models and their distribution parameters, the three probabilistic seismic risk formulations with the same formats for EDP, DM and DV levels are obtained via the methods of forward PBEE and backward PBEE. Through the study of this paper, the traditional seismic risk theory and the 2nd-generation PBEE are unified into a consistent theoretical framework.
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LITERATURE REVIEW OF RESEARCHES ON RIGID BODY MODEL OF ROCKING STRUCTURE
ZHAO Zi-xiang, SU Xiao-zu
Engineering Mechanics    2019, 36 (9): 12-24.   DOI: 10.6052/j.issn.1000-4750.2018.08.0454
Accepted: 29 April 2019

Abstract133)      PDF(pc) (701KB)(125)       Save
A rational theoretical model is essential for structure analysis. The most widely used model in theoretical research for rocking structure is rocking rigid body model, which is systematically reviewed in this paper. The research origin and research status of rocking rigid body model are introduced. The classical rocking rigid body model, and other typical rocking rigid body model, as well as related experimental research, finite element simulation and application in structure system, are discussed. The advantages and limitations of existing rocking rigid body models are discussed and key issues in future study of rocking rigid body model are highlighted, which provides reference for the establishment of a more complete and practical rigid body model for rocking structure and its application to the analysis of rocking structure.
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RESEARCH AND APPLICATION OF MODERN BAMBOO STRUCTURES
TIAN Li-min, JIN Bei-bei, HAO Ji-ping
Engineering Mechanics    2019, 36 (5): 1-18,27.   DOI: 10.6052/j.issn.1000-4750.2018.06.ST06
Accepted: 12 February 2019

Abstract172)      PDF(pc) (3115KB)(161)       Save
Bamboo is one of the renewable resources in the world. It is an ideal material for building industry because of its good mechanical properties. With the improvement of social economy, the development of science and technology, and the promotion of national policy, bamboo structures will be one of the development directions in the future. This is mainly because the whole life cycle of bamboo structures can achieve co-existence with an ecological environment. The basic methods for the research of bamboo structures can learn from more mature traditional structural studies. However, bamboo is the foundation of bamboo structures. This special material makes bamboo structures different from traditional structures in terms of members, joints and systems. At present, the research on bamboo structures lacks uniform material constitutive. Not only that, but the research methods are single, and the connection forms of nodes are limited. The above-mentioned problems limit the wide application of bamboo structures in engineering. An overall review is given on mechanical properties of bamboo, bamboo members and joints, as well as common bamboo structural systems based on published literatures and authors' research work. The structural system of sprayed composite mortar-original bamboo has a good mechanical behavior, functionality, adaptability, and efficiency. It can replace traditional brick concrete structures and is applied to township and rural low-rise buildings. The structural system of sprayed composite mortar-original bamboo has high application value.
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INERTER SYSTEM AND ITS STATE-OF-THE-ART
ZHANG Rui-fu, CAO Yan-ru, PAN Chao
Engineering Mechanics    2019, 36 (10): 8-27.   DOI: 10.6052/j.issn.1000-4750.2018.09.0496
Accepted: 12 April 2019

Abstract124)      PDF(pc) (3418KB)(98)       Save
An inerter is a two-terminal acceleration-dependent mechanical element for structure control systems. The inerter system is an integrated system for the structural vibration control with inerters. A large number of studies and research projects on the inerter systems have been comprehensively reviewed in this paper. The state-of-the-art of inerter systems in the field of structural vibration control system were discussed from the following three aspects:realization of the inerter mechanism; performance of the inerter system and design of the structures with inerter system. Compared with traditional vibration control systems, the inerter system has its advantages including:the inertia of the structure can be adjusted and the tuning can be achieved flexibly; additional physical mass is negligible when the inertia of the structure changes obviously; the efficiency of energy dissipation is enhanced. This review paper is intended to provide theoretical evidence and practical guidance for the design, application and further development of inerter systems.
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Development and key issues of reticulated shells with semi-rigid joints
FAN Feng, MA Hui-huan, MA Yue-yang
Engineering Mechanics    2019, 36 (7): 1-7,29.   DOI: 10.6052/j.issn.1000-4750.2018.06.ST05
Abstract123)      PDF(pc) (771KB)(98)       Save
The assemble joints which are usually connected with members by one or several bolts are named semi-rigid joints. Due to the limit study of assemble joints, they are assumed as pin joints during the analysis and design of structures. However, the study results show that assemble joints are typical semi-rigid joints, and some new assemble joints have the merits of being stiffer and more efficient, which can be used in a larger span single-layer reticulated shell. The reticulated shells with semi-rigid joints have a wide application prospect, and the semi-rigid joint systems and semi-rigidly jointed reticulated shells have become a new research hotspot in the field of engineering structures. A state-of-the-art review of research on the semi-rigid joints and semi-rigidly jointed reticulated shells are thusly present. The research findings are presented and some key issues for further study are suggested. The research on the semi-rigid joints and semi-rigidly jointed reticulated shells has already obtained certain positive results. However, more experimental and theoretical study should be carried out on the joints under complex load combinations, the new joint design for larger span structures, the static and dynamic stability of single-layer reticulated shells with semi-rigid joints. The results should be analyzed and summarized in detail to promote the practical application of single-layer reticulated shells with semi-rigid joints.
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COMPARISON STUDY OF CONSTITUTIVE MODEL OF CONCRETE IN ABAQUS FOR STATIC ANALYSIS OF STRUCTURES
NIE Jian-guo,WANG Yu-hang
Engineering Mechanics    2013, 30 (4): 59-67.   DOI: 10.6052/j.issn.1000-4750.2011.07.0420
Abstract2574)      PDF(pc) (964KB)(2109)       Save

The smeared crack and plasticity damage models in general finite element program ABAQUS were detailed introduced, including the uniaxial stress-strain relationship, crack model, yield criterion, flow rules and hysteretic rules. Then comparison and analysis were made on the key factors of concrete constitutive models that have effect on the static mechanical behavior of structural members. The mechanical behavior of reinforced concrete members and steel-concrete composite members under monotonic and cyclic loadings were simulated using various concrete constitutive models, thusly the suitable model could be chosen when analyzing structural members according to the comparison results.

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RESEARCH PROGRESS AND APPLICATION OF FLAPPING WING AERODYNAMICS
XIANG Jin-wu, SUN Yi, SHEN Tong, LI Dao-chun
Engineering Mechanics    2019, 36 (4): 8-23.   DOI: 10.6052/j.issn.1000-4750.2018.03.0175
Abstract94)      PDF(pc) (4943KB)(95)       Save
Insects, birds and bats have superb flying ability. They are the main imitators of a flapping-wing aircraft. In recent years, a great progress has been made in the field of flapping-wing aerodynamics. This paper summarized the main research results, and focus on the recent advances in flapping-wing aerodynamics, including the flapping-wings lift mechanism of insects, birds and bats, the effects of wing morphological parameters and microstructures, wing flexibility, dynamic deformation, wing-wing interference, wing-body interference, inter-individual interference, and ground effect on the flapping wing aerodynamics. We also introduced the research progress of aerodynamic research on bionic flapping-wing aircraft design. At the end, the main problems and challenges faced by flapping-wing aerodynamics are presented.
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STUDY ON THE SEISMIC BEHAVIOR OF GRADED YIELDING METAL DAMPERS
CHEN Yun, JIANG Huan-jun, LIU Tao, WAN Zhi-wei, LU Zheng
Engineering Mechanics    2019, 36 (3): 53-62.   DOI: 10.6052/j.issn.1000-4750.2018.01.0036
Abstract127)      PDF(pc) (5460KB)(124)       Save
In this paper a new type of graded yielding metal damper composed of two annular metal dampers with different sizes was proposed. The seismic performance of the new damper was studied by cyclic loading tests. The failure mechanism and energy-dissipation mechanism of the damper were revealed. The hysteretic energy-dissipation behavior, strength and stiffness degradation, and fatigue resistance of the damper were analyzed. The experimental results show that the damper not only achieves graded yielding function effectively, but also possesses large deformation capability, full hysteretic loops and excellent anti-fatigue performance. The modification coefficient of the initial stiffness of the damper was obtained by parametric finite element analysis and regression analysis. The formulas to determine the performance points in the load-deformation skeleton curve were proposed. The calculated skeleton curves agree well with the experimental results. Accordingly, the geometry of the damper can be determined by the performance requirement. The research results of this study can provide technical support for the engineering application of the new metal damper.
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ROBUST OPTIMIZATION DESIGN METHODS OF STRUCTURAL DYNAMICS: A REVIEW
XU Ben-sheng, ZANG Chao-ping, MIAO Hui, ZHANG Gen-bei
Engineering Mechanics    2019, 36 (4): 24-36.   DOI: 10.6052/j.issn.1000-4750.2018.09.0484
Abstract120)      PDF(pc) (525KB)(85)       Save
How to improve the robustness of structural dynamic performance, and how to minimize the influence of various uncertainties on mean design are one of the hot issues both in academic and engineering fields. In this paper, the basic concept of structural dynamic robust optimization design is described. The robust optimization design methods of structural dynamics are reviewed from three aspects that are based on Taguchi method, multi-objective optimization and response surface methods. Taking a dual-rotor as an example, the dynamic robust optimization design is carried out by using the response surface modeling and multi-objective optimization methods. The results show that multiple robust optimization design schemes can be obtained based on response surface modeling and multi-objective optimization, and robust design methods have great potential for application in structural dynamics to deal with uncertain problems. Finally, the current research methods and future work are briefly summarized and prospected.
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A DISCUSSION ON BIG DATA IN STRUCTURAL ENGINEERING: PARADIGM, TECHNOLOGY AND EXAMPLE
CHEN Jun
Engineering Mechanics    2019, 36 (6): 175-182.   DOI: 10.6052/j.issn.1000-4750.2018.05.0279
Abstract88)      PDF(pc) (581KB)(82)       Save
Big data is no doubt the most popular topic currently in science and technology field. Application of big data has already reached the level as high as a national strategy. It brings new historical development opportunities to various interdisciplinary fields including structural engineering. This paper discusses, from the point of view of research paradigm shift, the impacts, problems and challenges along with the introduction of big data concepts and technologies to structural engineering. Potential applications of big data in structural engineering are then discussed according to the development trend of the third generation of structural design theory. Finally, an example is given which shows the application of big data idea for investigating live loads in a building.
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REVIEW OF THE RESEARCH ON STEEL STORAGE RACK STRUCTURES
ZHAO Xian-zhong, DAI Liu-si, HUANG Zhao-qi, REN Chong
Engineering Mechanics    2019, 36 (8): 1-15.   DOI: 10.6052/j.issn.1000-4750.2018.10.ST12
Abstract142)      PDF(pc) (1919KB)(81)       Save
With the rapid growth of logistics industry, steel storage racks are not just industrial products. They are commonly used in high-rise warehouses and clad racks. Therefore, the structural safety of storage racks is of vital importance. Steel storage racks are distinct from traditional moment resisting frames in the following aspects. Firstly, storage racks may carry extremely high live loads with comparatively light weight and reach up to 40 meters in height. Secondly, the uprights have open singly- or non-symmetric cross-sections and are continuously perforated along the length, the behavior of which is significantly influenced by local, distortional, global buckling and their interactions. Thirdly, the mechanical beam-to-upright connections and column bases are commonly utilized for their convenience in assembly and adjustment. Their nonlinear moment-rotation behavior and severely pinching characterization requires comprehensive investigations. Fourthly, the influences of the asymmetry configuration of the bracing system on the stability of the overall rack structure need to be carefully studied. Moreover, as for the aseismic behavior of rack structures, further investigations are required for the hysteretic behavior of beam-to-upright connections, the collapse mechanisms of the overall rack structures, and the sliding behavior between pallets and beams. It should be noted that besides usual local and global collapse mechanisms, the falling of pallets should also be considered as an additional serviceability limit state of rack structures. This paper reviews researches on the behavior of steel storage racks. A brief introduction of rack structures is provided, as well as the main research methodologies. The main research results on the static and dynamic behavior are then presented respectively. Finally, the key issues in studies of steel storage racks and the related research topics are proposed.
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Application of adaptive finite element method of lines in 2D unbounded domain problems
DONG Yi-yi, XING Qin-yan, FANG Nan, YUAN Si
Engineering Mechanics    2019, 36 (7): 8-17.   DOI: 10.6052/j.issn.1000-4750.2018.06.0351
Abstract87)      PDF(pc) (938KB)(80)       Save
Unbounded domain problems are frequently encountered in engineering. As a semi-analytical and semi-discretized numerical method, Finite Element Method of Lines (FEMOL) has shown good performance on this type of problems. Based on the proposed theory of infinite elements with mapping technique, the adaptive FEMOL with Element Energy Projection (EEP) super-convergent method is applied to the solution of 2D unbounded domain problems, in which users are only required to pre-specify an error tolerance and a rough initial mesh, and then an adaptive FEMOL mesh is automatically produced by the algorithm, on which the accuracy of FEMOL solution with both regular elements and infinite elements satisfies the specified error tolerance in maximum norm. An introduction of the theory of FEMOL and the infinite elements are given firstly, and then the strategy of adaptive FEMOL based on EEP method is presented. The feasibility of applying the adaptive FEMOL to unbounded domain problems is analyzed. Then three unbounded domain problems are adaptively solved, including the Poisson equation of flow around a circular cylinder, the plane problem of uniaxial tension of infinite plate with a circle hole in elasticity, and the semi-infinite half space body under uniformly distributed circular load. Finally the displacements (function solutions) satisfying the error tolerance can be obtained and the stresses (derivative solutions) with superior accuracy can be calculated. Therefore the adaptive FEMOL can be taken as a new approach for solution of unbounded domain problems.
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STUDY ON WIND TUNNEL WALL INTERFERENCE IN DYNAMIC AIRFOIL TEST
LI Guo-qiang, ZHANG Wei-guo, HUANG Xia, WANG Xun-nian
Engineering Mechanics    2019, 36 (8): 235-247.   DOI: 10.6052/j.issn.1000-4750.2018.07.0380
Abstract89)      PDF(pc) (8377KB)(77)       Save
The aerodynamic nonlinear characteristics of airfoil caused by dynamic stall are prominent, and the coupling effect with wall interference brings great uncertainty to wind tunnel test data. In view of this, the mechanism and influence law of the wall effect in the airfoil dynamic test are revealed by means of experiment and numerical method. The results show that:compared to the static test, due to the existence of the wall interference, both the total pressure and the static pressure distribution of the wake zone during the dynamic test of airfoil are even more inhomogeneous. The wind tunnel wall interference of dynamic airfoil test is more serious. The differences of the velocity and pressure distribution on the middle section and the end section of airfoil are more obvious. Compared with the pressure surface, the two-dimensional flow of the suction surface becomes worse. The side wall interference suppresses the flow separation near the middle section of airfoil, and induces a spanwise separation flow near the end. The unsteady pressure coefficient of the upper and lower wall versus real-time attack angle also shows a hysteresis effect, the direction of the hysteresis loop is opposite, and the main characteristic frequency of the wall pressure fluctuation equals to the oscillation frequency of airfoil pitching. Influenced by the wind tunnel wall interference, the three-dimensional dynamic stall vortex structure of the airfoil is "Omega" type. In the positive stroke, the lift coefficient and the lift line slope are increased by the upper and lower wall of the wind tunnel, and the airfoil is induced to be stalled in advance. In the negative stroke, the lift coefficient of airfoil is reduced. The sidewall interference induces a spanwise flow on airfoil surface, reduces the chord-orientation flow velocity of airfoil, causes the reduction of lift coefficient in the negative stroke, but the interference effect is less in the positive stroke, besides the dynamic stall is delayed. The upper and lower wall interference of the dynamic airfoil test in the FL-11 wind tunnel should be a dominant factor. However, the sidewall interference cannot be ignored, especially at the high angle of attack and negative stroke during the oscillation period of airfoil.
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STABILITY AND VIBRATION BEHAVIOR OF FGM BEAMS UNDER HYGRO-THERMAL-MECHANICAL-ELASTIC LOADS
PU Yu, ZHOU Feng-xi
Engineering Mechanics    2019, 36 (9): 32-39.   DOI: 10.6052/j.issn.1000-4750.2018.08.0443
Accepted: 17 May 2019

Abstract75)      PDF(pc) (427KB)(75)       Save
The stability and vibration behavior of functionally graded material (FGM) beams resting on a Winkler-Pasternak elastic foundation under the action of initial axial mechanical load considering the hygro-thermal environment is investigated. Three hygro-thermal distributions through the thickness of the beams are assumed. The material properties are temperature-dependent and are distributed according to the Voigt mixture power law model. An n-th order generalized beam theory is proposed. The governing equations of buckling and free vibration are derived from the Hamilton's principle, in which the fundamental unknown functions are the axial displacement, bending and shear components of the transverse displacement. Applying the Navier method, the analytical solutions of the buckling and free vibration responses of FGM simply supported beams are obtained. The availability and accuracy of the n-th order generalized beam theory are tested and discussed through several numerical examples. The results show that it refines the beam theories and can be used as a benchmark to verify or modify other shear deformation beam theories. The effects of three types of hygro-thermal distribution, moisture and temperature rise, initial axial mechanical load, length-to-thickness ratio, elastic foundation stiffness and material graded index on the stability and vibration behavior of FGM beams are analyzed.
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MECHANICAL PROPERTIES OF HIGH TENSILE STEEL CABLES AT ELEVATED TEMPERATURE
DU Yong, SUN Ya-kai, LI Guo-qiang
Engineering Mechanics    2019, 36 (4): 231-238.   DOI: 10.6052/j.issn.1000-4750.2018.03.0141
Abstract59)      PDF(pc) (1487KB)(74)       Save
This study is motivated by increasingly prevalent use of cable-tensioned spatial steel structures and suspension bridges. Fire is one of the extreme conditions that need to be taken into consideration in the design of such structures. Steady-state tests have been conducted on steel cables with tensile strength of 1860MPa, which consist of a group of 7-wire twisted strands, to study their full range of stress strain relationships at elevated temperature. The thermal elongation test of steel cables has also been conducted. A charge-coupled device camera (CCDC) system is used to capture the full range of the stress-strain relationship of high tensile strength steel cables till rapture at elevated temperature. The reduction factors of proportional limit, elastic modules, effective yield strength and rupture strength at different temperature were obtained from the steady state tests and compared with that proposed by EN 1992-1-2. The test data discovered that EN 1992-1-2 overestimated effective strain up to 2% and ignored the stress hardening phase for high tensile strength cables within the full temperature range. The effective yield strength with 1.25% strain and a full range of stress-stain model considering stress hardening phase, which has been ignored by EN 1992-1-2, are proposed by the present test data. Finally, several sets of reduction factors and thermal elongation coefficients as a function of temperature have been proposed by fitting test results. The present test data discovered that the reduction factors of pre-stressing strands proposed by EN 1992-1-2 for pre-stressing concrete is not suitable for steel cables which always employed by tensile steel structures. The reduction factors proposed by present paper are reasonable for steel cables. Furthermore, the comparison of reduction factors between steel cables and single wires, it discovered the effect of twist on the mechanic properties at elevated temperature.
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EXPERIMENTAL STUDY ON ASEISMIC BEHAVIOR OF LOCALLY USED HDC ASSEMBLED FRAME BEAM-COLUMN JOINTS
DENG Ming-ke, MA Fu-dong, YE Wang, YIN Peng-fei
Engineering Mechanics    2019, 36 (9): 68-78.   DOI: 10.6052/j.issn.1000-4750.2018.05.0263
Accepted: 29 April 2019

Abstract68)      PDF(pc) (1999KB)(70)       Save
In order to improve the deformation and energy dissipation capacity of fabricated beam-column joints and avoid the construction difficulties caused by crowded steel bars, high ductile fiber reinforced concrete (HDC) is used as the core material of beam-column joints. Considering the influence of axial compression ratio and stirrup ratio, 5 fabricated beam-column joints partly adopted HDC and 1 reinforced concrete (RC) beam-column joint were tested. The failure patterns, hysteretic characteristics, deformation capacity, stiffness degradation, energy dissipation capacity and shear deformation of the joint core area were analyzed. The results are as follow. First, failure position changed from node core area to beam end after adopted HDC in node core area. The design principle of a strong node is realized, and the deformation ability and energy dissipation capacity of frame nodes are effectively improved. Second, column ends should be strengthened because the failure position transferred to the end of column adopted HDC in the node area and beam end. Third, the amount of stirrups can be reduced when HDC is used in node core area.
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MECHANICAL PROPERTIES ANALYSIS AND EXPERIMENTAL RESEARCH ON MAGNIFIED VISCOUS DAMPING WALL
LIU Wen-guang, ZHANG Xin, GUO Yan, ZHANG Qiang
Engineering Mechanics    2019, 36 (8): 40-48.   DOI: 10.6052/j.issn.1000-4750.2018.10.0534
Abstract52)      PDF(pc) (879KB)(70)       Save
An amplified multi-lever parallel viscous damping wall was proposed. Given its structure and force characteristics, vertical pulling effect, the damping force and energy dissipation theoretical formulas of both common and magnified viscous damping walls were analyzed, as well as its deformation and energy dissipation. An experimental model of both common and magnified viscous damping walls with triple displacements was designed to carry out a reciprocating loading test under the action of a sine wave. The hysteresis curve of viscous damping wall was verified by the comparison between a theoretical curve and the experimental curve under different experimental conditions. Furthermore, the hysteretic curve of the amplified viscous damping wall was rounder than that of a normal damping wall, and the energy dissipation was more significant under the same displacements. Therefore, the three-storey concrete frame structure was used as the calculation model for seismic analysis, which confirms the influence of vertical pulling was effective to the structure of a magnified viscous damping wall.
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A SHEAR DESIGN MODEL FOR RC DEEP FLEXURAL MEMBERS CONSIDERING THE SIZE EFFECT
WEI Hui, WU Tao, LIU Yang, LIU Xi
Engineering Mechanics    2019, 36 (5): 130-136.   DOI: 10.6052/j.issn.1000-4750.2018.03.0169
Accepted: 28 March 2019

Abstract63)      PDF(pc) (405KB)(77)       Save
There is a lack of accurate and reasonable shear design models for reinforced concrete deep flexural members such as typical D-region shear components with complicated force mechanism and significant size effect. In combination with the advantages of the Tan-Cheng model that fully considers the softening effect of concrete and the size effect of struts, and on the basis of the deep understanding of the effect of diagonal strut angle α and composite tensile stress ft on the shear strength of deep flexural members, the relationship between the top node height lc and α was simplified and a modified Tan-Cheng model was proposed by reconsidering the effective action region of web reinforcement. The predictions of 308 deep flexural members from either foreign or domestic source indicate that the proposed model has a comparable accuracy with the Tan-Cheng model, and it can accurately consider the size effect of concrete struts through a concise calculation process. The comparison between the proposed model and current code provisions shows that the predictions by the proposed model has a better agreement with the test results. It further indicates that the proposed model can reasonably predict the shear strength of deep flexural members.
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STRUCTURAL SOLUTIONS OF LARGE-SCALE ENGINEERING PROJECTS BASED ON ENGINEERING MECHANICS
LÜ Hai-shuang, ZHOU Bei-lei, CAO Qian, WANG Yang
Engineering Mechanics    2019, 36 (3): 40-52.   DOI: 10.6052/j.issn.1000-4750.2018.08.ST10
Abstract145)      PDF(pc) (11893KB)(106)       Save
In recent years, lots of large-scale, complex, and “beyond-limit” building structures have been constructed both at home and abroad, most of which are irregular structures. In designing practice, we often encounter the problems out of the scope of regulations or the problems not specified in pertinent codes. The existing standards cannot be applied to these problems, and they are also lack of clear goals, evidence and methods for the problems. Under these circumstances, aiming at a series of large engineering projects of (ARUP) engineering consulting company in China, this paper introduces the solutions of the problems by engineering mechanics.
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COMPARISON ON THE SEISMIC DEISGN OF BASE-ISOLATED RC FRAMES USING TWO CHINESE CODES
YIN Chuan-yin, XIE Lin-lin, LI Ai-qun, ZENG De-min, CHEN Xi, GE Dong-dong, YANG Can-tian
Engineering Mechanics    2019, 36 (9): 197-204,212.   DOI: 10.6052/j.issn.1000-4750.2019.02.0044
Accepted: 23 May 2019

Abstract88)      PDF(pc) (651KB)(66)       Save
There will be two seismic design codes for the base-isolated structures in the near future in China, including Code for Seismic Design of Buildings and Code of Design for Seismic Isolated Buildings. It is notable that significant differences exist in terms of design methods and critical design indexes between these two codes. However, comparisons on the seismic design of base-isolated structures using these two codes are rarely reported. The seismically isolated reinforced concrete (RC) frame structure is herein selected as the study subject. Using three pairs of structure cases with different heights which were designed according to the two codes, the controlling factor for the seismic design of such structures using Code of Design for Seismic Isolated Buildings was identified. In addition, the seismic responses and economic investment of such structures designed according to the two codes were compared and analyzed. The results indicate that the abovementioned controlling factor is base shear ratio. For the superstructure, a smaller stiffness is selected if Code of Design for Seismic Isolated Buildings is adopted, and the corresponding seismic load reduces by approximately 15%~20% in comparison with that designed following Code for Seismic Design of Buildings. However, because the degree of stiffness reduction of superstructure is greater than that of seismic load reduction, a significant increase of maximum inter-story drift ratio (i.e., θmax) of superstructure is observed. Furthermore, the increment of θmax basically increases with the increase of total height of structure. As for the material consumption, the concrete consumption is reduced by 7.7%~12.1% while the reinforcement consumption is increases by 11.02%~26.29% if Code of Design for Seismic Isolated Buildings is adopted. With the increase of total height of structure, the reduction of concrete consumption increases, while the increment in reinforcement consumption decreases. The research outcome will assist in providing a useful reference for seismic design of base-isolated RC frame structures.
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EXPERIMENTAL STUDY AND NUMERICAL SIMULATION ON SEISMIC PERFORMANCE OF TWO-STORY PRECAST SHEAR WALLS WITH OPENING
CHONG Xun, ZHANG Lan-fang, WAN Jin-liang, WANG De-cai, YE Xian-guo, XIE Lin-lin, SHAO Hui-bin
Engineering Mechanics    2019, 36 (5): 176-183.   DOI: 10.6052/j.issn.1000-4750.2018.01.0083
Accepted: 09 April 2019

Abstract65)      PDF(pc) (1281KB)(65)       Save
To investigate the seismic performance of precast shear wall structure with openings, pseudo-static tests of two precast shear walls with different window-wall heights are conducted. Based on the test results, a refined finite element numerical simulation method is proposed, and the effect of window-walls to the structure is further evaluated. The experimental and numerical simulation results indicate that window-wall can work together with the coupling beam entirety at the preliminary stage. Then, a dual coupling beams mechanism is observed when the abovementioned two components separate. The failure modes of these two specimens involve crushes of the concrete at the plastic hinges formed at the bottom of walls and at two ends of the dual coupling beams. The load bearing capacity and initial stiffness of the specimen with a larger height of window-wall are larger, while its ductility and energy dissipation capacity are smaller. The window-walls can significantly improve the stiffness, load bearing capacity and energy dissipation capacity of such precast structure. Hence, window-walls are required to be considered in the seismic design of precast shear wall structure with openings.
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SEISMIC EXPERIMENT AND THEORETICAL ANALYSIS ON SELF-INSULATING STRUCTURAL WALLS WITH INNER SKELETON
SHI Feng-kai, LIU Fu-sheng, WANG Shao-jie, YUE Yi-bo, LIU Kang, HUANG Xing-huai
Engineering Mechanics    2019, 36 (4): 158-166,187.   DOI: 10.6052/j.issn.1000-4750.2018.02.0093
Abstract105)      PDF(pc) (2308KB)(65)       Save
A self-insulating structural wall with inner skeleton and its structural system were designed for realizing the integration of anti-seismic and energy-saving performance. A horizontal low-cyclic load test was conducted to investigate the wall's seismic performance, and it revealed the transformation process of the wall's failure mechanisms. Accordingly, the failure process was divided into three stages, including common working stage, transition stage and weak frame working stage. This study proposed cracking load and ultimate capacity formulas based on the wall's final failure mode and theoretical analysis of the test results. The two formulas were respectively established on the basis of the elastic equivalent model and the modified softened strut-and-tie model. The relative errors between theoretical analysis and test results were 3.2% and 3.3%, respectively, indicating the theoretical formulas have a clear physical significance and an adequate level of accuracy. Additionally, the experiment results verified the wall's superiorities, including seismic behavior, construction convenience and economic performance. The wall is well-suitable for application in multi-story residential buildings such as villages and towns.
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SOME NEW DEVELOPMENTS OF THE FIRE PERFORMANCE RESEARCH ON COMPOSITE STRUCTURES
SONG Tian-yi;HAN Lin-hai
Engineering Mechanics    2008, 25 (增刊Ⅱ): 230-253.  
Abstract1248)      PDF(pc) (1230KB)(579)       Save
The research on fire-endurance performance and fire-resistance design of composite structures is one of the hot topics in structural engineering. This paper briefly summarizes and reviews some of the recent progress on the fire performance of composite slabs, composite beams, composite columns, beam-column connections, frames and structural system. Finally, A number of issues need to be addressed on the fire performance of composite structures are identified and discussed.
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STUDY ON SHEAR STRENGTH ANALYSIS FOR A NEW TYPE LIGHT STEEL-FRAMED COMPOSITE WALL FILLED WITH FOAM CONCRETE
TIAN Wen-ling, WEN Xiao-dong, PENG Jia-bin, XU Li-li, LI Zi-xiang
Engineering Mechanics    2019, 36 (9): 143-153.   DOI: 10.6052/j.issn.1000-4750.2018.08.0448
Accepted: 15 April 2019

Abstract62)      PDF(pc) (1957KB)(63)       Save
To obtain a practical calculation method for the shear strength of light steel-framed composite walls covered with skin plates and a new type light steel-framed composite wall filled with foam concrete, four walls of identical dimensions, DD-1, DD-2, DD-1(D-300), DD-2(D-400), were subjected to monotonic loading and another two walls of identical dimensions, DZ-1(D-300), DZ-2(D-400), were subjected to reversed cyclic loading. On the experimental basis, a shear strength calculation method is established based on the bolt group failure model of light steel-framed composite walls covered with skin plates. The lightweight steel-lightweight concrete models and the strut-and-tie model are adopted to simplify the new type light steel-framed composite walls filled with foam concrete so as to derive a practical shear strength formula of the wall. The shear strength formula is revised according to the experimental results. The revised calculation results have good agreement with the experimental results. The lightweight steel-lightweight concrete model exhibits a higher agreement. The results can be used as a reference for structural design and construction.
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TIME DOMAIN CALCULATION METHOD BASED ON HYSTERETIC DAMPING MODEL
SUN Pan-xu, YANG Hong, ZHAO Wen-tong, WANG Zhi-jun
Engineering Mechanics    2019, 36 (6): 13-20.   DOI: 10.6052/j.issn.1000-4750.2018.05.0299
Abstract80)      PDF(pc) (551KB)(63)       Save
The free vibration solution of a complex damping time domain motion equation contains divergent items which make the numerical results of the time domain divergent. Based on the frequency domain motion equation of a complex damping model, the hysteretic damping time domain motion equation can be obtained. According to the characteristics of a hysteretic damping model, the time domain theoretical calculation method of the hysteretic damping model is proposed based on the complex plane method and trigonometric series expression of earthquake acceleration records. It is assumed that the structural vibration response is a harmonic vibration response in a short time step. Based on the average acceleration method, the time domain numerical calculation method of the hysteretic damping model is proposed. The analysis results show that:compared with the time domain numerical method of a complex damping model, the two proposed methods can avoid the time domain divergence phenomena effectively. The time domain calculation results of the two proposed methods are approximately equal to the frequency domain calculation results of a complex damping model. The correctness of the two proposed methods is verified.
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IDENTIFICATION OF STRUCTURAL PARAMETERS AND UNKNOWN EXCITATIONS BASED ON THE EXTENDED KALMAN FILTER
ZHANG Xiao-xiong, HE Jia
Engineering Mechanics    2019, 36 (4): 221-230.   DOI: 10.6052/j.issn.1000-4750.2018.03.0139
Abstract67)      PDF(pc) (735KB)(61)       Save
The classical extended Kalman filter (EKF) method is capable of accurately identifying structural parameters with known external excitations. However, in some practical situations, the excitations are difficult or impossible to measure. A time-domain approach based on EKF is proposed in this paper for the simultaneous identification of structural parameters and unknown inputs. A projection matrix is introduced in the observation equation, based on which the structural parameters are identified. The unknown inputs are determined by means of least squares estimation using the estimated parameters. The effectiveness and robustness of the proposed approach is verified through three numerical examples including a four-story benchmark model, a piecewise linear structure and a Duffing hysteretic structure. The numerical results show that the proposed approach can not only accurately identify the parameters of linear and nonlinear structures, but also satisfactorily estimate the unknown external excitations.
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STUDY ON SEISMIC PROPERTY OF STEEL COUPLING BEAM WITH RESTRAINED WEB
WANG Yu-hang, LIU Yuan-jiu, ZHOU Xu-hong
Engineering Mechanics    2019, 36 (6): 49-59,69.   DOI: 10.6052/j.issn.1000-4750.2018.08.0461
Abstract62)      PDF(pc) (1839KB)(61)       Save
With constraint plate on both sides of steel web, bearing capacity of Buckling Constraint Steel Coupling Beam can continue to increase after the shear yielding of web under cyclic shear loading. Compared with the traditional way of setting stiffeners on the web, Buckling Constraint Steel Coupling Beam has excellent energy dissipation capacity because the buckling destruction of steel web won't take place until the ultimate shear strain is reached. Five quasi-static tests on Buckling Constraint Steel Coupling Beam were carried out to study the impact of various constraint manners on seismic behavior of this type of steel coupling beam. Test results indicate that all the test specimens undergo shear yielding and achieve the increasing of bearing capacity, followed by two types of failure modes, i. e., constraint plate bending failure and fracture at the weld connecting link flange to end plate. The average over-strength factor of all specimens reaches 1.38, higher than the value of 1.1 required by GB 50011-2010. Specimens with 50 mm thick concrete constraint plate and 25 mm thick wooden constraint plate both have an over-strength factor larger than 1.5. Based on finite element analysis, the comparison between test results and parametric analysis was conducted, and the minimum thickness of constraint plate was proposed for practical design.
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Influence of self-weight on the fracture properties of three-point bending concrete beams
YIN Yang-yang, HU Shao-wei, WANG Yu-hang
Engineering Mechanics    2019, 36 (7): 48-56,108.   DOI: 10.6052/j.issn.1000-4750.2018.08.0458
Abstract83)      PDF(pc) (583KB)(61)       Save
Self-weight has a significant influence on the fracture properties of beams under three-point bending (TPB). However, the influence of initial crack mouth opening displacement (CMODini) caused by self-weight was rarely considered in previous research on concrete fracture properties based on TPB beams. To investigate the influence of CMODini on the fracture properties of TPB beams, a calculation formula of CMODini, effective crack length (ac) and unstable fracture toughness (KICun)considering the influence of CMODini are presented. The calculated results of the formula were compared with the experimental data of specimens of different sizes and initial crack-depth ratios. The results indicate that CMODini is slightly influenced by the specimen sizes. The influence of the self-weight on CMODini, ac and KICun is less than 5% even if the specimen size is 2200 mm×550 mm×240 mm and the initial crack-depth ratio is 0.4. CMODini is greatly influenced by the initial crack-depth ratio. The influence increases with the increase of the initial crack-depth ratio. Moreover, the influences of the self-weight on CMODini, ac and KICun are 24.26%, 1.73% and 17.31%, respectively, when the specimen size is 1143 mm×305 mm×76 mm and the initial crack-depth ratio is 0.818. Therefore, the influence of CMODini caused by the self-weight of TPB beams should be taken into account when both the specimen size and the initial crack-depth ratio are large.
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COMPARATIVE ANALYSIS OF THE ITERATIVE ALGORITHMS FOR NONLINEAR METHOD BASED ON THE WOODBURY FORMULA
JIA Shuo, LI Gang, LI Hong-nan
Engineering Mechanics    2019, 36 (8): 16-29,58.   DOI: 10.6052/j.issn.1000-4750.2018.06.0320
Abstract74)      PDF(pc) (1108KB)(61)       Save
The elements of the stiffness matrix are often partially changed in the solution of local nonlinear problems, in which the tangent stiffness matrix can be written as the sum of the initial stiffness matrix and its low rank perturbation matrix so that the displacement response in each incremental step can be efficiently solved by the Woodbury formula that is used to calculate the inverse matrix in mathematics. However, the iterative calculation is often unavoidable in the structural nonlinear analysis, and the performance of the nonlinear iterative algorithm also has a great impact on the efficiency of the structural nonlinear analysis. This paper studies the iterative solution of the nonlinear method based on the Woodbury formula. The Newton-Raphson (N-R) method, the modified Newton method, the two-point method with three convergence order, the two-point method with four convergence order, and the three-point method, are chosen to solve the equilibrium equations of the nonlinear method based on the Woodbury formula, and the performance of these five iterative algorithms is compared. The time complexity analysis models of the five iterative algorithms solving the equilibrium equations of the nonlinear method based on the Woodbury formula are obtained, and the efficiency of the five algorithms is quantitatively compared. The calculation performance of the five iterative algorithms is compared through two cases from the perspective of convergence rate, time complexity and error; then the applicable nonlinear problems of the five algorithms are analyzed. Finally, the comprehensive performance index of the five iterative algorithms solving the equilibrium equations of the nonlinear method based on the Woodbury formula is calculated.
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INVERSE ANALYSIS OF INTERNAL DEFECTS IN STRUCTURES USING EXTENDED FINITE ELEMENT METHOD AND IMPROVED ARTIFICIAL BEE COLONY ALGORITHM
WANG Jia-ping, DU Cheng-bin, WANG Xiang, JIANG Shou-yan
Engineering Mechanics    2019, 36 (9): 25-31.   DOI: 10.6052/j.issn.1000-4750.2017.11.0874
Accepted: 26 July 2019

Abstract72)      PDF(pc) (506KB)(60)       Save
The information of defect in a structure is determined using the extended finite element method combined with a kind of improved artificial bee colony algorithm, based on real structural response. As searching optimal value may appear in an arbitrary direction in traditional artificial bee colony (ABC) algorithm, weighted average mutation and a cross operator are introduced to avoid the local optimum in the optimizing. The presented inverse method is also used to determine the location of a single-circular-like defect and an elliptical-like defeat and two irregular defects, and the robustness of the algorithm under the condition of measuring error is also studied. The numerical results indicate that the adapting artificial bee colony (AABC) algorithm proposed can present the real information of defects accurately. The convergence speed of AABC is faster than that of traditional ABC, and it is unlikely that the local optimum will appear in the optimizing. The presented method can locate the defects accurately and show a high robustness.
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MESO-SCALE SIMULATION OF SIZE EFFECT OF DYNAMIC TENSILE STRENGTH OF CONCRETE UNDER LOW STRAIN RATES
JIN Liu, YU Wen-xuan, DU Xiu-li, ZHANG Shuai, LI Dong
Engineering Mechanics    2019, 36 (8): 59-69,78.   DOI: 10.6052/j.issn.1000-4750.2018.03.0144
Abstract76)      PDF(pc) (5327KB)(60)       Save
Great progresses have been made in static size effect of concretes, while few efforts have been conducted in dynamic size effect of concretes. Herein the study, in order to explore the size effect of concrete under dynamic loadings, considering concrete heterogeneities and the strain rate effect for the meso components, a meso-scale simulation method was built. Taking the double notched concrete specimens as examples, the dynamic tensile failure and the size effect of concrete under low strain rates from 10-5 s-1 to 1 s-1 were investigated using the meso-scale simulation method. The effect of strain rate on the size effect in tensile strength of concrete was also analyzed. Finally, based on the influencing mechanism of strain rate effect on dynamic strength and size effect, i.e. the enhancement of strength and weakening of size effect, a "static-dynamic unified size effect law" for dynamic tensile strength of concrete was established. The proposed size effect law was also calibrated by meso-scale simulation results.
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INVESTIGATION ON FLEXUREL CAPACITY OF RENINFORCED ULTRA HIGH PERFORMANCE CONCRETE BEAMS
LIANG Xing-wen, WANG Ping, XU Ming-xue, WANG Zhao-yao, YU Jing, LI Lin
Engineering Mechanics    2019, 36 (5): 110-119.   DOI: 10.6052/j.issn.1000-4750.2018.03.0164
Accepted: 09 April 2019

Abstract76)      PDF(pc) (822KB)(58)       Save
4 span-depth ratio of 16 reinforced ultra-high-performance concrete beams were fabricated for the investigation of their flexural behavior and flexural capacity. The variable parameters studied in the test were steel fiber volume fraction and longitudinal reinforcement ratio. Testing results show that increasing steel fiber volume fraction from 3% to 5% could increase the resistance of cracking (cracking load increased by 6.0% to 11%). However, it had little effect on the ultimate load capacity (only increased 1.4%~2.5%). The failure modes of the beams with the longitudinal reinforcement ratio of 3.21% and 6.74% were classified as under-reinforced failure and limited over-reinforced failure respectively. Increasing the reinforcement ratio could enhance the flexural capacity of reinforced UHPC beams (increased by 34.9%~36.5%). A tentative flexural capacity calculation model of reinforced UHPC beams was proposed based on the section equilibrium condition, the assumption of plane section, the material constitutive relation of UHPC, and reinforcement. The calculation results of flexural capacity are found agreeing well with the experimental results.
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AN EFFICIENT HYBRID METHOD FOR DYNAMIC ANALYSIS OF TRAIN-TRACK-BRIDGE COUPLED SYSTEMS BASED ON THE MODAL SUPERPOSITION METHOD AND DIRECT STIFFNESS METHOD
ZHU Zhi-hui, ZHANG Lei, GONG Wei, LUO Si-hui, YAO Jing-chuan, YU Zhi-wu
Engineering Mechanics    2019, 36 (4): 196-205.   DOI: 10.6052/j.issn.1000-4750.2018.03.0125
Abstract72)      PDF(pc) (2305KB)(58)       Save
To improve the computational efficiency for analyzing the vibration of train-track-bridge coupled systems (TTBSs), an improved hybrid method (IHM) is proposed by combining the direct stiffness method (DSM) and the modal superposition method (MSM) based on the hybrid method. The vibration equations of the train are established by applying multi-body dynamics. The vibration equations of the track are established by using the DSM, which can effectively display the local dynamic behavior with high frequency. The vibration equations of the bridge are established by using the MSM, a method that can efficiently reduce the degrees of freedom. The train and track are coupled as a train-track subsystem through the linear wheel-rail Hertz contact model. The train-track subsystem and the bridge subsystem are coupled by enforcing the compatibility of forces at the contact points between the track and the bridge. The proposed method is validated by the field measurement data collected from a 32 m simply supported girder bridge on the Shuo-Huang heavy-haul railway line. A numerical example of a CRH2 high speed train passing the Wan-Ning Bridge is provided to investigate the effects of the number of bridge modes on the accuracy of the dynamic responses. The computation time of the three different methods for analyzing the vibration of the TTBS is compared and the results show that the IHM has the most computational efficiency than the other two methods.
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ENERGY-CONSERVING TIME INTEGRATION METHOD FOR TIMOSHENKO BEAMS
YANG Hao-wen, WU Bin, PAN Tian-lin, XIE Jin-zhe
Engineering Mechanics    2019, 36 (6): 21-28.   DOI: 10.6052/j.issn.1000-4750.2018.01.0033
Abstract101)      PDF(pc) (460KB)(58)       Save
An energy-conserving time integration method is proposed for the nonlinear dynamic analysis of Timoshenko beams. Co-rotational techniques are used to consider its structural geometric nonlinearity, and a linked interpolation form is adopted in the spatial discretization to avoid shear-locking phenomenon of a beam. The multi-parameter correction method is used to modify the equivalent nodal dynamic equations in the time discretization, which results in the energy conservation of the discrete system under conservative loading. The method has second-order local accuracy and shows better numerical stability, compared to the average acceleration method and the implicit midpoint method. The proposed method is compared to the Simo's method in two-dimensional cases and it is found that the Simo's method does not conserve system energy under a conservative external moment. Finally, the excellent performance and energy-conserving characteristic of the algorithm are verified by three numerical simulations.
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RESEARCH ON SLIDING MODE DECENTRALIZED CONTROL BASED ON ADAPTIVE LEARNING RATE RBF NEURAL NETWORK FOR LARGE-SCALE ENGINEERING STRUCTURES
PAN Zhao-dong, LIU Liang-kun, TAN Ping, ZHOU Fu-lin
Engineering Mechanics    2019, 36 (9): 120-127.   DOI: 10.6052/j.issn.1000-4750.2018.07.0429
Accepted: 26 July 2019

Abstract42)      PDF(pc) (485KB)(58)       Save
This paper Proposes a decentralized adaptive learning rate RBF neural network sliding mode control (DALRBFSMC) algorithm for dealing with the influence and the uncertainty of the interaction forces between subsystems and the external loads. Lyapunov stability theory is employed to design the decentralized sliding mode control law which depends only on the displacement and the velocity response of relevant subsystems. Combined with RBF neural network theory and the classical gradient descent method, the adaptive learning rate of RBF network weights-adjustment is derived by using a Lyapunov function. And then the decentralized adaptive learning rate RBF neural network sliding mode control (DALRBFSMC) is designed, which can adjust the switching gain of the sliding mode control law in real time. An ASCE 9-story benchmark building is selected as a numerical example to evaluate the control performances of decentralized control and centralized control. Numerical simulation results indicate that the DALRBFSMC algorithm is suitable for different decentralized control strategy, and that overlapping decentralized control can perform up to a superior control performance when comparing with traditional centralized control, and also guarantee each of the actuators to be operating at maximum efficiency.
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