Dec 2009, Volume 3 Issue 4
    

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  • Research articles
    Initial stiffness and moment resistance of reinforced joint with end-plate connection
    Sufang WANG, Yiyi CHEN,
    2009, 3(4): 345-351. https://doi.org/10.1007/s11709-009-0054-x
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    In beam-to-column joint with bolted end-plate connection, the structural details of column flange reinforced by backing plate and column web panel reinforced by supplementary plate are analyzed. The joint is divided into some basic components, and the initial stiffness of each component is obtained. Especially, the initial stiffness of reinforced components is drawn by theoretical model and finite element analysis. The initial stiffness of reinforced joint can be obtained by assembling the initial stiffness of each component. The design moment resistance of column flange reinforced by backing plate is deduced based on yield line method, and the design moment resistances of other components are deduced based on present codes. The design moment resistance of the reinforced joint is then determined by the minimum of the design moment resistances of all components. By comparison with the results of finite element calculation, it is verified that the method to calculate the initial stiffness of reinforced joint is accurate enough to be used to estimate the rigid behavior of the joint and to make parametric study.
  • Research articles
    Mechanics analysis of thin-walled box continuous girder with variable cross-sections in considering effect of large deflection and shear lag
    Yuji CHEN, Qizhi LUO,
    2009, 3(4): 352-356. https://doi.org/10.1007/s11709-009-0057-7
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    In order to study the mechanics behavior of a thin-walled box continuous girder with variable cross-sections, using potential variation theories, considering the effect of shear lag of flange’s stress and the nonlinear geometry of vertical displacement, and evolving five generalized displacements with the spline function, the large deflection problem of the thin-walled box continuous girder with variable cross-section was transformed to a nonlinear algebraic equation, which was solved using the Newton-Raphon iterative method. The results of the calculation show that different shear lag warp functions to the cantilever, top and bottom plate should be taken to analyze the mechanics behavior of the thin-walled box continuous girder reliably. The thin-walled box continuous girder with variable cross-sections has more reasonable stress state and is more adaptable for the longitudinal change of internal forces than that with equal cross-sections. The effect of large deflection on the stress and displacement of the thin-walled box continuous girder with variable cross-sections depends on the values of the load.
  • Research articles
    Vortex-induced vibration of stay cable under profile velocity using CFD numerical simulation method
    Wenli CHEN, Hui LI,
    2009, 3(4): 357-363. https://doi.org/10.1007/s11709-009-0060-z
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    Vortex-induced vibration (VIV) of a stay cable subjected to a wind profile is numerically simulated through combining computational fluid dynamics (CFD) code CFX 10.0 and computational structural dynamics (CSD) code ANSYS 10.0. A stay cable with the inclined angle of 30° is used as the numerical model. Under a profile of mean wind speed, unsteady aerodynamic lift coefficients of the cable have been analyzed in both time domain and frequency domain when VIV occurs. The results indicate that the lift coefficient wave response of the stay cable under a wind profile is different from that of an infinitely long cable under a uniform flow in water (i.e., without consideration of profile) obtained by direct numerical simulation. Cable oscillations can severely affect the unsteady aerodynamic frequencies, change flow field distribution near the cable and affect the vortex shedding in the wake.
  • Research articles
    Numerical simulation and analysis for collapse responses of RC frame structures under earthquake
    Fuwen ZHANG, Xilin LU, Chao YIN,
    2009, 3(4): 364-369. https://doi.org/10.1007/s11709-009-0061-y
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    In this paper, a discrete element model for collapse simulation of RC frame structure is constructed by discretizing the structure into a few elements and spring groups. This model introduces special hysteretic models of connected springs for arbitrary loading path and also takes into account reasonable failure criteria for springs considering coupling effect of shear and axial force. Based on the discrete element model, a computer program is developed to simulate the whole process of RC frame structures from initial state to collapse under earthquakes. Particularly, the contact-impact problem between discrete elements has been treated with effective measures. Then, the program is employed to study the collapse mechanism of a real building in Wenchuan earthquake-hit area; the result of which shows that the simulation program developed based on the new model can realistically simulate the seismic collapse process of RC frame structures.
  • Research articles
    Experimental study on seismic behavior of mid-rise RC shear wall with concealed truss
    Wanlin CAO, Jianwei ZHANG, Jingna ZHANG, Min WANG,
    2009, 3(4): 370-377. https://doi.org/10.1007/s11709-009-0062-x
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    In this paper, mid-rise shear wall with concealed truss was proposed. This new composite shear wall includes two kinds of composition: one is the composition of two bearing systems, including truss and shear wall, and the other is the composition of two materials, including steel and concrete. Therefore, it is a double composite shear wall. The experimental study on the seismic behavior of six 1/3 scale mid-rise shear walls, including an ordinary mid-rise shear wall, a mid-rise shear wall with steel frame, and four mid-rise shear wall with concealed truss made of different materials, was studied. Based on the experimental study, the stiffness and its attenuation, bearing capacity, ductility, hysteretic property, energy dissipation, and failure phenomena of each shear wall were contrastively analyzed. The formulas of bearing capacity and stiffness were established. The results obtained from the formulas and those from experiment are in good agreement. Some suggestions for seismic design of shear wall are given in this paper. The experimental results show that the seismic behavior of the mid-rise shear wall with steel frame and that of every truss with different materials is obviously improved.
  • Research articles
    Seismic behavior experimental study of frame joints with special-shaped column and dispersed steel bar beam
    Shuchun LI, Bo DIAO, Youpo SU,
    2009, 3(4): 378-383. https://doi.org/10.1007/s11709-009-0064-8
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    To overcome the problem that steel bars are put too close at a flame joint with special-shaped beam and column, mechanical performance of three groups of six RC flame joints with special-shaped (L, T and+) column and dispersed-steel bars-beam on the top floor under cyclic loads were studied. Experimental comparison was conducted between special-shaped (L, T and+) column and normal beams. The cracking load, yielding load, ultimate bearing capacity, failure patterns, and hysteretic properties at joint core area were investigated. The seismic behaviors of the joints with different proportions of dispersed-steel-bar beams were analyzed. The results of experimental analysis indicate that the mechanical and seismic behaviors of frame joints with T-shaped and+-shaped column are nearly not changed when suitable proportion steel bars are dispersed to flange plane. Stiffness degeneration of flame joint with L-shaped column is rather serious due to concrete damage stiffness. Theoretical result indicates that distributing area of the dispersed steel-bar beams in the flange plate should be strictly controlled to avoid anchor destroy.
  • Research articles
    Parametric study on damage control design of SMA dampers in frame-typed steel piers
    Xiaoqun LUO, Hanbin GE, Tsutomu USAMI,
    2009, 3(4): 384-394. https://doi.org/10.1007/s11709-009-0065-7
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    This paper focuses on damage control design of SMA dampers in steel frame piers. A parametric study based on time history analyses is carried out on frame-typed bridge piers with axial-type SMA damping device. The parameters examined are design parameters of strength ratio αF and stiffness ratio αK. Seismic performance indexes on displacement and strain are investigated under three JRA recommended Level 2 Ground Type П strong earthquake motions. Design recommendations are suggested following the results of the parametric study.
  • Research articles
    Separation and extraction of bridge dynamic strain data
    Baijian WU, Zhaoxia LI, Ying WANG, T. H. T. CHAN,
    2009, 3(4): 395-400. https://doi.org/10.1007/s11709-009-0049-7
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    Through comparing the measured data of dynamic strains due to loading and temperature by the stain gauge and temperature sensor at the same location, the information in the strain data was divided into three parts in the frequency domain by using the defined index named power spectral density (PSD)-ratio index. The three parts are dominated respectively by temperature varying, stresses, and noises and thus can be distinguished from the determined the separatrix frequencies. Also, a simple algorithm was developed to separate the three types of information and to extract the strain caused mainly by structural stresses. As an application of the proposed method, the effect of strain deformation and noises on the fatigue assessment was investigated based on the separated data. The results show that, the determined values of separatrix frequencies are valuable for the monitoring data from other bridges. The algorithm is a multiresolution and hierarchical method, which has been validated as a simple and effective method for data analyses, and is suitable for the compression and preprocessing of the great amount monitoring data and easy to be integrated into the structural health monitoring (SHM) soft system. The strain due to temperature varying attributes a little to the errors of fatigue assessment; however, the noises or random disturbance existed in the monitoring data have much responsibility for the errors, and the main reason is that the random disturbance shifts the real strain/stress amplitude picked up by real structural stress or strain.
  • Research articles
    Control mode selection for modal control of long-span arch bridge
    Zhengying LI, Zhengliang LI,
    2009, 3(4): 401-406. https://doi.org/10.1007/s11709-009-0052-z
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    For seismic control of arch bridge, a model reduction of long-span arch bridge was implemented based on modal analysis. As for the critical mode selection, an approach based on the maximum modal displacement was presented. This approach takes into consideration the effect of external seismic excitation and is more reasonable than only considering dynamic bridge characteristics based on a modal contribution ratio. The time domain and frequency domain analysis method were used to verify the simplified model of the Nimu arch bridge in Tibet as an example. The numerical results show that the method of maximal modal displacement better analyze long-span arch bridge when multisupport seismic excitation must be considered. The reduced-order system also is more in line with the performance of the original model.
  • Research articles
    Temperature variation of concrete box girder bridge
    Jian WANG, Zhi FANG,
    2009, 3(4): 407-413. https://doi.org/10.1007/s11709-009-0053-y
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    On the basis of theoretical analysis and measurement on site, the temperature gradients and its variation on concrete box girder bridges resulting from ambient temperature, solar radiation, and structural temperature fields were discussed. With the help of the heat transfer theory and finite element method (FEM), the heat flux of the surface of concrete box girder was carried out, and all the heat fluxes were described as the convection. The results were compared with that from field measurements, and a good correlation was found. It was revealed that the methods, the parameters, the boundary condition used in this paper were reasonable. Last, some conclusions were obtained, which could provide the basis for box girder design under solar radiation.
  • Research articles
    Bioengineering protection mechanism of city rock slope and its laboratory test
    Desong JIANG, Minghua ZHAO, Chong JIANG,
    2009, 3(4): 414-421. https://doi.org/10.1007/s11709-009-0055-9
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    Based on the features of rock slope bioengineering protection, the ecology protection mechanism of the urban rock slope was discussed with the mechanics effect of plants and rock slope, and the reinforcement action mechanism of rock slope by plant root system was analyzed as well. Then, the corresponding mechanical model was proposed, from which the formula to calculate the increased shearing strength of the root system-earth compound body was derived. Moreover, the side slope rainfall interception, the runoff lagging, the soil antiseepage, and the soil layer consolidating effect were studied, respectively. Furthermore, the indoor model experiment of urban crag rock slope ecology protection was designed and completed, in which various grasses to plant in slope with different angles, solid earth forms, and the different strengthening earth mechanism were studied. Finally, the present method was applied in an engineering project, from which the antiwashing behavior of three kind of grasses (i.e., the Bahiagrass, the tall fescue, and the Bermudagrass) planted in the slope with an angle of 38°, 48°, and 58°, respectively, and different strengthening structures (i.e., the diamond wire netting, the geocell and the three-dimensional network) were obtained. The application results also show that the effect of geocell structure is the best one followed by the three-dimensional net and the diamond wire net. The antiwashing capability per unit area has a critical slope angle of about 25°. The reinforcing effect of Bermudagrass is better than the Bahiagrass and tall fescue.
  • Research articles
    Space-time evolution rules study on acoustic emission location in rock under cyclic loading
    Jiang XU, Shuchun LI, Yunqi TAO, Yongdong JIANG, Xiaojun TANG,
    2009, 3(4): 422-427. https://doi.org/10.1007/s11709-009-0056-8
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    An acoustic emission (AE) location experiment was performed on sandstone using an advanced AE test system. The space-time evolution rule regarding damage was analyzed under cyclic loading as well as AE. The results show that AE on static loading process is consistent with the damage evolution rule of compression and the elastic-plastic deformation phase; at the beginning of cyclic loading with low duration time and energy, AE events came from a small crack. The location result showed that most events occurred in the core zone forming at the static loading process, and the location points changed slowly. AE energy changed little during the metaphase of cyclic process. There was a modest increase of location points in every cycle. The tendency of steady development could be predicted from the AE location events. At the end of each cyclic loading, the quantity of AE events and energy increased quite rapidly, reaching a maximum at the last cycle. AE events had high energy and duration time. Location events changed quite rapidly and assembled and linked continuously in the core zone. At the same time, they expanded to the top of specimen. A macroscopic crack finally formed. In the postfailure process, some AE events still existed due to fracturing of gliding friction. Owing to the inner stress balance of rock even after loading stopped, minor AE events still occurred.
  • Research articles
    Structural characteristics of cement-stabilized soil bases with 3D finite element method
    Yunfeng PENG, Yunlong HE,
    2009, 3(4): 428-434. https://doi.org/10.1007/s11709-009-0059-5
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    Cement-stabilized soil bases have been widely used in expressways due to its high strength, appropriate stiffness, good water resistance, and frost resistance. So far, the structural characteristics and mechanical behaviors of cement-stabilized soil bases were not investigated so much. In this paper, the 3D elastic-plastic finite element method (FEM) was used to analyze the mechanical behaviors and structural characteristics of cement-stabilized soil bases from construction to operation. The pavement filling and the traffic loading processes were simulated, and a contact model was used to simulate the contact behavior between each layer of the pavement. Considering the construction process, the structural characteristics and mechanical behaviors of cement-stabilized soil bases were studied under asphalt-concrete pavement conditions. Furthermore, the general rules of deformations and stresses in cement-stabilized soil bases under different conditions were discussed, and some suggestions were put forward for the design and construction of cement-stabilized soil bases.
  • Research articles
    Experimental study on average movement characteristics of bed-load particles
    Limo TANG, Xingkui WANG,
    2009, 3(4): 435-439. https://doi.org/10.1007/s11709-009-0050-1
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    The three-dimensional movements of bed-load particles in an open channel with different grain diameters and different specific gravities under the conditions of different hydraulic gradient are measured by means of particle tracking velocimetry (PTV) technique. The average movement characteristics of the particles are analyzed by statistics. The results show that the longitudinal average velocities of the particles neither agree with the law suggested by Einstein nor obey the law assumed by Bagnold. Einstein’s law is that the particle velocity is equal to 11.6 times of shear velocity, and the Bagnold’s law assumes the velocity equal to the difference between flow velocity at corresponding water depth and settling velocity of particle. Two formulas for determining the velocity of particle in the forms of expression given by Einstein and Bagnold are obtained according to the statistical results of experimental data, respectively.
  • Research articles
    A rain-on-snow mixed flood forecast model and its application
    Jian WU, Lan LI,
    2009, 3(4): 440-444. https://doi.org/10.1007/s11709-009-0051-0
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    Based on summarizing the rule of rainstorm and snowmelt mixed flood, the structure of rain-on-snow runoff-generation is discussed; and critical temperature is used to determine the form of precipitation and snowmelt factor, taking into account rainfall volume of snowmelt. A rain-on-snow flood forecast model is developed by combining LL-Ⅰdistributed hydrology model. The Kalangguer River, an internal river in Xinjiang Autonomous Region, is taken for example. It is indicated that the model has a higher precision of forecasting; its determinacy coefficient is greater than 0.80.
  • Research articles
    Scientific significance of ancient maps of Yellow River and Grand Canal for water conservancy in China
    Xiaocong LI,
    2009, 3(4): 445-454. https://doi.org/10.1007/s11709-009-0063-9
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    Based on the study of ancient maps preserved in China and abroad, the systematic nature and practical meaning of the maps of the Yellow River and Grand Canal is demonstrated. It is pointed out that the ancient maps not only record the spatial information of the established water conservancy engineering for river harnessing but also the management systems of the rivers in history. Besides, the maps provide abundant information on nature, humanity, and geography and possess high value in academic research and art appreciation.
  • Research articles
    Experimental research on self-stressing and self-compacting concrete filled steel tube columns subjected to eccentric load
    Chengkui HUANG, Zuoqing SHANG, Peng ZHANG,
    2009, 3(4): 455-461. https://doi.org/10.1007/s11709-009-0058-6
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    A total of fifteen self-stressing and self-compacting concrete (SSC) filled steel tube columns and three common self-compacting concrete filled steel tube (CFST) columns are tested under eccentric compression load to analyze the effect of initial self-stress on the compression behavior of CFSTs. The results show that the elastic working range of the columns is lengthened because of initial self-stress and it slightly decreases with the increase of load eccentricity ratio and slenderness ratio. Because of the initial self-stress, the concrete core is always under compression in three directions, so the compactness is enhanced and the ultimate bearing capacity obviously increases; but the initial self-stress hardly affects the failure mode of the columns.
  • Research articles
    Field measurements on microclimate in residential community in Guangzhou, China
    Zhuolun CHEN, Lihua ZHAO, Qinglin MENG, Changshan WANG, Yongchao ZHAI, Fei WANG,
    2009, 3(4): 462-468. https://doi.org/10.1007/s11709-009-0066-6
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    Taking a certain housing in Guangzhou as an example, we conduct the field measurement of the microclimate at fixed points for air temperature, relative humidity, black globe temperature and wind speed, etc. We investigate the effects of manmade lake, shade of trees and ground surface character on outdoor thermal environment, and make a quantitative analysis on the weighting position of the landscape design factors in design behavior. The study intends to explore a method to improve the thermal environment of residential quarters by changing the corresponding factors.