Abstract:

Abstract:The shear bond behavior of the flat-type composite deck slab, Econdek65-675 is investigated primarily. Based on the Euro code 4, the relevant value, m-k, is achieved based on the test of 18 composite slab specimens. According to the thickness which is 115 mm, 150 mm and 200 mm respectively, these 18 specimens were divided into three groups with two sets in each group. One set was tested for shorter shear span loading and the other one was set for longer shear span loading. It is shown that the Euro code 4 is more accurate than the American code. Meanwhile, the calculation formula of longitudinal shear resistance of the composite slab as well as its relevant curve is presented. Compared with other similar composite slabs, it is proved that Econdek65-675 possesses reliable composite efficiency.

Abstract:In order to study the bond behavior, anchorage space and reasonable anchorage length of hybrid-bonding of FRP, the destructive tests of 17 experiment beams which with mid-span pre-cutting fissures have been done. Compared with EB-FRP system, it is found that HB-FRP system is improved a lot in ductility, bearing capacity, FRP’s peeling stress and so on. The formulas for calculating HB-FRP and EB-FRP’s induced peeling strength by middle crack and a more reasonable estimation formula for anchorage space are presented based on the experimental data and theoretical analysis. Calculating results are coincided with experimental results, which can serve as a reference for further researches and engineering applications.

Abstract:Neither the Carbon Fiber Reinforced Plastic nor the steel plate strengthening concrete components shows sufficiency in improving the structures' seismic behaviors independently, while they complement each other by the way of composite strengthening. Six reinforced concrete beams, five of which are strengthened, were comparatively and experimentally tested under low frequency cyclic load to investigate their mechanical performances such as characteristic of resilience, hysteretic curve, seismic behaviors, skeleton curve, degeneration of rigidity and loading capacity. It is indicated that the way of composite strengthening can boost the beams′ ultimate bearing capacity, ductility and deformability capacity effectively, and it can delay rigidity degeneration and improve the seismic behaviors of the beams. Also, the CFRP and steel plate can work together very well.

Abstract:The stability behavior of shuttle-shaped steel lattice columns subject to combined axial force and bending moment was examined through elastic buckling analysis and geometrically and materially nonlinear analysis. Firstly, the concept of section stiffness variation ratio is proposed for shuttle-shaped lattice columns and the elastic buckling behavior is discussed. Then, the effect of bending moment on the stability behavior of lattice columns is investigated, with the emphasis on the development of axial stress, bending stress and shear stress. The influence of column component spacing and diaphragm thickness on the stability bearing capacity is also analyzed. It is shown that the elastic buckling mode of the lattice column is dependent on its section stiffness variation ratio; for lattice columns with C-shaped buckling mode, the reduction in stability bearing capacity caused by bending moment is smaller than that of columns with S-shaped buckling mode; the maximum stability bearing capacity of the lattice column can be achieved by adjusting the column component spacing, and the spacing corresponding to the maximum capacity is basically consistent with the critical spacing for transformation of C-shaped buckling mode and S-shaped mode; and it is more effective to increase the thickness of columns with S-shaped buckling mode to get larger bearing capacity.

Abstract:In order to investigate the effect of prestressed binding bars on axial compressive behavior of rectangular concrete-filled tubular (CFT) short columns, five rectangular CFT short columns, three with prestressed binding bars, one with ordinary binding bars, the other with no binding bars, were constructed and tested under axial compressive loads. The binding bars were made up with high-strength bolts. As used for ordinary binding bars, the high-strength bolts were welded to the steel tube before the column was loaded to axial compressive force. As used for prestressed binding bars, the high-strength bolts were first tensed by screwed screw cap down to bring force to prestress the steel tube and its core concrete, then welded to the steel tube before the column was loaded to axial compressive force. Test results indicate that the bearing capacity and ductility of rectangular CFT short columns are increased by setting binding bars. Compared to ordinary binding bars, the prestressed binding bars can decrease the longitudinal displacements corresponding to ultimate strength, but have little effect on the ultimate strength and displacement capacity after ultimate strength of the columns. The longitudinal displacements corresponding to ultimate strength of the columns decrease with the decreasing of space between binding bars. With the same section width and amount of binding bars, the bearing capacity of the columns improves with the increase of section long-broad-ratio, while displacement capacity after ultimate strength decreases with the increase of section long-broad-ratio.

Abstract:Based on Drucker-Prager criterion with non-associated flow rule, numerical analysis of mechanical properties of concrete cylinders were carried out by using non-linear finite element method. The effect caused by various parameters such as wrap thickness, fiber orientation and concrete strength on axial mechanical properties of concrete cylinders is discussed. The results show that the results calculated by non-associated flow rule conform to that in the test. It is demonstrated that there is significant enhancement both in compressive strength and ductility of cylinders with the increase of wrap thickness. Moreover, the gain in axial compressive strength is observed to be higher for lower strength concrete and be highest in the cylinders wrapped with the hoop orientation.

Abstract:Based on the discussion of the simulation for the cable prestress, the rigidity theory was used to identify the geometrical dimensions of semi-rigid structures in zero state. When the structural geometry in initial state is given, the geometrical dimension in zero state is determined by the initial prestress distribution. The contribution-matrix method is firstly applied to get the initial lack of fit. However, the influencing factor of initial lack of fit on the displacement of control point is linear superposition, that is, the structural response is linear, and it is irreconcilable with the geometry nonlinear of semi-rigid structure. In order to reduce the error of nonlinear structural response, the influencing factor in the contribution-matrix method is revised, and modified contribution-matrix method is put forward. Programs by ANSYS parameter design language APDL are worked out for the form-finding analysis of beam-string structure of a practical project. The numerical results show that the modified contribution-matrix method reduces the errors of the assumption of structural linear response. And it can be applied to the form-finding of semi-rigid structures with small stiffness.

Abstract:To study their resistance performance, totally 222 specimens of panel-to-lumber nailed joints, in different configurations and used in light wood frame construction, were manufactured and tested under monotonic load. There are five kinds of destruction produced with nailed joints,which are model M-c1, rupture of panel, shear failure of panel, wood tear-off and push-through of nail. The resistance of nailed joints with vertical nailing is higher than that with toe-nailing, while the stiffness is almost the same. The angle between the panel orientation and dimension lumber wood grain affects the resistance and the stiffness of nailed joints little, while the angle between loading and dimension lumber wood grain affects the stiffness but not the resistance. The empirical equations to calculate the stiffness of the nailed joints are derived, thus providing reference for evaluating the performance of shear walls and diaphragm (floor and roof) in design of light wood frame structures.

Abstract:According to the solubility parameters of aged asphalt system, the effect of the recycling agent components on the compatibility of aged asphalt was studied by using the molecular dynamics method. And the mechanism between the recycling agent and the aged asphalt is investigated based on the interaction energies analysis. The results show that the aromatic is helpful to improve the compatibility of aged asphalt, and the more the aromatic is, the better the recycling effect would be. However, the effect of saturate is negative. These results are consistent with the experimental data. With the increase in dosage, the interaction energy between aromatic and aged asphalt increases significantly because of their bigger electrostatic interaction energy and smaller Van der Waals forces. However, the interaction energy between the saturate and aged asphalt shows no obvious change in which the electrostatic and van der Waals interaction energy is almost the same. The main factor for aged asphalt recycling is electrostatic interaction energy between molecules.

Abstract:Chongqing Chaotianmen Yangtze River Bridge is the world's longest-span arch bridge. The node connections on its main truss’s lower chords are to bear millions of large-amplitude stress cycles caused by automobile and light-rail train loads. However, there exists no referential designing and testing experience in such detailing on long-span steel bridges at home and abroad as yet. High-cycle fatigue behavior testing on a detailing model has been conducted to study the fatigue reliability of the bridge’s critical node connections. The testing cycling load on the model is determined according to conventional specifications and the expected traffic flow on the Bridge. The 1/2-scale detailing model is carefully fabricated to simulate the node prototype and undergo the 2 million-cycle testing with the design load. Through testing, fatigue reliability of Chaotianmen Yangtze River Bridge’s main-truss lower-chord node connections during the design service life is verified. In addition, static test data are compared with those calculated by finite element analysis to prove the validity of the node model. In the end, fatigue destruction test of the model was carried out to get the fatigue failure law of the node connection and provide necessary parameters and reference for designing and monitoring of this bridge in the future.

Abstract:In the study on the CRCP+AC composite pavement, the form and distribution pattern of cracks are two important factors influencing the performance and the lifetime of the pavement. The concrete damaged plasticity material model incorporated in the general purpose finite element software named ABAUQS was adopted to describe the mechanical characteristics of the CRC slab. Combining with the temperature field database drawn from the three-dimensional transient heat transfer analysis, the structural damage under the condition of temperature changing is analyzed. The structural damage evolution and the crack behavior of the CRC slab subjected to the thermal-mechanical coupling condition are further analyzed, which suggests that the role of the asphalt concrete surface is not confined only to the scope of improving the performance of the road, its capacity for improving the stress state of CRCP slab is worthwhile to be affirmed. And the reasonable thickness of AC layer should be designed in consideration of the thermal contraction and damage properties of the CRC slab comprehensively.

Abstract:In order to study the mechanical behavior and stress state of the high strength bolt friction grip long joint, fourteen different bolted connections are studied with the three-dimensional finite element analysis which is based on the general FE software ANSYS. The force-delivering ratio of each bolt, the stress concentration at the edge of the bolt hole, the stress state of the high strength bolt and the force-delivering coefficient before the bolt hole are specially studied. Also, the ranges of these parameters’ value are presented clearly. The results presented would be useful as references to these type joint's design and computation.

Abstract:The power consumption of frequency conversion chilled water pump of an office building regulated by constant pressure difference method with bypass valve is studied experimentally. A model of power consumption of chilled water pump is proposed. The effects of pressure difference set point of bypass valve on instantaneous and annual power consumption of chilled water pump are analyzed. The simulation results are validated experimentally, which shows that there is a maximum water flow rate which increases with the increase of the pressure difference set point of bypass valve at equilibrium state. There are three pressure operation regions of the bypass valve: under pressure region, constant pressure region and over pressure region. The power consumption of frequency conversion chilled water pump is affected by the pressure difference set point of bypass valve significantly, and it would be minimized as the pressure difference set point of bypass valve is equal to the pressure difference between supply water and return water of the farthest user.

Abstract:The forms of water transportation, arrangement and operation of pumps contribute to the water transportation energy consumption, which influences the energy-saving effect of surface water source heat pump. The relation between the pumping height and energy consumption of pumps is found by analyzing the model of pump energy consumption. The concept and calculation of critical pumping height is presented considering the limited rate of system energy efficiency. Based on the principle that the pump power changes with water flow rate, the determination of pumps arrangement of one or two stage pumps is described with a concrete example. The influence of water flow rate on heat pumps and water pumps is analyzed, and the energy efficiency of constant and variable water volume are compared. The operation way of this example is concluded for the optimal system energy efficiency. It is found that there is a critical pumping height for the energy-saving effect of surface water source heat pump compared with the traditional system. Moreover, the operation strategies should be determined by the system optimal model since the energy consumptions proportions of heat pumps and water pumps are variable.

Abstract:A new type of energy efficiency control method for fan-coil unit is presented. By introducing the conception of duty ratio into electric valve control, the cooling and dehumidifying capacity of fan-coil unit is fully utilized. By means of Mamdani type fuzzy rule and the Method of Functioning-fuzzy-subset Inference, duty ratio of valve and fan speed signal are identified according to deviation and deviation change of room temperature. It is shown that presented method could achieve at least 30% energy saving than traditional control method as well as a preferable room temperature control effect.

Abstract:The hydraulic characteristics and energy-saving performance of a chilled water system with primary pumps is analyzed. It is proved that the hydraulic characteristics of the system with terminal of the air conditioners tends to large temperature differences and small flow rate, while the hydraulic characteristics of the system with terminal of the combination of fan coil units and air conditioners tends to large flow rate and small temperature differences. When the cooling load is reduced, in order to ensure the energy-saving performance of the primary pump system, the fixed chilled water flow is required. If the fixed water flow system is adopted to regulate the outlet water temperature，the bypass water flow rate should be decreased as much as possible. If the pump frequency regulation is selected, and the proportion of energy consumption of the pump accounts for 30% of the total at the same time, the more the system’s hydraulic characteristics approaches that of air conditioners, the higher the energy-saving rate will be, which could be markedly greater than 10%. By regulating the water temperature and cold water quantity, over flow of chilled water still exists. Therefore, bypass water flow should be provided. And the bypass pipe diameter is determined respectively by the water flows which are 1.2 ~ 1.8 or 0.2 ~ 1.0 times larger than that of a single chiller when the pump works in frequency conversion and constant frequency.

Abstract:Sky luminance distribution is the basis of daylighting, and the reference sky classification is a prerequisite for determining the distribution of the sky luminance. Combining with the daylighting observation data of 1 minute in IDMP daylighting observation stations in Chongqing, by analyzing meteorological parameters affecting the sky brightness distribution, the meteorological parameters, such as the cloud cover, surface conditions on the sun, and the horizon to the zenith luminance gradient, are identified as key factors exerting influence on reference sky classification. On this basis, the reference sky is divided into six types.

Abstract:With the increasing demands for favorable living condition and environment, the traditional method of waste transportation cannot meet the people’s demand. The waste pneumatic pipeline transportation system noted for its cleanness, tidy, health, and economy is becoming the trend of discharging waste. A discrete phase model is presented and the operational parameters of the system on the transportation efficiency are discussed. The numerical results propose advices on the design and operation of waste pneumatic collection system.

Abstract:Combining with the data of Chinese body feature, the influence of age, gender and physical activity level on indoor occupant pollution source emission is analyzed based on emitting mechanism and characteristics of typical occupant pollutants. Method to determine the amount of carbon dioxide reduction caused by unstable factors of occupant body odor pollution is obtained with unsteady coefficient. Also, the effective emission model of occupant pollution source is presented according to superposition relationship between carbon dioxide production and reduction. It is shown that there exists difference between carbon dioxide emission level of male and that of female. Carbon dioxide emission level of human body is affected by age and gender. Moreover, the impact of occupant body odor pollution unstable factors on carbon dioxide reduction rate has significant change stage and relatively stable stage, which has connection with air change rate and occupant pollution source action time.

Abstract:The fibrous filter with random structure has been established based on the Matlab program and the Journal file in preprocessing software, Gambit. The gas-solid two phases flow characteristics in four fibrous filters with random structure are simulated by computational fluid dynamics (CFD) technology, and the predicted results are compared with the values of the empirical models. The results indicate that utilization of the modeling method proposed can obtain a filter geometry that is similar to the actual filter. The predicted values of the dropped pressure are in excellent agreement with the experimental correlation, and the error are less than 2%. Meanwhile, the predicted values of the collection efficiencies show a similar tendency as theoretical model, and the capture mechanism changes with different particle sizes. When the particle size is smaller than 0.5 μm, Brownian diffusion plays a significant role in the filtration process, while the inertial impaction becomes an important capture mechanism when the particle size is greater than 1.5 μm. When the particle size is in the range from 0.5 to 1.5 μm, the Brownian diffusion and the inertial impaction are both relatively weak. Additionally, the fiber diameter and the solid volume fraction (SVF) are important geometry parameters in the filter. The collection efficiencies of geometry 1(in which the fiber diameter and SVF are decreased along the gas flow) and geometry 3 (in which the fiber diameter and SVF are increased along the gas flow) are higher than those of geometry 2 (in which the fiber diameter is decreased and SVF is increased along the gas flow) and geometry 4 (in which the fiber diameter is increased and SVF is decreased along the gas flow), and for the pressure drop, the results are just the contrary. Meanwhile, the four geometries have different collection efficiencies for different particle size. For large particles, the collection efficiency of geometry 1 is higher than that of geometry 3. While for submicron particles, the result is the opposite. As for all types of particles, the collection efficiency of geometry 4 is higher than that of geometry 2.

Abstract:Possessing good particle size distribution, the mineralized refuse has high contents of Fe, Al, and Ca, which might be the phosphorus pool. The absorption and desorption of phosphorus, nitrification, and denitrification in the mineralized refuse and clay were investigated by using batch incubation respectively. The variation of phosphorous adsorption in the mineralized refuse and clay is fitted the Langmuir isotherm equation. The maximum phosphorus adsorption capacity of the mineralized refuse is 2914 mg kg-1. Both the maximum adsorption capacity and adsorption rate of phosphorus in the mineralized refuse are 3 times higher than that of the clay. The desorption rate of phosphorus in the mineralized refuse is only about 30%. The NH4+-N content in the mineralized refuse samples falls from 129 mg N kg-1 to 83.0 mg N kg-1 within the first 24 hours during the nitrification process. Accordingly, the NO3--N content in the mineralized is increased from 137 mg N kg-1 to 170 mg N kg-1. While the decrease of NH4+-N content and the increase of NO3--N content in the clay is only 1/2 and 1/6 as large as that in the mineralized refuse respectively. During the denitrification process, the K-value of the fitted zero-order kinetics for NO3--N denitrification in the mineralized refuse is 7.5 times higher than that in the clay.

Abstract:The effect of UV irradiation on bromate (BrO3-) formation is investigated in H2O-Br--Cl2/NH2Cl/ClO2 systems. It is found that partial bromide ion was oxidized to BrO3- by Cl2/UVC. NH3 can inhibit the forming of bromate effectively, and no production of bromate is observed by NH2Cl/UVC. The bromate formation capability of ClO2/UV system is weaker than that of the Cl2/UV. Furthermore, the amount of bromate produced in ClO2/UVC is larger than that in ClO2/UVA. Both the formation of bromate and the decomposition of chlorine dioxide are improved in acidic conditions, whereas alkaline conditions lead to reverse effects.

Abstract:Urban surface pollutant is now recognized as a major source of urban non-point pollution, thus, it is a key problem to scientifically understand and compute surface pollutants. In order to obtain the build–up law, starting in May, 2006, a study was conducted to measure surface pollutants from representative land uses types in Zhenjiang, Jiangsu Province. It is shown that surface pollutants increase to the maximum value gradually and change with the periodic variation. Based on the storage-input-output balance principle, the input speed coefficient and removal rate coefficient are introduced to establish the build -up model of surface pollutants. By fitting with the measured data and comparing with other models, the precision of the model is accurate, and the calculated results can be used as the input of the wash-off model, which provides the scientific basis for non-point source pollution control and management.

Abstract:Containing more SO3 and f-CaO, the fluidized bed combustion (FBC) ash and slag is easier to be in greater volume expansion when it is cured in the normal temperature. The linear expansion rates and the strength development of two FBC ashes and one FBC slag in autoclaved curing and normal curing are studied, and the hydrated products are also analyzed by X-ray diffraction (XRD) and SEM. It is shown that the expansion of FBC ashes is significantly inhibited by autoclaved curing. Also, there is no gypsum and ettringite but some tobermorite in the hydrated products which become richer and better crystallization,resuleing in the significant increase of the sevength.

Abstract:Through the method of accelerated freezing-thawing and room-temperature corrosion, the stress corrosion of three kinds of concretes subjected to 5.0%MgSO4(in mass)solution was studied. The considered concretes include High Strength Concrete(HSC), High-Volume Mineral Admixture Concrete(HVMAC) and High Durable Concrete(HDC) added with high-volume mineral admixture, air-entraining agent, superplasticizer, fibers and expansion agent. The results showed that the relative dynamic elastic modulus of concrete went through strengthen and deterioration stages subjected to stress corrosion, whether the room temperature or freezing and thawing conditions. The length of time of these two stages are closely related with the experimental temperature. Freezing and thawing action significantly accelerated the process of sulphate stress corrosion damage. Under the action of freezing and thawing, stress corrosion strengthening the period length of HSC shorter 96%, deterioration section of the length of time shorter 88%, compared with the length of time at the corresponding room temperature. Deterioration section of the length of time of HVMAC is reduced by 98%, while the HDC reduced by 71%. The effect of freezing and thawing, HDC freezing-thawing cycles when the stress corrosion damage occurred were longer 1.5 times and 13 times than the HSC and HVMAC. Thus in the cold regions, HDC showed more resistance to sulfate stress corrosion.