Abstract:

Abstract:A new kind of steel-concrete composite beam with notched web is proposed, and the bend and shear behaviors of this composite beam are investigated. First of all, the constitution, bearing characteristics and merits of the steel-concrete composite beam with notched web are introduced; then, a group of formulas about the bending capacity, slip between the steel beam and the concrete flange, and the deflection are introduced; after that, the bending behavior, slip effect and bearing characteristic of the steel-concrete composite beam with notched web are studied on 4 specimens, which are tested by applying two concreted vertical loads on the top of concrete flange. And the finite element model is adopted to analyze the results of the 4 specimens; finally, the reliabilities of the formulas are verified by comparing the results of theoretical formulas, the results of tests and that of finite element analysis. Study shows that the bend behavior and shear behavior are fine, and the popularization of this new kind of composite beam which can be broadly used in building engineering will save the consumption of steel.

Abstract:Based on a prestressed concrete girder with complex box-type section of 36m span, four models of 1/6 scale are made, and one of them is mixed with a kind of polymer latex. Experiments with monotonically and cyclically loading are carried out on the models to study bending fatigue behavior of the girder in service and under cyclic load exceeding the designed value, as well as the impact of polymer on fatigue performance of the girder. The results show that, under the cyclic load of value determined by the maximum and minimum stress at the key part of the girder in service, the fatigue performance is satisfactory and the fatigue behavior under a subsequent larger cyclic load is similar with that one under the same big cyclic load. Besides, the polymer has no negative effect on fatigue behavior of the model.

Abstract:China Pavilion for Expo 2010 Shanghai is designed with peculiar style and special structural system. The main structure is composed of four concrete tubes with steel-concrete composite floors. It is designed with a shape of inverted trapezoid in elevation. The fundamental vibration mode of this structure is a torsional mode due to the special shape with greater moment of inertia in upper floor, which exceeds the limit value stipulated in Chinese code. The seismic analysis of prototype is carried out by ANSYS program to evaluate its overall seismic performance and improve the structural design. At the same time, shaking table tests of a 1/27-scale structural model are conducted. It is faund that although the first mode is torsional, the torsional responses are not so large, which agrees well with the results of shaking table tests. Both the test results and calculation results demonstrate that the designed structural system satisfies the seismic damage patterns and meets the pre-defined performance objectives. Based on the test results, suggestions for improving design are also put forward.

Abstract:Bearing capacity behavior of roll forming filling screw pile (screw pile for short) is investigated through numerical calculation and static load test. The influence of pile-type parameters, such as width of thread tooth and thread pitch, on the ultimate bearing capacity of crew pile is studied; furthermore, the bearing capacity behavior of screw pile and that of pile with the same diameter are compared and analyzed through static load test. The results show that the ultimate bearing capacity of screw pile is a bit higher than that of pile with the same outside diameter; width of thread tooth has a distinct effect on ultimate bearing capacity which increases with the increment of width of thread tooth. When the screw pile is tested under light load, the resistance on pile side is distributed along screw pile, and tip resistance is small, but the resistance rises considerably with load increasing. Besides, the design formula of bearing capacity of screw pile is proposed.

Abstract:Bottom continuity tendons induce transverse additive effect while providing longitudinal compression during the construction of PC box girder. Taking a cross-sea bridge for example, the mechanism of bottom continuity tendon is investigated. The transverse effect and parameters study are conducted through a refined model. It is illustrated that the state of bottom flange is in a dynamic changeable process during the tensioning of bottom continuity tendons, and the transverse effect caused by the tendons is much more than that by dead loading and other prestressing tendons. The transverse effect is more sensitive to alignment and thickness of the bottom flange, as well as concrete cover of the ducts. Finally, based on the simplified frame analysis, the design method is proposed by introducing prestressing effect simplified factor and duct modified factor.

Abstract:Single-lap-joint adhesively bonded metal specimen which is the national standard experimental method in use has an extremely non-uniform distribution of shear stresses along the joint, and tensile stress concentration of high values is produced on the steel substrate interfaces. Therefore the test result, which is not the real bonding shear strength between adhesive and steel substrates, can only be used as a test index for qualities of adhesives not the strength criterion for load is capacity evaluation. The combined bonding disc specimen is adopted for measuring bonding shear properties of adhesive on steel substrates, has a very uniform distribution of shear stresses in adhesive and along the bonding surfaces of steel substrates, of which the uniform coefficient is greater than 0.97. Furthermore, when adhesive joint is treated as an arc and steel substrates are chamfered at both ends of the joint, tensile stresses on the bonding surfaces can be reduced to less than 20 MPa which can hardly cause tensile failure. Thus, the results of combined bonding disc specimens can actually represent the real bonding shear strength or bonding shear-compression strength between adhesive and steel substrates, which can be used as strength criterion for load capacity evaluation of bonding members.

Abstract:Information Value Model is used frequently in domestic landslide hazard zonation prediction, which plays a very important role for land-use planning especially in mountain area. Through theoretical analysis, the prerequisite of Information Value Model which should be used with influence-factors independent from each other is studied. Factor Analysis is adopted to evaluate and eliminate the influence of correlation between influence-factors in spatial prediction of landslides which are showed through case study. Relationships between landslides and influence-factors are studied based on a certain watershed in which the Information Value Model and Factor Analysis are applied. The probability of landslides changes regularly with the influence-factors, and based on which a method for the discretization of influence-factors is advised. The distribution of landslide susceptibility of above watershed is calculated and validated based on the area-ratio index with landslides occurring in nearly 5 years, which proves the credibility of Information Value Model.

Abstract:In order to investigate the dynamic behaviors of geogrid-reinforced pile-supported embankments under traffic loading, three-dimensional coupled mechanical and hydraulic numerical simulations are conducted using FLAC 3D. Four cases are studied including unreinforced and no-pile embankments, reinforced embankments, pile-supported embankments, and geogrid-reinforced pile-supported embankments. The behaviors of vertical displacement, horizontal displacement, pile-soil stress ratio, excess pore water pressure and acceleration under four cases are analyzed. It is found that the vertical displacement, nonuniform settlement and horizontal displacement of geogrid-reinforced pile-supported embankments are smaller than those of other cases due to soil arching effect and reinforcement effect. Pile-soil stress ratio decreases with the increase of loading number. The crest value of acceleration and the time for acceleration to be steady are also smaller than those of other cases. The dissipation velocity of excess pore is quicker than that of unreinforced embankments.

Abstract:With the GDS dynamic triaxial system, undrained dynamic triaxial tests on the saturated sand with different fines content are performed, and the effects of fines content on evolutionary characteristics of dynamic pore water pressure of saturated sands in the process of liquefaction are analyzed based on Seed pore water pressure stress model. It is found that fines content has great effect on the dynamic pore water pressure of saturated sands by the parameter θ for Seed model. The relationship between parameter θ and fines content isnt linear. Parameter θ decreases with the increase of fines content at first, and then reaches its smallest value when the critical value of fines content is 30%. After that, parameter θ increases gradually with the rise of fines content. According to the experimental study on effects of fines content on evolutionary characteristics of dynamic pore water pressure of saturated sands, the existence of critical fines content with 30% is further proved in the sandy soil used in the test.

Abstract:An advanced structure containing cavities is adopted in distribution layers. A series of large-scale similarity-simulation tests are carried out on defense effect of the four structures for mass ammunition, and numerical simulations are developed by LS-DYNA software. The results indicate that the stress peak is distinctively decayed behind the cavities, and the defense effect of circular-section cavity is more effective than that of rectangle-section cavity. But because the transmission coefficient of stress waves of the structure increases, the defense effect is weakened when a thin steel plate is laid above the cavities.

Abstract:Based on one-dimensional seepage and deformation governing equations, PDE software is used to analyze the coupled governing equations. The method is available to arbitrary functions of SWCC (soil-water characteristic curve), and it considers that both the coefficient of permeability at saturation and the porosity change with soil strain. Compared with analytical solution, the numerical solution shows high precision and it can effectively solve coupling problems. It is found that coupling effect of seepage and deformation in unsaturated soils plays an important role in the pore-water pressure profiles, and that the coupling effect should be considered during rainfall infiltration. At early stage of rainfall infiltration, settlement obviously increases with time, and the pore-water pressure considering the coupling moves more slowly than that without considering coupling due to positive H. The settlement is related with initial pore-water pressure profiles and H value. The coefficient of permeability at saturation and the porosity have an effect on rainfall infiltration and steady-state seepage, but their change has a weak influence on deformation in unsaturated soils..

Abstract:With the construction of deep-water bridge foundation, steel casing is left after the construction of cast-in place piles due to the dismantle difficulty. Then the pile actually forms a variable section pile which has bigger section area at upper part. Using the nonlinear NL method, the displacement and the internal force are analyzed for piles with and without casing in Sutong Bridge. It is found that the displacement of pile with casing can be reduced by 50%, and it can not be ignored for accurate calculation of displacement. 8 model pile tests are carried out, which suggests that the slurry thickness can significantly affect the capability of co-working between the pile and the casing.

Abstract:By adopting seven kinds of adhesive resins, the mechanical properties of the interface between pultruded Basalt fiber reinforced polymer plates and cast-in-place concrete is studied according to two groups of stretching double-shear test. And it is compared with the dry-bonding interface between BFRP plates and the precast concrete. Further study is conducted by comparing the damage features, load-displacement curves, effective bond length, bond slip relationship and interface fracture energy between the two interfaces. It is found that the effective bond length of the two interfaces are similar, but the bond strength of the wet-bonding is about half of the dry-bonding. Finally, the shear stress-slip model is proposed for the wet-bonding interface based on the experimental data.

Abstract:Considering the three-dimensional inhomogeneity of soil surrounding the pile, the response of non-uniform viscoelastic pile under axial dynamic loading is studied. Firstly, combining the boundary condition, the complex stiffness of axial different soil layers are obtained by the complex stiffness transfer model of radial multi-zone plane strain. Then, the analytical solution of dynamic response at pile top in frequency domain is proposed by solving the dynamic equation of non-uniform viscoelastic pile section one by one from the bottom up to the top, and the relevant semi-analytical solution response in time domain is adopted by the convolution theorem and the Inverse Fourier Transform. At last, the effect of parameters of pile and soil are investigated to get the nature of the dynamic response of pile top in frequency domain and time domain.

Abstract:Daylighting is one of the important aspects of sustainable building, but architectural daylighting in China is obstructed because of shortage of daylight meteorological measurement record. However, there are many data of solar irradiation. Therefore solar irradiance values are used to calculate outdoor illumination values. Luminous efficacy is introduced to show the relation between solar irradiance and outdoor illumination. Sunny index is used to represent the meteorological states of the sky. On the basis of measurement data in Chongqing from 1991 to 1992, new luminous efficacy calculation model is built to obtain the outdoor global illuminance values and the diffuse illuminance values. Measurement data in Chongqing in 1993 is used to evaluate the proposed mode, which shows the proposed models are reliable. In order to prove possibility of calculating illuminance in other places in China, the measurement data records of annually average global illuminance values in 32 cites are used to examine the calculation results. If the real-time solar irradiation data was input, the real-time illuminance values could be obtained with this model in China, thus millions of illuminance values could be used in future daylighting design.

Abstract:Based on the analysis of the outdoor weather condition in Chinas hot summer region, it is found that the full fresh air mode can work in the whole winter and half of the time in transition season. Thus, about 30%-60% runtime of the artificial cold source can be reduced. It studies the control strategies at different conditions of indoor load, ventilation and indoor air temperature and humidity by analyzing two control modes-enthalpy control and temperature control. It shows that the higher the indoor load is, the more efficient the full fresh air mode is. And the airflow is better to be set as 6~8 h-1. Since the indoor air parameter has great influence on energy saving, it is necessary to set different indoor air parameters in different seasons by taking the effect of temperature difference on human thermal comfort into consideration. It is also found that the enthalpy control mode can be used in winter and in transition season, while the temperature control mode can be applied in summer. If the full fresh air mode were adopted, it would cut down the energy consumption by 100~180 kWh/m2 and the carbon emission by 30~50 kg/m2 each year.

Abstract:In order to solve the frost-heaving safety problems of buried heat exchanger hydronic in ground-source heat pump, a mathematics mode1 and its contro1 equation were put forward according to heat transfer, filtration theory and mechanics of frozen soil, which is the couplings problem of temperature field, hydronic field and stress field. The temperature field, frost heaving displacement and stress distribution of ground-source heat pump in Daqing oilfield were simulated with finite elements method. The contrast and analyses are carried out according to the different soil depth, the different soil thermal conductivity in backfilled areas, the different spacing of tube foot. The results showed that the least temperature and heat affected zone in soil increases gradually with operating time. At the beginning of operation, the displacement of buried heat exchanger is small because the soil is not frozen. When the soil temperature reaches the phase temperature, soil volume increases in size, and then buried tube deforms. When soil temperature exceeds between -0.75℃ and -0.30℃, buried tube doesnt deform.

Abstract:A sewage-water shell-tube heat exchanger with the function of de-fouling was proposed and designed for sewage-source heat pump. Its new simulation program which relies on a distribution parameter computational method was set up. Then the model was solved with the method of Matrix Control. Based on the model, the distribution of bilateral fluid temperature were studied, under the conditions of different flow rates and heat exchange area before and after the de-fouling. Results showed that there will be heat anti-transfer phenomenon if the heat exchanger area is bigger than need and the region of this phenomenon was point out. Setting the function of auto-de-fouling in shell-tube heat exchanger and reducing the equipment's volume accordingly can make the sewage-water heat exchanger run in the best conditions.

Abstract:A 33-hour field test of outdoor thermal environment was carried out in a typical teaching building cluster located in the hot and humid zone in summer. From the experiment results of local climate data, air temperature, humidity, wind velocity and wet bulb globe temperature (WBGT) at the pedestrian-level, and the typical ground surface temperature, the main characteristics of summer outdoor thermal environment of teaching building cluster in hot and humid zone are obtained. The results show that the patio, overhead and porous pavement can reduce the pedestrian air temperature and WBGT effectively at summer daytime. And the function of the following design methods to improve the outdoor thermal comfort at the summer daytime has the order like overhead>patio>porous pavement>imporous pavement>concrete road. The WBGT at all measuring points at nighttime are almost the same. The test results are further used to verify the existing mathematical models of outdoor velocity and WBGT. The results show that the relative errors are within 6%. Then, the calculation values are in good agreement with the experimental values.

Abstract:Owing to the fluctuation of water quality in urban river which polluted by drainage along river, one-dimension uncertain water quality model embeded neural network is established. Genetic algorithms and a modified fitness function are used to optimize parameters of the uncertain model. Examples illustrate that the uncertain model has higher prediction accuracy with the average accuracy over 80% than the certain model, and is more sensitive to the fluctuation of pollutants discharged into the river. The uncertain model has a significant advantage of prediction and could better adapt to the changing urban water environment, especially at points close to the pollution sources.

Abstract:Formaldehyde (FA) is usually the most abundant air pollutant in the decorated residential buildings and also the most studied due to its potential role in allergic diseases and its carcinogenic properties. In the present work, according to Indoor Air Quality Standard (GB/T 18883-2002), a series of investigations were carried out at 83 decorative residences by Intescan 4160-19.99 formaldehyde detector in Changsha from November 2008 to October 2009. It is showed that formaldehyde pollution was very serious in decorated residences with a 100% occurrence in the specimens and mean concentrations of 0.11±0.07 mg/m3. Concentration of formaldehyde was ranging from 0.01 to 0.31 mg/m3 with 53.3% of the over the standard rate. The maxium level reached 4.5 times of the standard. The mean concentration of formaldehyde in different rooms was the following: Children room>bedroom (sanctum)>living room. Formaldehyde concentration in decorative residences was gradually on the decline with prolonged time. Indoor formaldehyde droped it concentration by 0.04 mg/m3seven months later. Therefore, the formaldehyde concentration in residential buildings was connected with the type of the room,decorated time, furnituring and other factors.

Abstract:In order to effectively remediate the dissolved petroleum hydrocarbon contaminants in aquifer, low temperature hydrocarbon degrading bacteria-peat-coarse sand and peat-coarse sand were adopted respectively to construct peat biobarrier and peat barrier. And the ratio of packing media, the removal efficiency of BTEX and PAHs were investigated through barriers in remediation of petroleum hydrocarbon contaminated groundwater. It is found that the hydraulic conductivity and available porosity of mixed media were 1.17×10-4 m/s, 7.5% respectively when peat and coarse sand at the optimum volume ratio of 20:80. For peat barrier, the removal rates of BTEX were 32.63%-79.15%, sorption life was 50-55d, sorption capacity of peat barrier to BTEX was xylene > ethylbenzene≈toluene> benzene, effluent concentration of naphthalene, α-methylnaphthalene, β-methylnaphthalene and phenanthrene were all below 2.85μg/L. The removal efficiency for BTEX, PAHs were 83.6%-97.83%, 97.48%-99.85% through remediation by peat biobarrier, and have an obviously effect on contaminants biodegradation, the degrading rates of BTEX were 75.66%-90.16%. The study indicated that removal mechanisms of hydrocarbon contaminants were peat sorption and biodegradation for peat biobarrier, peat had strong sorption capacity to petroleum hydrocarbon contaminants, especially for PAHs, contaminants biodegradation could efficiently prolong the sorption life of peat barrier.

Abstract:Taking indicators the case of an university campus runoff quality in Main Urban Area of Chongqing, three kinds of stormwater runoff quality were monitored, where indicators included pH, suspended Solids(TSS), chemical oxygen demand(COD), ammonia-nitrogen (NH3-N), total phosphorus(TP), and so on. The results show that the average concentration of stormwater runoff pollutants exceed the fifth level of the environmental quality standards for China except TP, SS concentration of runoff can reach 1 730 mg/L, COD and NH3-N concentration of runoff can reach 76.25 mg/L and 3.67 mg/L; First flush takes effect evidently, and SS、COD、NH3-N first flush concentrations of concrete road surface were 2330mg/L, 106.4mg/L, 5.64mg/L. First flush concentrations were equivalent to 2-4 times of Event Mean Concentrations(EMCs)，and the highest concentration value of pollutants appeared when runoff produced 10~15 minutes later。Comparison on runoff quality of three different rainfall intensity, higher intensity was positively correlated with TSS, COD, NH3-N, and TP concentrations，among which rainfall intensity taked greatest effect on runoff pollutants concentration of large slope road.

Abstract:Based on a series of recycle process, waste concrete can be made into fine recycled aggregate which can be used completely or partly to compound concrete as a substitute for natural sand. But the special properties of fine recycled aggregate make the performance of concrete with fine recycled aggregate different from normal concrete. Characteristics of fine recycled aggregate and its influence on physical and mechanical properties of concrete are studied. On this basis, the influence of fine recycled aggregate on gas permeation properties, chloride permeability, and carbonation resistance of concrete are also studied. It is found that fine recycled aggregate produces a lot of defects in crushing preparation. And the compressive strength, the chloride permeability and the carbonation resistance of the concrete with fine recycled aggregate as substitution show difference from that of normal concrete.

Abstract:The effect of dosage and modulus of water glass on the early hydration and setting performances of alkali-slag cement is very important. The variation of hydration heat and setting time and compressive strength of the alkali-slag cement with its modulus and alkali content are studied. It is found that with the increase of modulus, the hydration heat decreases and the setting time prolongs gradually, and the compressive strength increases first, then decreases. When the dosage of Na2O increases, the hydration heat increases. And the setting time increases slightly and the compressive strength shows the trend of increasing. The reasonable modulus of water glass Ms is about 1.0~2.0, and the dosage is about 3%~6% of the mass of slag.