Abstract:

Abstract:Cracking monitoring provides an important way to evaluate structural safety. Cracking monitoring method based on distributed optical fiber sensor can effectively avoid undetected phenomenon existed in point-wise test method, and it can run automatically. A theoretical model of cracking monitoring based on obliquely intersected fibers and Brillouin Optical Time Domain Analysis (BOTDA) is introduced, and the numerical equation among fiber strain, crack width and crack angle is established by the calibration experiment. The experiments are also carried out to study the performance of different kinds of cracking sensors with different gauge length and pretension. The quantitative relationship between optical fiber measured strain and crack (including width and angle) is established for the 300 millimeter crack sensor. The cracking simulation test proved that this new method can effectively record the width and the angle of cracks during the whole cracking process.

Abstract:Aiming at the design for distribution layer in defense works, attenuation mechanism and evolution law of stress waves in distribution layer with cylindrical shells were focused on. It was found that dispersion and diffraction effect of stress waves were occurred in the concrete medium on the basis of theoretical analysis and numerical simulations, which significantly weakened the strength of stress waves behind the shells. The position、interlayer spacing and the arrangement forms of the shells had great influence on the protection performance of the structures. The results show: in the structures with single-layer cylindrical shells, the smaller the space between the shells and the protected area is, the better the protection performance is; in the structure with two-layer cylindrical shells, the smaller the interlayer spacing is, the better the protection performance is, and the protection performance of the stagger structure is better than that of the aligned structure.

Abstract:The corrosion rate of steel in concrete is highly dependent on the heterogeneous structure of the concrete and the environmental exposure conditions. Temperature and relative humidity are two important environmental factors that simultaneously influence the corrosion process and cannot be separated or isolated from each other. The interaction of temperature and relative humidity for characterizing the corrosion rate has been sufficiently studied. The resules show that the higher the temperature is, the greater the relative humidity is when rebar corrosion rate reaches the max, and as to different relative humidity, the increasing extent of rebar corrosion rate with rise in temperature is different.

Abstract:Stress-strain mathematical model of FRP-confined concrete plays an important role in civil engineering, and it should be well understood. Based on first region slope, turning point coordinate and third region slope, the development of stress-strain curve of FRP-confined concrete column is analyzed, and conditions which ideal mathematical model need to meet are point out. A new composite exponent-line model is proposed, which overcomes the weakness of conventional model and is available for both hardening and softening type stress-strain curves. Approaches to determine parameters of the proposed model are presented. Finally, the capability and accuracy of the proposed model in predicting the complete stress-strain process of FRP-confined concrete under axial compression are demonstrated through comparisons between predictions of the proposed model and test results.

Abstract:A New-type Steel Tube Buckling-Restrained Brace with Reinforced Concrete outside (ST-BRB-RC) was introduced in this paper. Six specimens of the ST-BRB-RC were designed and cyclic loading test were carried out to study the hysteretic energy dissipation performance of the six specimens. And then, ABAQUS finite element analysis was used to study the performance of four specimens. The results indicated that the ST-BRB-RC had stable and full hysteretic curve. The bearing capacity of the ST-BRB-RC was stable and the hysteretic behavior was excellent. And the analysis model of ST-BRB-RC could be described by a bilinear model. The construction of the ST-BRB-RC was reasonable, and the energy dissipation mechanism of the ST-BRB-RC was clear. It is proved that the design philosophy of using reinforced concrete for exterior restrained element was available.

Abstract:A novel three-dimensional isolation bearing (3DIB) was proposed, based on respective mechanical characteristic of lead rubber bearing, combined disc springs and rhombic steel plated damper. Firstly, the configuration department and mechanical design methodology was introduced; the horizontal and vertical stiffness and energy dissipation performance test was performed on a full scale three-dimensional isolation bearing, respectively. The results indicated that the proposed three-dimensional isolation bearing has reasonable configuration and explicit mechanical transmission mechanism; appropriate stiffness and energy dissipation performance can be achieved by reasonable design, keeping favorable holistic stability at plentiful horizontal shear displacement.

Abstract:According to the spatial features of environmental actions, on the basis of the spatial multi-scale model framework (including the global environment, regional environment, engineering environment, surface environment and internal environment of concrete) and the mathematic model for environmental actions, the spatial multi-scale relative humidity values for concrete structures were studied. That is, based on the influential factors of relative humidity on the different spatial scales, the relative humidity values in concrete were deduced by adjustment step by step from the values on the global environment to the regional environment, the engineering environment and the surface environment of concrete. It was found that using the superposition method of conventional statistic model and spatial residual error, the quantitive relationship of relative humidity values in the regional environmental scale and the engineering environmental scale can be established effectively. Moreover, the relative humidity values on the surface of concrete structural elements are related with the temperature values on the surface of concrete structural elements, and the difference of relative humidity values between the surface and the inner part of concrete should be considered in the durability assessment of concrete structures.

Abstract:Urban rail transit is becoming an important means of transportation and elevated structure is one important part of urban rail transit. So the radiation noise induced by elevated structure attracts more and more attention. Based on the theory of Helmholtz integral equation of BEM and fluid-structure coupling system of FEM, the sound pressure transmission vector reflecting the relation between structural vibration acceleration and radiation of sound pressure is derived and solved by the element radiation superposition method. The calculated results are in good agreement with the experimental data from a viaduct section of the Beijing airport rapid rail transit.

Abstract:To deal with failure of wet joint between a closure segment and its neighboring segments of main girder in an existing prestressed concrete cable-stayed bridge, the technology on replacement of closure segment was presented. In order to analyze structural characteristics of this technology, its technical approaches and construction key points were introduced. Then a FEM model for a typical prestressed concrete cable-stayed bridge was established, and a construction stage analysis method was given in detail, including establishing a structural basement calculation model for replacement of closure segment and simulating its construction procedures. Based upon calculation results, variations of some structural state parameters with construction stages, such as deck deflection of main girder, longitudinal horizontal displacement at the top of pylons, cable forces, were analyzed. The results showed, this method could reflect actual change process of structural state and existing inspected results of cable-stayed bridge, and FEM results could well meet with construction monitoring results during replacement of closure segment. Thus variations of structural characteristics with construction stages could actually be revealed. This method could provide references for design and construction control of replacement of closure segment in existing prestressed concrete cable-stayed bridges.

Abstract:Damage localization in crack weakened rock mass is closely related to the crack growth pattern. Bifurcation of the alternative evolution of cracks occurs when the cracks grow to some extent, then some cracks keep on growing while other ceased evolving. It is found that damage localization in crack weakened rock mass is caused by bifurcation of the crack growth pattern, and the initial location is also determined by the crack growth pattern. Based on the analysis on the bifurcation of crack growth pattern, the critical length of wing crack and the critical stress of damage localization in crack weakened rock mass are obtained. Subsequently, the onset location of damage localization is determined by using the eigenvalue and eigenvector of coefficient matrix, and crack interaction is also taken into account in this model. Finally, the relationship between the interval between columns and rows, the orientation of crack, confining stress and the critical stress of damage localization is defined in the example.

Abstract:enhanced pipe piles are made by centrifugal rotation and steam curing under high temperature, so it is very difficult to embed concrete strain gauges during making piles. A new method is used to embed concrete strain gauges in piles. Based on the static loading tests on enhanced pipe piles, the load transferring mechanism of enhanced pipe piles is studied through analysing axial load distribution, behaviors of skin resistance and base resistance of piles, and load sharing of rims of enhanced pipe piles. Experimental results show that when axial load acts on the top of enhanced pipe piles, the upper rims of enhanced pipe piles act on skin resistance of piles before the lower rims do, and the rims of enhanced pipe piles remarkably reinforce skin resistance of piles.

Abstract:The seepage accident is very easily occurred, when the excavation engineering has been constructed in rainy season and it is very easily influenced by the coupling effect of seepage duo to heavy rain and water level fluctuation of neighboring river. So a coupling seepage equation that based on the theory of Dupuit has been established for the ground water in the layered foundation. And then, the water table surrounding the excavation engineering has been determined on the consideration of the coupling effect of seepage duo to heavy rain and water level fluctuation of river. In the meantime, by means of the theory of coupling analysis of stress and seepage and the software of Midas, a model of coupling analysis of stress and seepage has been built for the specific excavation engineering and the seepage destroy characteristics of this project has been researched.

Abstract:The illumination computational formula recommended by the International Commission on Illumination (CIE) does not adapt to the modern construction materials with mixed reflection characters. In order to find a new luminance computational method adapting to the modern construction materials and to save building energy and control urban nightscape luminance, 30 frequently-used construction materials with respect to various directions in photometric laboratory were measured. Then the luminance modified coefficient K(i,β) was figured out, and analysed the connection of reflection luminance and atmospheric attenuation in the process of divergence of light. The K(i,β) and viewing distance, light kinds, luminaire use, material cleanliness, maintenance condition of lighting system as modified coefficient was adopted to amend the computational formula of CIE, and then a new calculation model is derived. Through calculating and comparing, the luminance value of the new calculation model is one-third as much as that of the traditional one.

Abstract:This experiment tests the change rate of students α & β brain waves under different illuminance levels combining with three color temperatures (CCTs) to indicate the influence of light spectrum on human physiological rhythm.The result shows that the brain electrical activities have significant differences under various CCTs and illuminance levels.The excitement and sensitivity of brain are roughly proportional to the light CCTs and illuminance. Brain electrical activities are more sensible to high CCT illuminations. Keeping mental work in the same time period with the same study intensities, brain fatigue comes earlier and stronger in excitable state at high illuminace and high CCT illumination than in peacful state at low illuminance and low CCT illumination.This situation leads to the learning efficiency of students decreased sharply.An interesting phenomena is that when working in low illuminance and low CCT environment, learning efficiency of students rises with time passing by.That indicates this kind of lighting environment may lead to awake effect of brain. In some environments which have the same illuminance levels with different CCTs that bring about the similar brain activities, learning efficient change rates are different because of the diversity of light spectrum which may induce the different stimulus intensity.Further research work is needed to explain this phenomenon.This experiment points out that the long-term mental workload character during the process of study and comprehensive effect of time accumulationmust be seriously considered in classroom lighting design.

Abstract:High thermal resistance resulted by fouling in heat exchanger restricts the application of sewage source heat pump (SSHP) system. The fouling forming mechanism was applied with solid-liquid fluidized bed technique for fouling prevention and removing of SSHP system. Shearing stress model of solid-liquid fluidized bed heat-exchanger is analyzed, and collision stress model is modified. Preventing and removing fouling mechanisms of solid-liquid fluidized bed technique by shearing stress and collision stress was explained. An experimental study on how to solve the fouling problem (such as fouling prevention and removing, heat transfer enhancement, etc) is discussed. The results of theory and experiment show that solid-liquid fluidized bed technique can be used not only to increase convection coefficient, but also to restrict fouling growing, it can effectively solve the fouling problem in SSHP system.

Abstract:Building management control systems (BMCS) are widely employed in modern buildings. The huge amount of data available on central stations and outstations provide rich information for fault diagnosis of HVAC systems. An online fault diagnosis method for variable air volume air handling units was presented using self-tuning HVAC component models. The model parameters are tuned online by using a genetic algorithm (GA) which minimizes the error between measured and estimated performance data, so high modeling accuracy is assured. If the error between measured and estimated performance data exceeds preset thresholds, it means the occurrence of faults or abnormalities in the air handling unit system. The statistical method of selecting thresholds also is presented. The fault detection method was tested and validated using data collected from real HVAC systems. The results of validation show that the fault detection method can be integrated in BMCS systems to detect faults in air handling unit systems efficiently.

Abstract:Based on the stratigraphic configuration of the oil-contaminated sites in Northeast China, the efficient and best experimental conditions to remove oil pollutants in a relatively heterogeneous aquifer using air sparging were investigated. The results show that for Complex formation, the remediation of AS technology is efficient. It was shown that when air flow rate was 300ml/min, the removal rate of benzene, naphthalene were 99.54% and 11.58%, respectively. When the medium was layered heterogeneous porous media, the removal rate of continuous air sparging is superior to intermittent air sparging. In the whole experiment, the removal efficiency of naphthalene was very low which may be own to its structure and properties and the heterogeneous of the medium. When the Semi-volatile contaminants exist, considering the use of other combined remediation technique was necessary.

Abstract:The use of ultrasonic，H2O2and the combination of two kinds of technology approach to ultrasound H2O2 phenol wastewater, treatment effect of three methods were compared the differences, and discussed the ultrasonic power, the solution pH value, ultrasonic time and ferrous ions (Fe2 + ) the amount of the treatment effect. The results show that hydrogen peroxide and ultrasonic treatment efficiency of wastewater treatment is superior to ultrasonic treatment group and H2O2 treatment. Through orthogonal experiments of phenol degradation rate of the size of the order has to pH>ultrasonic power>ultrasonic time>adding 0.1mmol·L-1FeSO4 amount of the basis of the experimental parameters, in order to obtain high degradation rate and cost, various factors. Optimization of process parameters for the ultrasonic time of 60 min, power is 200 W, pH is 3, adding FeSO4 amount of 1.0 mL. Under optimum conditions in this experiment, the degradation of phenol was 81.50%. Ultrasonic is relatively separate and separate hydrogen peroxide, the use of ultrasonic hydrogen peroxide degradation rate of phenol, save time, the advantages of speed degradation.

Abstract:Among all the measurement methods on activity of urease, indophenol blue colorimetric method, higher accuracy of the measurement results and better reproducibility, is the most widely used measurement method on activity of urease. However, this kind of method also owns some drawbacks, for examples, filtered fluid of cultivated soil is muddy and concentration of substrate has a great influence on the activity of urease. Based on the former measurement methods, four crucial parameters was taken to, such as method of filtration, time of cultivation, concentration of substrate and choice of buffer solution, the comparative tests in order to improve the accuracy of the measurement results of indophenol blue colorimetric method. The result of improved method is closer to the real activity of urease in soil with the conditions that choosing 5% concentration of substrate and pH10.0 borate buffer solution during the cultivation, extracting and filtrating with potassium chloride solution after 24-hours cultivation. The result of improved indophenol blue colorimetric method is 2.46 times better than the traditional method.

Abstract:Ultrafiltration membrane was used to filter the Yangtze River water by powder activated carbon (PAC) pretreated, such as Tai Lake water by coagulation-sedimentation pretreatment. The changes of organic polar content were compared in each process. Combined with the scanning electron microscope(SEM) photographs of the membrane, the mechanism of slowing down membrane fouling by PAC and coagulation-sedimentation pretreatment was studied. The results showed that hydrophobic organic compounds were the main factors of membrane fouling, while hydrophilic organics had less impact. When the dosing quantity of PAC filtered by ultrafiltration membrane was 20 mg/L to pre-treat the water samples of Yangtze River, and that of polyaluminium chloride was 25 mg/L for the pretreatment of Tai Lake water samples, the flux could be recovered effectively after backwashing compared with filtering the two raw water directly. The cake layer formed on the surface of the membrane was looser after pretreatment, and could be discharged easily by periodic backwashing, The cake layer could prevent hydrophobic organic matters deposit on the surface of membrane directly, which will slow down the membrane fouling and improve the chemical safety of the membrane effluent.

Abstract:Excessive biomass accumulation is one main problem which will deteriorate the performance stability of biofilters during long-term operation. In order to systematically explore the feasibility of using ozone to control biomass accumulation within biofilters, the influence of ozone on toluene removal performance, pressure drop through filter bed and porosity, biomass growth and carbon balance of biofilters was examined. The results showed adding ozone of concentration no more than 220 mg/m3 wouldn’t adversely affect toluene removal capacity of biofilters. When the inlet ozone concentration achieved 180~220 mg/m3, ozone could significantly control excessive biomass accumulation, improve the filter bed structure and stabilize the pressure drop through filter bed. Furthermore, accelerating the mineralization rate of toluene was the dominant way of biomass accumulation control by ozone.

Abstract:A strain of aerobic denitrifier N1 screened from the biofilm of BAF combined reactor for treating high concentration organic pharmaceutical wastewater was found capable of aerobic denitrification, which can be used nitrate of potash by as sole nitro-gen source. The results indicated that the strain N1 was most similar to Pseudomonas monteilii based on the results of morphologic characteristics, physiological and biochemical properties and phylogentic analysis of 16S rDNA sequence, and the sequence had the highest similarity of 99.2% with 16S rDAN sequence of strain Pseudomonas monteilii strain CIP 104883 obtained from GenBank using BLAST. At present, there are few reports on the degradation of nitrate nitrogen with Pseudomonas monteilii. The nucleotide sequences of strain N1 have been submitted to the GenBank databases under accession numbers HQ840771. So far there are few studies related to aerobic denitrificaton of Pseudomonas monteilii. Therefore, the study is high valuable for treating nitrogenous wastewater using microbe technology.

Abstract:With polynaphthalene sulphona, lingosulphonate based plasticizer, Sodium gluconate, Mortar plasticizer, C18H29SO3Na, C15H34ClN, the performance of alkali-activated slag mortar was teseed. The results show that lingosulphonate based plasticizer and polynaphthalene sulphona have some plasticizing effect for alkali-activated slag mortar, and the effect of the former than the latter obviously. Plasticizing effect of polynaphthalene sulphona compound mixed with air-entraining agent than single-doped polynaphthalene sulphona obviously. Plasticizing effect of polynaphthalene sulphona compound mixed with lingosulphonate based plasticizer than single-doped super plasticizer obviously. When the same amount of water, lingosulphonate based plasticizer can increase the early strength of alkali activated slag mortar, polynaphthalene sulphona can reduce the early strength. The incorporation of slag in the mix of alkali and super plasticizer can increase the strength of alkali activated slag mortar. Lingosulphonate based plasticizer on the setting time of alkali-activated slag have a greater impact，alkali-activated slag mixed lingosulphonate based plasticizer fluidity smaller through time.

Abstract:The effects of sewage sludge dosage and firing temperature on the performance of fired shale sample were investigated experimentally. The volatilization of heavy metals in the firing process and the heavy metals solidification of fired sample, were studied by means of selecting three representative heavy metals and using excess heavy metals mixed with sludge and shale. The results show that when the sewage sludge dosage is 30% and the firing temperature is at 900℃, the compressive strength of fired shale sample could reach more than 10MPa. The addition of sewage sludge is beneficial to improve the plasticity of brick mixture and significantly reduce the bulk density of fired shale sample, whilst it can also increase the drying and firing shrinkage. The dosage of sludge should be controlled within 30%, and firing temperature should be controlled between 900~1000℃. Addition of sewage sludge will make fired shale sample efflorescent, and the more dosage of sewage sludge, the more serious efflorescence. Increasing the firing temperature can be suppressed the efflorescence to some extent. In the firing process of fired sample with sewage sludge and shale, the volatilization of heavy metals is far less than the sintering process of pure sludge incineration. The leaching concentrations of total copper, total chromium and total lead which come from fired sample made of shale and sludge are all within safety standards of the leaching toxicity.

Abstract:The performance of asphalt mixture is closely related with microscopic structure. Discrete element method (DEM) has the great advantage in solving microscopic problem of the asphalt mixture with complex, multiphase and discontinuous medium materials. To solve the problem the past DEM could not perfectly simulate aggregate particle shape in HMA, a geometric modeling method of DEM based on the digital image processing was established. Firstly, the aggregate and asphalt mastic were separated from the sliced image of HMA using features clustering method. Then the aggregate ranges were filled with balls as DEM “clump” using chain code boundary tracking algorithm and lines table filling algorithm. Finally, the asphalt mastic regions were filled with balls. The simulation test of dynamic deformation process of asphalt mixture under penetration load are in good agreement with those from practice.