Abstract:Fatigue failure is a fatal damage for the reinforced concrete structure bearing fatigue load repeatedly. That how to estimate or describe the degree of fatigue damage is a challenge in areas of structure damage and lifespan estimation. Structure's stiffness degenerates irreversibly along with the damage progress. There is a certain inherent relevance between stiffness degeneration and fatigue damage. A series of fatigue tests were carried out to study stiffness degeneration regulation due to its simplicity and feasibility. According to the test results, reinforced concrete beam's stiffness degeneration presents a three-stage rules obviously, and the stiffness degeneration curves accord with "S" style. Based on the stiffness degeneration regulation, the reinforced concrete beams' stiffness degeneration calculation formula is obtained by fitting experimental data. The formula has a perfect goodness of contact area with 10 test beams' experimental results, and it can describes reinforced concrete beams' stiffness degeneration perfectly. The formula can be used to forecast the deformation developing. Meanwhile, the residual life of the structure can be used to decision structure's fatigue fracture and the degree of performance degradation.

Abstract:According to the generalised beam theory based on the exist studies, the aim of this paper is to derive the distortional buckling formulae of pined or fixed cold-formed thin-walled rack members upright with rear flanges and additional lip stiffeners. The formulae is adopted to calculate the distortional buckling load and the buckling half-wave length of the member subjected to axial compression or minor and major axis bending. Meanwhile, the results are compared to those of finite strip program CUFSM and other analytical formulae. The derived formulae is proved to be accurate enough. As a result, it may be directly used in practical design as well as further study.

Abstract:Weak interfaces may be induced during the process of substituting the damaged cover by corroded RC beams or strengthening directly with CFRP. The two possible causes are the combination between the new-old concrete and expansive cracks. In this study, nine strengthened beams were designed to investigate the effects of weak interface on CFRP debonding along with the effectiveness of conventional confinement provided by U-strips. The test results showed the structural integrity of strengthening system was impaired considerably by both types of weak interfaces. Furthermore, it easily led to CFRP debonding failure. Weaker the interface was, the less ability transfer shear forces are. Debonding failure could be effectively prevented by U-strips. Meanwhile, consequently flexural CFRP sheets performed mainly well. However, local cover delamination and premature rupture of flexural CFRP may still occur due to the effects of the weak interface. Therefore, the allowable tensile strain of flexural CFRP must be reduced, and stricter measures of confinement and anchorage must be taken in application.

Abstract:it is necessary to balance the failure risk and the maintenance expensive. A methodology for reliability based maintenance optimization of steel bridge welded joints subjected to fatigue is proposed considering linear elastic fracture mechanics (LEFM), the structure reliability, life cycle cost method and maintenance strategies. The maintenance cost is divided into inspection, repair and failure sections according to the whole life cycle cost methodology. And the maintenance strategy is transformed to the minimum expected lifetime costs with a constraint of the minimum acceptable reliability index. An case concerning to a transverse stiffener of bottom flange welded joint of Qingcaobei bridge is studied with a certain number of simplifications. Some sensitivity analysis is provided. Among all the parameters, discount rate is the most remarkable.

Abstract:The reservoir sandstone is the sedimentary rock with many cemented sand particles. The different physical property of the reservoir even in the same area results in different mechanical response and sand production of the sandstone. Taking two types of the reservoir sandstones as research subjects, a numerical model based on 3-Dimensional Particle-based Distinct Element (PFC3D) under cylindrical coordinate system was used to simulate the micro-micro response of the sandstone considering the given confining pressure and the oil flow rate. Meanwhile, the sanding initiation and the process of the development were analyzed. The macro stress indicated that the reservoir sandstones with weaker cemented sand particles and less percent of the cemented materials would yield and fail more easily, the sand production was initiated more easily as well. Meanwhile, the stress of the parallel bonds indicated that the reservoir sandstones with granule and less cemented materials dislodged from the sandstone more easily, and the force on the particle contact was larger and the sandstone failure was more serious.Hence, the probability of the dislodged particles flowing into the wellbore was also much more. In addition, the particle displacement and rotation indicated that the physical property of the sandstone played a significant influence on the mechanical response and the sand production, the results also agreed with the above results. Therefore, the sand mechanical response and sand production of reservoir sandstone are both different due to different physical property of the reservoir. As a result, the reliable measures of the sand prediction and sand control will be adopted based on the reservoir physical property and conditions.

Abstract:There is no suitable condition to build any shaft(vertical or oblique shafts) due to the complex geological environment of Lianghekou. Furthermore, the tunnel has to be constructed blind heading. So the problem of ventilation is serious. Based on the theory of CFD，the wind current produced in forced ventilation is simulated by 3D RNG k-ε Turbulent Model，and then the Time-dependent Variation Rules of the flow field and the concentration field during the construction period are shown by numerical simulation of 3D. Results show that the backflow area which is located near the working face has the complex situation of wind current, and the air current distribution becomes stable gradually when it is far away from the backflow area. Meanwhile, the movement of the harmful air produced after blasting can be described as “moving” and “diffusing”. The result of moving makes the harmful air run out of the tunnel from working face. The result of diffusing makes the harmful air deliquated along with the process of moving. In addition, the time that the workers spend on getting into the tunnel has been studied according to the concentrations of CO (in and allowance concentrations respectively).

Abstract:For non-ideal interpolation results of complex implicit nonlinear functions between non-normal distribution response and standard normal distribution inputs using stochastic response surface method, radial basis functions was used to replace Hermite polynomials so as to solve complex implicit nonlinear function interpolation problem for its excellent performance on scattered data interpolation. A few nonlinear analytical functions and uncertainty problems of the load carrying capacity of single circular concrete filled steel tubule (CFST) arch were used as examples to test and verify the precision of proposed method in non-normal distribution response interpolation and its engineering applicability. The results show that stochastic response surface method based on radial basis functions performs well in fitting highly nonlinear input implicit functions, and can achieve high precision on multi-parameters CFST arch load carrying capacity uncertainty problems. Meanwhile, the method has less sample points compared to the Hermite polynomials method.

Abstract:Equilibrium equation and compatibility equation are deduced to get the cable force equation and cable displacement control equation. Then the expression of characteristic parameter λ 2 in cable force equation is deduced. Meanwhile, the influence on the increment of cable force and displacement caused by λ 2 and load ratio P is analyzed. On this basis, taking 3 000 m span suspension bridge as a calculating example, the characteristics of the increment of cable force and cable displacement under symmetrical and asymmetrical load are studied. In this case, two different conditions are considered. One takes the elastic elongation into consideration, but the other does not. At last, compared with the steel cable, the influence on the parameter in cable force equation and displacement control equation caused by span is analyzed. The influence of the static performance of suspension bridge by parameter changing is analyzed as well. The substantive characteristics of the static performance of super span CFRP suspension bridge are cleared and the superiority and characteristics of CFRP cable structure are demonstrated in theory.

Abstract:Internal defects of decorative layer on exterior wall, including mortar and ceramic tile decorative layers, were detected using thermal infrared imager. Variable characteristics of surface temperature for decorative layer heated by external heating source were studied. The distribution and variation law of surface temperature on decorative layer with time and space were obtained，and the influences of thickness，area and embedded depth of internal defect on image quality were analyzed. It is revealed that the thicker, bigger and shallower internal defect are more easily detected. The surface temperature of internal defect is maximum temperature point of approximate symmetry along with width direction. Based on the test results, the prediction model of dimensions for internal defect was established through statistical analysis technique, which can provide a reference for the related follow-up study and practical project application.

Abstract:The effective sewage intake technology is prerequisite for the untreated sewage source heat pump system to run steadily. In terms of the insufficiency of current sewage intake technologies, an open sewage intake integration technology is proposed. The mathematical model and the distinguish basis of critical state are established for the sewage intake characteristic by defining some important operating parameters, such as the blocking coefficient, the contamination density and the section coefficient. Furthermore, the change rule of each critical operation parameter is observed along with the various initial parameters. The result can provide the theoretical basis to design the open intake integration technology.

Abstract:An analytical model of the unglazed solar collector/regenerator(C/R) was presented. There was an optimum flow rate per unit collector area at normal temperature which led to the maximum evaporation rate. The inlet temperature of absorbent solution and the wind velocity are key parameters to determine the optimum flow rate, in addition, the concentration of solution and solar radiation intensity have obvious effects on the maximum evaporation rate. When the outlet temperature of solution is higher than the inlet temperature, there is not an optimum flow rate, which reflects that the more the flow rate of solution is, the better regeneration efficiency is. With the 2m/s of wind speed, the evaporation rate reaches the peak. In this paper, kinds of factors influencing the performance of solar C/R were evaluated as well.

Abstract:The DeST-H, developed by Tsinghua University, was used to analyze the Heating and cooling energy consumption of the typical design project obtained from the General Dwellings Atlas of Chongqing Ba-Yu New Rural Residential. The whole year energy consumption after opting energy-saving measures was simulated by varying the relevant parameters. Meanwhile, the technical and economic performance were analyzed by taking the cost increment into account which was caused by energy-saving measures. Based on the optimization results, the priority design parameters adapted to residential buildings of new rural development in Chongqing are summarized as follows: exterior wall thermal insulation with 30mm EPS board; the external window of the main function room with Low-e film hollow glass or others with ordinary single 6 mm glass; strengthened ventilation at over-season; indoor temperature in summer is set to 28℃, the heating temperature in winter is set to 16℃; building orientation is north-south.

Abstract:Thermal performance of the green roof is an important basis for energy-efficient design and evaluation. However, the current studies on the thermal performance of the green roof seldom involve thermal inertia of the green roof. Based on a long-term experiment of an extensive green roof in natural ventilation state and a five-month ongoing measured data in summer, thermal inertia of the extensive green roof was studied by statistical analysis method. The results show that thermal decay to outdoor climate effect through green roof was increased by more than 100% and delay time of thermal response to outdoor climate on internal surface of the green roof was reduced in comparison with that of the bare roof.

Abstract:Dynamic membrane bioreactor (DMBR) based on activated carbon sponge materials was studied and developed independently. The pollutant removal efficiency and operational characteristics were investigated in detail, and the feasibility of DMBR application in transformation of real wastewater treatment plant (WWTP) was discussed by comparing the effluents. Results showed that the concentrations of COD, NH3-N, TN and TP in effluents were below 35.0 mg/L, 1.4 mg/L, 10.2 mg/L and 0.3 mg/L, respectively, with the HRT of 8 h and MLSS of 8 000 mg/L. The ultimate effluent was qualified to standard A of “Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant” (GB 18918-2002). Adsorption of activated carbon and the spatial structure of sponge synergistically strengthen the pollutant removal. DMBR can be used in upgrading and transformation of WWTP by replacing the existing advanced treatment process. The flux of the DMBR was recovered by intensified aeration backwashing and maintained steadily at the level of 30 L/(m 2·h).

Abstract:Consolidation deformation can lead to changes of structural and permeable characteristics of clay impermeable layer, which will affect the distribution of seepage field and concentration field, and then affect the transport law of contaminant in impermeable layer. Based on the Biot consolidation theory, the transport law of contaminant in deforming soil is studied taking account. Meanwhile, the effects of consolidation pressures and adsorption parameters have been analyzed separately. The results show that consolidation deformation retards the transport process of contaminant and shortens the transport depth of contaminant. In addition, the retardation of consolidation deformation on the transport process of contaminant becomes stronger as the consolidation pressure increases. Meanwhile, under the condition of a linear adsorption mode, the decreasing rate of migration depth increases gradually as the adsorption parameter decreases. It is shown that the retardation of consolidation deformation on the transport process of contaminant becomes more visible when the adsorption parameter decreases. The results have important theoretical significance for the design of effective thickness of the simple constructed garbage dump and bottom sediment dump, as well as the safety evaluation of impermeable layer.

Abstract:Different extra carbon sources(glucose, sucrose and straw powder）were added during sewage sludge composting. According to the results, separate add of the glucose(2.46 g/kg·ds）and sucrose(2.17 g/kg·ds）could reduce NH3 emission compared with the amount of NH3 emission(3.05 g/kg·ds). No significant reduction of nitrogen loss was found in the mixture of P3 amended with straw powder alone(3.1 g/kg·ds). Adding the mixture of sucrose and straw powder had significant effect on reducing ammonia emission(1.92 g/kg·ds). A good linear correlation between the carbon degradation rate and ammonia emission was found with correlation coefficients of -0.94(p<0.005). The combination of straw with glucose and sucrose could enhance the decomposition of organic carbon. The carbon source which has more readily degradable composition is helpful to nitrogen immobilization.

Abstract:In this study, the concentrations of PM10, PM2.5 and PM1 in a residential building in Shanghai were measured under minimum ventilation rate (external doors and windows closed), and the relationship between the indoor and outdoor PM concentrations (I/O ratio) and the influence of temperature and relative humidity were analyzed as well. Results showed that, the percentages of the concentrations of fine particles (PM2.5) of the indoor and outdoor air were 65% and 87% of the inhalable particulate(PM10)concentration during the test respectively. The I/O ratio was less than 1 without significant indoor sources. Meanwhile, the figure decreased as the size of particles decreased. Results also indicated that, the correlation between indoor and outdoor PM concentrations, PM1 and PM2.5 were more obvious than PM10, and the correlations showed obvious differences according to the weather conditions.The PM concentration was influenced by temperature and relative humidity, which was presented to be complex when affected by weather conditions.

Abstract:Contaminant diffusion in layered soil is very complex. The diffusion process is simplified as a one-dimensional diffusion mode. The Laplace transformation and Laplace numerical inverse transformation are adopted. The proposed solution can be degraded to a single layer case. The obtained results are well consistent with those obtained by the classic theory. The correctness of the presented solution is verified by comparing the calculation results with the results generated by existing numerical software. One case study is conducted and the calculation results have a good agreement with measured data, which prove the reliability of the proposed method. The presented method can be used to solve more complex boundary conditions of contaminant migration.

Abstract:The simulation of Eulerian multiphase flow model with two-phase (air & water) in membrane bioreactor were aimed at obtaining and comparing gas hold-up distribution, velocity field and membrane surface rate among the two reactor internal configuration of “alignment” and “alignment” diversion. Furthermore, the gas distribution mode was analyzed as well as optimized. The mini-model experiment was conducted to validate the simulation result. It is shown that: the bubbles track of internal field tended to flow to the membrane assembly center position, and then dispersed on the top of membrane modules in the two reactor configurations; the influence of diversion on gas holdup distribution was in apparent while notable on the velocity field distribution. The simulation results of an experimental model shrunk 100 times was proved to be consistent with the experimental results. Through an optimization simulation of gas distribution mode, the non-uniform gas distribution mode was proved that it can improve the range of gas distribution and the turbulence intensity.

Abstract:The changes of redox environment conditions and the concentrations of BTEX in different conditions are monitored in this study through setting simulated column. The results showed that the concentration of redox components presented zoning in the simulated column. Oxygen reduction zone formatted in 80～98 cm away from the source， Nitrate reduction zone formatted in 60～80 cm， Iron reduction zone formatted in 35～60 cm， and Sulfate reduction zone formatted in 30～50 cm. At the bottom of the column, the methane zone formatted in 0～30 cm because of the decreasing of HCO3-. The concentration of BTEX components showed a sharp decline. The degradation rates of benzene, toluene, ethylbenzene, xylene and o-xylene reached 99.94%, 99.96%, 99.94%, 99.49% and 98.3%, respectively.

Abstract:At present, the malodorous gases as a main environmental problem derived from livestock farm have been taken seriously. Meanwhile, it is urgent to eliminate the odor pollution. The combination of high-pressure hydrothermal method and impregnation CuSO4 method is used to modify the raw activated carbon. The adsorption performance of H2S derived from livestock farm on modified activated carbon (MAC) has been investigated at different conditions in self-made fixed bed. The results show that, lower temperature makes for H2S physical adsorption on MAC, but it against chemical adsorption on it. The ability of H2S chemical adsorption improves with the increasing temperature, at the same time, the ability of H2S physical adsorption weakens. The optimal adsorption temperature is 80℃, which balances the chemical adsorption and physical adsorption on MAC. The gas flow rate goes up with the space velocity increases. The time that H2S stays in fixed bed is shortened and the H2S adsorption capacity on MAC declines as well. The H2S removal efficiency and breakthrough time on MAC decreases along with the increase of the H2S concentration in the range of 150-850 mg/m 3. Moreover, the physical and chemical structures of raw activated carbon and MAC have been characterized by FTIR, TPD, Boehm methods. The results demonstrate that the pore structure of the activated carbon, the types of carbon functional groups and the surface basic of activated carbon have significant influence on the H2S adsorption ability on activated carbon.