Abstract:Based on the technique proposed by Muki & Sternberg, a rigorous analytical method for calculating the interaction factor between two piles with different lengths, diameters and properties is presented. The pile group in layered soils is calculated by using the principle of superposition. The validity of the presented method has been verified through comparing with those from other existing solutions. A parametric analysis is made to study the pile group settlement and the loads shared by the individual pile. The proposed interaction factors of pile-pile can consider the strengthening effect of intervening piles. The proposed method can be used to analyze the large pile group.

Abstract:In order to solve structural multi-damage identification problem, a two-stage method based on Bayesian theory and immune genetic algorithm (IGA) is presented. Firstly, structural modal strain energy and frequency are considered as two kinds of information sources, and Bayesian theory is utilized to integrate the two information sources and preliminarily detect structural damage locations. Then, immune genetic algorithm is used to identify structural damage extents. Considering the convergence rate of basic IGA is still not very good, some improved strategies, such as culture vaccine, two termination conditions, are presented. It is shown that the two-stage method can precisely identify structural damage locations and extent, and the calculated results of the proposed improved IGA are obviously better than those of both the basic IGA and simple genetic algorithm.

Abstract:Four series stud push-out specimens were conducted to study static mechanical behavior when stud shear connectors of composite beams were corroded. Firstly, the studs were manually rapidly corroded by electrochemical methods, and then a static load test was performed on them. Test results show that when corrosion occurs at stud rod especially close to combined surface, the ultimate bearing capacity reduces most by 18%, slip under the same load increases, and slip relative to the ultimate load reduces most by 12%. When corrosion occurs at the large end of stud, it has little effect on ultimate bearing capacity of push-out specimens, but deformation performance of stud shear connectors is affected seriously.

Abstract:Considering the compression of medium and fluid, coupled vibration of saturated fractional derivative type viscoelastic soil and a circular tunnel with partially sealed shell lining in the frequency domain is investigated according to theories of Biot and elastic shell. The stress and displacement constitutive behavior of the soil skeleton is described by fractional derivative model which reflects the rheological properties of the medium while regarding soil as a liquid-solid saturated porous medium. The expressions of displacement, stress and pore water pressure are obtained while the inner boundary of circular tunnel is subjected to axially symmetric radial traction and axially symmetric fluid pressure respectively by introducing a partially permeable boundary condition. With the parameter analysis, it is revealed that the order of fractional derivative model on the responses for the system subjected to the symmetric radial traction is much greater than that of the system under the axially symmetric fluid pressure. And resonance phenomenon occurs obviously. Nevertheless the system responses do not have remarkable resonance phenomenon under axially symmetric fluid pressure.

Abstract:In order to find out the current basic wind pressure in China, the parameters were estimated based on Gumbel distribution by statistically analyzing the annual maximum values of wind speed of 159 typical cities in China between 1951 and 2008. The basic wind pressure values for 10-year, 50-year and 100-year return periods were calculated based on moment method and Gumbel method, respectively. The distribution function was tested by the Kolmogorov criterion. Finally, the calculation results were compared with those in current design codes and the results of the correlative literature. The results show that basic wind pressure values worked out by Gumbel method are better than those by moment method in most cases when the statistic of the annual maximum values of wind speed is conducted and analyzed by Gumbel distribution. There are significant differences between the basic wind pressure values for 10-year, 50-year and 100-year return periods in Loading Code for Design of Building Structures and the results calculated with the annual maximum values of wind speed in recent decades, which shows that the sample data in Loading Code for Design of Building Structures are relatively insufficient and cannot reflect the present true condition in China. Therefore, basic wind pressure value should be revised accordingly.

Abstract:The relationship between equivalent time and rheological velocity is studied in the frame of viscous continuum theory. If rheological velocity is only determined by stress and strain, the rheological velocity in the simple loading history is equal to that in the complex loading history when they have the same stress and the same strain. Then the rheological velocity re-calculated in the simple loading history can be used to establish the model in the complex loading history. The lasting time used to re-calculate rheological velocity in the simple loading history is called the equivalent time, and the stress-strain relationship at the same equivalent time in the set of simple loading histories is called the equivalent time line. According to the above idea for formulating model, the relationship between equivalent time and rheological velocity is established for clay with nonparallel equivalent time lines, and a nonparallel equivalent-time-lines rheological model for clay is achieved. This model can be degenerated into Yin-Grahams 1-D rheological model when equivalent-time-lines are parallel to each other. The parameters of model are determined by trial data and the model is further verified to be valid from laboratory test for clay.

Abstract:One-dimensional nonlinear consolidation equations have been established taking into account the effect of structure stress ratio of natural clay and stepped time-dependent construction loading. Crank-Nicolson formula is adopted to solve these equations using the finite difference method. Numerical results are compared to those of linear and nonlinear consolidation taking no account of structure stress. Finally, effects of nonlinear parameter η/c on consolidation are analyzed, which indicates that consolidation rate increases with the decrease of η/c. Numerical results of considering structure stress or not are similar initially. With the development of consolidation, the nonlinear results of not considering the structure stress overestimate the effect of nonlinearity.

Abstract:With the increase of platform size, pipe piles with super large diameter and deep penetration are increasingly used in practice. In order to make accurate prediction of pile drivability, it is essential to evaluate the change of the soil properties under pile driving exactly, and it is the premise to predict the pile bearing capacity after pile driving. In order to learn more about the change of clay properties during pile driving, analysis on the pile driving record of 36 piles in Bohai area is conducted. According to the analysis, the soil resistance in the clay layers decreases as the depth increases, and it is very different from that in the sand layer. The FEM method is used to discuss the mechanism of this decrease. The back analysis is carried out to get more information. The results show that the clay properties are affected by the dynamic effect. The undrained shear strength of clay approximately decreases with the increase of thickness of the layer linearly. At the same time, a prediction is conducted based on results, and the result is closer to the pile driving record than that calculated by method normally used today.

Abstract:The chloride ion transport in concretes with different size of splitting cracks at marine tidal zone is investigated. The splitting crack widths of concrete are about 003 mm, 005 mm, 010 mm, 015 mm and 030 mm. The cracked concrete and sound concrete are placed at marine tidal zone for 30 d, and the chloride ion content in crack zone and perimeter zone of concrete, chloride ion penetration depth and steel bar corrosion area are quantitatively determined. It is shown that splitting crack will be recovered when the concrete is unloaded in split test. And the splitting crack width of concrete should be characterized by the value of displacement sensor when the concrete is unloaded in split test. The chloride ion content of cracked concrete decreases with increased depth, and then gets to remain steady from 10 mm to the inner. The relationship between chloride ion content and crack width in the steady zone can be regressed as the exponential function and the linear function for the crack zone and the perimeter zone of concrete, respectively. Due to away from the crack zone, the influence of splitting crack width on accelerated chloride ion ingression in the perimeter zone is less than that in the crack zone. When the splitting crack width is more than 005 mm, the chloride ion penetration depth in crack plane and in vertical crack plane of concrete is 50 mm and 20 mm, respectively. And the steel corrosion area enlarges with the increasing crack width. And the chloride diffusion coefficient of cracked concrete is closely related to the resistance capacity to chloride penetration of concrete, crack density (matrix width, crack width), and chloride binding capacity of concrete. When the crack density of concrete is less than 70, the chloride diffusion coefficient of cracked concrete increases with decreased crack density linearly. The chloride penetration will accelerate near the crack zone. And the raised splitting crack width will lead to its influence area in concrete increased quickly.

Abstract:Arexperiment was carried out for the analysis of time-varying regularity of early-age concrete strain under the influence of free air temperature changes. The strain data and the weight of specimens were collected. It is found that the severe shrinkage of early age (≤3d) concrete appears in the course of heating and cooling of daily temperature. And the magnitude of the severe shrinkage is 100×10 -6. The expansion strain difference is up to 100×10 -6 for different water cement ratio concrete, and the shrinkage strain difference is up to 200×10 -6.

Abstract:Considering the damage of concrete mechanical properties and bonding behavior between the steel bar and concrete after the freezing and thawing function in the numerical simulation, the nonlinear analysis on flexural performance of reinforced concrete beam which experiences different salt-frost cycles is conducted, and the evolution law of resistance performance of reinforced concrete beam is studied. It is shown that, in the salt-frost environment, the decrease of concrete mechanical properties is the main reason that causes the degeneration of RC beam on flexural performance, while the reduction of bonding property has an unobvious effect on the beam resistance performance. When the salt-frost cycles reach a certain level, the beam failure pattern would change from the under-reinforced failure to over-reinforced failure. The freeze-thaw damage of bonding property in the beam-ends anchorage zone has a certain effect on the beam resistance behavior, especially for the more serious freeze-thaw degree, the resistance performance of the beam reduces about 4% than the perfect anchor beam.

Abstract:Seven specimens were loaded with axial force and horizontal cycle force to analyze the hysteretic performance and the influencing factor as well. The influence of axial compression ratio and aspect ratio on the hysteretic performance was investigated, including the buckling behaviors and the energy dissipation. And the positive role of combined effects on the hysteretic performance of cold-formed specimens was studied emphatically. The experiment reveals that a large axial compression ratio incurs a serious decrease on hysteretic performance, while the combined effects give an increase on it. In addition, the numerical mode is set up. Considering double nonlinearity, the results of experiment and simulation match each other well. Based on the data, it is obtained that local buckling plays a great negative role during the loading course. At last, the characteristics of hysteretic performance of cold-formed steel specimens are concluded and some suggestions are given.

Abstract:Ten specimens with perforated ribs, which can be divided into two series, were made to observe the behavior of steel-concrete composite pylon under axial load and cyclic load respectively. The experiment reveals the ultimate capacity and failure mode of two types of specimens under the cyclic load with different actual axial load level. Furthermore, it can be concluded from the results that the failure mode can be divided into two types, that is compression failure and tension failure. And the behavior of those specimens under cyclic load is influenced significantly under high axial load or without axial load at all. In addition, perforated ribs will prevent the plates under compression from overall buckling effectively based on the observation that the wavelength of plate is limited between two neighboring perforated ribs. At last, comparison on the interaction behaviors of the axial load (N) versus moment (M) is made between the results of experiment and calculation according to the criteria.

Abstract:Based on Swedish slices limited equilibrium method, a new computation formula of stability safety factor is presented for interior stability analysis of soil nailing wall in non-homogeneous soil. A new genetic algorithm is put forward by adopting dynamic self-adaptive technology and nonstandard genetic operators. Applying the dynamic self-adaptive technology and nonstandard genetic operators into the field of soil-nailing wall interior stability analysis, the dynamic adaptive genetic algorithm for searching the arbitrary critical slip surface is established. It is shown that the dynamic adaptive genetic algorithm has better performance in finding optimal solution, quicker convergence than traditional algorithm as well as more reasonable results.

Abstract:Considering the significant influence of spatial correlation in long-span spatial structures, seismic response analyses of traveling wave excitations in cylindrical reticulated mega-structure were conducted under one-dimensional and multidimensional severe earthquake by using dynamic time-history method. Elastoplastic displacement and stress, stress range, distribution and development of yield members of the structure under traveling wave excitations were researched via inputting horizontal transverse wave and longitudinal wave separately firstly. Then traveling wave effects of the structure were studied under different dimensional earthquake inputting and different spans. It is shown that the response effects under traveling wave excitations differ from that under simple support excitations and the diversity changes under different earthquake inputting and different span, which proves that the effect of traveling wave excitations should be taken into account under different earthquake inputting in long-span spatial structures.

Abstract:The influence of applying different heat transfer models coupled different data processing methods on determining the ground thermal properties and borehole resistance is analyzed and studied in allusion to constant heating flux method of thermal response test. Results indicate that the calculated thermal properties and borehole resistance are different when applying line heat source model and cylindrical heat source model respectively; volume specific heat barely affects the unknown thermal conductivity, but affects the borehole resistance. Three-parameter estimation has good credibility in determination of thermal properties and borehole resistance. However, the stability of three-parameter estimation on the determination of thermal diffusivity is not good. Finally, the approach of three parameters estimation coupled the line heat source model and cylindrical heat source model is proposed to determine the thermal properties and borehole resistance based on the analysis of the minimum average error on the two heat transfer models.

Abstract:When a fire happens at the subway platform, the downward ventilation at the staircase which connects the hall and platform can prevent smoke spreading into the hall and provides guiding air for evacuation people. To investigate the influence of the ventilation rate on the smoke movement, the air velocity at the staircase was measured under three ventilation modes. Numerical model was established to simulate the real fire scenario. It is shown that the downward air velocity under fire is greater than that without fire, and the traditional design procedure without considering complex factors interaction in real fire scenario should be improved; when fire is near the staircase, smoke easily spills from the smoke screen to the concourse. And smoke concentration of concourse is even higher than that of platform because the hall is under air supply mode; when the fire locates at the public area of the platform, turning on the tunnel fans can increase the downside flow at the staircase. However exceeding high flow can produce disturbance and destroy the smoke stratification, so more area will be filled with smoke. Therefore, reasonable smoke management scheme is as important as smoke exhausting system capability.

Abstract:Climate has a determining influence on building energy consumption. Since 1980s, the global climate has appeared excessive warming, which inevitably causes the change of building energy consumption. The climatic simulation was used to forecast meteorological data from 2021 to 2050 for five cities in China. The five cities represent five different climate types in China. According to the Analysis of Energy Efficient Meteorological Year (AEEMY), model of meteorological data for building energy simulation based on TMY2 was presented. At the same time, meteorological data for DOES was also made from 1971 to 2000. A high residential building was respectively simulated in five cities under two kinds of meteorological data by using DOE2 software. The model of simulation was proved by the simulation result.

Abstract:Purple soil and yellow soil of Three Gorges Reservoir Area were submerged and incubated under a nitrogen atmosphere to study the effect of redox process on chemical form of Cd. It is shown that the pH and Eh decrease in the redox process. With the transition of soil redox condition, the content of CEC increases to 1753 cmol·kg -1 for purple soil and 2794 cmol·kg -1 for yellow soil, and the content of Fe (II) increases to 3 15630 mg·kg -1 for yellow soil and 44656mg·kg -1 for purple soil. The soluble Cd concentration declines after submergence for the purple soil and yellow soil, and 99.9% of soluble Cd is absorbed by soils. Chemical form of Cd in soil is significant correlated with the physical-chemical indexes of soil. In the process of redox process, part of Exc-Cd (exchanged fraction) transforms to Carb-Cd (carbonated fraction) and Oxide-Cd (oxide-bound fraction), and the content of Exc-Cd decreases to 456 mg·kg -1 for purple soil and 102 mg·kg -1 for yellow soil. The stability of Cd in yellow soil is higher than that in purple soil.

Abstract:To deal with the issue of municipal solid waste incineration fly ash, are melting treatment technology was developed in combination with electric arc furnace metallurgical processes. Glass-ceramics was made of arc-melting slag from waste incineration fly ash and additional glass cullet through crushing, pressing and sintering at temperature between 750 ℃ and 1050 ℃. The crystallization behaviours of the glass-ceramics were examined by differential thermal analysis (DTA), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). It is shown that main crystalline phase of the glass-ceramics are wollastonite (CaSiO3) and diopside (Ca(Mg,Al)(Si,Al)2O6), and the diffraction peaks become more intensive at higher temperature. It is found that the glass-ceramics sintered at 850 ℃ has the optimal physical, mechanical and chemical characteristics, and it has density of 262 g/cm 3, bending strength of 5496 MPa, chemical resistance of 27% and 0.9% in acid and alkali solution respectively. Furthermore, the leaching concentration of heavy metals is very low.

Abstract:260 tons concentrated leachate per day is produced at the leachate treatment plant at Changan landfill, which is considered to be recirculated into the landfill of municipal solid wastes. The effect of leachate recirculation on the slope stability of the landfill should be evaluated. The results from engineering geology and hydrogeology survey were firstly presented. Three-dimensional unsaturated-saturated seepage analyses were carried out by using GMS software to predict the change of leachate level as a result of the leachate recirculation. Based on the leachate levels and pore-water pressures obtained from the seepage analyses, slope stability analyses were carried out to evaluate the safety of the landfill. Some control measures were proposed to eliminate the adverse effect of leachate recirculation on the landfill safety. The analyses indicate that the factor of safety (FS) for the landfill with the current leachate level is slightly greater than the safety requirement (FS=13), and the current leachate level happens to be the critical level. Direct leachate recirculation will result in a significant rise in leachate level, which will cause a significant decrease in the landfill safety. The landfill is likely to fail after a direct leachate recirculation. If the leachate recirculation is executed after the current leachate level is lowered down by 3 m and the resultant leachate level will be lower than the current leachate level, the landfill can remain safe. Vertical pumping wells are proposed to implement the drawdown work, and if 45 wells are used and pumping is conducfed for 3 mouths, the leachate level will decrease by 3 m, which meets the safety requirement.

Abstract:Two enhanced biological phosphorus removal (EBPR) sludges were used to investigate the effect of nitrite on anaerobic metabolism of phosphate accumulating organisms (PAOs). It is found that tolerance of PAOs to nitrite in two sludges were different. In the sludge with enriched PAOs cultures treating synthetic wastewater, when nitrite is above 10 mg/L, it inhibits VFA-uptake of PAOs, leading to decrease of PHA synthesis and increase of phosphate release. In the sludge with nitrogen and phosphorus removal by shortcut nitrification treating real domestic wastewater, anaerobic metabolism of PAOs is not inhibited even when nitrite is 30 mg/L; however, the presence of nitrite in anaerobic period causes denitrifying bacteria compete for limited carbon sources with PAOs, resulting in decrease of PHA synthesis and phosphate release. For the enriched PAOs cultures, the ratio of P/VFA obviously increases when nitrite is added in the reactor, indicating increased energy requirement for PAOs to take up VFA. The quantification results for PAOs in two sludges using fluorescence in-situ hybridization (FISH) show that the PAOs level is 55% in the enriched PAOs cultures, and 7.6% in the sludge with nitrogen and phosphorus removal by shortcut nitrification.

Abstract:The changing mechanisms of air saturation in groundwater in different air travelling modes during surfactant-enhanced air sparging were investigated using a series of one-dimensional column experiments with the media of medium sand (025～050 mm) and gravel (5～10 mm) respectively. The results demonstrate that when air travels in the form of discrete channels, air saturation increases gradually with surface tension decreasing. When the surface tension is 495 mN/m, air saturation would not increase but slightly decreases instead. The decrease of capillary pressure caused by surface tension reduction is the main cause of increase of air saturation. When air travels in the form of bubbles, the air saturation improves gradually as the surfactant concentration decreases when the SDBS concentration is lower than 1 000 mg/L, and air saturation in porous media is directly affected by foam stability.

Abstract:Without natural lime stone, clay, shale and sandstone, with the mass fracrion of demolition concrete in raw meal up to 95%~99%, along with ordinary calcining process, the cement clinkers (hereinafter called recycled clinkers for short) were produced. Experiments and analysis were employed to compare these recycled clinkers with the cement clinker which was manufactured by natural lime stone and sandstone. It is shown that the two types of clinkers have completely the same positions of characteristic peaks of XRD; the clinker minerals of recycled clinkers are formed normally; the two clinkers have similar chemical composition, and the rate value design of recycled clinkers are more likely to higher calcium and lower silicon; the content of f-CaO of recycled clinkers meets the requirements of soundness; the 3d strength of cements produced by recycled clinkers reaches the requirements of 42.5 grade Portland cement, and the 28d strength reaches the requirements of 52.5 grade.

Abstract:Sawdust, coal gangue and paper sludge were chosen as pore-forming agents of sintered shale brick. The pyrolysis behaviors of different forming agents were studied and the influences of the agents on bulk density, compressive strength, porosity, and water absorption properties of the shale brick were also investigated. It is shown that, with the increase of the dosage of sawdust, pore number of the sintered bricks and water-absorption increase, while the volume density and strength fall rapidly. Thus, the dosage of sawdust should be controlled within 6%. Because of poorer plasticity and lower ignition of coal gangue as well as low porosity rate of sintered bricks, the water-absorption of sintered bricks is poor, and decreases of density and strength are not obvious. In practical production, according to the requirements of brick-making heat and plasticity, a moderate amount of coal gangue can be added. The plasticity of the bricks improves as the dosage of paper sludge increases due to its good plasticity. However, excessive dosage of paper sludge will result in large shrinkage of sintered brick, low strength and high water absorption; therefore, the dosage should not exceed 7%.