Abstract:

Abstract:The finite element of a prestressed concrete (PSC) beam is analyzed in a case of diverse prestressing forces. The mechanical model applied is that advanced by Clough for a concrete beam bearing axial force. The results indicate that the beam frequencies decrease with increasing prestressing force. A dynamic experiment of a nonbonded PSC beam was carried out to validate the veracity of the finite element analysis. Test beam frequencies increase with increasing prestressing force. The analysis model thus is unfit for frequency analysis of a PSC beam. The determinant factor of frequencies is analyzed, and the dynamic model is modified according to experimental results. The modified model analysis result shows that: the calculated frequencies of mode 1 agree with the test results well; the frequencies of mode 2 posses some errors; and, the modified model can reflect the direction of frequency change along with the change of prestressing force well.

Abstract:The particle swarm optimization (PSO) algorithm developed in recent years is a stochastic optimization algorithm based on swarm intelligence. It possesses advantages such as being a simple concept, ease of implementation and low resource occupation. The PSO algorithm was adopted to solve the problem of size optimization of truss structures with stress and displacement constraints. We present the basic principle of the original PSO algorithm in detail, and then introduce a constriction coefficient to modify it. Moreover, reasonable values of the coefficients are proposed for the modified PSO algorithm. Several classical problems are solved using the modified PSO algorithm, and the results compared with those using traditional optimization algorithms and genetic algorithms. Numerical results show that the modified PSO algorithm has good convergence and stability, and can be applied to the size optimization of truss structures.

Abstract:The crack tip region in an elastic composite can be divided into three different zones. The constitutive equations corresponding to these zones and the extent of the saturated damage zones are derived. The damage isotropy in the largest saturated damage zone is expressed by utilizing the Monte Carlo technique to create uniform distribution microcracks. The interaction between the main crack and microcracks can be evaluated by an alternating iteration scheme. In the assumption of a dilute concentration of microcracks, the interaction among microcracks is neglected, and the stress intensity factor produced by interaction between the main crack and each microcrack can be superposed. Two sources of loading are analyzed: one is for the main crack microcrack interaction under an applied remote load, and the other is for the main crack microcrack interaction accompanied by the relief of residual stresses on the microcrack surfaces. The results show that two sources of loading can shield the main crack tip, and microcracks behind the main crack tip can create the most shielding whereas the microcracks ahead of the main crack tip play no role in shielding.

Abstract:Abrasive water jets can incise objects with strong rigidity under water. The analytical means of kinetic theory is optimal for theoretical problems of submerged abrasive water jets. The flow characteristics in submerged abrasive water jets were analyzed based on kinetic theory for multiphase flows. The impact characteristics of every phase in submerged abrasive water jets was analyzed and continuity and momentum equations subsequently were developed for solid, gas and liquids in submerged abrasive water jets. It is shown that if the distributing function of every phase were given, the law of its movement could be ascertained.

Abstract:According to the onedimensional Terzaghis consolidation theory, the relationship between the consolidation coefficient and time is deduced based on a genetic algorithm (GA), which could be used to propose a new method for evaluating the analytical solution of the consolidation coefficient. This new method avoids the disadvantages of graphical methods and eliminates the influence of initial settlement and secondary consolidation. Simulation software can be used to process the original data based on the GA principle. Compared with other traditional methods, the new method can determine the consolidation coefficient in practice with high accuracy, reliability and convenience. In addition, the GA can diminish jamming and produce a precise result.

Abstract:The formation mechanism of the arching effect between cantilever piles is studied according to their stress characteristics. The soil arch is classified into three types based on its position in a space coordinate system, namely, a horizontal arch, a vertical arch and a freeface arch. The master factor for distribution of unloading area between piles is the horizontal arch effect. The range of effective unloading area is defined. Based on the failure pattern of soil arches and the relationship between soil strength theory and the static equilibrium principle of soil arches, a calculation model is established by considering the presence of geostatic stress and sliding thrust force. The relation between soil strength and critical height is studied by variation of cohesion and friction angle. In addition, the impact of canonical distributions of the earth pressure to the vector height of unloading area is also discussed. Finally, the calculation model is verified by an example from real engineering work.

Abstract:An analytical solution of the elastic circular plate on multilayered soil can be obtained by using the transfer matrix solutions for displacements and stresses of multilayered soil. This solution is based on the continuity of vertical displacements and the smooth contact conditions between a multilayered soil surface and the elastic circular plate. Numerical calculation and analysis are carried out by the computer program compiled for this purpose. The numerical results show that the rigidity of the elastic circular plate greatly influences the displacement of the circular plate and the normal stresses under the center of the circular plate.

Abstract:Deformation monitoring and control measures of a shallowburied largespan tunnel constructed using the pilebeamarch (PBA) method are described, taking the North Gongti Road Station of Beijing Metro line 10 as an example. Based on the monitoring datum, the crown settlement, convergence, ground settlement of the tunnel and the bridge foundation settlement are analyzed. The results show that (1) the PBA tunneling method can restrain the ground settlement and deformation of a shallowburied largespan tunnel; (2) the depth, tunnel span and pilot tunnel construction may influence the deformation of a shallowburied largesection tunnel significantly; and, (3) advanced conduit grouting, timely preliminary support and permanent lining construction can reduce the deformation effectively.

Abstract:Through technological research of foundation treatments in the collapsible loess areas, we recommend a method of treating foundations in collapsible loess with quicklime piles. We set forth the basic principle of this expansive method. When a very thick foundation in collapsible loess is treated, the computational formula for the volume of expanding material in a quicklime pile is deduced based on cavity expansion theory. This theory is applied to engineering practice. Physical and mechanical properties of the compacted soil are tested. The result shows that the collapsibility of a foundation in loess has been eliminated, its physicomechanical indexes have been improved, and the soil compressibility and the modulus of compressibility also increase remarkably, demonstrating the correctness of the computation theory. The feasibility of the expansive method for very thick collapsible loess areas is further established.

Abstract:Intelligent materials, control devices and intelligent control algorithm research and development in recent years have opened a new world for seismic resistance and disaster reduction in civil engineering. We designed and fabricated a new piezoelectric friction damper. In our research, we regarded the piezoelectric friction damper as the control device. We proposed a fuzzy control algorithm for reducing nonlinear seismic response of a 3story benchmark building and established the interactive relationships between structural responses and fuzzifier factors, defuzzifier factor. A numerical simulation is carried out to analyze the nonlinear seismic responses of the controlled 3story benchmark building. The simulation results are compared to those of other control strategies. The results show that the fuzzy control can reduce the nonlinear seismic response of 3story benchmark building and minimize the structural damage caused by strong earthquakes.

Abstract:In civil engineering, the aseismic theory based on displacement generally is used in vibration damping design. This theory cannot be applied to reinforced concrete (RC) arched bridges, however, due to the tremendous rigidity of these bridges. To address this situation, a new vibration damping method called an “intelligent aseismic control system with changed rigidity of RC arched bridges” is suggested. With this method, the system of the main arch will be changed, the rigidity lowered, the deformed capability increased, and the displacement and stress can be under double control. When an earthquake occurs, the RC arched bridge stress can be lowered while the displacement is not obviously increased with this method.

Abstract:Three reinforced concrete plane frames with total heights of 6, 10, and 16 stories, respectively were taken as examples. Nonlinear dynamic responses of three frames under excitations of seven earthquake waves with varying earthquake intensities were selected as the datum mark of a comparison study. The changing rules of the responses analyzed by four kinds of ordinary Pushover Analysis and Modal Pushover Analysis were studied by reviewing the interstory drift ratio and rotation at beam and column ends. Results show that the error of interstory drift ratio analyzed by Modal Pushover Analysis essentially is invariable when the total frame height increases, while the error of ordinary Pushover Analysis is added corresponding to a larger fundamental period. This indicates that Modal Pushover Analysis can cover the influence of higher modes more reasonably. When nonlinear responses of frames were more severe, the interstory drift ratio errors of Modal Pushover Analysis and ordinary Pushover Analysis also increase correspondingly. The errors of rotation at upper story beam ends and the majority of column ends analyzed by Modal Pushover Analysis are smaller than those of ordinary Pushover Analysis.

Abstract:A majority of reinforced concrete frame structure failure patterns resulting from the May 12, 2008 earthquake in Wenchuan County, P. R. China were analyzed. It was found that the main failure mode of frame works was “strong beam, weak column”, which conflicts with the design criteria of “strong column, weak beam”. The cause of this failure pattern was analyzed. A new concept is put forward that should be considered in design work. The overstrength caused by slabs connected monolithically to the beams is analyzed. The joint types, transverse beam stiffness and lateral drift influence the reinforcing effect of the sla, Moreover, a reinforced concrete frame model was simulated using the program ABAQUS. The slab reinforcement stress distributions at different lateral drifts were analyzed and the effective flange width value proposed.

Abstract:Random spectrum excitation samples of a road surface profile are investigated. The displacements, velocities, accelerations of a vehicle and a bridge structure are discussed using certain samples. The road excitations are numerically simulated by the random phase cosine method of the power spectral density. The vehicle bridge system responses are obtained using the vehicle bridge differential equations for different road surface profiles. It is concluded that the random phase has critical effects on the road surface profile curve shape, and the power spectral density on the curve value. The random samples possesses the same statistical characteristics. The system response values are affected more by the road surface profiles, and the response shapes are affected more as the vehicle velocity varies. Some engineering advice is proposed based on the numerical calculation with the different random excitation inputs for their significant differential responses.

Abstract:On the basis of continuum damage mechanics theory, the effective stress theory of damaged porous media was presented and its modified selfcontained seepage differential equation was deduced. The traditional DruckerPrager yield criterion subsequently was modified, and a coupled seepage and damage finite element computer program compiled that was combined with the modified Biot consolidation equation. A simple roadbed foundation model then was analyzed and calculated using the computer program we compiled, and the typical node settlement, pore pressure, and damage variables were discussed and compared with those from the analytic solution. The results show that the damage finite element program we compiled is reasonable and effective.

Abstract:The rutresistance properties of largestone flexible bases are studied, taking into consideration heavy loads and using computer simulation and numerous indoor tests. In computer simulations of largestone flexible bases, a calculation method was formulated for predicting asphalt pavement rut under dynamic loads. The method was based on the coupling of vehicle dynamic loads and pavement surface unevenness. The results of indoor testing and threedimensional numeric calculation under dynamic loads are confirmed by tracking observation results of a test road. We conclude that the rutresistance properties of largestone flexible base asphalt pavement built using lowgrade asphalt and low crush value high performance aggregate with reasonable gradation is no worse than that of the semirigid base asphalt pavement, and that ruts mainly are caused by the lateral shear.

Abstract:Based on the measured data from the construction site, the prediction uncertainty of the CEBFIP MC90 due to the variation of the calculation parameters (i.e. the external uncertainty) and their sensitivity are analyzed with the help of statistical method and Latin Hypercube sampling method. Three conclusions can be deduced from the analysis. Those are a)the external uncertainty and its decreasing rate of the CEBFIP MC90 reduce with the time increasing, b)the creep coefficient increases with the increasing temperature while decreases with the increase of other calculation parameters, c)in accordance with the degrees of effect to the creep uncertainty, the first three calculation parameters are relative humidity, loading age and temperature, if the variation of the loading age is not taken into acount, the uncertainty of the creep pridection will be underestimated. Also, a method to analyze the uncertainty of the bridge structure due to the creep prediction uncertainty is proposed after the creep uncertain factor, which is the standard of the uncertainty of the creep, is introduced. An exmaple is analyzed in this paper using the random sampling method and the method presented in this paper. Through drawing a comparison between the results from different methods, the method presented in this paper appears to be feasible and efficient.

Abstract:Since P. R. China has experienced extensive land resource use, environmental degradation, lagging rural development and other difficulties in 20th century, urbancountryside integration and ecological planning has become an important subject to build a harmonious society in the 21st century. The country attempted to use complexity science and ecological thinking based on recognizing the relationship between the city and countryside and raising the citycountryside space ecology coupling concept to construct a citycountryside space planning methods system consisting of the identification of urban and rural land uses, urban and rural nonconstruction land planning, citycountryside coupled environmental conditions assessment, coordinated citycountryside space development and citycountryside space system fractal optimization, and more.

Abstract:We studied the dynamic characteristics of dehumidification and regeneration of CaCl2 solution, based on building dehumidification load and economical operation and conducting an experiment on a smallscaled liquid dehumidification air conditioning system. Experimental results show that three main factors affect the performance of CaCl2 solution: solution temperature, solution concentration, and inlet air humidity. The dehumidification capacity of the CaCl2 solution is 32 g/kg in experimental conditions. Its regenerating performance is approximately 1.3~9 times than that of dehumidifying. After summarizing, we consider the liquid desiccant dehumidification with CaCl2 solution has substantial potential to be improved and generalized.

Abstract:We used the variance analysis method to analyze the effects of the proportion of the actual operated load, the pulseon degree of guide baffles, the temperature of cold water of the outlet, and outdoor relative humidity on the coefficient of performance (COP) of centrifugal refrigerating units. When the confidence level is set as 95% and 99%, respectively, the results of singlefactor variance analysis of the above four parameters show that the test statisticF of the pulseon degree of guide baffles is higher than its critical value F0.01 (r-1,n-r), which establishes that its influence on the COP is quite remarkable. The test statistic F of the proportion of the actual operated load and the outlet temperature of cold water are higher than their own critical value F0.05 (r-1,n-r), which shows that their influence on the COP is remarkable. The test statistic F of outdoor relative humidity is lower than its critical value F0.05 (r-1,n-r), which demonstrates that its influence on the COP is unremarkable. The results of the twofactor variance analysis of the cold water outlet temperature and outdoor relative humidity show that the test statistic F of their interaction is higher than its critical value F0.01 (r-1,n-r), which indicates that influence of their interaction on the COP is very remarkable. The actual COP value of centrifugal refrigerating units can increase by 6.885% in average on the condition of the invariable refrigerating capacity after adjustment according to the analytical results.

Abstract:The geothermal heat exchanger is the key component of groundcoupled heat pump systems. We discuss the key parameters method of calculating geothermal heat exchanger length based on linesource theory. Typical meteorological year data is used to determine the hottest month, the coldest month and annual average surface temperature. The building hourly load can be obtained by introducing the concept of equilibrium temperature. The cooling fraction and the heating fraction then can be calculated using building hourly load and performance parameters curvefit of a water source heat pump unit. The method for selecting the hottest and lowest entering fluid temperature and calculating the borehole and ground thermal resistance is given. A vertical Utube heat exchanger length calculation procedure is proposed.

Abstract:The current status of leachate treatment in garbage landfills and its treatment difficulties were elaborated and summarized. Based on the advantages and disadvantages of various landfill leachate treatment technologies, a multistage treatment composed of pretreatment, biotreatment and deep treatment was suggested as an ideal treatment. A new way to treat landfill leachate was presented. It combines electrochemical and oxidation ditches with sand filtration. The advantages of the new technique were also analyzed.

Abstract:With societal development, wastes exist in industry, agriculture and human life. In particular, a large volume of urban industrial sewage is discharged and pesticides and fertilizers are widely used, leading to groundwater pollution in many areas. Based on a water quality model of hydrodynamic dispersion and the multielement balance (MEB) method, a general program for simulating groundwater flow and quality is carried out using the program VC++ for visual presentation. Using this program in a case study, the transportation mechanism of groundwater flow and quality is simulated numerically. The result indicates that the program is visual and can be manipulated well. It offers a point of reference for the reasonable exploitation, protection and utilization of the groundwater.

Abstract:Blind number theory was used to evaluate water environmental carrying capacity (WECC) in mining cities of central Liaoning Province, P. R. China to prompt the balanced development of water environment with human activity. The research was based on the characteristics of water environment systems with numerous uncertainties such as random, fuzzy, and grey ones which may occur simultaneously or partially in a system. An indicator system for WECCs was established. The indicators were set as blind number and the WECC in mining cities of central Liaoning Province subsequently were calculated. Study results show that from 1997 to 2005, the WECCs in the mining cities Anshan and Fushun of central Liaoning Province were below the safe level, but the WECC in Benxi city was rather safe. By the comparative analysis of a system under uncertainty with that under a condition of certainty, the results of the blind number model regarding WECC was reasonable. This model is well adapted for WECC assessment.

Abstract:We analyze the generation, transmission and living mechanism of indoor airborne microbes and present two commonly used engineering control methods for microbial contamination: ventilation and air filtration. A mathematical calculation model is developed to incorporate the two ways likely having significant impact on microbial contamination control. We also discuss the relationship between different ventilation parameters and microbial concentration, provide some design equations for determination of microbial filtration efficiency, and calculate the efficiency of air filters used in certain buildings. The results show that the natural ventilation is not a good contamination control for airborne microbes when they are a main indoor pollutant; mechanical ventilation should be used in such cases. If the atmospheric airborne microbes cannot be neglected or its indoor concentration is high, incorporating ventilation with air filtration is a good way to control indoor airborne microbial contamination. Enhancement of filter efficiency at various levels used in central airconditioning systems is helpful for improving indoor microbial contamination control condition.

Abstract:This study was focused on preparation technology of the high range water reducing agents of polycarboxylic series with allyl alcohol polyoxyethylene, acrylic acid, maleic anhydride and Sodium methyl acrylamide as the main raw material. Various factors influencing performance of water reducer were exploited and optimum technologies of the water reducer were obtained. Furthermore, tests were made on properties of the reducer.The result shows that this water reducer has the features of small dosage, good dispersibility and high water reducing rate. At the solid dosage of 0.25%, the original fluidity of cement paste with this water reducer can attain 310mm,and the waterreducing rate reaches 30.5%. Also, this water reducer can remarkably enhance the strength of concrete and be used to prepare high performance concrete．

Abstract:Based on the latest research, we introduce asphalt foaming principles and their characteristics and analyze the influencing factors from macro and micro perspectives. The methods of designing foamed bitumen mixture, the optimum mixing water content, the influence of curing conditions, laboratory testing methods, mechanical characteristics, and the influencing factors of foamed bitumen mixture are discussed. We outline some new asphalt foaming technologies used in warm mix asphalt. Viewpoints regarding the development of foamed bitumen are put forward by analyzing the design and the evaluation methods of foamed bitumen mixture, the development and the selection of asphalt foaming additive, the improvement of the manufacture techniques of foamed asphalt, and the technology of modified asphalt foaming.

Abstract:To recycle wetdischarged flyash and carbide lime effectively, a highlyactivated mineral admixture slurry consisting of both these components was investigated. The preparation technology of mineral admixture slurry made from a composite of wetdischarged flyash and carbide lime and the strengths, hydration products change (XRD, SEM) of cement paste made by the slurry were studied. The results indicate that the optimal proportion between wetdischarged flyash and carbide lime (solid content) is 75:25 in the process of wetmilling preparation. The alkaline environment provided by carbide lime with high Ca(OH)2content and cement hydration accelerated by modified agents can promote early activation of flyash, and accelerate its secondary hydration reaction.