Abstract:The method of damage identification in soil-wall system was studied; a new approach based on improved multi-population genetic algorithm (IMGA) was developed. First, the simplified dynamic-detection model of soil-wall system was established, meanwhile, the theoretical analysis of characteristic equations in soil-wall system was conducted when soil in damage status. The objective function based on characteristic equations was established. Then, the improvements of multi-population genetic algorithm, including the adoption of real-valued representation, adaptive cross operator and adaptive mutation operator, were conducted. Finally, the localization and quantification of the soil-wall system damage were performed by IMGA with and without the consideration of noise, respectively. The results indicate that damage location and damage extent can be detected efficiently, and anti-noise performance is better.

Abstract:Based on stress dropping model, an elastoplastic-brittle model was established by using a softening threshold value to model the features of the geotechnical materials. According to the Mohr-Coulomb criterion, the radius of the rupture and plastic zone, the displacement and stress expressions of surrounding rock were obtained with the consideration of the strain-softening and dilatancy of geotechnical materials. Furthermore, the model was verified by case study and the influence of strain-softening, dilatancy and elastic modulus deterioration on calculation result were presented.

Abstract:A full-scale model test was conducted on the low silt soaking subgrade of the alluvial flatlands flooded by the Yellow River. The test mainly studied the mechanical characteristics and vertical deformation of the silt subgrade under grade cyclic loading in different water immersion conditions. The test demonstrates that the silt subgrade has intense capillarity and water sensitive characteristics; the additional stress is large in the roadbed of the new and soaking silt subgrade, and it decreases sharply as the depth increases; the phenomenon of strength degradation is obvious in the soaking subgrade; the elastic and plastic deformation is large under overloading force and the deformation increases as the water immersion level ascending; The plastic deformation of the subgrade is easy to accumulate in water-saturated areas, where large plastic deformation still occurs in low stress level.

Abstract:According to the features of stratification and obvious inhomogeneity in geological soil in Huaibei plain, BP neural network prediction method for stratification and bearing capacity calculation of multiple cross-bedded foundation was proposed. By comparing the results of drill sampling, static cone penetration tests and screw plate tests, plate loading tests, penetration resistance ps value was found as an evaluation index for stratification and bearing capacity prediction of cross-bedded foundation. Moreover, gradient descent algorithm and conjugate gradient algorithm BP neural network models were obtained, and the calculation results of the two algorithms were comparatively analyzed. The results show that penetration resistance value can be taken as an evaluation index for stratification and bearing capacity prediction of cross-bedded foundation in Huaibei plain. Gradient descent algorithm and conjugate gradient algorithm BP neural network models have good results for soil identification and bearing capacity determination, which can meet the accuracy requirements of actual engineering. However, the computational efficiency of gradient descent algorithm is significantly lower than that of conjugate gradient algorithm.

Abstract:The influence of forepoles on the patterns of a single tunnel plastic collapse was discussed using Acutronic 661. A series of plane strain centrifuge model tests in over-consolidated clay were conducted. Tests were carried out in a circular cavity with stiff resin inclusions embedded around the tunnel vault. These inclusions simulated elements of a secant pipe or forepole arch system. An image processing system was used to measure displacements below surface level and displacement transducers at the surface level of the models. The aim of the experimental work was to study the ground response due to simulated tunnel construction and to analyse how the vault stiff inclusions affect tunnel stability. According to the principle of the upper bound theorem of plastic limit analysis, a collapse mechanism of the single circular tunnels with embedded forepoles in cohesive soil was established. An upper bound equation of stability ratio was obtained. The upper bound solutions of stability ratio under different soil cover above the tunnel, undrained shear strength at tunnel axis level and embedded forepoles range were discussed from the equation. In the end，the correctness of the upper bound solutions was proved by the results of centrifugal model tests.

Abstract:Accurately predicting the residual displacement of reinforced concrete (RC) structures after an earthquake is of great significance in post-earthquake structural performance evaluation and control. To study the residual deformation of the structure, seismic time-history responses of single degree-of-freedom (SDOF) systems with different parameters were analyzed. Based on the analytical results, simplified models for estimating the likely residual deformations of structures characterized by Takeda and Kinematic hysteretic models were proposed respectively, and the residual deformation was found to be sensitive to hysteretic characteristics, stiffness ratio of structures, peak ground acceleration (PGA), as well as maximum elasto-plastic deformation. A case study for RC single-column bridge pier was provided to illustrate the process of residual deformation calculation and post-earthquake performance evaluation by using the proposed methods. Calculation results indicate that the residual deformation of the single-column pier characterized by the Takeda model often is much larger than that of columns characterized by the Kinematic model.

Abstract:In order to ensure the function of building in the earthquake, reduce economic losses and facilitate post-disaster relief, it is necessary to accurately evaluate the seismic performance of pipeline system on the structure under seismic excitation. Considering this practical need, seismic response calculation methods of piping systems on structures were systematically studied. Firstly, theoretical derivation was performed based on the pseudo-excitation method for seismic response of pipeline system. It is found that the formula in previous studies has obvious defect: the accurate relative displacement values of degree of freedom near the supports can not be obtained in the formula. Thereby, the theoretical basis for derivation was mended to correct the defect, and the uniform combination expressions available for pipeline's seismic response calculation which is in the form of ground response spectrum or floor response spectrum were presented. Moreover, the simplified formulas and calculation method of correlation coefficients in the obtained expressions were put forward according to the assumption of white noise earthquake excitation. Finally, case studies were adopted to verify the proposed method's effectiveness and applicability in the seismic response calculation of pipeline system.

Abstract:The cable's motion was modeled by a spring-mass-damper system. The flow field was calculated by RSM combined with the enhanced wall function model and the vibration equation of the cable was solved by the Four Step Runge-Kutta Algorithm, which was written into FLUENT software to be analyzed. It was adopted to analyse the factors influencing vortex-induced vibration of submerged floating tunnel cable, such as mass ratio, damping ratio of the cable and whether to consider streamline movement. The main conclusion included: mass ratio has little influence on the transverse vortex induced vibration amplitude of the cable, but has a big influence on the region of the reduced velocity; damping ratio almost has little influence on the region of the reduced velocity of cable's viv, but has an influence on the cable's vibration amplitude significantly; In the case of low-mass ratio, considered the impact of the cable streamline movement, the transverse vortex-induced vibration amplitude is bigger than not considered the case.

Abstract:The problems rendered from the conventional time marching, referring to stepwise time marching scheme (STMS) adopted in boundary element method (BEM) for chloride diffusion in concrete structures, were investigated, and a new time marching, referring to initial time marching scheme (ITMS) in BEM, was developed for evaluation of service life of the concrete structures under chloride environment. Results of the numerical examples show that the ITMS-BEM proposed can eliminate domain integral and simplify the computational model, so that the stability in iteration process can be improved, resulting in better efficiency and accuracy, compared with the STMS-BEM. It can also be concluded that the dimensions of the diffusion of chloride can affect the service life of the concrete structure significantly, which should be taken into account in structural design.

Abstract:Based on the twin shear unified strength theory which considers the influence of intermediate principal stress and the strength-differential of materials，the mechanical behavior of concrete-filled steel tube(CFST) short column is investigated. Whilst considering the influence of slenderness ratio， unified solution of ultimate bearing capacity for CFST column with initial stress under axial compression is developed. Through comparing the results of proposed formula with that of experiments，the rationality of proposed formula is proved. Furthermore，according to the investigation，a new influence coefficient of initial stress is deduced. The results can provide some theoretical references for the study of CFST columns considered the effect of initial stress. And the solution may have some important practical value.

Abstract:There are subjective uncertainty and randomness in concrete carbonation depth forecasting model and the model distribution parameters, which cause significant errors in application to practical engineering. Actual inspection data can not often be used to forecast concrete carbonation depth in the actual project due to its small sample size and lack of sufficient completeness. The weighted value of several model calculations was used to forecast the concrete carbonation depth. By using Bayesian approach, the inspection information and the prior prediction model were incorporated, and the prior model weights and model distribution parameters statistics were updated. It is more accurate to forecast the carbonation depth using the updated model weights and model distribution parameters. The procedure for updating the mechanical model selection and distribution parameter statistics was illustrated with a 10-year-long concrete carbonation test.

Abstract:A three-span regular continuous RC girder highway bridge and two bins of real accelerograms were selected for incremental dynamic analysis to study the correlation of the dispersions of response spectra of earthquake ground motions and probabilistic seismic demand assessments of bridge structures. It is found that the dispersions of seismic demands are closely related to the dispersions of response spectra of selected ground motions. The rational selection of real earthquake ground motions to be rationally chosen for dynamic analysis can make the probability distribution of seismic demands in accordance with the real situation and improve the computational precision and efficiency of the probabilistic seismic demand assessment and fragility curve for performance-based earthquake engineering and seismic design of bridges based on probability theory.

Abstract:Axial bearing capacity of three times cold-formed thin-walled lipped channel short column with holes was studied and calculated by finite element software ANSYS. The comparative analysis was carried out to the ANSYS, Chinese code and North America code to make out the influence of hole on the bearing capacity of the column. The results show that distortional buckling appears in the failure mode of axial compression column. Effective width method in Chinese code indirectly considers the impact of distortional buckling, and it has a good agreement with the results of North America code. Holes obviously decrease the axial bearing capacity of the column, and the variation is not according with conventional axial compression member. Opening reduction to the carrying capacity of three times cold-formed thin-walled lipped channel should be emphasised in design. Reduction factor can be taken as K=2.41×10 -5λ 2-3.78×10 -3λ+9.59×10 -2 to cross-section of the article.

Abstract:The shear tests were conducted on 18 different groups of deep beams with steel fiber and polypropylene fiber and two groups high performance concrete deep beams without fiber according to the orthogonal experimental design. By a definition of shear ductility index shear ductility of deep beams was analyzed quantitatively. The influence of six factors on improving shear ductility of deep beams was compared by direct-viewing analysis of the orthogonal experiment. The contributory factors such as the species of steel fiber, the volume fraction of steel fiber, the length/diameter aspect ratio of steel fiber, the volume fraction of polypropylene fiber, the ratio of web horizontal reinforcement and the ratio of web vertical reinforcement were analyzed. Results show that the volume fraction of steel fiber plays the most important role in improving shear ductility of deep beams exceeding the ratio of web horizontal reinforcement and the ratio of web vertical reinforcement, whereas species of steel fiber has minimum effect. Hybrid fiber can be used to greatly increase shear ductility of deep beams and shear ductility is at the most increased by 40.7% although it can not change the brittleness of shear damage. The full-range shear behaviors of deep beams through ABAQUS are analyzed and the calculated results are in good agreement with test results.

Abstract:Based on the fact that existing bend component is tend to produce inflection point on the steel strand by its small radius, the experiment is designed to study the influence of steel strand mechanical properties by bend component with specific radius R and bending angle θ. The law and mechanism of ultimate strength, ductility of steel strand and prestressing loss due to friction affected by R and θ is analyzed detailly. The results show that the radius of bend component should be as large as possible to improve the mechanical property of steel strand, and it shouldn't less than 100mm when the size is limited. In addition, the uniform calculating formulas of prestressing loss due to friction is presented based on experiment data, which take the affection factor of R into account.

Abstract:The space of mountain center city has diversified characteristics, which has interactive relations with the city overall function. Based on analyzing the contradictions between the characteristics of central city and the form of mountainous city, following the mountainous central cities' characteristics of multi-group, multi-center, multi-dimensional and multi-level, the theoretical model which reflects mathematic and abstract relationship between the characteristics and the overall function of the mountainous central cities was constructed. On the basis of the mountainous cities' characteristics and the scientific planning, the model develops the mountainous cities space and macro-functions theory.

Abstract:A new composite coagulant polymeric aluminum ferric sulfate (PAFS) was synthesized using FeSO4·7H2O and Al2(SO4)3 (industrial) by the direct oxidation method. The optimization of preparation process of PAFS was investigated using single factor and response surface methodology based on Box-Behnken central design. Parameters affecting the coagulant performance, such as reaction temperature, time, SO4 2-/Fe, NO3 -/Fe, Al/Fe, PO4 3-/Fe, and OH/Fe molar ratios were examined. The results show that when temperature, time, SO4 2-/Fe, NO3 -/Fe, Al/Fe, PO4 3-/Fe, and OH/Fe molar ratios were 84℃, 48 min, 0.38, 0.47, 0.11, 0.14, 0.03, respectively, it is the optimum conditions for synthesis. In this condition TP removal was 98.67%, and the experimental results were in good agreement with the predicted values of the model equation with 0.38% deviation. Furthermore, COD (chemical oxygen demand) and turbidity removal efficiency were 79.13% and 98.12%, respectively.

Abstract:Taking cement as primary raw material, a porous hardened cement paste synthetic filter material was prepared by steam curing in a reaction kettle. The optimum process combination condition of the filter material was determined. By orthogonal experiment, the optimal combinations of technical conditions were determined: water-solid ratio is 0.25, and pore-forming agent/cement equals to 0.3 with steaming temperature at 180°C in the reaction kettle for 4 h. Effects of pH value, dosing quantity and the initial concentration of phosphorus on phosphorus removal by using the filter materials which prepared under the optimal conditions were tested. The results show that the phosphorus removal rate reaches all above 95.3% and the highest one is 99.8% when the initial concentration of phosphorus is 5~10 mg·L -1. When the amount of filter material is added 2.5 g/100 mL, under the experimental condition of pH neutral, the top phosphorus removal rate reaches 89.6% when the concentration is 50 mg·L -1. The analysis of adsorption kinetic process shows that the pseudo-second-order kinetic is fitted to the adsorption characteristics of filter material and the adsorption rate is controlled by the intra-particle diffusion.

Abstract:The settling property, COD removal rate, Ca 2+ retention rate, variations of biofacies and the effect of sludge reduction of the high hardness wastewater of the activated sludge process by adding green and safe scale inhibitor PESA (Polyepoxysuccinic Acid) during the experiment have been studied for the COD was 100～300 mg/L, calcium concentration was 110～280 mg/L of the high hardness of wastewater. The results show that MLSS was less than the ordinary activated sludge reactor, the content of the inorganic substrate in activated sludge was significantly reduced and resulted in the decrease of calcium activated sludge putout, the reduction reached to 41.33%, The purpose of calcium wastewater treatment sludge reduction was achieved.The COD removal rate of PESA activated sludge reactor reached above 90%, the Ca 2+ retention rate reached above 80%. PESA inhibits the sedimentation of a part of calcium salt in activated sludge surface, bioactivity was kept well, and in this concentration range, indicative microbial were able to grow and reproduce. The ability to resist impact load has been enhanced in high hardness water, sludge age extension.

Abstract:In order to analyze the hydraulic characteristics of the leaky water distribution system (WDS) caused by earthquake, the method to calculate the leakage flow of WDS in a possible earthquake was improved by introducing the formula suggested by Japan Water Works Association (JWWA) to calculate the failure probability of pipes in an earthquake, and the hydraulic model for leaky WDS caused by earthquake was established. A novel method of hydraulic calculation named “two-step iteration” was developed specially to simulate the WDS with deficient operating pressure, so as to realize the quantitative analysis of leakage flow, pressure and flow of WDS in different earthquake intensities. Finally, the proposed model and method were implemented to predict the performance of a sample networks in different earthquake intensities based on the EPANET software. The prediction results indicate that the proposed model can describe the hydraulic characteristics of damaged WDS in a possible earthquake reasonably; the presented method can avoid the iteration divergence and improve the rate of iteration convergence in the process of hydraulic calculation. Furthermore, the model can be solved by the existing calculation software directly.

Abstract:By adding small amount of dihydrate gypsum (CaSO4·2H2O) and silica fume in steel slag-cement system, steel slag-cement binding materials were prepared. And the dosage of CaSO4·2H2O and silica fume on the properties of steel slag-cement binding materials was studied. Hydration properties and paste structure were investigated by SEM and XRD. The results show that both CaSO4·2H2O and silica fume can improve the strength of steel slag-cement binding materials. Compared with single-doped, compound of CaSO4·2H2O and silica fume has much better effect on strength of steel slag-cement binding materials. The optimum proportion of CaSO4·2H2O and silica fume are 1% and 4%, respectively. The 3 d compressive strength is increased by 59.0%, and the 28 d compressive strength is increased by 36.5%. No matter adding CaSO4·2H2O and silica fume or not, the steel slag-cement binding materials have the same hydration products. However, the content of C-S-H gel and AFt crystals is higher, and the content of Ca(OH)2 crystals is lower in steel slag-cement binding materials containing CaSO4·2H2O and silica fume than those in steel slag-cement binding materials without CaSO4·2H2O and silica fume.

Abstract:Strength properties and permeability of the self-compacting concrete, which are reinforced with polypropylene monofilament fiber of different volume fractions, were investigated through mechanical test, water permeability test and chloride permeability test (chloride penetrability based on charge passed). Then, the microstructure of the polypropylene fiber reinforced self-compacting concrete (PFRSCC) was observed through scanning electronic microscope. The impact of polypropylene fiber on strength properties and permeability was analyzed according to the material composition and fracture theory. The results show that: 1) PFRSCC, when the volume fraction of polypropylene monofilament fiber is less than 0.15%, has good impermeability, characterized with high impermeability mark (＞S 35, based on Chinese Standard Test Method T 0568-2005); 2) When the volume fraction of polypropylene monofilament fiber is less than 0.10%, PFRSCC’s strength properties and water impermeability increase with the addition of polypropylene fiber, and electric flux increases slightly. Whilse when the volume fraction of polypropylene fiber is higher than 0.15%, electric flux increases dramatically; 3) Compared with ordinary self-compacting concrete, PFRSCC, 0.10% polypropylene fiber has 16.4% increase in flexural tensile strength, 13.4% increase in splitting strength and 57% decrease in permeation depth, and chloride ion penetrability is low, about 919 C at 56 d.

Abstract:A method of orthogonal test was used to optimize the strength of the cementitious material for preparing the concrete of high-strength artifical reefs.The results show that with the ratio of iron slag:steel slag=7:1,and when 10% cement clinker and 10% gypsum of Flue Gas Desulfurization Waste (FGDW) was mixed with 80% iron and steel slags powder,the mixed cementitious material had an optimized strength.The optimized specific surface area are 480 m 2/kg and 550 m 2/kg for iron slag and steel slag powder respectively.The ordinary portland cement can be totally substituted by such a mixed cementitious material with iron and steel slags as its major components in preparing the concrete for building high-strength artificial reefs.A concrete with a compressive strengh over 65MPa can be prepared by using such a mixture as a cementitious material and steel slag grains as its fine and coarse aggregats which have been stubilized by a hot-simmering method. Hydration processes of net slurry were analysized by XRD and SEM methods. The results show that the hydration products in the system are mainly AFt and C-S-H gel. The results also show that the pozzolanic reaction of iron slags could be largely promoted by the coordinations of steel slags,clinker and FGDW.

Abstract:Due to their enhanced cost-effectiveness and efficiency over traditional borehole exchangers, energy piles are increasingly used in Ground Sourced Heat Pump (GSHP) projects. In this paper, the structural characteristics of these two types of heat exchangers and their heat transfer mechanism were discussed firstly. The thermal response tests (TRT) were performed on two testing energy piles in one GSHP project in Nanjing, China. The TRT results were then used to verify the numerical simulations, which suggests that the heat exchange performance of energy piles is superior to that of the traditional borehole exchangers. Meanwhile, the numerical simulation method used in this paper was considered applicable to the optimization design of ground heat exchangers in GSHP system.

Abstract:The administrator boundaries in room were modeled by digital filters of complex impedance in finite-difference time-domain (FDTD) method. Doors, windows and walls were described respectively by their complex impedance boundaries with digital filters. Impulse responses in a room were calculated with the FDTD model, and typical room acoustics parameters were obtained from the responses. The high correlation coefficients between the calculated and measured impulse responses and the good agreement in acoustic parameters show that sound field in room can be properly simulated by this FDTD model.

Abstract:Five color temperature LEDs were compared to traditional light sources (HPS and MH) under three lighting levels and negative contrasts to study the effect of light sources color on tunnel lighting. Through the experiment of reaction times, the relation between light sources color and reaction times, and the relation between light sources color and pupil size were studied, respectively. The experiment result shows that visual performance and cirtopic with high color temperature LED are the most significant under high lighting level. The visual performance and cirtopic with middle color temperature LED are the most significant under mesopic lighting level. It is shown that comprehensive influence of light sources color on visual performance and cirtopic must be considered for choosing appropriate light sources in different sections of tunnel lighting.