Abstract:Gravity shear ratio and slab reinforcement ratio were adopted as the two test variables of competitive experiment to study the failure process of interior slab-column connections by means of 4 specimens. The formation and development of inner shear crack were monitored by using a special strain measuring rod during the experiment. The test results showed that the failure pattern of specimens was related to both gravity shear ratio and slab reinforcement ratio; unbalanced moment bearing capacity of the same gravity shear ratio specimens could be improved effectively by increasing reinforcement ratio; the inner shear crack had been generated before punching shear failure happened, and developed from the compression zone nearing the column to the tension zone locating at the bottom of slab. Based on the results in this study and current test data, the calculation method based on eccentric shear stress model which was adopted by GB50010—2010 was compared with the one used by Eurocode2-04, and the reasons for the shortcomings of eccentric shear stress model were analyzed.

Abstract:Based on Code for design of concrete structures (GB 50010—2010),six knee joints with HRB500 rebars on top story of reinforced concrete frame structure were designed and tests on their seismic behavior were conducted under reversed cyclic loading. The effectiveness of code provisions on seismic detailing of such knee joints of reinforced concrete frame was revealed. Mechanic properties, failure modes and comprehensive seismic performance of these top story knee joints reinforced with 500 MPa rebars was analyzed. Furthermore, these joints were compared with those similar joints reinforced with 335 MPa rebars. Different ductility index were used to discuss difference of ductility of joints reinforced with different strength rebars to provide reliable evidence for the application of 500 MPa rebars in the joints.

Abstract:The earthquake ground motion is non-stationary, and the dynamic reliability of the connected structure with different locations of connector is investigated using pseudo excitation method. The stiffness degradation of Bouc-Wen model is used to simulate the hysteresis of the tower structure, and the nonlinear motion equation of the connected structure is established. The system response for each moment is calculated by mixed precise integration method and the time-history variance of the structure under non-stationary earthquake excitation is obtained. Based on the first passage criterion and Markov assumption, the connected structure reliability are calculated. As a result, the random earthquake response and dynamic reliability of tall double-tower linked with strong connected structure subjected to 8 degree rare earthquakes are analyzed on base of those theories. The results show that the tower displacement responses are non-stationary under the earthquakes, and the change of connector location has a significant impact on the random seismic response and dynamic reliability of the strong connected structure.

Abstract:Corrosion pit is the main cause of mechanical performance degradation for the cable of cable-supported bridge.Considering corrosion pits andwith the safety factor of cable under load less than 2.5 as failure criterion， the method for assessing the safety capability for cable was established based on equivalent crack for corrosion pit and fracture mechanics. The Yuanzhou bridge wire corrosion rate data was taken to perform the parameter sensitivity analysis., The quantity of broken wires when cable failed and the time with safety coefficient less than 2.5 were studied. The results showed that this method could predict wire fracture number and the time with safety coefficient less than 2.5 and compared with uniform corrosion theory model, this mehtod provided theoretical reference for cable-supported bridge operation and maintenance.

Abstract:In order to determine the reasonable lateral seismic constraint system of cable-stayed bridge under strong earthquake, the nonlinear time history analysis method was used to analyze the seismic responses of long-span bridge with four lateral connection systems based on the Ke-Ke-da-la bridge . The impact of four constraint systems including transverse sliding system,fixed system,and seismic isolation system adding displacement dependent and velocity-related type on the yield load of steel dampers and the viscous dam-per position and relevant parameters were investigated and the seismic responses were compared with other systems. The results indicated that ,for large span bridge, the transverse sliding system and whole limit system were not ideal seismic system under the action of earthquake; seismic isolation device could significantly reduce the bottom of the pier and the tower seismic shear force and bending moment.However, in typical circumstance, transverse steel damping device was superior to the viscous dampers between tower and beam.

Abstract:In order to understand the cables forces and girder forces state of concrete cable-stayed bridge before the cable replacement construction, and to establish the analysis model of the bridge，the influence factors such as concrete creep & shrinkage, stress relaxation of prestressing tendons, element damage, overload of dead need to be evaluated . Creep, relaxation and shrinkage are closely associated with the material nonlinearity which dependent on time and stress history so it’s reasonable to adopt the finite element analysis technology based on elastic-plastic incremental load method. Based on the specified time intervals, the incremental elastic-plastic finite element equilibrium equation is deduced which includes the effect of creep, relaxation and shrinkage. For the time increment step, numeric expressions of creep, shrinkage and stress relaxation are established for beam element. Methods are proposed to analyze the influence of stay-cables damage and overload of dead. The methods will improve the structure state analysis techniques for the concrete cable-stayed bridge in service period.

Abstract:Based on the theory of chloride diffusion and pore fractal theory a new model is proposed on the base that the sinuosity of chloride diffusion characterized by the axis fractal dimension of the small pore and the porosity of concrete modified by the surface fractal dimension of large pore. The model was applied to analyze 14 d and 28 d age concrete with different proportions and the results, showed a linear relationship with those of he Coulomb electric charge determined by The Rapid Chloride Permeability Test (RCPT)—American Society of Testing and Materials (ASTM) test method C1202. The Chloride diffusion coefficient modified by pore fractal theory was presented in this study. Two different chloride concentrations in different depths of concrete were calculated by modified Chloride diffusion coefficient and orthodox Chloride diffusion coefficient. The comparison between two different Chloride diffusion coefficient indicated that the chloride concentration calculated by modified Chloride diffusion coefficient agreed better with the measured chloride concentration.

Abstract:Based on the revised Fick's second law, a chloride diffusion model was established for bonded strengthened concrete. The influence of bonded reinforcement was considered as change of boundary conditions. This model could be applied to predict chloride diffusion in both non-strengthened and strengthen concrete. Numerical simulation of chloride diffusion in a reinforced concrete beam strengthened by externally bonding was carried out by ABAQUS, MATLAB PDE tool, MATLAB programming. Comparison of chloride diffusion in strengthened and non-strengthened specimens was conducted. The simulation results showed the service life of RC specimens could be extended by bonding externally.

Abstract:Without comprehensive consideration of the strength parameters statistical properties, the slope reliability index calculation value become smaller and the failure probability become larger, often more than 10%, which was difficult to adopt in design.Hence, the foundation reliability norm’s formulate and implement made slow progress. Take a completely weathered granite soil slope of an expressway as engineering background, and based on the analysis of the statistical characteristics of soil parameters, the limit equilibrium theory and monte carlo simulation method were used to systematically analyze the soil strength parameters’ mean uncertainty, variability, correlation and interval characteristics and spatial variability of impact on the reliability of the slope stability. The results showed that all kinds of statistical features of soil parameters had varying degrees impact on slope stability reliability. The reliability index calculation value increased with the decrease of the sampling distance, increased with the increase of the mean values of c or φ, decreased with the increase of the variation coefficientc and φ, increased with the increase of the correlation coefficient absolute value of c and φ, and the reliability index calculation value became obvious bigger when interval characteristics were considered. The findings indicated that variability was adverse to the slope stability and the correlation, interval characteristics and spatial variability were good for the slope stability. Therefore, with accurate and comprehensive consideration of the soil parameters statistical features, especially with the consideration of space variability and interval characteristics on the basis of the consideration of parameters variability and correlation will be more in line with the engineering practice, and the calculation results tend to be more reliable. It is advantageous to the adopt reliability norm and safety evaluation of slope engineering.

Abstract:Traditional limit equilibrium methods of slope stability fails to consider the influence of soil strength indexes variability. Based on probability analysis principle of limit state, Monte-Carlo method is used to calculate the reliability of stability of homogeneous embankment slope. And with constant safety coefficient, changes of slope failure possibility with different levels of soil strength indexes are studied. The corresponding relationship between safety coefficient and reliability index of the slope and changes of safety factor with variation levels of soil strength indexes are analyzed. Results show that: the slope reliability is affected by soil strength indexes variability significantly, indicating sharp decreases with increase of soil strength indexes variation levels; in order to get the slope the identical reliability, safety coefficient should be changed according to soil strength indexes variability. The safety coefficient should be changed according to reliability index and soil strength indexes variation levels and based on which three parameters function is put forward.

Abstract:In the self-balanced pile test in the deep excavation, effective measures are taken to eliminate the side friction effect after excavation. The unloading of deep overburden excavation caused decrease in soil confining pressure surrounding engineering pile and as a result reduce of the upper load box pile pullout capacity. Based on the additional correlation analysis method, the negative friction, base and relevant soil mechanics theory, a simplified analysis method of Mindlin and negative friction-additional stress solutions are proposed. The column pile in a subway station in Beijing is studied to estimate the loss of upper pile bearing capacity caused by deep excavation soil unloading. The results of the two methods show significant difference and the reasons are discussed. The applicability and accuracy of the two simplified analysis methods require further study..

Abstract:Aiming at the test results of shear band angle under plane strain conditions for anisotropy sand, a comparative analysis was carried out based on the three traditional theories and bifurcation theory. The results of shear band under plane strain condition described by the three traditional theories showed the traditional theories could estimate the minimum, middle and maximum values of the shear band angle of sand, whilst it could not t explain the anisotropy behaviors of shear band. The shear band under the plane strain conditions was easily observed, and it induced shear bands that reduced material strength when the directions of shear band and sand deposition were the same. It resulted in the different anisotropy characteristics in the conventional triaxial conditions and plane strain conditions. Such different characteristics could be explained using bifurcation theory together with anisotropy model. With the direction variation of sand deposition, the model ccould explain the monotonic behaviors of shear angled under conventional triaxial condition from microscopic viewpoint, the bifurcation theory combined with the model could describe the behavior of shear angled under plane strain condition which decreased first and then increased. The comparative analysis of four theories showed that bifurcation theory together with anisotropic model well explained the different shear properties between plane strain and conventional triaxial under various stress conditions, and one could well explain it from the microscopic viewpoint.

Abstract:Both water content and stress influence the deformation of unsaturated soils. Although the formula established by introducing water content to the unsaturated soil calculation model is empirical formula, it is extremely intuitive, and important to develop further. Based on the relation of test parameters of harden curve and water contents, and the relation of secant modulus of harden curve and water content, two approaches where water content is taken account of are established. Experiment is conducted to present the realizing processes of two methods, and the models are also verified. The results show that the results of the two methods both agree with test data very well. and the results of method one are smaller than those of method two.

Abstract:Burst is one of the main disasters in the foundation pit engineering. However, the current methods for analyzing burst stability of the foundation pit on confined water could not reflect the failure mechanism. According to mechanism of hydro-fracturing, the seepage-stress coupling should be considered when burst is studied. The coupling model for the foundation pit burst in hydro-fracturing process is established based on Biot's consolidation theory, and the dynamic evolution of soils permeability and mechanical characteristic are considered. The possibility of burst is explored by analyzing the change of stress field and seepage field during the excavation process. The results show that burst begins in tension failure in aquiclude of foundation base, whilst the periphery of foundation base is where more likely burst occurs;hydro-fracturing caused by water wedge effect of weak surface infiltration (it is the initial tension crack) provides the channel for burst and a confined bed with high pore water pressure is the precondition for burst, but high hydraulic gradient is the root cause for burst.

Abstract:The majority of underground cemented soil projects contact with underground corrosive medium environment directly, which will lead to the deterioration of cemented soil material gradually or even failure. The discharged polluted water from the open channel near construction site is used as a kind of corrosive medium to produce test pieces of cemented soil with different cement content. In both polluted water environment and clean water environment, the compressive strength and shear strength of cemented soil with different cement content and different ages are compared. The results show that when the age is 30 days, compressive strength of cemented soil with the same cement content is almost the same in polluted water environment and clean water environment. Compressive strength of cemented soil gradually increases with the increase of the age. However, the increase extent of compressive strength in polluted water environment is significantly less than that in clean water environment. After 90 days, compressive strength of cemented soil no longer increases in clean water environment, and compressive strength begins to decrease in polluted water environment. The internal friction angle and the cohesion of cemented soil gradually increase with the increase of the age and cement content in polluted water environment and clean water environment. The internal friction angle and the cohesion begin to decrease in polluted water environment after 90 days.

Abstract:The β-hemihydrate gypsum was prepared from phosphogypsum and the effects of the soluble anhydrous AⅢ were investigated. The Conventional analytical methods, TG-DSC, XRD and SEM were used to analyze and characterize the β-hemihydrate gypsum and their products. The thermal analysis results showed that two endothermic peaks in the phosphogypsum dehydration reaction, and those two peaks overlapped partly.The difference between the two peaks was only 6 ℃, which indicated that the dehydration reaction included two steps of different reactions and the β-hemihydrate gypsum existed as mixed phase structure. The optimal conditions for β-hemihydrate gypsum calcinations were 170±5℃ for 2 hours. The content of the crystal water in β-hemihydrate gypsum was about 3.0%. The properties of the gypsum powder could be improved if the content of the crystal water content changed in range of 4.8~5.2% through aging process. The highly activity and fast hydration rate of AⅢ offset the effect of the water reducing agents during the hydration of β-hemihydrate gypsum indication that AⅢ affects the performance of β-hemihydrate gypsum. The addition of water reducing agents could improve the strength of gypsum products. When 0.7% HC polycarboxylate was added, the strength of β-hemihydrate gypsumcan reached to 15.0 MPa, nearly an increase of 64.84%. When 0.7% superplasticizer-FDN was added, the strength reached to 14.8 MPa, nearly an increase of 62.64%, and when 0.7% lignin was added, the strength increased nearly by 52.75% to 13.9 MPa.

Abstract:An artificial rainfall device and a data acquisition system are designed to study the rainfall-runoff processes of an extensive green roof with matrix of 57.0% ceramsite, 41.5% peat, and 1.5% super absorbent polymer. Based on 37 times artificial rainfall tests, the fundamental processes of rainfall infiltration and runoff are illustrated. The effects of rainfall intensity, matrix depth and initially water content on the rainwater retention features are studied. The results show that the effects of matrix depth and initially water content are significant. The rainwater storage in matrix will increase with lower initially water content and higher depth. A multiple linear regression equation is presented for the delayed time of runoff. It shows that the delayed time of runoff is negative related with rainfall intensity.Meanwhile the delayed time of runoff are affected by initial water content and depth. With the increase of wetting and drying times, the matrix depth tends to decrease, the rainwater storage gradually declines, and the delayed runoff time tends to shorten.

Abstract:A questionnaire investigation was carried out on the residential heating area of northwest rural, village scales and building density. The main limiting factors of the development and the adaptabilities of concentrated solar heating in rural were analyzed. The results showed that the following factors requirements should be satisfied before concentrated solar heating was applied. Firstly, the average area required for collector installation per household was was30~40 m 2 in Xi’an, 40~50 m 2 in Lanzhou, Yinchuan, 45~60 m 2 in Urumqi, and 20~30 m 2 in Xining and Golmud, respectively. Secondly, the minimum building volume rate required was 0.38~0.41 in Xi’an, Xining and Golmud rural village, 0.27~0.31 in Lanzhou, Yinchuan, and Urumqi, respectively. However, the questionnaire investigation of current situation in northwest rural showed that more than 80% of the villages in Xi’an and Lanzhou failed to provide enough space for concentrated heating. Less than 30% of the village had building volume rate that met the requirement. of conditions.