Abstract:Based on the review of domestic and foreign researches on the shear failure mechanism of slender reinforced concrete beams without shear reinforcement, the basic assumptions, the key points and the calculation methods for shear strength of different models were introduced and commented, such as the modified compression field theory, the critical shear crack theory, the plasticity theory, the compressive force path theory, the splitting failure theory and the strain based shear strength model. Using the test data from the related experimental programs and the ACI-DAfStb shear database of slender beams, impact assessments of important design parameters and statistical evaluations were conducted on the calculation methods for shear strength of different models. Some points of view on expectation of shear failure were presented. The results showed that the absences of direct experimental proofs of some hypotheses were apparent and different opinions on the shear transfer contribution of diagonal tension (splitting), shear (aggregate interlock) and the flexural compression zone were the main divergence of the shear transfer mechanism. Further improvements in the rationality of the considerations for different factors and the accuracy of the calculation methods for shear strength were essential. In subsequent research work, the random and physical characteristics of shear failure should be considered synthetically. Advanced testing technology and analysis of the evolution of the stress field can be utilized in revealing the mechanism of shear failure.

Abstract:The study of rock fragmentation mechanism by TBM cutters is the key to guide the development of TBM cutterhead and the selection of cutterhead in different geological conditions. The formation, propagation and coalescence of cracks in rock masse is the precondition of understanding the rock fragmentation mechanism by TBM cutters. Therefore, the study of rock fragmentation mechanism by TBM cutters is significant for engineering application. At present, the study of rock fragmentation mechanism mainly concentrates on the single rock. However, the complicated geological conditions are often encountered during the excavation of tunnels by TBM. In this paper, a discrete element method is employed to study the fragmentation mechanism of the composite rock mass. It could be obtained from the numerical results that the propagation of microcracks initiated from the interface leads to the coalescence of Hertzian cracks between two cutters, and the formation of chipping. Therefore, under certain conditions, the formation of chipping in composite rock mass by TBM becomes easier than that in the single rock.

Abstract:Based on the unified strength theory and the influences of intermediate principal stress and the material of tension and compression ratio were considered when coming down to the ultimate bearing capacity of square steel tube-reinforced high strength concrete column. Effective constraint coefficient and ineffective constraint coefficient were introduced to consider the different constraint functions of concrete derived from the stirrups, the constraint concrete outside steel tube was divided into effective constraint region and ineffective constraint region. The square section was equivalent to circular section to consider the double constraint function to concrete in steel tube derived from steel tube and outer steel reinforced concrete. Then a new method for the axial ultimate bearing capacity of square steel tube-reinforced concrete column was deduced. The results were in good agreement with the experimental results and the correctness of the theory formulae was proved. Influential effects of some parameters were analyzed and the analysis results showed that the ultimate bearing capacity of square steel tube-reinforced high strength concrete column increased with the increase of the side pressure coefficient. Influence coefficient of intermediate principal stress, the material of tension and compression ratio and the longitudinal reinforcement ratio, while it decreases with the increase of radius-thickness ratio.

Abstract:Combined with "Ying Zao Fa Shi", the size of the four type of song dynasty wooden components and related contents in the design of the roof are introduced. On the basis of the facts that the weight of roof became heavier because of rain and snow, a method of calculating the weight of the roof was proposed under different cases considering construction and using period. The simplified method of working condition combined with the calculation results was put forward. The relationship between yellow pine and larchen had been clear. There was a corresponding relationship in the load effect between the various modular. The results would provide reference for calculating similar wooden roof weight, and further exploring the similarity relation in CaiFen system and model tests.

Abstract:Shear connectors are the important detailings affecting the mechanical properties of GFRP-concrete composite beams/decks. Rectangular rib and T-type rib GFRP shear connectors are put forward to improve the interfacial bond properties between GFRP and concrete. Eight push-out tests are conducted to evaluate the mechanical behaviors of two rectangular perforated rib GFRP shear connectors and three T-type perforated rib GFRP shear connectors, as well as three T-type rib GFRP shear connectors. The failure patterns, ultimate bearing capacities, load-slip behaviors and load-strain regularities are obtained by contrast tests. Results show that T-type perforated rib GFRP shear connectors show higher strength and better ductility than rectangular perforated rib GFRP shear connectors, and T-type perforated rib GFRP shear connectors show higher strength and better ductility than T-type rib GFRP shear connectors. An empirical equation to predict the ultimate shear resistance is proposed and validated by the experimental data. Idealized load-lip models and equations to predict the load versus slip relationship for all specimens are proposed. Curve fittings are performed to find fitting parameters for all tested specimens and the results show a very good correlation with those of the experiments. An empirical equation to predict the shear rigidity is proposed.

Abstract:Settlement of soil around the foundation pit caused by dewatering, deformation of retaining structure and foundation pit uplift are considered to be the three factors causing ground surface settlement. Using layer-wise summation method to calculate the settlement of surrounding soils caused by dewatering according to the soil settlement mechanism of dewatering. By studying the law of the settlement of the soil caused by the foundation pit excavation, the theoretical formula for the settlement of the soil caused by the foundation pit excavation is deduced. Add up the subsidence caused by the foundation pit precipitation and the settlement caused by the excavation of foundation pit, and revise the results with Modified coefficient, eventually the settlement of soil around the foundation pit is reasonably calculated by the simplified theoretical formula. Through specific engineering verification shows that the derived theory analytical solution is very close to the measured data, the derived theory analytical solution can effectively predict the soil settlement around the foundation pit, thereby this will provides the reliable theory basis for the main body of the construction scheme, to reduce as much as possible the effect on the surrounding environment.

Abstract:Explicit dynamic finite element program ANSYS/LS-DYNA is adopted. According to the method of fluid-structure interaction, profiled steel-concrete composite slab is simulated under near explosion in different conditions. And the stress form, the dynamic responses and failure process were analysed. Numerical analysis results show that the largest displacement of composite floor slab can be significantly reduced with increasing the thickness of the concrete and improve the strength of the steel plate. The ductility and anti-explosion performance of composite floor slab can be improved. The anti-explosion performance of composite floor slab has less effect by changing reinforced spacing. The reference and basis can be provided for antiknock design of profiled steel-concrete composite slab.

Abstract:WD displacement sensor with a range of ±500mm is developed in order to measure large horizontal displacement. And the parameters analysis of WD displacement sensor are carried on using the orthogonal test method. The strain-displacement relationship of sensor is obtained. Six static parameters of WD displacement sensor are calculated. The experimental results showed that WD displacement sensor could measure the non-linear large displacement which is difficult to be measured directly by traditional electrical resistance sensor and all the static parameters are in good condition.

Abstract:Web cracking mechanism of long span rigid-frame prestressed concrete bridge construction stage was presented. Based on the elasticity theory, the 2-D stress function of web under patching load was deduced, the function curve of the horizon stress of different coefficient (d/a) was drawn, then a horizon stress function was fitted, and the method of equivalent pressure prism selection method was put forward. Later the 3-D situation horizon stress along the tendon line was considered based on 2-D horizon stress function. To verify the theory function, 0~3# rigid frame bridge segment finite element model was established, the concrete web cracking analysis was carried out in different prestressed level. The results showed that the crackling area of the web in the bridge was coincided with the finite element analyze, the lower limit stress of the finite analysis was also coincided to the theory calculated of transverse stress function put forward by this paper.

Abstract:The orthogonal design and multi-factor analysis of variance is adopted to analyze the relationship between macroparameters and microparameters of flat-jointed bonded-particle material and to establish the calibration method of microparameters. Firstly, the orthogonal design is adopted to conduct the macroparameters of flat-jointed contact model and the uniaxial compression, direct tension and biaxial compression numerical test is used to calculate the macroparameters of rock. Then multi-factor analysis of variance and regression analysis are adopted to analyze the relationship between macroparameters and microparameters. On this basis, calibration method of microparameters for rock is proposed in this paper. Based on laboratory tests of limestone, the microparameters of limestone are calibrated. The simulation results are closed to the laboratory test results, and this validated the significance of the proposed method.

Abstract:A joint plate cable foundation is established and offered patent of invention to improve the deficiencies of present widely used compression and pulling resistant foundation. Based on the study of anti-tensile mechanism of joint plate cable foundation and belled pile foundation, the ultimate uplift force that the joint plate cable foundation and belled pile foundation can bear is further analyzed. The anti-tensile mechanism of the joint plate cable foundation is revealed through comparatively studying the joint plate cable foundation and belled pile foundation. The issue of designing and verifying the joint plate cable foundation is solved by using the allowable uplift force and the stability verification equation of the belled pile foundation, which provides theoretical and technical support to the promotion of such kind of foundation.

Abstract:SEM and direct shear tests were conducted to study the influence of freeze-thaw action on the microstructure and strength of xi'an Q3 undisturbed loess under the closed system. The experimental results showed that the microstructure of loess changes significantly during the freeze-thaw process, with the number of large particles aggregate decreasing, the proportion of small particle size increasing, and the ratio of pore increasing. Based on the damage mechanics theory, the freezing-thawing damage degree versus freezing-thawing times was established. Analysis indicated that the freezing-thawing damage degree exponentially increased with the increase of freezing-thawing times, representing that the structural strength of loess can be destroyed by freezing-thawing. However, the structural strength eventually reached a residual strength value after repeated freezing and thawing. Freezing-thawing made the surface structure of soil destroyed, and had a bigger influence with the increace of water content. The cohesion exponentially decreased with freezing and thawing times increasing, and had a smaller attenuation amplitude and rate with the increase of water content. With the increase of water content, the cohesion linearly decreased, and had an approximately same variation after freezing and thawing. The internal friction angle had no obvious variation during the whole freezing-thawing process. The freezing-thawing damage coefficient of cohesion exponentially increased with the increase of freezing-thawing times, and also increased with water content increasing. A cohesion strength deterioration model was developed based on the laboratory test results, and the model can be used to well describe the strength deterioration regularity by the test verification.

Abstract:Static test and finite element analysis of high strength cold-formed thin-walled channel flexural members with three types of stiffeners in the flanges and the web were conducted respectively to investigate the mechanical properties and design method of G550 high strength cold-formed thin-walled channel flexural members. The results showed that stiffener type had a significant effect on the member's bending strength and buckling modes. V type stiffeners in the flanges could increase the bending strength more significantly than V type stiffeners in the web. The change law of the bending strength was related to the buckling mode. Based on the existing direct strength method (DSM) formulas as standard, the revised DSM formulas of high strength cold-formed thin-walled channel flexural members were established according to finite element analysis results.

Abstract:Grouting pressure is down-hole pressure on the crack of grouting hole. Due to the constraints of grouting art, the grouting pressure is presented by the pressure of up-section of pipe, which produces measurement error of grouting pressure. the fluid flow model of grouting pipe for numerical computing is constructed, and orthogonal experimental method to analysis the error of grouting pressure influenced by cement grout ratio, grout velocity and grouting depth is adopted. And the significant factor is presented based on statistical method in different grouting conditions. The results demonstrate that grouting pressure is lower, the error of grouting pressure is bigger,and the relative error would exceed the up-bound precision of pressure sensor with 0.5%, and the measuring value must be revised. Secondly, the analysis of range results demonstrate conditions. The research results demonstrate that grouting pressure is lower,the error of grouting pressure is bigger,and the relative error would exceed the up-bound precision of pressure sensor with 0.5%, and the measuring value must be revised. Secondly, the analysis of range results demonstrate the grouting depth is the main factor of error,And the flow velocity of grouts is in sequence. The absolute error is bigger with smaller grouts ratio on the same grouting depth and flow velocity. Combining orthogonal test method and numerical computing, a computing method of grouting pressure in the grouting hole is presented.

Abstract:The effect of content of fly ash, load age and stress on the deformation and strength was investigated at early age. The results indicated that creep of FA (fly ash) concrete decreased as content of fly ash increased and the maximum reduction was 33.6% when the content was 30%. Advancing load age and magnifying stress could increase the deformation. Effect of magnifying stress on deformation was drastically, as final creep of FA concrete loaded at stress ratio of 60% exceeded that of concrete loaded at stress ratio of 20% by 277.2%. Advancing load age and magnifying stress could decrease the axial compressive strength of FA concrete after being loaded. Effect of loading stress on the strength was more obvious than loading age.

Abstract:The regularities of early age tensile creep and compressive creep and theories of calculation method for creep stress are key factors for the crack prediction and prevention. Currently, the study on concrete creep focuses on matured concrete, while for early age concrete further study is still needed. The research status, test method and creep stress calculation method of compression and tensile creep for early age concrete are summarized in detail. The results demonstrate that: (1) At present, there is no standard for the test of tensile and compressive creep for early age concrete, and the test data is relatively short. (2) The nonlinear property at low stress level for early age concrete has not been considered in the creep prediction model. (3) The nonlinear creep stress analysis method for early age concrete structures is inadequate. Based on systematically experimental research and solidification creep theory, the nonlinear creep model for early age concrete can be established. With early age tensile creep and compressive nonlinear creep stress considered, finite element simulation accuracy of early age structure should be improved.

Abstract:The difference on physiological adaptation of autonomic nervous regulation and subjective evaluation between residents of southern and northern in a neutral environment in China were studied. Using the experimental design, selection of 16 south college students and 16 north of the college students, the physiological parameters test including skin temperature, heart rate, heart rate variability (HRV), blood volume pulse(BVP), electromyography(EMG), Filling in the subjective questionnaire. The results showed that: 1) the north crowd feeling was comfortable, evaluation index was near to neutral and moderate, data was relatively concentrated compared with the south people feeling was a bit hot, evaluation data was discrete in neutral environment, but thermal comfort (TCV) (p=0.106>0.05), an acceptable level (p=0.838>0.05) were no significant differences compared with the north people; 2) The average skin temperature had significant difference (p=0.006<0.05), and the body skin temperature was significantly higher than limb skin temperature(p=0.009<0.05;p=0.043<0.05;p=0<0.05;p=0<0.05;p=0.002<0.05), limb skin temperature difference was not significant, electromyography was not significant difference (p=0.961>0.05). Heart rate value and LF/HF value of heart rate variability were both differences, but not significance(p=0.265>0.05;p=0.618>0.05). But BVP was significant difference (p=0<0.05).

Abstract:Urban construction was an important driving factor result in the urban heat island. In order to reveal the relationships between urban construction and urban heat island, taking Kaizhou District, as an example, land surface temperatures (LST) and urban construction index were extracted using ArcGIS spatial analysis tools, and the relationship between the two was analyzed in SPSS on three spatial scales: land patch, regular grid and building lot. The results showed that LST varied greatly from land use type, and the correlations between LST and urban construction index were different among three scales. On land patch scale, there were significantly negative correlations between LST and greening ratio (GR), floor area ratio (FAR) and building density (BD) respectively and there were significantly positive correlations between LST and building bottom area (BBA) and total construction area (TCA) respectively. On regular grid scales, the correlations between LST and urban construction index increased along with the increase of grid area, and almost all correlation coefficients reached maximum values on the 840-meter grid scale. The LST was negatively correlated with GR and was positively correlated with BD and FAR respectively. Then the multiple regression model was established between LST and BD and GR. On building lot scale, there were significantly positive correlations between LST and BD and FAR respectively. However, there were significantly negative correlations between LST and building floors (BF) and strong positive correlations between LST and TCA. Although, urban construction index had great influence on urban heat island, not all urban construction index were positively correlated with LST. The results implied that urban heat island intensity and its spatial distribute were also affected by other various factors including topography, local climate, urban morphology, designated function of city, urban transportation and building material and color. Furthermore, the impact of various factors on urban heat island may be a nonlinear complicated and dynamic process.

Abstract:In recent years, LED advertising screens have been widely used in cities around China. However, LED screens have induced serious chromatic light trespass problem to residential area around. 17 cases of LED advertising screens and residential buildings affected in Beijing-Tianjin region are studied to make clear influence degree and control measures of the light trespass. The survey is conducted by subjective questionnaire and objective measurement, as LED screens are tested for color coordinates and corresponding brightness range. A total of 187 valid questionnaires and 288 sets of valid test data are collected. The questionnaire and test data show that 3 factors (relative location, brightness and its variation, colors change in rotation) is the key factors of intrusive effects. The range of wavelength and their corresponding luminance ranges for chromatic lights are summarized. Finally, some design recommendations are provided concerning LED screens setting.

Abstract:Two double U-type buried tube energy piles in Xinyang region were investiguted. Long time TRT tests and temperature recovery-TPT test are conducted to simulate the operating state of energy piles under intermittent conditions. Sensors are prepared in the energy pile wall and soil, the distribution of temperature field during the operation of energy piles is measured.? The research results show energy piles in the operating process of heat transfer performs three-dimensional characteristics, the soil temperature in pile end position changes lag to the middle region of the pile body. It is hence suggested that the increace of the buried pipe in pile end position could increase energy pile heat exchange efficiency. The test results show the temperature of the soil around the pile is increased about 1℃ after temperature recovery about 25 days after the 172 h TRT, verifying the slow conduction and good heat storage of the rock and soil body. At the same time, the importance of the cold and heat imbalance of the ground source heat pump system is also predicted.