Abstract:

Abstract:The characteristics of deformation failure and stress brittle drop of granite under loading and unloading conditions are studied respectively based on two unloading stress path cases and conventional triaxial compression experiments. The experiments show that the primary deformation of rock is rebound or tension in the (main) unloading direction, but plastic deformation in the non or subunloading direction is not significant. And the curves of stressstrain after peak strength present obvious brittle. Whilst the primary deformation of rock under loading is axial pressure deformation, and plastic deformation increases with the raise of confining pressure. The fracture is characterized by strong tensile, and all tensile cracks are fully developed. Furthermore, when the rock samples are unloaded in two directions, and even normal to unloading direction, subunloading annular tensile cracks are produced. The shear fractures is obvious comparatively when confining pressure becomes higher, and it develops following tensile cracks with more microtension cracks formed in two sides along shear plane. But the fracture is characterized by shear under conventional triaxial compression with little tensile cracks; the coefficients of brittles stress drop of granite is increased with the growth of confining pressure under conventional triaxial compression and reduced under unloading. When the initial confining pressure is the same, the coefficients of brittles stress drop under unloading is less than that under loading. In SchemeⅡ, the coefficients of brittles stress drop reaches negative when initial confining pressure is up to 30 MPa, and the one （R）is RⅢ>RⅠ>RⅡ in three test cases.

Abstract:Based on Twerskys theory, with the multiple scattering of plane acoustic or electromagnetic waves by an arbitrary configuration of parallel cylinders, a new method differing from the conventional ones is developed to figure out the plane SH waves scattered by rigid piles to solve the problem of the environmental vibration isolated by pile rows. This new method eliminates the disadvantages of the single scattering hypothesis which does not consider the coherent phase relations between the waves. Also, the influence factors on screening effectiveness including the orders of scattering, the space between pilerows and separations between the adjacent piles are investigated.

Abstract:To achieve sustainable development of construction industry, the application of HRB500 reinforcement with high strength and high ductility in RC structures is being promoted in civil and structural engineering in China. But few studies focus on seismic behaviors of RC structures reinforced with HRB500 bars. In this analysis, three RC frame structures on the Zone of Fortification Intensity 8 (0.3g) in China reinforced with HRB500, HRB400 and HRB335 bars respectively, are designed confirming to the latest draft of the revising Code for the Design of Concrete Structures. Then inelastic seismic response analyses of the three frames with multiple inputs of ground motions are conducted. The seismic response rules and seismic performances of the RC frame reinforced with HRB500 bars are compared with those frames reinforced with HRB400 and HRB335 bars. The analytical results indicate that under ground motions in rare earthquake level, the maximum displacements of the frame reinforced with HRB500 bars are roughly the same as those of the frames reinforced with HRB400 and HRB335 bars, while the rotation ductility demand of elements in the former structure is smaller than those of elements in the latter structures. It is also found that the frame reinforced with HRB500 bars develops a plastic energy dissipation mechanism that is dominated by beam hinges under major earthquake, and the maximum interstorey drift of the frame can satisfy the requirement in the Code for the RC Frame Structures.

Abstract:Field test is a better way to find sensitive factors, explore movement law and get movement parameters in rockfall study. To analyze the influence of rockfall shape, size and movement patterns on its movement law, 112 rockfall field tests are implemented. Statistics of horizontal movement distance and velocity under the influence of rockfall shape, size, and rebounce time are conducted. The results show that no matter what shape rockfall is, its movement mode are limited to rolling and bouncing, and there is no apparent sliding section. And about 59% test rockfalls are intercepted by the platform of slope and roadside trench which can be selected as passive mitigation measures. The spherical, square and short cylinder rockfalls have longer horizontal movement distance, bigger faster velocity, and the same movement features. But the rectangular and sheet rockfalls have poor movement capacity, and their movement features are similar to that of the long cylinder rockfall. To sum up, the cylinder assumption for rockfall movement calculation is more realistic. The rockfalls with smaller quality have the worse movement capacity but the greater randomness. When the rockfalls roll mainly, the kinetic energy loss is serious, and both horizontal movement distance and velocity are greater when it bounces mainly. Furthermore, when rockfall collides with the slope surface, its movement parameters and direction will change dramatically.

Abstract:A new punching failure model has been developed for thinner slabs (≤120 mm thick) yet with a larger reinforcement ratio (＞085). On the assumption that the trigger of ultimate failure is the loss of dowel action caused by concrete splitting along the horizontal surface at longitudinal bar level, an equilibrium equation was established and an upperbound solution was obtained. The computation of punching shear capacity shows that for a total of 194 specimens collected, the mean and the coefficient of variation are 1072 and 0.250 respectively. As for the 116 members (out of all 194 ones) with the above character, it is found that there is little change of the mean (equal to 1017) yet an apparent decrease in the coefficient of variation (equal to 0184), which justifies the proposed hypothesis and refined mode in estimating punching resistance of such members.

Abstract:Soil arching effect is important for stabilizing the soil behind antisliding pile. The creep of soil mass will inevitably lead to the formation of soil arching, which has time effect. In this analysis, an indoor thrustpile model test is proposed. The characteristics of stress distribution in the soil and the time effect of soil arching behind antisliding pile are analyzed. The experimental data acquired by the soil pressure cells arranged along the normal direction of the thrust show that soil arching effect is enhanced with the increase of thrust.The thickness of soil arch increases with time.And the data obtained by soil pressure cells arranged along the direction of the thrust show that the horizontal soil arching effect increases and then gradually extends.The scope of stress dispersion has very large growth along the normal direction as time goes on.

Abstract:According to the structural features of three main trusses continuous platetruss composite bridge, two compositebeam methods are presented by constructing the displacement mode of compositebeam elements and deriving the stiffness matrix of compositebeam elements. The characteristic of compositebeam method one is that the bridge slab is taken as the top flange of the chord of main truss and combined with the chord of main truss to form a steelconcrete composite beam; the characteristic of compositebeam method two is that the bridge slab is taken as the top flange of longitudinal and traverse beam and form a steelconcrete composite beam with longitudinal and traverse beams. And as for the conventional platebeam composite method, the slab is characterized by forming bridge slab system with continuous isotropic sheets and longitudinal and traverse beams to bear load. Also, the comparison between theoretical results and experimental ones verifies the effectiveness of the above three methods.

Abstract:According to unsaturated soil basic theories, equilibrium moisture of clay subgrade is predicted based on the updated studies of soil suction and soil water characteristic curve. Also, the bilinearity constitutive experience model of resilient modulus of clay soil is presented by triaxial repeated loading tests in laboratory. Using abovementioned results, a prediction method of equivalent resilient modulus of clay subgrade is established by comprehensively considering subgrade moisture and stress condition. Then, based on the concrete engineering, the prediction function of equivalent resilient modulus of the clay subgrade is provided by taking ground water table and subgrade height as centers. Compared with the results of other traditional testing methods on the same test road, the new prediction method may be used in practice. The results provide new perspectives and standpoints to determine the equivalent resilient modulus mechanics features of clay subgrade structure from two aspects of equilibrium moisture and stress condition.

Abstract:From the point of view of system theory, the landslide hazard system includes two subsystems: subsystem of hazard and subsystem of stricken. The consequence of landslide hazard is based on the interaction of these two subsystems. previous studies concenerate on evaluation of landslide stability. Hence, the study of a typical element at landslide risk is focused. And a method to calculate failure probability of typical element (frame structure) at landslide risk is discussed. Furthermore, the influences of both impact force and impact resistancecapability of element at risk on failure probability are analyzed, which shows that, for each elements at risk, the landslide impact area can be divided into absolutely dangerous zone, relatively dangerous zone and absolutely safety zone. In addition, with the condition that the structure failure probability is above 50%, as the variability of impact force increases, the structure failure probability decreases; with the condition that structure failure probability is below 50%, as the variability of impact force increases, the structure failure probability also increases.

Abstract:The load carrying test for four steel plate shear walls specimens with various ratio of widththickness are carried out so as to test the failure mode and the shear strength of steel plate with trilateral constrained, and the lateral stiffness and the buckling mode are investigated in the test. The result indicates that the ratio of widththickness of steel plate exerts effects on the shearcarrying capacity and failure mode; the buckling of steel plate does not have lateral stiffness. Based on the failure mode of steel plate, the computation model of lateral performance is presented by theoretical analysis. The restraining stiffness of double angle and the bucklingrestrained stiffness of steel plate are the important design conditions. Formulae to determine the elastic lateral stiffness and the angle type is proposed, which can be used in the preliminary design of steel plate with trilateral constrained.

Abstract:Under the dynamic load of vehicle, the bridge will vibrate and radiate lowfrequency noise which is harmful to human health. A method for predicting the lowfrequency noise is proposed based on the analysis of vibration of bridge deck. The prediction includes the analysis of vehiclebridge coupling vibration considering the bridge deck and the analysis of sound radiation and propagation in the air. By taking a bridge with lowfrequency noise as example, the vibration and sound radiation of the bridge are analyzed respectively by the current method and the previous method based on the grillage model. The results show that the prediction based on the vibration of bridge deck is more accurate. Furthermore, the measures to reduce the noise of bridge are explored, and the results indicate that a smoother road surface leads to lower noise. But when the condition of road surface is up to the extremely good standard defined by ISO, the effect of reducing the roughness of surface is not significant. Also, strengthening the crossbeam in the bridgehead is a simple and effective way to reduce the lowfrequency noise of bridge.

Abstract:Considering the nonhomogeneity and anisotropy of the undrained shear strength of soft clay, the face stability of shield tunnel was studied by upperbound limit analysis, and the formula for calculating the limit support pressure was obtained. The influences of nonhomogeneity and anisotropy on the limit support pressure amplify with each other.The relationship between limit support pressure and tunnel depth also depends on the nonhomogeneity and anisotropy; the limit support pressure reaches maximum value at a certain tunnel depth when nonhomogeneity and anisotropy are strong enough. These results show the nonhomogeneity and anisotropy of clays cannot be neglected when analyzing the stability of tunnel face.

Abstract:A physiological and psychological experiment was conducted in summer, 2008 to ascertain the effect of air flow on human thermal comfort in hot summer. The statistics analysis shows that air flow makes physiological index and thermal sensation an obvious drop tendency, which is correlated to the air temperature of indoor environment. The lower the air temperature is, the greater the physiological index and the thermal comfort drop. But when the temperature is up to about 34℃, the air flow almost does not make any change to physiological index while the human sensation is still improved. These results indicate that air flow can improve human thermal comfort to some extent, but the improvement has limits. Higher air temperature, strong wind and long time exposure to wind can lead to uncomfortableness.

Abstract:The performances of energy storage modes are experimentally analyzed in the artificial environment in order to study the effect of energy storage modes for defrosting of air source heat pump with phase change energy storage. Results indicate that suction and discharge pressures are stable at 038 MPa and 165 MPa under the series energy storage mode, and suction and discharge temperatures are 6.9℃ and 75.0℃ respectively. However, the suction and discharge pressures are as low as 012 MPa and 116 MPa in parallel and single energy storage modes individually, and the discharge temperature is up to 1225℃. In addition, in series energy storage mode, the phase change material can completely change from solid to liquid in energy storage process. The temperature difference is about 18.0℃ for indoor coil, and the input power to compressor is 825W. Therefore, the system pressures and temperatures are most stable in the series energy storage mode and the time for energy storage is short, which can meet the need of defrosting energy.

Abstract:For the capillary mats using wet construction, a winter experiment designed to investigate the heat transfer performance was described, and the heat transfer performance analysis which contains the comparisons between different pipe space and different thickness of cement mortar surface was carried out. As a result, compared with that of the traditional radiant heating pipes, the capillary mats of wet construction require supply water with lower temperature, and it shows good heat transfer performance and system energy efficiency as well. According to the demand of indoor heat dissipation and human comfort as well as the coupling relationship between the temperature of supply water and surface construction thickness, it is suggested that the proper construction method should be comprehensively considered in practical applications.

Abstract:The flame ceiling jet is easily formed while the onfire train stops in the tunnel. The iterative formula is derived to calculate the average temperature of the flame ceiling jet when the fire source is set on the center of the train by establishing a onedimensional model of the unit control volume, and the heat exchange is considered among the flame smoke and the wall of the tunnel and the train. Undetermined coefficients in the iterative formula are determined by smallscale model experiments with the scale factor of 1:8 and numerical simulation. The calculated values of temperature by the iterative formula are consistent well with the measured values, and the maximum error of calculation is no more than 7%, which indicates that the iterative formula is reliable. The results show that the distributions of the average temperature of flame ceiling jet are in the exponential form, but there are some differences between that above the train and that in the tunnel. Two prediction formulas for the flame ceiling jet average temperature changing along the longitudinal tunnel are obtained by the subfitting method. The results can provide reference for the alarm parameter selection, device settings in tunnel, safety evacuation of the passenger, as well as the analysis of the destructive effects on the tunnel lining structure caused by tunnel fire.

Abstract:The flow of people changes very greatly in the public areas of public buildings, so the energy demand should also change with the flow of people. However, under the traditional model, the pedestrian flow is rarely considered when accounting energy output, which causes some of the energy invalid. How to assess the energy efficiency to reduce energy waste is an emergent problem to be solved for building energy conservation. The concept of energy utilization efficiency is put forward to judge the degree of utilization of energy, and the formula for calculating energy utilization efficiency is also provided. In a hospital public waiting area, a lot of experiments have been carried out. By comparing the energy consumption before and after the experiments, it is found that energy utilization efficiency can assess the effectiveness of energy. And to improve the energy efficiency of buildings greatly in public areas can be realized by promoting the energy utilization efficiency.

Abstract:Solar Ventilation System is unstable and uncontrollable, so a new technology is proposed to get a system that takes solar energy as heat source and applies phase change material in daytime to store energy which is used to keep ventilation in nighttime by thermal pressure. This new system is helpful to get the ideal ventilation effect for buildings. Through the experiments on ventilation with PCM of 63℃ and 44℃, ventilation rate change curve is obtained to analyse ventilation system efficiency. The results indicate that using the PCM of 63℃ and 44℃, the total ventilation of the solar ventilation system in 10 hours are respectively 8066 m3 and 6154 m3 at night, and the average ventilation per hour and area are 538 m3/h and 41 m3/h. Based on the experiment, when PCM is palmitic acid, the ventilation effect is superior than that of lauric acid. To sum up, the system of conventional solar rooftop ventilation system combined with phase change materials can intensify the nature ventilation effectively in nighttime for buildings, improve indoor thermal environment and reduce the energy consumption in air conditioning building.

Abstract:With the influence of the different gas Reynolds number and liquid Reynolds number on falling film heat and mass transfer of subway station plate evaporative cooler, the experiment was carried out by noncontact infrared thermal imaging technology under gasliquid crossflow condition. The results indicated that during the increasing of liquid Reynolds number the thickness of liquid film increased and the temperature difference between liquid film inlet and outlet decreased in determined heating water temperature which weakened the heat transfer of liquid film. However, the increase of liquid Reynolds number strengthened the liquid film turbulence that enhanced heat transfer. Under the synergistic effect of these two factors, there was an optimal liquid Reynolds number which minimize thermal resistance and maximize heat and mass transfer coefficient of liquid film.

Abstract:The conception of independent exergy evaluation of temperature and humidity control in HVAC systems is proposed with the corresponding evaluation indexes presented. This type of evaluation process is illustrated in an air conditioning system with primary return air from the view of thermodynamics. The results show that exergy efficiency of sensible heat is larger than that of latent heat. The reason lies in the fact that the destructions in reheat process and condensed water are very serious. It is concluded that the surface air cooler is not an energysaving equipment in respect of exergy utilization, and the regeneration of the supply air stream at the state of dew point would improve its exergy efficiency of latent heat. The analysis indicates that this independent exergy evaluation is benefit for the exergy evaluation for HVAC systems, and it provides effective resolutions.

Abstract:In order to enhance the heat transfer in the phase change heat storage device, a rectangular cavity filled with metal foam / paraffin wax is made. The melting heat storage experiment of foam metal / wax composite phase change material was carried out in the transverse wall temperature conditions. The temperature change curve is drawn according to different heating temperatures. Both the effects of natural convection in rectangular cavity on temperature distribution and the impact of heat transfer temperature difference on the thermal storage time are analyzed. The results show that the melting process of the paraffin in the body cavity is reinforced by the high thermal conductivity of copper foam. The remaining solid paraffin is accelerated to melt by the natural convection of the liquid paraffin formed near the heating surface; and the greater the heat transfer temperature difference is, the greater the natural convection is and the shorter the time for heat storage is.

Abstract:The carbon emission during sewage sludge treatment is an important source of greenhouse gas. For the carbon reduction, the emissions from common treatment technologies are calculated with the mass balance model, then their lowcarbon degrees are evaluated, and finally the lowcarbon treatment strategies are put forward for different requirements. The results show that the technologies, such as digestion for methane recovery, incineration or coincineration for power production after drying with industrial waste heat, are the ones with the lowest carbon emission. Their lowcarbon degrees are 89.6%, 80.3% and 76.6% respectively. In the area where the above technologies cannot be applied, aerobic composting or landfill with aerobic stabilization pretreatment are the effective methods to reduce carbon emission. The lowcarbon treatment strategy, a new part of sludge treatment strategies, should be applied combining the local economy, technology and social conditions, so that it can meet the different requirements from sanitation to carbon emission reduction.

Abstract:In the framework of critical state soil mechanics, a simplified hardening law is proposed to describe the change between subloading surface and the normal consolidation surface with plastic deformation based on subloading surface concept proposed by Hashiguchi. The characteristics of overconsolidated clays, such as stressstrain relationship, strain hardening and softening and stress dilatancy are simulated, and the results are in accordance with the data from triaxial drained compression test. Numerical model is also used to predict the stressstrain relationship in the isotropic consolidation condition and the stress paths in the undrained triaxial compression tests.

Abstract:The cement paste added with chemical admixtures is kept out (5±2)℃, 5% in mass MgSO4 corrosion solution in 300 d of immersion. Its visual appearance, compressive strength and erosion products are studied. Its erosion products are analyzed by the way of Xray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). It shows that the calcium formate can delay the TSA of harden cement paste to occur, but can not stop the development of TSA. The resistance of mortar to TSA increases with the raise of calcium formate in the range of 03% to 07%. The reason why barium nitrate can inhibit the formation of thaumasite is that it can combine with SO2-4 which is essential for the forming of thaumasite. Thus, the TSA of mortar is reduced in degree. The harden cement paste shows good resistance to TSA when barium nitrate is approximately 1% of cement.

Abstract:Seepage resistance and moisture proof of concrete structure is a hard work in civil engineering. The influence factors of seepage resistance and moisture proof of concrete using ElectroOsmotic Pulse (EOP), such as electric voltage, water to cement ratio of concrete, ion concentration in liquid phase, and pulse frequency, were analyzed. Simulating experiment of EOP used to drain water and reduce relatively humidity of concrete structure is executed. The results show that, volume of water seepage is improved due to application of EOP in concrete with increase of electric voltage, W/C of concrete, and concentration of sodium sulfate. And pulse frequency has little effect on volume of water seepage. The results are also presented that effect of dewatering and humidity reducing are remarkable when EOP is applied in concrete structure.