Abstract:

Abstract:A zero-length-section element is proposed to model the construction joint. Based on fiber model theory, the qualitative description and the stiffness matrix of zero-length-section element are listed. Furthermore, a fiber line element model is derived which is constructed by a zero-length-section element at the end of a nonlinear beam-column element. Investigation of the static nonlinear responses of a cantilever column with construction joint by finite element procedure OPENSEES is played. It is shown that the model proposed here is reasonable and efficient in the nonlinear numerical analysis of reinforced concrete members with construction joint.

Abstract:Thick steel plates are widely used in high-rise buildings and large-span steel structures. However, the increase of steel plate thickness will induce variations of mechanical properties of steel plates, especially the thickness properties. The mechanical properties of structural steel Q345B with plate thickness from 60 to 150 mm were tested at low temperature through round bar tensile specimens which included two types, i.e. transverse specimen that is perpendicular to the rolling direction and Z-direction (or through thickness) specimen. The indices of yield strength fy, ultimate tensile strength fu, percentage reduction of area ψ and their variations with temperature and sampling locations were measured in the experiments; the corresponding indices for thorough thickness properties were also obtained. it is indicated that: (1) when temperature decreases, fy and fu of thick plate increase while ψ value decreases; (2) from surface to center of the thick plate, ψ values for transverse specimens decrease; (3) with the increase of plate thickness, ψ values for Z-direction specimens decrease and are smaller than those of transverse specimens. Useful material property data of thick steel plate are provided for thick plate steel structures.

Abstract:Wind tunnel tests were carried out to study the wind pressure on principal square building adjacent to another one in tandem. The interference effects on local pressure of the principal building were analyzed with different positions and heights of interfering building. It is shown that as height ratio is fixed, mean pressures on windward face are suctions when spacing ratio is less than 3, otherwise they are positive. The magnitudes of mean suctions on the side and leeward faces and fluctuating pressures on each face all get their maximums when spacing ratio is 3. As height ratios change, the magnitudes of mean suction on windward face increase with height ratio, meanwhile, the magnitudes on other faces obtain their minimums as the height ratio is 1.0 and the spacing ratio is less than 3. The fluctuating pressures on the windward and side faces get their maximums and that on the leeward face reaches its minimum as the height ratio is 1.0. When the spacing ratio is greater than 3, mean pressures on each face decrease, while fluctuating pressures on the windward and side faces increase as the height ratio increases, and the fluctuating pressures on the leeward face get the minimum when the height ratio is 1.0.

Abstract:It is complicated to found continuity equation for unsaturated soil because of the uncertain volume of air phase. In order to solve this difficulty and to derive the consolidation equation for unsaturated soils with high degree of saturation, one-dimensional continuity equation of three-phase soil was created compactly in the principle of mass balance. Supposing Terzaghis principle of effective stress was still applicable to this type of soils, one-dimensional consolidation equation was derived. On basis of Terzaghis hypotheses and supposing that the degree of saturation was constant during consolidation, the analytical solution was presented. Then the consolidation characteristic of soils was analyzed. And It is shown: 1) the form of consolidation equation of soils with high degree of saturation is the same to Terzaghis one-dimensional equation, but the coefficient of consolidation is different. 2) Because of the instantaneous deformation, the degree of consolidation in early stage is much bigger than that of saturated soils, and subsequently the gap is reducing; when the time factor is 1.0, the degree of consolidation is almost equal to each other. 3) The time needed for soils with high degree of saturation to complete consolidation is extended comparing to the corresponding saturated soils; the smaller the degree of saturation is, or the more compressible the soils are, the bigger the ratio of time for completing consolidation is.

Abstract:Tunnel portal section mostly faces unfavorable geologic and topographical conditions, such as broken surrounding rock, shallow and unsymmetrical loadings. The current Chinese code for design of road tunnel provides the load calculation method of tunnel under unsymmetrical. However, according to the mechanic and deformation characteristics of the tunnel lining on site, the assumption is not suitable for the shallow tunnel under unsymmetrical loadings in broken surrounding rock. Therefore, through engineering case analysis and results of three-dimensional numerical analysis, the failure mechanism of shallow tunnel under unsymmetrical loadings in broken surrounding rock is presented firstly, that is, deep buried side broken surrounding rocks slump down after excavation and squeeze the lining, which makes the lining deform outward and bear passive earth pressure. Through the failure mechanism, the surrounding rock mainly includes slumping area and passive area. Then the corresponding formulas are deduced based on limit equilibrium theory. Finally, a case study is adopted to verify the feasibility of the new method. It is show that the new method is more reasonable than the method of current code.

Abstract:New types of precast concrete ribbed panels are developed in order to adapt to the complex loading conditions and different floor spans. Based on the yield line theory, equations for the ultimate bearing capacity and yield patterns of two-way composite slabs of different edge conditions and under uniformly distributed loading are developed, and the simplified formulas for the ultimate moment per unit width are proposed. The plastic limit analyses of two examples on the simple support and the fixed support are conducted, and the calculation results show good agreement with the experimental data.

Abstract:Four evolution patterns of rock permeability in damage process are summarized. And how rock pore, micro cracks and lithology form the four patterns of rock permeability evolution is analyzed. The impact of confining pressure on permeability is also presented. The permeability reduces along with the increase of confining pressure before rock failure, however， it is complex after rock failure, and it is necessary to do further research. Statistical analysis is carried out to analyze the variation range of permeability in the process of damage, which shows soft rocks vary less while hard rocks vary more. In the experiments in which the confining pressure is between 1 MPa to 40 MPa, permeability variation of 85.9% rock is within 100 times, 97% within 1000 times. Furthermore, the difference between instability of seepage and that of structure under the function of seepage is distinguished. It is proposed that the presence or absence of non-Darcy flow should be considered from the point of effective stress law.

Abstract:Based on concepts of mechanics, a mechanical model of novel type of steel plate composite shear wall is presented. The novel type of structure is formed by steel plate shear wall and T-shaped solid-web composite columns. Flexural stiffness of steel beams, lateral stiffness of the T-shaped solid-web composite columns, shear stiffness of steel plate composite shear wall and shear stiffness of beam-column connection are taken into account in the mechanical model. And the equivalent damping between steel plate and boundary is considered. Based on the deformation features of structures and the calculation hypothesis, the lateral stiffness model and the energy dissipation model of structures are developed. Meanwhile, the calculation equations of elastic ultimate and plastic ultimate of shear strength of structures are set up. The theoretical analysis results inosculate better with the results of experiment. The comparison between the result calculated from the formula and the experimental result shows that the calculation precision is high enough to meet the demand of theoretical analysis. The difference, including equivalent model, stress states, manufacturing defect and installation error, between the formula and the experiment has been further discussed.

Abstract:In order to investigate the creep laws and the relation between particle breakage and creep strain of some certain rockfill, a series of constant-stress drained creep tests were conducted on rockfill materials with the large-scale triaxial apparatus. Tests were carried out under different confining pressures and stress levels. Particle breakage degrees of this rockfill were measured by sieve test after creep tests. It is indicated that creep deformation of rockfill has something to do with confining pressures and the stress levels. The axial creep strain and the volumetric creep strain increase with the increase of stress levels, and also increase with the increase of confining pressures under same stress level. The strain-time relation can be described with power function. The stress-axial strain and stress-volumetric strain behavior can be described with hyperbolic and linear function, respectively. Particle breakage degrees increase with the increase of stress levels and confining pressures. The relative particle breakage index can be adopted to descript the particle breakage of rockfill. And the axial creep strain and volumetric creep strain are linearly dependent on this index.

Abstract:The distribution characteristics of shape factors and fluctuating wind pressure coefficients on two vaulted shells were investigated by simultaneous measurement of external and internal wind pressures on static models in wind tunnel. The effects of orifices on bottom and blocking at ends on wind loads distribution are discussed. It is shown that the wind pressure distribution is significantly affected by changes on orifices at bottom and blocking at ends. Wind pressure on ends decrease effectively and wind pressure on surface is distributed smoothly by blocking ends with highly curved surface shell. Small orifices at bottom not only contribute to degreasing negative pressure because of count acting effects of internal and external pressures, but also to extending the positive pressures region and increasing positive pressures. Wind loads suggestions on these structures are described at end.

Abstract:To study stress distribution in fixed anchor length of compression type rock anchor cable, field test was carried out. Strain sensors were placed in the grout paste in fixed anchor length with certain interval. Axial and radial strains of the grout were noted by test. Shear stress distribution curve along the fixed anchor length was obtained by stress-strain relationship and static equilibrium analysis. Analysis results prove that maximal shear stress on the interface can achieve upper level and move forward when the load increases; the transmission length is short; shear stress transfers forward; and three dimensional state is obvious around capacity plates in soft rock mass.

Abstract:To investigate the effect of consolidation soft soil, three groups of model tests were designed. The first group was PVC pile-net composite foundation, the second was pile-cap-net composite foundation, and the third was PVC and sand pile composite foundation. Butter was coated and plastic membrane was covered on inner side wall of model cast to reduce border effect. The gauges were glued with epoxy on the surface of the model with PVC piles and geogrids to measure the stress of PVC piles and geogrids. Soil pressure cells were installed in the middle of piles and the top of the sand piles, and dial indicators were installed in the middle of road and road shoulder to measure deformations. It is that shown: 1) as for the distribution of the road settlement and the differential settlement, the settlements of the third group are the largest and those of the second group are the least; 2) in terms of the stress ratio of PVC pile and soil, the values of the first group and the third group are similar, while the value of the second group is much larger; 3) the change of geogrid strain is disorderly. There are periodic peaks in the strain of geogrid of pile top and periodic troughs in the soil between the piles. The geogrid strain of the second group measured in the corresponding spot is much larger than those of the other two groups. The results of three groups of tests illustrate that if the condition is permitted, it would be the best to adopt the scheme of pile-cap-net composite foundation, which has better reinforcement effect for soft soil.

Abstract:Under multi-support earthquake excitation, the damping is proportional to the relative velocity in relative motion method, While the damping is proportional to the absolute velocity in method of direct solving absolute displacement, and the damping assuming difference may cause the calculation errors on structural responses. The structural response errors of the dynamic component of power spectral density between the two solving methods are derived by random vibration theoretical analysis in Rayleigh damping model, which include damping ratio and the ratio between excitation frequency and fundamental frequency of the structures. Based on probability theory, the variation errors of dynamic component response between the two solving methods are also derived by theoretical analysis, and some numerical examples are provided to verify the error analysis. At last, it is pointed out that the calculation errors between the two solving methods decrease with damping ratio, and it is negligible when the damping ratio of structure is less than 5%.

Abstract:The physical and mathematical model of three dimensional unsteady coupled heat transfer in the ground heat exchanger is proposed, and corresponding numerical simulations for actual ground heat exchanger and operation condition are carried out. The computed results are compared with those of the thermal resistance test of the ground heat exchanger, which proves the correctness of the model and corresponding numerical methods. Then, the effects of thermal conductivity and specific heat of the ground backfill material on the ground heat exchanger are investigated, which provides theoretical guidance for the thermal response test and the engineering design of the ground heat exchanger.

Abstract:Soil temperature prediction model around the subway metro tunnels is constructed with the consideration of coupled heat transfer between range temperature and surrounding soil. Finite difference method is adopted for numerical solution of the model, and the solving results in certain conditions are compared to validate the analytical solution. The high-frequency thermal disturbance brought by train operation is simplified into three different forms, and the predictive model of soil temperature is used to calculate the corresponding soil temperature response. It is indicated that temperature fluctuations of range air and the wall are accompanied with high-frequency thermal disturbance, but the impact on soil temperature distribution inside is limited.

Abstract:Solar chimney is effective to enhance the natural ventilation by heating the air with solar radiation. Based on the research by other authors, a revised mathematical model is proposed. One dimensional heat conduction model is proposed when the thermal resistance of both the glass cover and heat absorbing wall are taken into account. The mean temperatures of the air and heat absorbing wall, the air mass rate and heat collection efficiency in the solar chimney are calculated with the present model. The results of the present model are compared with the related experimental data and reasonable agreement is validated. It is shown that the present revised model is able to predict the temperatures of the air and wall, the air mass rate and heat collection efficiency more preciously than the original model.

Abstract:The internal shading can both impact on the sunshade and indoor daylighting, and work as an indoor heat source by absorbing heat. Presently the evaluation of overall energy efficiency of the internal shading is perceptual and qualitative. Therefore， the tests of the internal surface temperatures of house envelopes and the daylighting illuminance were carried out. It is shown that the surface temperature of interior walls with internal shading are 0.6℃～1℃ lower than those without; however，the surface temperature of internal shading is 3℃～5℃ higher than that of the interior walls. It can be seen that internal shading also forms an indoor heat source. The energy consumption of air-conditioning with internal shading decreases by 17.24% than that without, which indicates the internal shading can certainly reduce the indoor air conditioning load; however, the daylighting illuminance declines by 81%, with the results that the artificial lighting energy consumption is 1.88 times as much as that without the internal shading.

Abstract:Taking residential buildings as the study objects, for three different residential load types such as low load, medium load, and high load type, indoor thermal environments of different load sharing-rates are simulated, respectively. Indoor thermal comfort and indoor air quality of different load sharing-rates are also analyzed and evaluated. And the appropriate range of cooling load sharing-rates are given from the view of both occupants thermal comfort and occupants health. When ωc (the sensible heat load sharing rate of the radiant terminal device) <0.7, the human thermal index in work region can be controlled within the range of thermal comfort standard. From the point of avoiding local discomfort, ωc is suggested to take 04~1. As regard to indoor air quality, for the constant air volume mode, ωc is suggested to take 0.5~0.9 under low and middle load conditions, and ωc is suggested to take 0.35~0.6 under high load conditions. For the variable air volume mode, the smaller the value of ωc is, the better indoor air quality is.

Abstract:According to the work of Motakef and EI-Masri, the wall was divided into dry-wet-dry zones. Based on the heat and moisture transfer through porous media, considering the vapour condensation as a vapour sink, water source and heat source, coupled heat and moisture equations for wet zone were established. Closed-form analytical expressions for the condensation rate, moisture content and the time when critical moisture content value reached are obtained. It is indicated that the condensation rate exhibits a strong dependence on the temperature difference of the two sides of wet zone, and the maximum condensation rate value is reached at the boundary of wet zone close to lower temperature.

Abstract:The optimal preparation conditions and coagulation/flocculation performance of polymeric phosphate-aluminum chloride (PPAC) were measured. Some parameters such as acid dosage, temperature, reaction time and P/AL molar ratio were investigated. Also, infrared spectroscopy and scattering electron were used to characterize the structure of PPAC. In addition, the coagulation/flocculation process was carried out for wastewater treatment. It is shown that the maximum alumina content is achieved when acid dosage, temperature, time and P/AL molar ratio are 48 ml, 100 ℃, 180 min and 02 respectively; infrared spectroscopy analysis fits well with the product structure; scattering electron analysis suggests a large surface area and a strong condensed state for PPAC; the removal efficiency of 731% and 990% for COD and turbidity respectively are obtained when coagulant dosage, pH value and agitation speed are 032 ml/L, 75~100 and 40 min respectively.

Abstract:Bench experiments were carried out to evaluate the removal of chlorobenzene in raw water by conventional water treatment process. And a batch system was applied to study the adsorption equilibrium and kinetics of chlorobenzene(CB)from raw water by powdered activated carbon(PAC). The experimental data obtained were mathematically modeled with Freundlich and pseudo-second-order kinetic model for the equilibrium isotherm and kinetics, respectively. It is shown that the conventional water treatment process can not remove chlorobenzene from water effectively. PAC can rapidly adsorb chlorobenzene with 80% and 98% of the equilibrium adsorption capacity at 5 min and 30 min, respectively. A theoretical formular was established to express the relation of PAC dose to the initial concentration of chlorobenzene and adsorption time, and it was verified by the results of bench experiments. The maximum concentration of chlorobenzene corresponding to different PAC dose was obtained with the adsorption time of 30 min.

Abstract:The hydration process, activity and microstructure of composite cement-based materials containing fly ash(FA)and flue gas desulphurization gypsum(FGD)were investigated by using DTA-TG, XRD, SEM, hydration shrinkage and compressive strength tests. And then the hydration kinetics of composite cement-based materials was discussed and summarized. It is shown that the ettringite(AFt)DTA endothermic peak of the harden cement paste containing FA and FGD is stronger than that of the reference specimen. The secondary hydration effect of hardened FA-FGD cement paste is more obvious under the effects of mutually active excitation and the added activators. The results of SEM and XRD indicate that the AFt in harden cement paste is significantly found and the surface of FA particle is eroded, further illustrating that the early activity of composite cement-based materials is effectively motivated, and ensuring the comprehensive properties of hardened composite cement-based materials. On the other hand, the test results of microscopic test were confirmed by the hydration shrinkage and compressive strength tests. Therefore, this research and application of FA-FGD composite cement-based materials can consume a lot of industrial wastes discharged from the power plant. It is a kind of “green” building material.

Abstract:On the basis of characterization of property of traditional sticky rice-lime mortar, influence of admixtures (aluminum sulfate, gypsum, paper fiber) on properties of traditional sticky rice-lime mortar and their scientific mechanisms are discussed by means of SEM and XRD. It is indicated that paper fiber is the most effective admixture to endure freezing-thawing cycles and increase compressive strength of sticky rice-lime mortar due to disorderly distribution and water-retaining of paper fiber, and the use of aluminum sulfate reduces dry shrinkage values and improves compressive strength because of formation of ettringite in sticky rice-lime mortar. Gypsum is proved to be ineffective to modify freezing-thawing cycles of sticky rice-lime mortar. Meanwhile, compressive strength and surface hardness of sticky rice-lime mortar with gypsum decline as gypsum amounts. It is suggested that 6% aluminum sulfate or 3% paper fiber can be used as admixtures of sticky rice-lime mortar in conservation of cultural relics.

Abstract:Effect and mechanism of activation of activator to fluorgypsum, strength, softening coefficient and leaching toxicity of composite cementitious material are studied. Through activation testing of NaOH, Na2SO4 and NaF, the optimum adding quantity was defined as 1%. On the basis of it, 80% fluorgypsum was further processed to improve its quality with slag, fly ash and clinker. With 1% Na2SO4, 25% slag, 5% fly ash and 89% fluorgypsum, the cementitious material properties were excellent; the 28-day compressive strength could reach 12.25 MPa; the softening coefficient was 0.70; and the concentration of fluoride could be reduced to 0.7485 mg/L. The analysis of SEM and XRD show that gypsum, a few calcium silicate hydrate, ettringite and calcium fluoride are filled and packed each other, which hampers water enter particle structures, increases the water resistance of cementitious material and reduces leaching toxicity of cementitious material.

Abstract:The characteristics of EPDM waterproofing membrane are analyzed. Due to the effect of heat and oxygen, aging occurs to EPDM waterproofing membrane with a protective layer to some extent. And the decline of mechanical properties and plasticizer migration are particularly outstanding, resulted in a reduction in service life of the material. Unaged and aged samples were tested by SEM and FTIR. Furthermore, by using accelerated thermal aging and thermal analysis kinetic method, mode of EPDM waterproofing membrane between performance indicators and service life under certain conditions was established to predict its service life, which provides technical support for architectural design, building construction and material research.