Abstract:Based on analysis of the test results of 50 RC specimens of circular columns failed in flexure, an expression for defining the hysteretic loop is proposed and a model for predicting the equivalent damping ratio is developed. The procedure for associating the equivalent damping ratio of a structure as a whole with those of its element is established by an example of double-column pier-bridge. It’s indicated that the expression of hysteretic loop proposed well defines the hysteretic loops of RC columns. Rational outcome can be expected when performing pushover analysis using the relationship of equivalent damping ratio of a bridge as a whole with those of its element. The target displacement predicted with the proposed model is different from those predicted with Rosenblueth’s model and Kowalsky’ model.

Abstract:The wind field of a mountain bridge site always shows a strong randomness and uncertainty. As a result, setting up its computational domain in CFD simulation by a simply reference to the existing experience causes a large amount of model errors and huge additional computational overhead. To solve this problem, a method to the selection of CFD computational domain of complex terrains is explored and verified. To start the procedure, a large reference computational domain should be chosen and preliminary solved. Then, its solution should be post-processed to draw the following curves or contour images: range of mean pressure coefficient align with height, static pressure deviation contour of the horizontal plane near the top of the bottom surface,the root-mean-square error of the static pressure of the crosswind planes compared to the corresponding edge surface. According to these curves and contour images, areas parts which have slight contribution on the overall wind field are figured out and abandoned, and the selected computational domain is constitutive of the rest parts of the reference domain.

Abstract:Shear transferring mechanism of the plasterboard wall reinforced with in-filled RC columns was studied. It is found that plasterboard ribs can transfer shear between in-filled RC columns effectively and have great effects on the behaviour of the composite wall. Equivalent slitted shear wall model is then presented. Slits are arranged on the equivalent shear wall to ensure it has same elastic lateral stiffness as the composite wall. Comparative analysis shows that plasterboard wall reinforced with in-filled RC columns has similar load bearing mechanism as the slitted shear wall and can be simulated by the proposed equivalent slitted shear wall for both elastic and plastic states.

Abstract:The similar materials is used to simulate the soft rock-mass on the basement of tunnel in the high speed railway. Based on the method of loading control and the cyclic loadings of non-symmetrical sine wave, the dynamic fatigue test of three axial and the damage detection test are carried on for soft rock-mass specimens. With analysis of the results of tests,the polynomial model with three parameters to calculate the fatigue life and the polynomial model with four parameters to calculate the cumulative damage are established for soft rock-masses. And then, some characteristics of fatigue damage has been obtained about the soft rock-mass, such as the fatigue failure of soft rock-mass mainly shows two composite modes those are the tension-shear on the end and the compression-shear on the central of specimen. The whole process of fatigue damage is shown three stages those are the compaction of initial micro-pore, the occurrence and stable propagation of new cracks,and the accelerating development of crack damage. The fatigue life of soft rock-mass mainly depends on itself strength and the level of dynamic stress. The higher strength of itself and the lower level of dynamic stress,the longer fatigue life of rock-mass will be. If the level of dynamic stress has not been changed, the fatigue life of soft rock-mass will be increased linearly with its elastic model.

Abstract:To overcome the existing problems of bamboo reinforced concrete structure, several processing methods are proposed to improve the performance of bamboo bar. Experiments on twelve flexural members, including eleven bamboo reinforced concrete beams and one steel reinforced concrete beam, is carried out. The mechanical properties, failure modes and influential factors of flexural beams with different processing methods and reinforcement ratios are studied. The results show that: bamboo could improve effectively the flexural capacity of concrete beam, and the effective bonding between bamboo reinforcement and concrete could be achieved if the bamboo is processed by proper methods. Moreover, the plane-section assumption can be used for bearing capacity calculation of bamboo reinforced concrete beams. The failure mode of bamboo reinforced concrete beams is brittle fracture and the detailed fracture pattern is related to reinforcement ratios.

Abstract:Significant creep deformation occurs in steel subjected to elevated temperatures and loading, and thus affects the deformation and load capacity of steel Structures in fire. Currently there are many creep models, which are not widely suitable. Significant effect on fire resistance analysis of steel beam can be observed using different creep models. In order to quantity this effect, comparison was made to analyze five kinds of creep model. Fire resistance of restrained beam under five creep models was analyzed using computer program and the results were compared with test data. Norton creep model revealed best agreement with test data. Finally, parametric study was conducted on the parameters affecting the fire resistance of restrained steel beams. It is showed that Harmathy creep model had a greatest effect on fire response of restrained steel beams. The degree of creep influence to fire resistance of restrained steel beams for different creep models under different load ratio and restraint were different.

Abstract:Considering the coupling effect between fluid phase and solid phase, the site soil on bedrock is considered as two-phase saturated porous media. In order to consider the viscoelastic characteristics of the saturated site soil, the stress-strain relationship of soil skeleton is described by fractional derivative Kelvin viscoelastic model, and the motion control equations of overlying fractional derivative viscoelastic saturated site soil under the action of harmonic earthquake wave are established. Using the properties of fractional derivative and considering the boundary conditions and permeable conditions, the vibration problem of overlying fractional derivative viscoelastic saturated site soil under the action of harmonic earthquake wave is solved, and the seismic displacement amplification coefficient of the saturated site soil is also obtained. The influences of the order of fractional derivative, liquid and solid coupling coefficient, model parameters of soil, and bedrock and soil shear modulus ratio on the seismic displacement amplification coefficient are analyzed and discussed by numerical examples. The results show that the order of fractional derivative, liquid and coupling coefficient, model parameters of soil, bedrock and soil shear modulus ratio have great effects on the seismic response of the site soil. The fluid and solid coupling coefficient could the increa of be increased and the seismic response can be decreased by compacting the saturated soil. Meanwhile, the viscosity and shear modulus of the saturated site soil can also reduce the seismic response.

Abstract:The traditional stress state is composed of two normal stresses and a shear stress in the two dimensional space, and three normal stresses and three shear stresses in the three dimensional space. Therefore, six stressometers at least are necessary to determine the stress state at a point in space. Based on the stress state theory, a stress apparatus that can detector the three dimensional stress states is devised. The apparatus is made up of six one-way stressometers which are disposed at the edges of a tetrahedron. The tetrahedron is regular of all even arbitrary shaped in theory considering rational, logical, stability and conveniently. The mapping transformation, from the traditional stress state to the stress state illustrated by the edges of the tetrahedron is constructed. Furthermore, the traditional stress state can be derived from the data collected by the three-dimensional stress apparatus, and causes of errors are analyzed.

Abstract:In order to explore the feasibility of AC resistivity method for monitoring zinc contaminated soil, the resistivity of zinc contaminated sand was tested, and the influences of current frequency, water content, void ratio and zinc contamination content on sand resistivity were analyzed. Therefore, an AC resistivity empirical formula of zinc contaminated sand was proposed. The results indicated that the resistivity decreased rapidly with the increase of current frequency, whereas gradually stabilized when the current frequency was higher than 50 kHz. When zinc content was lower than 50 mg/kg, the electrical resistivity was more sensitive to the change of current frequency. Then,The electrical resistivity decreased with the increase of water content, and lower the water content was, more quickly the resistivity changed. The resistivity increased slowly with the increase of the void ratio, and decreased rapidly with the increase of zinc content. Whereas it gradually stabilized when the zinc content was higher than 250 mg/kg. There was a highly relevant power function relationship between resistivity and zinc content. Based on saturation, void ratio and zinc content, an electrical resistivity empirical formula was proposed.

Abstract:Geosynthetic clay liner (GCL) has been increasingly used as a hydraulic barrier for tailing impoundment. Under the action of different concentrations of heavy metal ions (heavy metal compounds are CuCl2 and ZnCl2), the change regulation of the free swell index, liquid limits and GCL hydraulic conductivity is researched, and the correspondences between them are analyzed. It is shown that when the concentration of heavy metal ions ranges from 0.01 mol/L to 0.1 mol/L, the free swell index and liquid limits decease with the increase of concentrations of heavy metal ions. However, further increasing of the heavy metals ions concentration ( from 0.01 mol/L to 0.5 mol/L) can’t cause the two index properties decrease continually. In the permeation test, when the concentration of heavy metal ions ranges is lower than 0.01 mol/ L, the hydraulic conductivity of GCL can remain stable. By contrast, when the concentration of heavy metal ions is up to 0.02 mol/L, the hydraulic conductivity of GCL increases with the increase of heavy metals ions concentration. Results of the study show that the index properties of a bentonite has good correspondence with the hydraulic conductivity of the corresponding GCL when the heavy metal ions concentration is higher than 0.02 mol/L and they can be used to estimate the hydraulic conductivity.

Abstract:In order to reduce the production cost of Engineered Cementitious Composites (ECC), it is very necessary to substitute part of the expensive Japanese PVA fibers with the homemade PVA fibers for the ease of extensive application of the practical structures.Based on the ECC design theory, an optimal design for the fiber volume content of hybrid PVA-ECC is analyzed, taking both compressive strength and tensile strain capacity into account. The mechanical behavior of hybrid PVA-ECC is obtained through the four-point bending test and uniaxial compressive test. Experimental results indicate that the strain hardening and multiple cracking behavior of hybrid PVA-ECC are observed in the test, and the long-term compressive strength is distinctly increased. Furthermore, a modified inverse method based on the UM method is proposed, to use the measured data of four-point bending test to calculate the tensile strain capacity of ECC, and the proposed method is verified with the experimental results of hybrid PVA- ECC specimens.

Abstract:The strong acid and salt composite groundwater in Guizhou province is simulated in the lab, and the influence of single addition and composite addition of mineral admixtures such as fly ash, slag and silica fume etc. on corrosion resistances of cement mortar using the evaluation indexes such as anti-corrosion coefficient, mass change fraction and chloride ion relative diffusion coefficient in the simulated solution is systematically studied. And its anti-corrosion mechanism of cement mortar is discussed. The results show that the single or composite addition of mineral admixtures results in the improvement of anti-corrosion coefficient, the reduction of chloride ion relative diffusion coefficient and the increase of mass change fraction of mortar compared with the control mortar. The three proposed evaluation indexes can evaluate the corrosion resistance of cement mortar exposed to strong acid and salt composite groundwater from different perspectives.

Abstract:Triaxial compression tests for concrete of size Φ300 mm×600 mm was carried out under different strain rate (10 -5,10 -4,10 -3,10 -2/s) in 0,10,50 cycle of pore water and low strain rate (10 -4/s,10 -3/s) in different cycles pore water pressure(0,10,50,100,200 times). Comparatively analysis the changes law characteristics about of basic physical mechanics parameters, such as peak stress and absorption of concrete under different loading rate are analyzed. The results show that: concrete peak stress increases with strain rate and with the number of pore water pressure cycles,. the concrete peak stress increases at the first and then declines. with the number of pore water pressure cycles, shows the change of stages; Concrete absorption energy capability is loaded with the strain rate, and showed significant increasing trend. Energy absorption capacity of concrete pore water pressure increases with the number of cycles showed shows some discrete, but overall increase first and then decrease;Finally, choose sectional dynamic damage constitutive model of concrete material which is based on statistical theory Weibull is applied to of sectional dynamic damage constitutive model based on Weibull for analyse concrete material fitting oto fit with f experimental data, verified, and the results show that this model has good agreement with the test results.

Abstract:The time-varying distribution behavior of sulfate with diffusion is investigated for bored pile internal mixed corrosion at different amounts of service times. The formulation of diffusion, based on Fick-second law combined with the initial condition and the boundary condition, for sulfate in the bored pile is formed with the method of separation of variables. A model of concrete pile is offered as an example for illustrating the time-varying distribution behavior of sulfate and making comparison with the traditional model. Further, the influence factors and their effects on the sulfate diffusion distribution are also analyzed. The results show that the application of traditional method in analysis of sulfate diffusion in bored pile has some limitations and advantages of the proposed method are obvious. The radius of bored pile decreasing induces the discrepancy of sulfate distribution increasing with employing the traditional method, while the discrepancy increases over time. The time-varying distribution of sulfate in bored pile resembles hourglass figure that along the radius direction, diffusion behavior at x=0 and surface of pile is significant. In the region near x=0, the diffusion rate of sulfate is fast during the first year and then the diffusion rate is dramatically reduced to constant rate during the 50 years. Diffusion coefficient and the concentration gradient of sulfate in bored pile have a pronounced effect on the time-varying distribution of sulfate.

Abstract:In order to find out the optimal period of time of natural ventilation in winter, the realizable k-ε turbulent model of CFD is adopted to numerically analyze the pollutant concentration field in a residence in Lanzhou when the unsteady heat transfer through outerwalls is considered. The results indicate that the inlet temperature has significant effect on the indoor pollutants profile and migration, and different ventilation period corresponds to different duration under the same opening patterns. Considering the pollutants elimination efficiency and thermal comfort simultaneously, the ventilation beginning at 17:00 is the optimal ventilation mode.

Abstract:The correlations among the building energy consumption factors can corrupt the prediction model’s performance, and get undesirable results. A prediction model based on KPCA-WLSSVM is proposed to forecast building energy consumption. The kernel principal component analysis (KPCA) method could not only solve the linear correlation of the input and compress data but also simplify the model structure. A novel hybrid chaos particle swarm optimization simulated annealing (CPSO-SA) algorithm is applied to optimize WLSSVM parameters to improve learning performance and generalization ability of the model. Furthermore, the KPCA-WLSSVM model is applied to the energy consumption prediction for an office building, and the results show that the KPCA-WLSSVM has better accuracy compared with WLSSVM model, LSSVM model and RBF neural network model. and the KPCA-WLSSVM is effective for building energy consumption prediction.

Abstract:There is a dynamic relationship between outdoor air temperature and solar radiation. Based on the meteorological data of 13 typical cities in south China and by the regression analysis method, the dynamic fitting function between the solar radiation and the land surface temperature and the function of temperature difference between the air and land surface changing over time are established. And the correlation coefficient R 2 are over 0.97 which indicates that the results can significantly reflect the variation of data points，then the dynamic relationship between outdoor air temperature and solar radiation is obtained. The results suggest that solar radiation is a linear function of the outdoor air temperature and time in the plateau, while logarithmic function of both in the plains. The study will provide convenient method for building cooling load calculation, and provide scientific basis for studying the dynamic relationship between the solar radiation and the building cooling load as well as the suitability of the solar energy air conditioning.

Abstract:An indirect evaporative cooler installed with a rotary water distribution device which is driven by a low-speed motor, was proposed to solve the installation location problem of cooling tower in subway station. Single factor experimental method was used to investigate the heat transfer performance of indirect evaporative cooler under two types of arrangement. And under the optimal arrangement, the factors that affected the heat transfer performance were analyzed by orthogonal experimental method. The experimental results showed that the distance between nozzle and evaporative cooler and the distance between two sets of heat exchange coil under two types of arrangement both had optimal values. Rotating water on both sides was superior to rotating water on the one side. Heat exchanger arranged parallel to the air flow with nozzles rotating water on both sides was the better arrangement. And under this arrangement, heat exchange increased with the increase of spray water quantity, rotational speed, air velocity, cooling water flow rate and cooling water inlet temperature, and the decrease of spray temperature and air temperature. The cooling water inlet temperature had the most significant effect on heat transfer performance and other factors that affected the heat transfer performance from main to secondary were spray water quantity, air temperature, air velocity, spray temperature, rotational speed and cooling water flow rate.

Abstract:A series of experimental tests using NORDTEST method for evaluating the moisture buffering capacity of different porous hygroscopic materials have been carried out in the Yangtse River downstream area (Nanjing for example),. The impact of MBV on building energy consumption and indoor humidity has also been investigated. The test results show that the MBV of porous hygroscopic materials is larger under higher humidity range, and there was obvious difference when using diverse materials. Research indicates that it may be possible to reduce up to 10% cooling energy consumption in the Yangtse River downstream area(hot and humid climate) in China, when applying hygroscopic materials with well-controlled HVAC systems. Meanwhile the indoor humidity can also be modulated to a certain extent.