Abstract:To improve the strengthening effect and reliability of concrete structure strengthened with carbon fiber sheets, a new hybrid bonding pre-stressed carbon fiber sheets technique is developed. This technique combines the pre-stressed carbon fiber sheets with mechanical fastening of pre-screwed bolts. In accordance with the fracturing characteristics and the strengthening method of aging RC beam bridges, different carbon fiber sheets strengthening technology were applied on the intact and destructive RC beams. And a series of experiments were conducted to examine and assess the flexural performance of RC beams. Then, a new type of tensioning equipment was invented to meet the need of tensioning carbon fiber sheets in practical engineering. The experiment results show that the hybrid bonding pre-stressed carbon fiber sheets is a more reliable strengthening technique which can not only improve the flexural capacity and the section stiffness of RC beams during normal use stage, but also can increase the cohesive force between carbon fiber sheets and concrete interface. It can make full use of the tensile strength of carbon fiber sheets and can restrain the opening and developing of the cracks.

Abstract:In order to investigate influence of T-type rib on flexural fatigue behavior of concrete composite slab with precast prestressed ribbed panel, experiment is conducted to study the concrete composite slab with precast prestressed T-type rib panel and cast-in-place slab. The factors influencing the fatigue failure pattern and fatigue damage, such as T-type rib and fatigue load parameter, are studied by fatigue tests. The dynamic deflection, strains of concrete and prestressed tendons, and residual deflection are measured. Stiffness degradation, strain distribution, crack distribution and residual bearing capacity are analyzed. Results show that composite slabs with precast prestressed T-type rib panel can achieve the same flexural fatigue behavior as cast-in-place slabs. Design formulas for normal section bending fatigue strength of concrete composite slab with precast prestressed ribbed panel are put forward with reference to the four assumptions of traditional prestressed concrete flexural member.

Abstract:The gravel soil red clay was used to in resilient modulus test under the condition of different initial dry density and the the resilient modulus variation was studied. The prediction model of resilient modulus was established. The test results show that:(1) With the same gravel soil content, when the initial dry density increases,the resilient modulus of red clay increases. When the initial dry density increases from low to maximum dry density, resilient modulus grow faster and when the initial dry density increased after exceeding the maximum dry density, esilient modulus grow slower; (2) With the same initial dry density, when the gravel content increases from 0 to 30%, the growth rate of resilient modulus is lower and when the gravel content continues to grow, the growth rate of resilient modulus is greater;(3) When the initial dry density increases from 1.6 g·cm^-3 to 2.0 g·cm^-3, resilient modulus growth values gradually increases with increasing content of gravel soil;(4) The prediction model of resilient modulus was established the and the accuracy of the prediction model was, verified.

Abstract:The permeability coefficient is important to investigate permeability coefficient spatial distribution of groundwater flow. Based on Gardner model, the permeability coefficient vertical distribution model is established, expressed as exponential, which is controlled by saturation permeability coefficient, dimensionless depth and dimensionless flow rate. The model shows that the permeability coefficient vertical distribution for homogeneous typical soils is influenced by the difference between flow rate and aturation permeability coefficient. And then, simplifies the model is simplified as linear model based on Taylor's series and permeability coefficient of groundwater level and the earth's surface as control conditions. The error of linear model with the method of Taylor's series increases when dimensionless depth increases. The calculation results of the simplified model and the original model are compared. The result shows that the linear model with the method of permeability coefficient of groundwater level and the earth's surface as control conditions is more accurate than the linear model with the method of Taylor's series.

Abstract:The dynamic stability of slopes is influenced by the horizontal and vertical earthquake forces. The traditional method of calculating the seismic permanent displacement does not take enough consideration about the vertical seismic effect. However, considering the combined effect of horizontal and vertical accelerations is more accord with the engineering practice. Based on the upper bound limit analysis and the model of Newmark's rigid-plastic block, an approach for evaluating the permanent displacement of slopes based on the actual horizontal and vertical earthquake acceleration time-history curves is proposed. Three types of engineering slopes are studied to discuss the impact of two typical earthquake ground motions on seismic permanent displacement. The results show that: this method is compatible with the previous method without considering the vertical acceleration; the combined effect of horizontal and vertical accelerations is different for various earthquake records, and the influence of vertical acceleration on the permanent slope displacement cannot be ignored.

Abstract:The influence of water to binder ratio, rubber pretreated method and dosage to water absorption on the capillary porosity, drying shrinkage and mechanical properties of rubber concrete was studied. The results indicated that the NaOH pretreatment could help improve overall performances of rubber concrete, while its influence is dependent on water to binder ratio of concrete. It is suggested that the improvement of concrete by NaOH pretreatment was enhanced at a higher water to binder ratio.

Abstract:Based on the modular modeling framework of ABAQUS program, a simplified mesoscopic model is proposed for masonry structure. The mortar-joint and bond were replaced by a single interface. Shear-compression behaviour and tension behaviour were modeled through the normal and tangential mechanics properties of interface. Sticking mechanics property was adopted to model tensile behavior, and the evolution index α of bonding soft was obtained by equivalent with axial tensile constitutive express. Based on shear-friction theory, shear-compression model was conducted by sticking mechanics and coulomb friction, and through the nonlinear properties of block, the principal compression stress was adopted as the master damage threshold under high axial compression ratio. Simulation of the shear-compression relationship and a brick wall model with shear failure were conducted, and the corresponding failure modes and curves were similar with that theory and test results.

Abstract:Experiments on axial compressive property, shear performance along horizontal bed joint and behavior under combined compressive and shear loadings were carried out to study the failure characteristics and failure mechanism of the shale fired heat-insulation block masonry. The results showed that the main cracks were formed nearby the vertical mortar joint when shale fired heat-insulation block were failed under axial compressive and the skin of masonry were fallen close to ultimate load. The main failure pattern of shear along horizontal bed joint of masonry was mainly single shear failure and its failure was obvious brittle failure. There were shear friction failure, shear compression failure and diagonal compression failure under combined compressive and shear loadings. Test average result of axial compressive strength was higher than code values; the average result of shear along horizontal bed joint and shear under combined compressive and shear loadings were lower than calculating values and the formula for were established separately. The strength of shear under combined compressive and shear loading increased with increasing axial pressure. The calculation formula of stress-strain relation of shale fired heat-insulation block masonry was established. Poisson ratio and elastic modulus of shale fired heat-insulation block masonry was proposed.

Abstract:In order to solve the transient heat conduction problems in three-dimensional(3D) axisymmetric continuously nonhomogeneous functionally graded materials(FGMs) more effectively, a novel numerical method based on the meshless natural element method is proposed. Axial symmetry of geometry and boundary conditions helps to transform the 3D axisymmetric problem into a two-dimensional(2D) prolem. In order to simplify the imposition of the essential boundary conditions, the natural neighbour interpolation is adopted to discretize the temperature field within the cross section. The variations of functionally graded material properties are simulated by employing proper material parameters at Gauss points. The spatially discretized heat conduction equation is solved numerically with the traditional two-point difference technique in the time domain. The present method not only broadens the application scope of the natural element method, but also will be generally available to transient heat conduction analyses of 3D axisymmetric solids.

Abstract:To address the limitations of existing building energy benchmarking methods, a new method has been proposed for residential buildings. Grey relational analysis is used to define the correlation between different influencing factors(i.e., typical parameters) and total building energy consumption. The correlation is used as the weights of corresponding factors. Based on the weighted parameters, Cluster Analysis is performed to classify buildings into different groups. For each group, Accumulative Frequency Distribution is then conducted to identify its energy benchmarking value. This value also makes it possible to evaluate the energy-saving potentials of different buildings. The method was applied to a residential building energy consumption database established by the Architecture Institute of Japan. The results show that the method can classify buildings into different groups by both taking into consideration various influencing factors of building energy consumption as well as their weights. It can also determine building energy benchmarking values for each group and helps identify energy-saving potential of buildings and provide energy-saving strategies for occupants.

Abstract:An experiment and simnlation of solar ejector-compression combined refrigeration system were conduced, and the results of the simulation model was verified with experimental data. The influence of the generator temperature and middle-temperature on solar ejector-compression combined refrigeration system has been studied. Research shows that: with the increasing of generator temperature,it is found that the COP and the EER increase first and then decline, and the power consumption decreases first and then increases at the same time. In addition, it was seen that there exists the optimal generator temperature and the optimal middle-temperature,and the optimal generator temperature and middle-temperature are between 78 and 80℃, 7 and 10℃ over the range of research conditions respectively. The minimum total power consumption can be obtained, when the optimal generator temperature are from 78 to 80℃,and the maximun cooling capacity and EER can reach to 2 245 W,0.34 respectively when the optimal middle-temperature and from 7 to 10℃.

Abstract:The indoor thermal environment and bed climate directly affect the sleeping thermal comfort of human head and the covered body, respectively. In order to analyze the matching relationship between the two thermal environment so as to meet the body's sleep thermal comfort level, the skin temperature of the subjects and the thermal sensation and thermal acceptability level of the subjects were recorded with various temperatures of bed climate and indoor temperatures. The results show that the thermal sensation is more sensitive to bed climate than to the indoor thermal environment during sleep. In addition, the comfortable range of thermal sleep environment is obtained through analyzing the relationship between the sleeping thermal environment and the subjective evaluations for partial and overall human body.

Abstract:Early warning of leakage, especially small leakage, is significant for safety maintenance of thermal pipeline. Due to spatial resolution, the measuring accuracy of distributed fiber optic sensor for local temperature variation caused by small leakage is low and the measurements are quite different from the actual temperature field. Based on Brillouin optical time domain reflectometer(BOTDR), a new method to establish a mapping relationship between the BOTDR measurements and the actual temperatures is proposed. Laboratory experiments were carried out to simulate small leakage and achieve the measurements of gradient temperature fields. Feature extraction of the measured data is then conducted through Gaussian fitting. With artificial neural network(ANN), a mapping model of the actual and measured temperature features is established. The results demonstrate that: the designed experiment can accumulate enough prior data to derive an ANN model, based on which a mapping relation of the actual temperature field and the BOTDR measurements can be achieved to improve the measuring accuracy of BOTDR and provide a reference to propose warning strategy.

Abstract:The accurate energy consumption perdition for building is critical to improve the energy efficient of the operation of the operation of large-scale central air conditioning system in summer. Firstly, the influencing factors of cooling load were identified to determine the inputs of cooling load predition model. Then, the indirect measurement method was proposed to obtain the shopper rate based on the supply frequencies of new wind-8units to identify the custom number in summer. Last, an AFC-HCMAC neural network algorithm is proposed to for dynamic cooling load prediction. The results show that compared with the traditional HCMAC algorithm, the proposed AFC-HCMAC algorithm can effectively reduce the neural network nodes and improve the prediction accuracy. The shoppers rate plays an important role in the cooling load prediction for shopping mall. Increasing shopper rate in the inputs of prediction model can significantly improve the prediction accuracy of dynamical cooling load forecasting for shopping mall.

Abstract:A new method of measuring the albedo of urban prototype is proposed. The method is used to measure ten urban prototypes with different pavement reflectivity and with south-north orientation, west-east orientation and cross-street orientation, respectively. The results are compared with those obtained by the ASTM E1918-06 and the modified ASTM E1918-06. It is found that when the variation of the incident solar intensity is less than 20 W/m²(a tolerant error stated by ASTM E1918A), the ASTM E1918-06 can either underestimate or overestimate the albedo of the urban canyon prototype up to 0.10. For an urban canyon(UC) with an aspect ratio of 1.0, an change from 0.15 to 0.65 of pavement albedo would cause an increase of the albedo of the UC from about 0.15 to 0.35 if the albedo of the roof and wall is about 0.40. Raising the albedo of the pavement in a UC is not an effective way to increase the albedo of the urban area, especially for UC with great aspect ratio. For low aspect ratio UC, raising the albedo of the pavement or of the parking lot introduces a sizable additional diffuse reflected radiation to the pedestrians. Therefore, it should be cautious to developing reflective pavements as an urban cooling strategy.

Abstract:A simplified mathematical model was established to calculate the heating transfer capacity through MATLAB program. Compared with the results of thermal performance test, the mathematical model was reasonable with a maximum error less than 5.15%. According to the results of model and experiment, in the constant flow condition, heating capacity of the ceiling increases as the temperature increases, meanwhile heating capacity decreases as the heat exchange coil spacing increases.

Abstract:It is important to analyze the hygrothermal processes of building envelopes and the material properties are critical in the analysis. The hygric properties of the commonly used porous building materials in China are insufficient. Measurements on the B07-level autoclaved aerated concrete are carried out at 20~25℃ based on ISO and ASTM standards of static gravimetric tests, pressure plate tests, cup tests, capillary absorption tests and vacuum saturation tests. All the hygric properties have been obtained, including sorption isotherms, the water retention curve, the vapor permeability, the liquid diffusivity, the capillary absorption coefficient, as well as the capillary and vacuum saturated moisture content.

Abstract:An exergy analysis model was developed for a novel ice storage system with cold air distribution and its main surface air coolers. Based on this model, the influence of heat and humidity ratio, fresh air ratio and temperature difference between supply air and indoor air on the exergy efficiency of the system and the exergy loss rate of its surface air coolers was studied. Finally the important parameters for system optimization were identified. The simulation results show that the exergy loss rate of the surface air cooler for secondary mixed air is positively proportional to the variation of heat and humidity ratio, while it is inverse for the other; the exergy loss rate of the surface air coolers for fresh air is positively proportional to the variation of fresh air ratio, while it is opposite for the other; the exergy loss rate of the surface air cooler for primary mixed air is positively proportional to the variation of temperature difference between supply air and indoor air, while it is inverse for the other.