Abstract:In order to investigate the reinforcement effect and calculation method of stone arch bridge strengthened with injecting high performance cement composite concrete, an unreinforced stone arch bridge model and an load-carrying stone arch bridge model strengthened by injecting high-performance cement composite concrete were made for the destruction test.The experiment results show that the ultimate compressive bearing capacity of stone arch bridge model strengthened by injecting 60mm high-performance cement composite concrete can be improved by 25%, when the sustained load reaches 70% of the failure load.Strengthening stone arch bridge by injecting high performance cement composite concrete can effectively improve the failure load and properties of brittle failure, which is an economical and effective arch bridge strengthening method.The calculation results of strengthening arch bridge bearing capacity were in good agreement with experimental results, and the calculation method can be employed to design in strengthening engineering.

Abstract:Based on the assumption of transversely isotropic property of material, the nonlinear in-plane dynamical behavior of CFRP cable under forced load was investigated.The partial differential equation for in-plane dynamics of the inclined CFRP cable was obtained by reducing spatial kinetic theory.Then, the ordinary differential equations for analyzing the dynamic behavior were obtained in Galerkin method and through dimensionless treatment.The 4-order Runge-Kutta method for differential equations was utilized to get the time history, phase and power spectrum for understanding the nonlinear dynamic behavior of inclined CFRP cable.The rich nonlinear dynamic behavior and phenomena were observed.

Abstract:As there are geometrical nonlinearity and concrete shrinkage and creep in long-span flexible structures such as concrete cable-stayed bridges, so, based on differential method, the geometrical nonlinearity balance equation for large rotation displacement - small strain analysis was deduced under co-rotational coordinate system, which considered the initial strain.Combining with finite element formula for equivalent nodal force of shrinkage and creep by using initial strain method, then, through building total and incremental relationships derived from differential equations of nodal displacements and forces, a practical algorithm for geometrical nonlinearity analysis of the plane beam considering concrete shrinkage and creep under global coordinate was obtained, and its calculation flowchart was also given.The geometrical nonlinearity analysis of the tower of long-span concrete cable-stayed bridge with hybrid girder considering concrete creep was performed.The results demonstrate that the algorithm developed can solve the above mentioned problems and has some engineering application value.

Abstract:To address the damage identification problem of frame structures after earthquakes, a new damage identification method based on the wavelet packet decomposition was proposed.The structural vibration signal under environmental vibrations was used to constitute damage indicator (DI) as follows: the vibration signal was decomposed into each frequency band with wavelet packet decomposition, then, a damage indicator was established on the basis of the energy ratio variation on frequency domain.On the above basis, a 3D finite element model of a frame structure was created by calculating DI using the proposed method.The influence on the damage identification of different floors and different types of excitation was discussed.The results show that the DI proposed can be used to identify damage effectively and the DI value is approximately linear to the damage degree.Damage identification based on vibration signal of higher floor is better than that of lower floor and the damage identification effect with velocity signals is better than acceleration signals.

Abstract:Experiment results of RC beam-column subassemblage show that the slippage of the longitudinal bar within joint and shear deformation of joint have significant influence on the seismic behavior of the subassemblage, but this kind of joint inelastic deformations has always been ignored in the seismic response analysis of RC frames.In order to simulate the effect of the inelastic deformations of beam-column joints, a zero-length section element was combined to the ends of the beam based on the fiber model.Longitudinal bar slippage was modeled with stress-slippage constitutive model, while stress-equivalent slippage constitutive model was adopted to simulate longitudinal bar slippage and joint shear deformation simultaneously.Nonlinear responses of a typical RC planar frame under rare earthquake excitations were investigated, and the effect of joint inelastic deformations on the global and local responses of the frame was analyzed contrastively.The results show that the maximum top displacements and maximum inter-story drift ratios increase or change slightly, the quantities of the plastic hinge of the beam and the column ends decrease, and the rotation ductility demand of the beam and the column decreases as a whole when joint inelastic deformations are considered.There is a certain safety margin for the joints of the frame to avoid shear failure.Ignoring joint inelastic deformations will result in significant errors if the seismic response of RC frame is large, and the ordinary finite element model of ignoring joint inelastic deformations can be adopted if the seismic response of the structure is relatively small.

Abstract:To study the energy dissipation capacities of double-wall precast concrete (DWPC) shear wall and to provide reliable scientific basis for the local standards, three kinds of full scale specimens of different boundary element details and shear span ratio were tested and compared under low-cyclic reversed loading, including six DWPC shear walls and three normal cast-in-situ shear walls.First, hysteretic behaviors and energy dissipation capacity of all specimens were analyzed synthetically.Then, equivalent viscous damping coefficients were calculated and compared.The result shows that the hysteretic behaviors and energy dissipation capacities of DWPC shear walls are close to those of cast-in-situ shear walls.It also shows that the DWPC shear walls have remarkable energy dissipation capacity as well as high seismic performance.The study contributes to the seismic design and in-depth study for DWPC shear wall structure.

Abstract:The genetic evolutionary structural optimization (GESO) is used for single loading case study, but it still needs to be improved in practical engineering.In this paper, Separated elements model GESO was used to design reinforcement layout of the reinforced concrete (RC) members under complex elements stress states and multiple loading cases in order to fulfill the needs of engineering application.Separated elements model GESO involves the nonlinear analysis of ANSYS finite element software as a platform, in which solid65 element is chosen as the concrete element, while link10 element is regarded as the reinforcement element herein.Separated elements model GESO is further verified by considering deep beams and shear walls with openings as the numerical examples.The reinforcement layout of RC members under complex stress states can be optimized under multiple loading cases including loading combination.The influence of subjective factors has been dramatically reduced with intuitive reinforcement layout results, which are in accordance with the stress mechanism and will not lead to centralized reinforcement layout.The application of separated elements model GESO can save steel consumption by comparing with elastic stress design method, since the utilization efficiency of reinforcements is also improved.

Abstract:As it is difficult to repair the damaged conventional coupling beams, the concept of providing an energy dissipation fuse in a coupling beam has been developed and investigated over the past few years.The energy dissipation fuse is designed to dissipate seismic energy in moderate earthquakes or rare earthquakes, and can be replaced easily after the earthquake.Based on the ABAQUS procedure, a refined analytical model of large scale coupled shear wall specimen with replaceable coupling beams was established to conduct static push-over analysis.The material constitutive model and modeling approach were also introduced.By comparing the computational and experiment results, it can be found that the replaceable coupling beams can make the damage and energy dissipation concentrate in the replaceable fuse, and the simulation methods can precisely predict the initial stiffness and peak bearing capacity of the new shear wall.In addition, the simulation can well predict the yield sequence of shear wall specimen.It is hoped that the proposed simulation methods can be widely used to simulate similar shear wall structures in future.

Abstract:3 groups of 18 shear specimens were tested to investigate the failure processes，failure characteristics and ultimate capacity.It was shown that, due to the knocking out of the slot rib, the upper and lower core columns were connected and thus made them collaborate.As a result, the shear strength of the grouted slotted block masonry was moderately higher than that of the ordinary grouted masonry.Based on the shear mechanism of concrete block masonry, a shear strength formula of grouted slotted block masonry was built with Hoffman criteria, and a uniform shear strength formula suitable for both slotted and unslotted block masonry was proposed.The calculated values, which were generated by formula developed in this method, were in good agreement with the test results.

Abstract:The response law of micro environmental temperature in one dimensional concrete under the natural environment with/without shelter was studied.Based on the Fourier heat conduction equation and third boundary condition, the response mode of micro environmental temperature in one dimensional concrete under the natural environment was inferred, and the test was carried out to testify the rationality of the mode.In addition, a new method was summarized to solve the parameters, such as thermal diffusion coefficient and surface heat transfer coefficient.The results show that the modes of micro environmental temperature in one dimensional concrete under different conditions were fitted to describe the temperature response law in concrete.The response laws were observably affected by the condition of with/without shelter, and the differences were manifested in the amplitude, extremum and occurrence time, which was caused by the difference of the heat exchange pattern.The parameters, such as the thermal diffusion coefficient and surface thermal conductance, which was inferred from the test, are high precision.

Abstract:Taking the pile unit and the soil unit for force analysis, the basic differential equations were established.The equivalent stiffness coefficients of the pile and the unit thickness of soil around each pile were developed, taking into account the pile group effect and the interaction between the pile and the soil in the load transfer method.Based on the relation between pile-soil-cushion and boundary conditions, the pile-soil stress ratio and the influence of important parameters were obtained.In the meantime, the pile group effect and the soil lateral pressure were taken into account in the proposed method.The pile-soil stress ratio calculated agrees well with those measured from the model test of pile foundation, showing the rationality of the approach and guiding significance in engineering practice.

Abstract:In order to discuss the torsional behavior of single pile in layered subsoil, various bearing states (elastic and plastic) of the subsoil were considered, and the double broken line model (i.e., the ideal elastoplastic model) was used to simulate the load transferring law along the pile shaft.The plastic zone developmental depth in the subsoil was chosen as an independent variable to derive the solutions for the torque-twist angle curve at the pile top and the torque-angle distribution curves along the pile shaft in layered subsoil.A recursive algorithm was presented to calculate the torque and the twist angle with the computer program worked out as well.Based on the solutions obtained, the torsional behavior of the pile shaft in the single-layer and the double-layer subsoil was analyzed respectively.Finally, an engineering project was used to verify the present method and to carry out the parameter analysis.The result shows that the consideration of various elastic or plastic states of the subsoil will result in a more reasonable outcome, compared with engineering practice.Furthermore, for a constant torque T, the torsion angles φ at the pile top will decrease with the decrease of the shear modulus Gp and radius r0 of pile shaft.An obvious effect of r0 on the Tφ curve was observed, in which the torsional bearing capacity may be increased 4~6 times if the value of r0 was doubled and other conditions remained unchanged.The upper soil layer may be treated to improve the torsional performance with an advised effective treatment depth of 0.2 times the pile shaft length.

Abstract:Numerical simulation research has been conducted in order to reveal the mechanism of the layered fracture within surrounding rock in deep-buried tunnel.Analysis of the history of the rock mass and its environment suggests that the mechanism of the deep rock mass was located in the post-peak stage, the post-peak characteristic indexes and the excavation response equations were selected based on the post-peak stress-strain characters of rock mass.A numerical model was established, a monitoring scheme of surrounding rock response was designed which was caused by excavation, and a fair amount of excavation was completed by numerical simulation method, and the phenomenon of layered fracture within surrounding rock was reproduced in the numerical simulation.According to the monitoring results about the rock stress and deformation distribution from the experiment, and based on the critical conditions under which the layered fracture in surrounding rock was emerged, the relationship of the fracture layer number of surrounding rock, the radius of layered fracture zone and the maximum peak stress with the post-peak characteristic indexes were studied.Based on the surrounding rock stress redistribution related to the excavation of underground structure and the fracture mechanism of rock mechanics, this paper analyzed the mechanical mechanism of the formation of secondary free-surface and multiple excavation surface.The numerical results provide the basis for the layered fracture in deep surrounding rock, and the confusion about the unobserved phenomena of layered fracture in numerical simulation is also eliminated.

Abstract:Based on Winkler foundation model and indirect adjustment theory, this paper proposed a fitting model to reconstruct the deflection curve for the structural performance evaluation of the buried pipeline by using multi-point subsidence measurements.According to error propagation theory, the precision of the derived deflection and the stress of the pipeline structure were investigated.Two analytical examples of the pipelines under a concentrated load and a uniformly distributed load were given, which demonstrate that the proposed model has achieved greater accuracy in the estimation of pipeline deflection and stress by comparing with the conventional polynomial model.Combined with the application to a practical project regarding a buried gas pipeline in the vicinity of the construction site of a high-rise building, the effectiveness of the fitting model in the stress analysis and safety evaluation of buried pipeline was verified as well.

Abstract:Taking the water temperature of lakes and reservoirs as the research object, a lake water temperature calculation model was built.The correctness of the calculation model was validated by comparing the model results with measured data. The variation and influencing factors of the water temperature of lakes and reservoirs in Changsha area were studied with the model.The load capacity of heat and cool supply of lakes and reservoirs were calculated, and the influencing factors of the load capacity of the heat and cool supply were analyzed.The results can provide references for the design of water source heat pump system using lakes and reservoirs as the heat source.

Abstract:Based on the two-dimensional heat transfer model for single U pipe in GSHP (Ground Source Heat Pump) system, this paper analyzed the influences of main different multi-variables on the heat resistance, including the heat conductivity coefficient of backfill materials, the buried pipe spacing in the borehole and the water velocity in the pipes.Improved Genetic Algorithm (IGA), in which elitism selection and migration were combined, was used to optimize the heat resistance in the borehole based on foregoing multi-variables.According to the optimized result, the minimum heat resistance was obtained when the heat conductivity coefficients of backfill materials, the buried pipe spacing and the water velocity in the pipes reached their maximal designed values.The results are useful for the optimization of the heat exchanger design of GSHP.

Abstract:The concept of air stability is derived from atmospheric stability, which represents the extent of stability of room air.Experiments on thermal manikin were performed to investigate the effect of air stability on the dispersion of exhaled flow.Seven cases with the combination of three ventilation patterns (no ventilation, mixing ventilation and displacement ventilation) and two breathing modes (continuous and periodic) were applied.The trajectory of exhaled flow was visualized and measured by smoke visualization and velocity measurement, respectively.The results show that both the continuous and periodic exhalation are significantly affected by the air stability with respect to the trajectory and velocity decay.Meanwhile, the turbulence highly develops in the periodic flow, making the contaminant mix well with the ambient air and the flow flatter in comparison with continuous jet.As the stable condition restrains the upward movement of the flow, it becomes flatter under stable condition compared with neutral condition even though they have similar Ar and body plume.In addition, the velocity decay is smaller for stable condition because it entrains less ambient air.

Abstract:The Typical Meteorological Day of Guangzhou summer was realized in Hot-Wet Climatic Wind Tunnel, and the thermal transfer process of two specimens with the same construction was studied in the wind tunnel.In the experiment process, one of the specimens was watered and the other one was not watered.The experiment result illustrated that the evaporative cooling effect was very significant when the specimen was watered.Compared with the non-watered specimen, the highest outer surface temperature and the highest inner surface heat flux of the watered specimen decreased by 10.9 ℃ and 14.8 W/m2, respectively.Additionally, the thermal resistance of the watered specimen was one time bigger than that of the non-watered specimen.It was demonstrated that the watered specimen had better heat-insulating property than the non-watered specimen.Moreover, the Penman-Menteith model was used to calculate the hourly evaporation of the watered specimen.The total hourly evaporation was divided to thermal evaporation and dynamic evaporation.The variations of the total hourly evaporation, thermal evaporation and dynamic evaporation were analyzed.The hourly evaporation data were used to calculate the surface thermal balance equation.The result illustrated that 64.5% incoming short wave radiation was consumed in the evaporating process.In summer, evaporating process could decrease the solar radiation illuminated on the building surface, diminish the surface temperature, reduce the thermal flux flowing into the room and save the air-conditioning energy consumption.

Abstract:We constructed a Bayesian quantile linear regression model based on Gibbs-DA sampling algorithm for the uncertainty risks of quintile regression model parameters.According to the normal-exponential representation property of asymmetric Laplace distribution, we established a working likelihood function for the quantile regression model with latent variables, gave its parameters' posterior distribution with a multivariate prior distribution, whose full condition distribution is generalized Guassian.We also used Gibbs sampling technique and data argumentation method to design a Gibbs-DA simulation procedure.Finally, we made an empirical study to analyze energy consumption in China.The results have shown that Bayesian procedure can be efficiently used to build quantile regression models and applied to the elasticity of energy consumption.