Abstract:The influence law of failure time and residual bearing capacity of the steel columns on progressive collapse of steel frames was studied by using a single degree of freedom (SDOF) model. The displacement of the steel frames decreases as the failure time and residual bearing capacity of the steel columns increase. On the basis of the theoretical solution of the SDOF model, boundary condition of the model was determined to consider the failure time effect. τ was defined as the ratio of the failure time to natural period of the SDOF model. For τ<0.2, the failure time can be ignored. For τ>3.0, a static method can be used to estimate the structure behavior. However, for 0.2<τ<3.0, the failure time should be considered in the progressive collapse analysis. When the resistance model is ideal elastic-plastic and rigid-plastic, the equivalent SDOF model of the steel columns can be theoretically analyzed to determine the calculation method of the failure time. Considering the deformation of the steel columns after explosion as the initial state, the calculation process for the residual bearing capacity of the steel columns is gained by combining with numerical calculations. The results show that the failure time and residual bearing capacity significantly influence on the progressive collapse of the steel frames, and those effects should be considered in the progressive collapse analysis.

Abstract:This paper study discussed the applicability of Park-Ang model modified by Wang based on the pseudo-static test results of reinforced concrete columns. The structural damage index based on the component level was selected, and both the incremental dynamic analysis and fragility analysis of the reinforced concrete frame were conducted. Additionally, the prediction by the modified method to evaluate the seismic performance in terms of the damage index of the RC frame was compared with the maximum inter-story drift ratio of the fragility analysis result. The analysis results show that the modified Park-Ang model that considers the loading path effect predicts well the cumulative damage process after the first damage, which discriminates the specimen damage status accurately, the damage development process, and the overall and local failure mechanism. Further, the weak links can be accurately distinguished. However, the damage index higher than 1.0 may be caused by using these methods, which cannot accurately reflect the basic meaning of the original definition. Compared with the maximum inter-story drift ratio, the seismic performance evaluation method using the damage index considers the structural response and properties. The modified method can be used to evaluate the structural performance more comprehensively and predict the failure probability of the structures under different earthquake loads.

Abstract:This study focused on the behaviour of the frame-supported grid light-weight slabs (FSGL slab) with different forms under low-cycle reversed loadings. Compared with the existing evaluation models showing different damage performances, a damage model was proposed for the FSGL slab system. The mechanical properties of the FSGL slab system were investigated by OpenSees simulation, and the corresponding mechanical parameters were obtained to verify the proposed damage model. Meanwhile, the range of damage index value corresponding to the cumulative damage stage was provided. Furthermore, on the basis of test results, the cumulative damage of FSGL slab system at each stage was described by ANSYS software. Finally, the post-repair recommendations for FSGL slab system were given.

Abstract:During the initial impoundment of mass concrete dam, the reservoir water with low temperature would be critical to the temperature field of dam body, which affects the deformation of dam body and even results in temperature cracks. Therefore, in order to investigate the thermal stress distribution of mass concrete during the initial impoundment, the concrete was assumed as a continuous porous media in this paper. In consideration of the basic theories of solid mechanics, hydraulics, and thermodynamics, the multi-field coupling equations of unsaturated porous media that include momentum conservation, mass conservation, and energy conservation were provided as the function of displacements, pore liquid pressure, pore gas pressure, temperature, and porosity. The finite element analysis program was then developed. A mass roller-compacted concrete block was considered for coupling analyses on the seepage field, temperature field, and stress field. The analysis results show that the temperature reduction and principle thermal stress of the concrete block considering the multi-field coupling process are greater than those without the coupling effect.

Abstract:According to the structural properties and basic isolation theory, a new three-dimensional composite isolation pier was developed, which can effectively reduce the horizontal and vertical loads due to earthquake. This study introduced the isolation device configuration, work principle, and design theory. To evaluate the structural performance of the three-dimensional composite isolation pier, shaking table test of the rigid body mass was carried out. The test results show that the composite isolation device exhibites superb isolation performance. Furthermore, the proposed composite isolation device improved the cost-effectiveness and constructability, which can be used for the practical engineering in the Chinese rural area.

Abstract:For the composite bridge deck system composed of orthotropic steel deck and ultra-high-performance concrete (UHPC) layer with 35 mm UHPC plate and 20 mm wearing layer, the UHPC layer is too thin to use conventional shear connectors. Therefore, an innovative shear connectors using the welded rebar mesh was proposed. Load-slip curve and ultimate bearing capacity were evaluated by push-out test. In the background of a Yangtze River Bridge, the optimal lay out of shear connectors was investigated by segmental model of a bridge deck. The test results showed that the brittle failure of the shear connectors occurred, and the ultimate bearing capacity of the shear connector with the 50 mm welded rebar mesh was 119kN. The slippage of the shear connector with the welded rebar mesh was less than that of the stud under the same load ratio. Furthermore, the stress at the bottom of UHPC layer should be considered in the arrangement of the shear connectors. Increased layout density of the shear connectors reduced the transversal and longitudinal tensile stress at the bottom of UHPC layer up to 36.3 %.

Abstract:Based on the Eulerian-Eulerian two-phase flow theory, the live-bed pier scour was carefully simulated with the consideration of suspended load. The riverbed variations were obtained using the non-equilibrium sediment transport model by calculating the mass exchange between the suspended load and traction load. By redeveloping a Computational Fluid Dynamics (CFD) software, i.e., ANSYS Fluent, the sediment transport rates and exchange flux between the suspended load and traction load were calculated using the shear stress of sediment and sediment concentration. By doing this, the riverbed boundary can be real-timely updated according to the calculated riverbed variations to conduct the live-bed scour simulation. The accuracy and rationality of the proposed simulation was fully verified by comparing with the classic theory and several experimental results from the viewpoints of the suspended load distribution, scour depth, and scour hole profile. The significant influence of the sediment concentration on the scour performance was finally proven by a parametric study. It can be concluded that using the live-bed scour models based on the two-phase flow theory should be very necessary for an accurate simulation.

Abstract:In order to study the mechanism of new one-way pre-stressed tendons applied to cable-pylon anchorage zone, as well as to clarify the actual stress distribution of the tendons, a full-scale model test and finite element analysis were conducted. As the construction background, Xijiang River Bridge of Guangzhou - Zhongshan - Jiangmen highway was considered. To simulate the large-tonnage inclined load of the cable, four short parallel wire cables and a reaction beam were designed and manufactured. Strains, displacements, and cracks of the structure were measured. The predictions by the finite element analysis agreed well with the test results. The linear strain distributions of the structure were measured even at 1.2 times of designed load, and cracks did not occur in the main load-resisting members. In addition, the safety coefficient 2.04 was estimated to prevent cracks, and enough prestress reserve was provided by the one-way pre-stressed tendons placed in the longitudinal direction wall.

Abstract:This paper presented the analysis results of the wind field characteristics and wind pressure of the roof on the basis of the measurement data of the roof obtained in an instrumented low-rise building, which sits in Wenzhou and was affected by the typhoon Fitow. The results reveal that, with the decrease of the average interval, the maximal average wind velocity increases; the turbulence intensity tends to decrease with an increasing average wind velocity. Furthermore, the average wind pressure at the edge of the building roof and ridge is negative with large fluctuation. The variation tendencies of wind velocity and wind pressure show the obvious correlation between the velocity in wind field and wind pressure on the roof. The correlation analysis between the wind field characteristics and wind pressure on the roof was then conducted within different time intervals. The analysis results show that the wind velocity and wind pressure are correlated well at an average interval of 5 minutes, which indicates that the average interval of 5 minutes can be reasonably used to calculate the wind load.

Abstract:To study the wind-induced strength and stability properties of large cooling towers with different aerodynamic measures, the pressures of the rigid-body models without or with three different aerodynamic measures were measured by the wind tunnel tests. A nuclear super-large cooling tower inland was considered as the test specimen. The surface wind mean and fluctuating pressure characteristics were investigated from the test results. Furthermore, finite element analysis was conducted to evaluate the dynamic characteristics of natural vibration, the wind-induced response, and the overall and local stability. Finally, the effective rules of the different aerodynamic measures on wind resistance for super-large cooling tower were proposed.

Abstract:In order to investigate the eccentric compression performance of side pressure laminated bamboo lumber (LBL), 18 LBL column specimens with the slenderness ratio of 36 and cross-section of 77 mm × 77 mm were designed considering different eccentricity, and loaded under tangential eccentric compression. The test results show that the bamboo-strip connections and bamboo joints are the weak zones for the LBL columns under tangential eccentric compression, which determine the failure modes. The ultimate longitudinal and lateral strains for Face C increased with the increase of the eccentricity ratio, while these values for Face A, Face B, and Face D decreased. The discreteness for the ultimate longitudinal strain of the specimens with small eccentricity was relatively large. However, the ultimate lateral strain values for all specimens exhibited obvious discreteness. After the ultimate strength, the load-carrying capacities of the specimens with small eccentricity decreased significantly compared with those of the specimens with large eccentricity. However, the smaller eccentricity resulted in more evident discreteness of the ultimate load values. In addition, the strain was distributed linearly at the cross-section of the columns, which satisfies the plane-section assumption. Furthermore, an equation to predict the eccentricity influencing coefficient on the bearing capacity of laminated bamboo lumber columns was proposed. The predictions gave a good agreement with the test results.

Abstract:In high-rise buildings, construction process and non-load effect are not considered in conventional finite element analysis. In this paper, for the construction project of Shenzhen Pingan Financial Center (PAFC)， which is the highest tall building under construction in China, full construction process simulation was conducted by dividing the structure into 25 construction stages using Midas/Gen software. Vertical cumulative deformations of the concrete core-wall and mega columns, and the deformation variance due to the shrinkage and creep of concrete were studied. The simulation results show that vertical deformation caused by the shrinkage and creep causes more than half of the total deformation, and the effect of the shrinkage and creep cannot be ignored. In addition, the internal forces of the critical members in the building structure including belt trusses, outriggers, mega diagonal brace, and V-typed brace during construction were also investigated. The different loading conditions were applied to the structural members at different locations. The stress of cord members in the trusses changes little, while the stress of web members in the trusses changes significantly during the construction process, which indicates that the design of the structure members can be varied with the loading conditions. In the final construction stage, the stress of the structure members is less than the material strength with a certain safety margin, and the measurement data can be used as reference for actual construction.

Abstract:The backward tracing method of the shortest path ray tracing algorithm with dynamic networks can solve the unstability problem in the backward tracing procedure of the LTI (Linear Travel-time Interpolation) algorithm, but the computational efficiency of the method is low. This study presented an improved method on backward tracing. According to the location information of the secondary sources for the nodes and the law of wave propagation, a large number of redundancy calculation are excluded in the backward tracing of the dynamic networks tracing algorithm. The numerical examples show that the improved method exhibits the higher computational efficiency. The calculation efficiency of the improved method is several times that of the backward tracing method of the dynamic networks tracing algorithm. When the improved method is applied to the improved algorithm of the shortest path ray tracing with dynamic networks, the computational efficiency of the algorithm can be increased by about 100 %.

Abstract:In this study, a new four-order moment method for reliability analysis of slope stability was proposed. The reliability analysis of slope stability was conducted by the combination of the uniform design method, the RBF neural network technique, and the maximum entropy principle. The network training sample space of cohesion and internal friction angle was firstly determined by the uniform design method, and the slope safety factor related to the samples was obtained by the strength reduction method using the finite element analysis. The RBF neural network was trained by the samples and their corresponding safety factors. The safety factors of the slope satisfying the statistical requirement were obtained by the well-trained neural network, and the first four-order moments of the slope safety factor were calculated. Furthermore, the approximate expression of probability density function of the slope safety factor, the slope failure probability, and the corresponding reliability index were investigated by the maximum entropy principle. Compared with the results from Monte Carlo method, the proposed method shows high precision.

Abstract:The granular material pile has its own deformation characteristics under vertical loads. The granular material pile shows not only a vertical compressive deformation but also a radial expansion near the top of the pile. According to the study of this load transfer mechanism, a new equation was developed to calculate the compressive deformation of a single granular material pile. On the basis of this investigation way, a new method to predict the settlement of the composite foundation reinforced by granular material piles such as stone columns was developed. In the analysis model, the granular pile was treated as an elastic material satisfying Hooke's law, and the lateral confining support provided by the surrounding soil was assumed as lateral soil pressure. Further, the beneficial influence of the lateral restraint of the reinforced cushion as well as its development within depth on restricting the lateral bulging of the granular pile was taken into account. Finally, a case study was performed to validate the proposed method. The foundation settlements predicted by the proposed model were close to those of existing calculation methods. The prediction results indicate that the proposed method based on the load transfer mechanism is more practical because the proposed method can consider the variation law that the depth of lateral deformation of the pile increases with the increase of the vertical load acting on the top of the pile.

Abstract:In order to explore the performance of European rock asphalt modified asphalt binder, laboratory tests on asphalt binder modified by different contents within 25% of the rock asphalt were carried out. On the basis of the test results, the properties of the modified asphalt binder such as penetration, penetration index, equivalent softening point, equivalent fracture point, softening point, ductility, viscosity, mass loss after RTFOT aging, retained penetration, and aging index were presented and analyzed. The test results and analyses indicated that the high-temperature behavior, temperature susceptibility, applicable temperature range, and aging resistance of rock asphalt modified asphalt binder were improved considerably as the rock asphalt content increased. However, the low temperature behavior and ductility of the rock asphalt modified asphalt binder were deteriorated by the increased rock asphalt content. Therefore, additional tests on the asphalt mixture are needed to evaluate the performance of the rock asphalt modified asphalt binder, particularly for low temperature behavior.

Abstract:This paper proposed an innovative design for in-door electrical heating system that uses commercially available carbon fiber tape (CFT). The design of the heating panel, layout and the construction of a prototype were presented with experiment results. The heating panel was made of three carbon fiber tapes and embedded in cement mortar. Each CFT was 50 mm wide with a spacing of 200 mm. Several experiments were conducted to examine the performance, temperature variation with time and location, and energy consumption of the proposed system. The experiment result has shown that the heating system performs satisfactorily and is heated up quickly with an average speed of 1.83 °C/min. The temperature gradient in the vertical direction is much larger than that in the horizontal direction. The electrical resistance of the CFT is stable, and the reflective membrane and insulation board are effective in reducing the heat transfer towards the bottom. The automatic temperature control device can reduce the energy consumption significantly.

Abstract:An equivalent thermal resistance model for the heat transfer calculation of radiant floor based on shape factor was developed in this study. The proposed model was verified by numerical simulation, and compared with the data from the universal single power function of ISO standard, the fin model in ASHARE handbook, and the equivalent thermal resistance model in design handbook. The heat transfers obtained by the numerical simulation disagreed significantly with the existing methods including the universal single power function of ISO standard, the fin model in ASHARE handbook, and the equivalent thermal resistance model in design handbook. The maximum error rates were 20.2 %, 30.4 %, and 22.8 %, respectively, when the tube space ranges from 50 to 250 mm, the thickness of fill layer above pipe ranges from 25 to 65 mm, and the average hot water temperature ranges from 25 to 45 ℃. On the other hand, the maximum difference of the heat transfer predictions between the proposed model and the simulation software was less than 3%. When the tube space ranges from 50 to 200 mm, the thickness of fill layer above pipe ranges from 15 to 55 mm, and the average cold water temperature ranges from 10 to 20 ℃, the maximum error rates of the heat transfer predictions between the numerical simulation and the existing methods were 80.1 %, 17.7 %, and 16.8 %. On the other hand, the heat transfer predicted by the proposed model showed less than 2 % of difference from that of the numerical simulation.

Abstract:Taking temperature and humidity independent control air conditioning system as the research project, different models of the system have been established.Through analysis and calculation of each system's COP of a practical engineering project, it reveals the differences in performance and regional differences of the independent control system itself. By comparison,the heat pump wheel dehumidification system should be considered first，where the outdoor air humidity ratio is relatively small. On the other hand,the liquid desiccant dehumidification system and condensate system may be better where the ratio is relatively large.

Abstract:The statistics of energy consumption and carbon emission of building during the whole life have the characteristics of poverty and great fluctuation in China, especially during the preparing stage of building materials. Further, analysis models to predict the energy consumption and carbon emission with high-accuracy and operability have not yet been developed. In the present study, the unequal interval grey model was introduced for the analysis and prediction of the energy consumption and carbon emission of the residential building materials at preparation stage in Hefei City. The test results with sufficient accuracy were obtained according to the posterior-variance-test. An evaluation index selecting the standard coal as the reference was proposed on the basis of the proposed model to express the energy utilization ability under unit carbon emission. The prediction results show that the energy utilization ability of building materials at preparation stage is still much lower, which can be improved considerably by comparing with the reference index. The proposed method can be employed to evaluate the energy utilization carbon emission in other building form as well as the unfinished deserted building and vacant house.